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March 13

Changes in personality test results and IQ when the subject is drunk

It is common knowledge that people change their apparant personality when drunk, but are there any research papers that compare the results obtained on Big Five personality traits personality tests and IQ tests for the same subjects after consuming alcohol and when completely sober? Thanks 92.15.8.206 (talk) 00:24, 13 March 2011 (UTC)

There is a lot more research on the effects of personality on alcohol consumption than on the effects of alcohol consumption on personality. There seems to be a general consensus that drinking increases impulsiveness, but I didn't spot any research that assesses this using standard personality tests. Looie496 (talk) 01:30, 13 March 2011 (UTC)

I suppose the problem with personality tests is that they ask the subject to recall their past behaviour or attitudes, eg "Do you like parties?" which would not be much affected by current intoxication. 92.15.26.29 (talk) 21:35, 13 March 2011 (UTC)

Why do nuclear reactors have batteries for cooling?

They could obtain all the energy they wanted from the heat of the rector. —Preceding unsigned comment added by 212.169.190.126 (talk) 03:12, 13 March 2011 (UTC)

As far as I understand, normally that's exactly what they do - they need to power the pumps that take the water in, but when the tsunami hit they shut down the reactor and went to diesel to continue cooling. The diesel then failed and they had to go to battery to power the pumps. Again, as far as I know, that's the main power need - pumping, venting, etc. SamuelRiv (talk) 03:52, 13 March 2011 (UTC)

The first backup, before they had to go their diesel generators, is to take power from the grid. This was impossible because the earthquake had caused all the power stations along the coast to go into auto-shutdown, including their own one. This left them on tneir own with only their own diesels and batteries, which worked fine until the subsequent tsunami flooded them. SpinningSpark 11:29, 13 March 2011 (UTC)

Also note that according to (most of) the news stories, the batteries were for instruments and controls, and were not for running the cooling pumps. -- 119.31.126.69 (talk) 12:06, 13 March 2011 (UTC)

Yes, I get the idea that a shut-down generator won't generate electricity directly. However, a shut-down reactor still generates heat (right?), so you could connect a Stirling engine with a cooler to generate all the electricity that you want. A part of the cooling would be passive, through the cooler of the Stirling engine, and the rest would be through the power generated through this process. 212.169.183.128 (talk) 12:53, 13 March 2011 (UTC)

Whether you could even do that in theory would really depend on how you had the plant set up. Have you actually been inside a nuclear power plant? They are not like those idealized reactor diagrams you see that explain how they work. They are massive industrial facilities, the size of many factories put together, with miles of pipe, concrete, and so forth. The turbines themselves fill gigantic rooms, deafeningly whirring away. They are quite a spectacle and I do recommend trying to visit one at least once in one's life, just to get a sense of the scale of the things and the work that goes into running them. I went on a tour of one awhile back and was bowled over by the complexity — you're not just going to rush in and tinker with them, especially not in an emergency situation. It sounds to me like you are either proposing that they'd have such a system already in place (which is probably not economical, considering the specific situation in which it would be useful, which would be quite rare) or adding one on the fly, which seems totally impractical, and not as easy as just using batteries. --Mr.98 (talk) 15:41, 13 March 2011 (UTC)

"Not as easy as using batteries"?? The technical implications of the size & complexity of a NPP plant have obviously gone over your head! Batteries are just about THE most impractical solution available. Bigredtoe (talk) 03:56, 17 March 2011 (UTC)

No, I was not thinking about an on-the-fly solution after an accident and also not an add-on solution to an already built nuclear power plant, but as an ideal solution. You need a backup cooling anyway, and this cooling system needs to be connected to the reactor somehow, so generating power shouldn't be a problem for it. You are right at pointing out that the nucleus quite rarely melts out (even if it might be happening right now). But, if it does, then the harm is apocalyptic (at least on a local scala). 212.169.183.128 (talk) 15:59, 13 March 2011 (UTC)

What happened in Japan (earthquake + Tsunami) is probably rare enough, so no one was prepared for this specific case. Once again, accidents happen, when people think they are prepared for something.Quest09 (talk) 16:58, 13 March 2011 (UTC)

If I understand things correctly, tsunamis are highly correlated with earthquakes; an earthquake that moves the seafloor is highly likely to create a tsunami. Why should one expect the combination to be rare? –Henning Makholm (talk) 20:50, 13 March 2011 (UTC)

It's the 8.9 earthquake that's rare. --Mr.98 (talk) 00:27, 14 March 2011 (UTC)

Yes. I expressed myself poorly. The combination (earthquake + Tsunami) is not rare. The violence of both (which also correlates) is not rare. But having such a violent earthquake and violent tsunami is quite uncommon. Quest09 (talk) 02:02, 14 March 2011 (UTC)

Batteries strike me as being far more flexible and adaptable (and I'm failing to see why they are insufficient). In any case, why assume your engine is going to not be damaged by the quake that damages the plant to that degree? --Mr.98 (talk) 00:27, 14 March 2011 (UTC)

They had diesel engines as backup power source. The batteries are said to be for other purposes. Quest09 (talk) 02:02, 14 March 2011 (UTC)

Undersea nuclear reactors - all the emergency cooling you want. 92.15.26.29 (talk) 21:36, 13 March 2011 (UTC)

The batteries and the diesels are not necessarily for different purposes! Although with a BWR plant they maybe. Power backup systems generally work thus: Immediately main power fails battery energy is automatically used to maintain power and the process of starting and bringing up to speed of the diesel driven generators is commenced. Only when the generators are running correctly (engine speed = output frequency etc)can the system "cut over" to run off the diesels. (You always have at least half of your diesels "ready to run" - some places i've worked at 1 unit was always started and brought up to speed before any servicing/repairs where commenced on the 2nd unit and first unit kept running until serviced unit was bought back into service, started, run and proved!) Assuming the diesels have enough capacity the battery banks then go into recharge mode.

With a sensible amount of diesel fuel stored on site you can run for days or weeks, and with the relative ease of obtaining diesel refueling you could run for months/indefinitely. You generally have 2 gensets or twice as many as you need. There is a lot of energy in a 44gallon(200 litre) drum of diesel. On the other hand to run for weeks or even days on battery alone you would need a stack of batteries of an insane size. (Mr.98 wrote "Batteries strike me as being far more flexible and adaptable (and I'm failing to see why they are insufficient).") That's why. I heard that they had enough battery capacity to run for 8 hours. "..but when the tsunami hit they shut down the reactor and went to diesel to continue cooling.." That is not quite right. Immediately the quake happened all 3 reactors automatically did an emergency shutdown, as did most if not all other reactors in the region. (The other 3 reactors at the site were not running and in a cooled down state.) As the generators driven by all the reactors went offline the power in the main grid would have browned/blacked out, even if the grid itself was undamaged by the quake itself. The transition to diesel power via battery appears to have gone ok and they were running ok "for about an hour"?? then water flooded the diesel gensets AND it seems associated equipment (switchboards, cabling, junctions etc). That appears to be complicating attempts to connect other power sources?

Where batteries may have a special separate roll in a BWR plant is to directly power special emergency backup pumps whose only job is to inject "neutron poison" (boron, boric acid etc) directly into the reactor if other measures to shut it down fail. Not a step operators want to rush into because it means a big cleaning job/lots of work if you ever want to start that reactor again!

But whether the reactor is shutdown by control rods or neutron poison or both, there is still a lot of cooling to be done over an extended period which requires a lot of pumping which is an energy hungry pastime. Using battery power for this is just not feasible. — Preceding unsigned comment added by Bigredtoe (talk • contribs) 23:11, 14 March 2011 (UTC)

Bigredtoe (talk) 19:11, 14 March 2011 (UTC)

Batteries were used to operate steam driven pumps (located in the reactor building) to flood the core and to monitor key parameters of the reactor. But with no Diesel generator the cooling function was actually lost since sea water pumps were flooded by the tsunami.--Franssoua (talk) 13:51, 14 April 2011 (UTC)

production of hydrogen from cooling water in nuclear accident -- was it a thermal decomposition?

It couldn't have been alpha particles or free protons finding electrons, right?

I know how to find the equilibrium reversal temperature to be 2300K. But obviously the pressure conditions are higher inside the nuclear reactor, and both temperature and pressure are increasing at the same time. How do I find the temperature where the equilibrium constant is 1?

Suppose I did start at some reactor pressure T1 -- perhaps I could draw a pressure-temperature curve as the reaction proceeds to T2? How do I calculate the total heat capacity of this reaction? (Is the heat capacity constant within this range, or do I have to account for this too?)

Also, does the presence of thermal decomposition provide a natural sort of "superboiling point" for water? That is, if I were superheating steam initially at 2300K at 1 atm, and suppose pressure were constant (the rxn is taking place in a large bladder or a balloon), would the steam basically stay at this temperature until all of it had converted to 2300K? John Riemann Soong (talk) 03:50, 13 March 2011 (UTC)

Is it accurate to model water as an ideal gas at 2300K and 600 kPa? John Riemann Soong (talk) 03:59, 13 March 2011 (UTC)

Fukushima I Nuclear Power Plant mentions caesium-137 as a fission product. It is radioactive, but as long as it hasn't decayed yet, it reacts chemically as an alkali metal -- like sodium except more so -- dissociating the cooling water into H₂ and OH^-. My understanding is that the systems that ordinarily disposes of the released hydrogen safely failed due to the loss of power. –Henning Makholm (talk) 04:45, 13 March 2011 (UTC)

A nuclear scientist on BBC News last night (sorry, don't remember his name) speculated that the hydrogen was produced, after the cooling pumps had failed, by the oxidation of the zirconium cases drawing oxygen out of the water leaving hydrogen as a by-product. SpinningSpark 09:10, 13 March 2011 (UTC)

Right. The zirconium is a not very reactive at low temperatures, but at higher temperatures it readily converts with water to the oxide leaving the hydrogen. This is a known problem in nuclear reactors.--Stone (talk) 20:01, 13 March 2011 (UTC)

say me what are you thinking about this subject

about formation of planets in solar system--78.38.28.3 (talk) 05:20, 13 March 2011 (UTC)

Akbar Mohammadzade wrote:

According to recent 30 years observations and increasing knowledge of man about the earth and planets in solar system , some astronomers are trying to give suitable theory about the formation of planetary system . My study has one difference with those theorems , for my goal of finding any solution for several paradoxes that i had list in my last article . from the angle of sun pole with planetary system quarter to existing of heavy elements in our system and the inner heat of earth ,..... Noticing to the recent studies about the origin of heavy elements in first solar nebula I focused on the properties of super novas , if there was this complex of element in thus nebula , that might be huge part of them in sun , but it has made of helium and hydrogen in general , this fact together with defragments of matter in terrestrial planets and giant planets says us some new rules about planetary system . I found out an approach for solving this problem , that it might be this system had created in two or three steps , first the sun and gas giant planets , second the creation of terrestrial planets with matter sent by neighborhood exploded supernova (in place where that conjunct with sun and solar system )and final creation of satellites and moons . In this sent article I say that supernova was send matter toward sun by 17degree angle(orbit of Pluto) and that reached here molten and changed sun quarter angle 7 degrees . akbar mohammadzade Iran university of science and technology --78.38.28.3 (talk) 05:20, 13 March 2011 (UTC)

That would appear to be an attempt to explain why the Sun and gas giants have fewer heavy elements than the terrestrial planets, moons, and smaller objects. However, that is already explained with a simpler theory, in that small planets, having insufficient gravity, lose their lighter elements, like hydrogen and helium, and thus become proportionally enriched in heavy elements. So, to propose an alternate theory (and expect it to be accepted) you would need to find a way to discredit the existing theory and prove your own. StuRat (talk) 08:46, 13 March 2011 (UTC)

(after edit conflict with StuRat) It is difficult to give a proper view on the works of Mr Mohammadzade without seeing the full paper, but I presume that it is not available in English as you appear to have translated an abstract yourself. The standard theory of planet formation is explained at nebular hypothesis, and we also have an article on star formation. A few comments on specific points:

• It is quite correct that the universe is 90% hydrogen and 10% helium with very little else. It is not true that this is not the make-up of our own solar system. Most of the mass is in the sun and jupiter which are both mostly hydrogen. The reason that on earth there is little hydrogen (other than in compounds such as water) and virtually no helium is that these elements are too light to be bound by the earth's gravity and 'evaporate' into space.
• It is correct that the heavier elements originate from supernovae. Elements up to iron in the periodic table are produced by nuclear fusion in large stars. These are later spread around by supernovae explosions. Heavier elements are produced by nuclear fission in the actual supernovae explosions themselves. The standard theory would have these heavier elements in place at the time of formation of the solar system, not arriving later as seems to be suggested by Mr Mohammadzade.
• It is quite unlikely that the curreent position of Pluto is where it originated (see Pluto#Origins and cannot therefore be taken as evidence of early solar system events as Mr Mohammadzade suggests.

SpinningSpark 09:01, 13 March 2011 (UTC)

notice this discussion :

The mater is separated such as spectrum from mercury to Neptune ,the question is this :suppose one element or particle at any place of first nebula , how did it found that’s same particle from distance which light spends in 22 hours to produce core of earth from nickel and iron?--78.38.28.3 (talk) 09:49, 13 March 2011 (UTC)

I'm not sure what that is saying, I can't quite parse the sentence. First of all, in a nebula material is drawn inwards and may eventually form stars and planets; material does not travel outwards from the centre. If the question is concerning the differing structures of the planets, there is general principle that the innermost planets have the largest nickel-iron cores (Mercury's core is particularly large in proportion to its size) and the outer planets have the smallest. This is simply because metal is more dense than rock or ice. Likewise rocky structures give way to ices in the outer reaches of the solar system. SpinningSpark 11:51, 13 March 2011 (UTC)

Hypertension and Asthma

How important are the blood pressure readings for a person who is suferring from hypertension and asthma? What is the significance of blood pressure in a person suffering from hypertension and asthma ? aniketnik 08:22, 13 March 2011 (UTC) — Preceding unsigned comment added by Aniketnik (talk • contribs)

I'm not sure if high blood pressure itself causes or triggers asthma. However, stress may cause both, so there could be a linkage between BP and asthma that way. StuRat (talk) 08:39, 13 March 2011 (UTC)

In case you don't already know, "hypertension" means high blood pressure. thx1138 (talk) 12:32, 13 March 2011 (UTC)

Yes, I do know that. I was using them as synonyms in my reply to avoid sounding repetitive. Or was that comment meant for the OP, and just indented improperly ? StuRat (talk) 13:02, 14 March 2011 (UTC)

Regardless of asthma, hypertension must be controlled because it leads to other comorbidities, primarily diabetes and high cholesterol. Therefore, it is important to get a hypertensive patient's blood pressure below 140/90 (the current standard) or 130/80 (for patients who are diabetic or have chronic kidney disease). Many studies have shown that controlling blood pressure limits progression to other comorbidities and greatly reduces cardiovascular disease risk (see Framingham Risk Score for information on how blood pressure is used to calculate CVD risk). So, knowing blood pressure is very important for hypertensives. -- kainaw™ 18:25, 13 March 2011 (UTC)

Hypertension leads to diabetes? And high cholesterol? Rather than all being correlated with obesity? So, someone who is overweight but has lower than average blood pressure is not at increased risk of diabetes and high cholesterol compared to someone not overweight? 86.163.4.134 (talk) 22:09, 14 March 2011 (UTC)

All three are heavily correlated. Having one leads to gaining another (and then the third if you live long enough). It is true that obesity is an underlying factor. There are many other underlying factors as well, so there is no single "cause". Note that I did not state that uncontrolled hypertension causes diabetes. I only stated that having uncontrolled hypertension leads to diabetes. In other words, a lifestyle that includes uncontrolled hypertension is a lifestyle that often includes diabetes and high cholesterol. -- kainaw™ 05:33, 15 March 2011 (UTC)

Why so cloudy on Venus ?

That is, why hasn't the thick atmosphere been lost to space, since Venus has no substantial magnetic field to deflect the solar wind ? StuRat (talk) 09:08, 13 March 2011 (UTC)

Our solar wind article says "...planets with a weak or non-existent magnetosphere are subject to atmospheric stripping by the solar wind. Venus, the nearest and most similar planet to Earth in our solar system, has an atmosphere 100 times denser than our own. Modern space probes have discovered a comet-like tail that extends to the orbit of the Earth." Which implies that it is being stripped but presumably will take a long time because the atmosphere is so dense. SpinningSpark 09:27, 13 March 2011 (UTC)

If it's been blowing off for billions of years, shouldn't it all be gone by now ? Or is it being resupplied in some way ? StuRat (talk) 10:04, 13 March 2011 (UTC)

Multiple sources confirm that it is being stripped, but I could not find anything to give a timescale (other than it is a lot slower than at Mars). Closest I could find was

"The precise evolution of Venus' atmosphere is not known. Nevertheless, it seems that there is an agreement among specialists that the terrestrial planets' atmospheres result from an evolutionary process which takes several hundred million years (Walker, 1975, Hart, 1978, Melton and Giardini, 1982, Zahnle et al, 1988, Hunten, 1993, Pepin, 1991, 1994). The present atmosphere of Venus is then a secondary atmosphere that acquired its major properties about 1 Gyr after the formation of the Solar System (eg. Hunten, 1993, Kasting, 1993)." [1].

SpinningSpark 10:58, 13 March 2011 (UTC)

Why is it slower than Mars ? Shouldn't the solar wind be much greater at Venus ? StuRat (talk) 12:10, 14 March 2011 (UTC)

Venus has Earth-like gravity. Mars doesn't. --Carnildo (talk) 02:00, 16 March 2011 (UTC)

OK, the gravity on Mars is 0.376 g while Venus is 0.904 g, so that's a valid point. However, Mars is approximately twice as far from the Sun as Venus is from the Sun, so I'd expect the solar wind to be four times stronger at Venus. So, how do gravity and solar wind figure into the calculations ? Do we have a formula for the rate of atmospheric loss ? StuRat (talk) 07:27, 17 March 2011 (UTC)

Note that Venus is believed to be still geologically active. Count Iblis (talk) 14:35, 13 March 2011 (UTC)

Also note that on Earth, volcanoes are the dominant source of non-anthropogenic and non-biological CO2. On the early Earth, they accounted for virtually all of Earth's greenhouse gases. There might also be other sources of CO2 production; for example, see this paper about the calcite + quartz reaction. --99.237.234.245 (talk) 23:26, 13 March 2011 (UTC)

Is Venus hot enough to drive CO2 out of Calcium Carbonate? Perhaps it has Calcium Carbonate in its geology that releases CO2. Googlemeister (talk) 13:00, 14 March 2011 (UTC)

Video

I'm trying to watch one of my video tapes, but every time I play it, it just grinds to a halt. How can I fix this? jc iindyysgvxc (my contributions) 11:24, 13 March 2011 (UTC)

Sounds like there is something wrong with the tape itself. I used to work at a video rental store (back when they used to rent videos!!), and it is relatively easy to take them apart and check if everything is spooled correctly. This post explains how to do it. If it were me, I would take it apart, see if everything looks right (nothing is jammed or twisted). I'd also try playing another VHS in the player, just to make sure it isn't the player that is broken. --Mr.98 (talk) 11:53, 13 March 2011 (UTC)

(ec) Take it to a TV repair shop? Sometimes this is due to the tape becoming loosley wound. If your player will fast forward it without sticking, try winding it fully to the end and then fully rewinding before attempting to play it again. If your player won't do this you could try manually tightening it, but this can be quite tedious. Have you checked if your other tapes play ok? If they don't there is probably something wrong with your player so it needs repairing; if the others do play ok you could also look for dirt or obstructions fouling the tape cassette mechanism. SpinningSpark 11:59, 13 March 2011 (UTC)

To boldly go, though dead, where no man has gone before...

Suppose I wanted my ashes, or to make this quite silly - my brain - to leave the solar system and voyage between the stars like the Voyager probes. Is it within the realm of private citizens to create a rocket that could escape the Sun's gravity? Can I fling my remains out of our solar system? The Masked Booby (talk) 11:58, 13 March 2011 (UTC)

Not sure about out of the solar system for the price of $995 you can have them sent into space.--NortyNort (Holla) 12:51, 13 March 2011 (UTC)

For current state of play see space burial (we really do have an article on everything !). The only person whose remains are currently en route out of the solar system is Clyde Tombaugh - approximately one ounce of his ashes have hitched a lift on the New Horizons spacecraft, which crosses the orbit of Uranus in a few days time. To escape the Sun's gravity you either need a dumb payload and a *very* big rocket, or you need a smaller rocket and a mission plan that include one or more gravity assists, which in turn assumes a capability for deep-space tracking and in-flight manoeuvres. Or you could develop a very efficient but highly sophisticated inter-planetary propulsion system, such as an ion thruster. Any of these routes is beyond the reach of any private citizen. Your most affordable option is to pay NASA to put a small portion of your remains on their next flight out of the solar system - I imagine that would cost you around $10 million (the going rate for a space tourism trip on the ISS is $15-$20 million). However, in the current economic climate, you might have a long wait for the next bus. Gandalf61 (talk) 13:17, 13 March 2011 (UTC)

Well, to expand on the OP's idea, why does it have to be ashes? Why couldn't an uncremated human body make the trip? --KägeTorä - (影虎) (TALK) 13:22, 13 March 2011 (UTC)

It could, but it might be significantly more expensive, as long as the commercial price tags for lifting stuff into space (even just geostationary orbit) lie at tens of dollars per gram. Of course if you can't find an existing interplanetary probe to hitch a ride on, the cost lifting the payload into Earth orbit might not even dominate. –Henning Makholm (talk) 15:50, 13 March 2011 (UTC)

I hope the moon is not being contaminated by people's ashes, as the first link claims. 92.24.186.239 (talk) 13:28, 13 March 2011 (UTC)

The Moon is already "contaminated" by 6 Apollo Lunar Module descent stages, 3 Lunar Roving Vehicles, 2 Lunokhod rovers and umpteen other lunar probes. Compared to the hardware already left on the Moon, a few grammes of sterile human ashes will have little impact. I would be more concerned about the waste of resources involved in a dedicated lunar burial flight (as opposed to hitching a lift on a pre-existing science mission) - it is the complete opposite of a green burial. Gandalf61 (talk) 13:49, 13 March 2011 (UTC)

See List of man-made objects on the Moon. 75.41.110.200 (talk) 19:16, 13 March 2011 (UTC)

I hope the moon will never be used as a deliberate rubbish-tip, even if its for human ashes. It would not be nice to look at the moon and think that it has been despoiled with waste. Exploration-related artifacts are a different matter. I hope governments forbid its use in that way. 92.15.11.100 (talk) 12:23, 14 March 2011 (UTC)

Why bother? The Earth is, sort of, a giant spaceship... Count Iblis (talk) 17:10, 13 March 2011 (UTC)

There are not a lot of probes leaving to the interstellar space New Horizons spacecraft was the last one. With 2 billion dollar you would be on the save side. NASA or ESA would make a nice mission to a Kuiper belt object and would take your (sterilized) brain with them if you donate the money with a good contract attached to it. Cheaper would be to become the discoverer of Nemesis (hypothetical star) and die well before a mission to that place, like Clyde Tombaugh the discoverer of pluto, who is just now on the way to pluto. Even cheaper would be that your brain gets a Tire balance for a space craft. before launch the moment of inertia is determined and a few weights are installed to adjust the rotation axis. If you can talk NASA into using your brain this would get you to interstellar space.--Stone (talk) 23:38, 13 March 2011 (UTC)

Since probes are expensive people want to be sure that they reach interstellar space, instead of crashing in somewhere, but suppose one just gives the best shot to create a rocket that can go as fast as needed for leaving the solar system - wouldn`t that just take a large load of fuel and building materials for the rocket? ~~Xil (talk) 02:47, 14 March 2011 (UTC)

(edit conflict with Xil) You're vastly overestimating the cost, I think. New Horizons is expected to have a 15 year mission cost of just 650 million USD, and that includes the launch costs + spacecraft cost (design and materials) + mission operations + data analysis. If your just sending your body into space, the cost for everything but the launch vehicle is negligible. I can't find a good cost breakdown for that particular rocket configuration (Atlas V 551), but it's certainly less than 300 million USD, probably closer to 200 million USD (the slimmer 401 configuration is cited at 187 million USD). And New Horizons weighs about 1000 lbs. If you can find 5 close friends to get launched into a solar escape trajectory with you, you can cut the costs to less than 50 million USD a piece. If you're cremated (ashes weigh , on average, ~5 lbs per person), you can send about 200 sets of remains into a space, for a per capita cost of under 1.5 million USD. Of course, that means you have to find 200 millionaires who want to be sent out of the solar system after they're dead. Buddy431 (talk) 03:00, 14 March 2011 (UTC)

Re-read Gandalf61's post, above. To get out of the solar system with a rocket like the one that launched New Horizons, you have to do gravity assists, which means you need a sophisticated spacecraft with onboard engines and computing power, and active tracking and management of the craft from Earth. You need, basically, the whole New Horizons mission except for the scientific payload. If you want to just use a dumb rocket and get onto a solar escape trajectory, that rocket has to be much more powerful and expensive. It takes a lot of energy to get from Earth's surface to a solar escape trajectory.--Srleffler (talk) 03:47, 15 March 2011 (UTC)

Re-read New Horizons. New Horizons did use one gravity assist (Jupiter), but it was on a solar escape trajectory before it even reached Jupiter. The gravity assist made it's trip to Pluto faster, but it was not necessary. Buddy431 (talk) 17:58, 15 March 2011 (UTC)

With so many power plants out of commission, how will Japan import the needed power in the shorter term?

In the longer term, they replace or repair the damaged plants. Right now, nearly all(?) of Japan has rolling blackouts 3 hours a day. (Hopefully from 2-5 AM, but probably not.) That can't keep happening until the power plants are fixed/replaced.

Couldn't they use undersea cables to import power from other nations? What are some other power solutions in the meantime? --70.179.169.115 (talk) 14:57, 13 March 2011 (UTC)

You must know Japan's Asia-facing side is much less developed than the Pacific Ocean-facing side. Tokyo and Osaka, two largest Japanese cities are facing the Pacific Ocean and they are separated from Continental Asia by mountains and pretty wide seas. On the other hand, many Korea-facing Prefectures, such as Niigata and Toyama are much more fishery or agricultural. You must know a very great percentage of Japan's lands are nothing but mountains. There are only pockets of small plains. Unfortunately, these Asia-facing areas are generally very narrow strips of rice paddies backed by very very very high mountains. You can ride a Suzuki from the sea shore to the nearest mountain foot within an hour. If you take train, you can see the sea on one side and the mountains the other side. These areas are usually not industrialized. They use much less energy than the Pacific Ocean side. Flat lands like Tokyo and Osaka are rare and mostly on the Pacific Ocean side. Please consult Google Maps. They have terrains. I think the most likely candidate for direct energy importation is Fukuoka which is very close to Korea's Busan City. To long haul electricity under salt water, you must use high-voltage direct current (HVDC). -- Toytoy (talk) 14:59, 15 March 2011 (UTC)

I imagine that a more efficient model that undersea cables would be to just import big generators and fuel for them. You can move a lot of coal very cheaply and very efficiently on big boats, more cheaply than building undersea power cables, I imagine. But this is just a guess — I haven't run the numbers. --Mr.98 (talk) 15:32, 13 March 2011 (UTC)

Rolling blackouts have to happen all through the day. Different places get power at different times - that's what "rolling" about them. They could use underpower cables, but only if they are already there - it takes a long time to lay such cables. We have an article, Electricity sector in Japan, but it doesn't cover this question. Since it doesn't mention electricity imports (just fuel imports), I guess there aren't many, which means they won't be able to increase them quickly.

They will have to reduce demand instead. That usually means cutting off the supply to big factories. They've probably already done that (if any big factories are even able to operate at the moment), but this disaster is on a scale much greater than anything they are prepared for, so it's still not enough. They'll probably get things sorted out over the next few days in terms of supply. What will take longer is fixing the distribution network - there are downed power lines all over the place.

--Tango (talk) 16:45, 13 March 2011 (UTC)

Perhaps they won't have to cut the power, or maybe have. Grandiose (me, talk, contribs) 20:55, 13 March 2011 (UTC)

I was thinking a similar thing (as well as it's entering spring and the temperatures are more mild) but per the OP and news reports, they are instituting rolling blackouts and encouraging people to save power so clearly the reduced power usage due to factories etc shutting down to assess damage (or because they are damaged) isn't enough. On the other hand, I would guess precisely how many power plants are sufficiently damaged that they can't be used remains unclear. I would presume many are shut down at the moment for the same reason as the factories, so the damage can be properly assessed and some of these could potentially be safely operated whether at reduced or full capacity while they are repaired. While likely a high priority task, they are also have tasks with higher priority so this may still take a while yet. Of course other then power plants offline I would guess the national grid has suffered some damage Nil Einne (talk) 00:14, 14 March 2011 (UTC)

In most places a proportion of theoretically active power plants are down for maintenance, refueling (for nuclear), etc. Those can be brought back on line and restore some capacity, but it takes time to complete whatever the work might be. Lots of utilities keep plants in reserve to meet peak loads. Even so, twelve (?) 500mw - 1 gw plants being off-line, particularly since nukes are considered "baseline load" plants for normal production is hard to make up for. I'm certain that some fossil plants are off-line, and bringing up a damaged grid is a slow process, to ensure that surviving generating units aren't harmed. Acroterion _(talk) 02:17, 14 March 2011 (UTC)

According to the Telegraph, Russia will supply power through an existing undersea cable [2]. Acroterion _(talk) 14:05, 14 March 2011 (UTC)

I have mentioned above, Japan's Asia facing side is much less industrialized than the Pacific Ocean facing side. Russia may lay a section of HVDC cable to Hokkaido. But it's a very long haul. Between Korea's Busan and Japan's Fukuoka you may lay another piece of HVDC cable. However, this part of Japan is least affected by the earthquake and tsunami. It helps, even though it's not very helpful. Importing energy from North Korea is out of the question. They are in an even worse shape. From China is really not very feasible. China is way too far from Japan. Even though Japan has a long history of invasions. I really don't think it's technologically feasible to transfer electricity from China to Japan. Between Russia and North Korea, there's a very small tip of China facing the sea. That part of China does not touch the sea and you have to lay cables over North Korean or Russian lands to reach the sea. It was supposedly Chinese land taken over by Russia more than a century ago. Anyway, China is unlikely to provide direct help because of the very long distance between two countries. -- Toytoy (talk) 15:14, 15 March 2011 (UTC)

You guys may have already noticed that the Tokyo Bay's opening to the sea is facing south west, shielded from the tsunami by a whole Chiba Prefecture. As a result, Japan's largest harbor and metropolitan area are protected from the quake and tsunami by the geography. If this tsunami occurs in July or August when people are going to the seas for fun, the death toll could be several times higher. The epicenter is about 400 km from Tokyo and it occurred in winter when very few people go to the seas probably saved countless lives. -- Toytoy (talk) 15:26, 15 March 2011 (UTC)

Form work of Plinth Beam or Shuttering of Plinth Beam

How to Calculate Form work of plinth beam in Running Feet. —Preceding unsigned comment added by 182.178.71.47 (talk) 20:11, 13 March 2011 (UTC)

Note: this question was also asked on the math desk. I don't understand it well enough to figure out which desk is the proper one, but whomever can offer an answer, please add a pointer to the other copy. –Henning Makholm (talk) 20:46, 13 March 2011 (UTC)

I suggest you consult a professional engineer on how to build formwork for a plinth beam. I suspect there are too many variables involved for us to be able to provide a useful (and safe) answer here.--Shantavira|^{feed me} 21:26, 13 March 2011 (UTC)

This appears to be a question concerning estimation of materials quantities ("shuttering" or "forrmwork"), rather than a structural question, but Wikipedia's not really the right place for this question in either case. Acroterion _(talk) 00:28, 14 March 2011 (UTC)

R68: Possible risk of irreversible effects

What does EU R-phrase 68 actually mean? It seems pretty vague to me. I mean, thanks to entropy pretty much everything has irreversible effects. Horselover Frost (talk · edits) 21:54, 13 March 2011 (UTC)

And there's R39, too: "Danger of very serious irreversible effects." (Somewhat less vague at least;). WikiDao ☯ 22:07, 13 March 2011 (UTC)

I think that any answer to this question would have to come from the official specification. They never define "irreversible", but it appears to refer to bodily damage that never heals, as you'd expect. -- BenRG (talk) 23:07, 13 March 2011 (UTC)

Like pulmanary scarring from enhaling corrosive vapours? Plasmic Physics (talk) 23:45, 13 March 2011 (UTC)

Relativity postulates/ Frames of reference/ Escape velocity

As we all know that the laws of physics are the same in all inertial frames of reference but since speed of light (pulse) is way way greater than its Escape velocity in any inertial frame of reference except black hole therefore shouldn't a pulse of light clock be moving freely and independent of frame of reference of spaceship or any other arrangement carrying the light clock assumably74.198.150.224 (talk) 23:03, 13 March 2011 (UTC)Khattak#1-420

There is such a thing as a light clock, but it follows the usual rules of time dilation. I'm not sure I understand your question. -- BenRG (talk) 23:09, 13 March 2011 (UTC)

Thanks for your swift response. As we all know that in order to "break free" from any inertial frame of reference (gravitational field) an escape velocity/ speed is needed. Therefore laws of physics are not the same  in aforementioned reference frames for something if at or greater than escaping speed.

Simple example

An object on the surface of earth if to be freed from its reference frame needs an escaping velocity of 11.2 km/s.

Thus if this correct then

1- A pulse emerging from top mirror in spaceship moving close to c should follow the same original downward path instead of vertical for inside and inclined for outside observers. 

2- Similarly in relativity of simultaneity the two strobe of light striking the front and rear would be the same for both inside and outside observers74.198.150.224 (talk) 04:22, 14 March 2011 (UTC)khattak#1-420.

Inertial reference frames and gravitational wells are totally different things. There's no such thing as "escaping from an inertial reference frame". -- BenRG (talk) 05:05, 14 March 2011 (UTC)

The comoving frame of an object on the surface of the Earth is not an inertial frame of reference. For example, if you're standing on the Earth, as measured in an inertial frame of reference you are being accelerated upward, due to the force exerted by the Earth's surface on the bottoms of your feet. An inertial frame of reference is the comoving frame of an object in free fall. Red Act (talk) 12:14, 14 March 2011 (UTC)

Bus travel

Is it generally safer to sit in the front or back of the bus? Imagine Reason (talk) 23:59, 13 March 2011 (UTC)

Safer from what? Crashes? Mugging? Molestation? Travel sickness? All risks combined? {The poster formerly known as 87.81.230.195} 90.201.110.135 (talk) 01:34, 14 March 2011 (UTC)

Google searches generally seem to say that any forward facing seat is fine, with some people opining that the seats immediately behind the driver are safest, but none of that seems to have any statistics or any objective research behind it. This guy says that the best seat is towards the middle, though it's played more for humour. Matt Deres (talk) 02:22, 14 March 2011 (UTC)

Seats at the rear of aircraft or trains are safer, so I expect that rear of buses is also. Wear the seatbelt if the bus has one. But I think bus travel is safer than car travel. 92.15.11.100 (talk) 12:28, 14 March 2011 (UTC)

If it's 1955 in Alabama and your name is Rosa Parks then it would be less bother for everyone if you sit at the back of the bus. Cuddlyable3 (talk) 13:29, 14 March 2011 (UTC)

But Rosa did the right thing and made it difficult for everybody - for a while - and now it's a whole lot easier for a whole lot more people. The poster seems to be in London so we might need to consider upstairs and downstairs as well as front, back or middle. Richard Avery (talk) 16:33, 14 March 2011 (UTC)

Is this guy seriously referring to the civil rights movement as 'bother'. Disgraceful. —Preceding unsigned comment added by 92.20.217.50 (talk) 23:03, 14 March 2011 (UTC)

Well, Rosa Parks not sitting in the back was quite bothersome, which is precisely why it was so important and catalytic when she did it, and why she is honored for it. Yes, it would have been less of a bother for everyone had she sat in back. She probably ruined everyone on that bus's day, made a scene and a fool of herself, and made the rest of the ride awkward for everyone else.

As for bus safety in collision, though, it really depends on the type of impact that occurs. I'm not sure if the front has a crumple zone in case the driver veers off and smashes into a pole, but my bus was hit on the side by a car whose brakes failed on a snowy day, thus running a red light. Luckily the collision was relatively low-speed, but it still left a good dent at 20mph - perhaps it would have just been a jolt had it hit the bumper. SamuelRiv (talk) 08:57, 15 March 2011 (UTC)

March 14

Best tsunami strategy for boats?

Assuming you had warning, like everyone on the US west coast did, what would be the best strategy for minimizing damage to your vessel? It seems to be that heading directly out to sea would be the best choice, in order to get past the point where the tsunami begins to stack up and form a real wave. Out in open water the tsunami is only a meter high, or even less, with an enormous wavelength, right? Leaving your boat moored would be the worst choice, would it not? The Masked Booby (talk) 02:17, 14 March 2011 (UTC)

Heading out to sea is definitely the best choice. That's what most of the fishing boats in Crescent City did, as I understand it. Many, though, for various reasons were not able to do it. Looie496 (talk) 03:33, 14 March 2011 (UTC)

Concur with Looie496. See Tsunami Safety Rules (3rd from bottom), which recommends "move your vessel to deeper water (at least 100 fathoms)." But you might also take your vessel out of the water, if possible. Several fishing ports received signficant damage to vessels in port and infrastructure. See also:

• Santa Cruz, California#Recent History,
• Crescent City, California#Tsunamis and
• Brookings, Oregon#2011 Tsunami - 220.101 talk^\Contribs 15:48, 14 March 2011 (UTC)

Tsunami's are barely noticable in the deep ocean, so the best advice is to take it out to sea. There was an expert on NPR shortly after the earthquake discussing the physics of tsunamis and how they differ from ordinary surface waves; a Tsunami may have an amplitude of several meters, but a wavelength of 300 kilometers in the open ocean. In other words, while the crest of the wave may be taller than your boat, that crest is spread out over 300 kilometers or so; meaning that the effect of the tsunami passing under you will be negligible and indetectable. When the tsunami reaches the continental shelf, the wave gets backed up, meaning that by the time it reaches land, much of that wavelength has been "pushed together" resulting in a huge, devastating wave; so the key to surviving on a boat is to get the boats out to deep sea. --Jayron32 23:58, 14 March 2011 (UTC)

How far inland did the Sendai tsunami wave travel?

How far inland did the Sendai tsunami wave travel? —Preceding unsigned comment added by 173.49.10.83 (talk) 03:33, 14 March 2011 (UTC)

Most places are saying "More than 5km". APL (talk) 04:22, 14 March 2011 (UTC)

Likely too early for a really reliable source, but see "At the scene" sidebar here. BBC reporter claims 10km (six miles), ref from 2011 Sendai earthquake and tsunami - 220.101 talk^\Contribs 17:51, 14 March 2011 (UTC)

"BBC reporter claims 10km (six miles)" Ok lets do the maths on that!!

reporter = divide by 2 = 5km BBC = reduce by 20% = 4km (American media reduce by 40% Australian reduce by 55%) Bigredtoe (talk) 19:24, 14 March 2011 (UTC)

Actually 4 km would match the extent of tsunami sand deposits on the Sendai plain from previous large earthquakes, like the 869 Sanriku earthquake and tsunami. Mikenorton (talk) 19:21, 15 March 2011 (UTC)

A wave question

Dear Wikipedians:

I had been working on the following wave question:

If a sinusoidal wave has a frequency of 479 Hz and a velocity of 373 m/s, what is the distance between two points that differ in phase by π/3 rad?

My solution is as follows:

λ = v/f = 373/479 ≈ 0.7787

d = λ(π/3)/(2π) = λ/6 ≈ 0.1298 m

However, I am not too sure how valid my second step is, I basically reasoned that the phase difference tells me how much of the 2π cycle is taken up by the horizontal distance between the two points, so that the proportionality would allow me to find the original horizontal distance between the two points. Is this valid?

Thanks,

174.88.32.181 (talk) 03:35, 14 March 2011 (UTC)

Your method of calculation looks OK. Graeme Bartlett (talk) 06:52, 14 March 2011 (UTC)

Yes, you are correct right down to rounding the answer to 4 decimal places. Cuddlyable3 (talk) 13:17, 14 March 2011 (UTC)

The answer is correct but incomplete. The full answer is d = λ |1/6 + n|, where n is any integer. Dauto (talk) 23:43, 14 March 2011 (UTC)

Lack of preparation for foreseeable events at nuke plants

(Title of thread changed from "Explosimeters: broader issues) There has reportedly been a second hydrogen explosion at a Fukushima 1 nuke plant (Unit 3, after the earlier Unit 1 explosion), blowing off the masonry walls and roof around a reactor containment. An Explosimeter or combustible gas detector is a gadget which detects when any combustible gas has reached the lower explosive limit of admixture with air. Utilities have used them for many decades to test tor combustible gases in enclosed spaces. Hydrogen detectors are also time tested devices. Do Japanese nuclear plants not have them installed in the outer containment buildings? If they had them, why wouldn't they vent the enclosures with outside air to keep the concentration below the amount which could cause the two violent explosions observed, each of which reportedly injured several workers? Areas which might have combustible gases usually are required in the US and Canada to have all switches, relays and contactors fully enclosed so that a spark cannot ignite an explosive gas mixture. Is thus a not a rule in Japanese nuclear plants? How can they allow two giant explosions in 2 days? Hydrogen is not an exotic substance. Large power generators (not reactors) have been filled with hydrogen for low viscosity cooling of the windings for maybe 80 years, and blowups or fires are rare because hydrogen leaks or buildups are detected and ventilated. There was a hydrogen bubble in the Three Mile Island reactor vessel, but it did not cause an explosion to demolish the building. They had the sense not to just vent it into the containment building and wait for a spark. Edison (talk) 04:17, 14 March 2011 (UTC)

They might not have wanted to risk contaminating the area with radioactive "stuff" by venting the enclosure? —Ruud 05:33, 14 March 2011 (UTC)

Nils J. Diaz, a nuclear engineer who led the United States Nuclear Regulatory Commission, blamed it on the Japanese perfectionist culture. [3]F (talk) 11:15, 14 March 2011 (UTC)

Agreeing opinion on not wishing to contaminate the surrounding area here. Nanonic (talk) 15:29, 14 March 2011 (UTC)

According to Fukushima I nuclear accidents#Explosion of reactor building: "Safety devices should ignite the hydrogen before explosive concentrations are reached but apparently these systems failed." —Ruud 05:39, 14 March 2011 (UTC)

Isn't it quite easy to put a number of large slow-burning candles in high places to ignite the hydrogen gas? -- Toytoy (talk) 12:09, 14 March 2011 (UTC)

I'm not sure they can get in to the vessel in question. And yes, I think the problem with venting is that the stuff in the reactor building is generally stuff you don't want to vent. --Mr.98 (talk) 14:31, 14 March 2011 (UTC)

So you let the thing explode instead? Sorry I just don't get the reasoning. Vespine (talk) 22:41, 14 March 2011 (UTC)

After the power fails, the backup power fails, the back-up back-up power runs out - what do you have left to run the ventilation? They brought in fire trucks to pump seawater into the reactors - until it ran out of petrol and may have resulted in a partial meltdown in unit #2. These are very desperate measures. 75.41.110.200 (talk) 23:40, 14 March 2011 (UTC)

Yeah, better to let an explosive hydrogen air mix accumulate and blow the upper portion of the building off and injure people and damage pumping equipment at the adjacent reactors. Not. A completely forseeable and automatic sequence of events: they let the coolant drop below the fuel, the zirconium cladding oxidizes, hydrogen is generated as pressure in the inner reactor vessel builds, they vent hydrogen into the upper masonry enclosed space to reduce pressure in the inner reactor vessel so water can be pumped in, an explosion results when there is a spark (why allow a spark?) An alternative would be to knock 2 holes in the masonry and attach a fan powered by a portable generator, if they were so idiotic as not to have allowed for a power failure. Then the upper structure would never have accumulated an explosive hydrogen/air mixture. Power plants took great pains to avoid explosive hydrogen accumulations in battery rooms since the 1880's. How could 1970's reactor design have been so behind the times? And no one anywhere has broached the dangers from embrittlement of the metal inner reactor vessel due to years of neutron bombardment, which was a concern for reactors such as the GE Mark 1 reactors even back in the 1980's. If the steel is embrittled, and they negligently allow the water to drop below the core, then the fuel gets to several thousand degrees, then they pump in cold water, the reactor vessel is apt to fracture, leading to more problems, such as the loss of cooling water, the complete melting of the fuel, its melting through the concrete into the soil below the reactor, and a steam explosion releasing Chernobyl amounts of radioactive material. The plant operators also lost the cooling pumps on one reactor when they ran out of diesel fuel. (Gee, we should have ordered some fuel). Now a third reactor has had a hydrogen explosion which blew off the top of the building. Anyone see a pattern? Edison (talk) 01:05, 15 March 2011 (UTC)

There is no need for a spark - the vented steam is hot enough to self ignite as soon as it finds oxygen. Ariel. (talk) 01:18, 15 March 2011 (UTC)

If there were a red hot igniter by the vent, or if the vented steam were hot enough to ignite hydrogen in oxygen, then why wouldn't the hydrogen have burned off harmlessly (save for warming the enclosure)? Thus no explosion would be possible, which is counterfactual.Perhaps the vented steam was not hot enough to ignite hydrogen. Please reanalyze. How did there accumulate a sufficient inventory of unburned hydrogen to blow the sturdy masonry structures to flinders? The structure must have remained below the lower explosive limit while steam and hydrogen vented until an explosive mixture evolved, or until there was an ignition source. And how was this not foreseeable? Edison (talk) 01:27, 15 March 2011 (UTC)

There was no oxygen in the vented gas. It took a while to mix with ambient air (and probably cooled in the process). Then some fresh, hot, gas got vented and set off the whole thing. And not only was it foreseeable, they knew it would happen, but did it anyway because the outer building is unimportant. Also, I've seen no suggestion at all that they ran out of fuel (it makes no sense that they did since it's not that hard to send some fuel). Ariel. (talk) 01:48, 15 March 2011 (UTC)

"Unimportant?" It injured numerous workers and impaired pumping efforts at adjacent reactors, thus "IMPORTANT." News reports indeed said that the pumps at one reactor stopped because they ran out of fuel. I agree that the Japanese government (or most world governments) would likely have cheerfully transported some fuel if the folks in charge had requested it in a timely manner. You didn't hear about it? See [4] "Later in the day, a backup pump to a third reactor ran out of fuel, causing water levels to fall so low that the fuel rods were fully exposed." In a nuclear reactor, anyone with any knowledge at all of their operation would agree that letting the cooling water drop below the recently used fuel rods was an extremely bad idea, to be avoided at all costs. Edison (talk) 01:58, 15 March 2011 (UTC)

It's really too bad. With the latest news of a leak it looks like nuclear power may be delayed again in the US, and I'm not happy about that. I live in an area with lots of pollution from coal plants, and I would gladly trade the certainty of health problems from hydrocarbons for the risk from a nuclear plant. Ariel. (talk) 03:32, 15 March 2011 (UTC)

More precisely, the plants were designed with an electrical burner on the vent to burn off any hydrogen that was vented. Of course, with the total loss of power, that wasn't working. Dragons flight (talk) 11:17, 16 March 2011 (UTC)

I'm not sure that they have as much control over the reactor facilities as you seem to think. Sensors and vents are only useful if they're functioning and still connected to their control systems. APL (talk) 04:11, 15 March 2011 (UTC)

The lower explosive limit for hydrogen gas in air is 4%, per Flammability limit. "Control over the reactor facilities" could amount to mechanically breaching the wall of the upper nonpressure structure, or having a pair of sealable bulkhead doors which could be opened from some distance via a lever or cable. Air flowing through would then have kept the hydrogen concentration below 4%. The concept of a "hatch" is not exotic sci-fi. What is the point of having a masonry structure which cannot be ventilated when the basement floods (foreseeable) and electrical panels are shorted out (electrical fires are foreseeable and occur somewhere every day), with the pressure vessel (foreseeably containing hydrogen) vented into the structure rather than the great outdoors? Why not vent out through the roof rather than into the building? What was supposed to happen to the hydrogen inside the masonry building other than achieving an explosive concentration? The consequence of not being able to vent the hydrogen is that numerous workers have been injured by the explosions, and now the workers at the plant have reportedly exposed to radiation levels (400 mSv per hour, or 40 Rem per hour) which could cause radiation sickness in 2.5 hours or death in 12.5 hours of exposure. (I hope they are shuttling workers in and out to limit exposure, but that does not make for continuity of action, and there are only so many workers with knowledge of a plant and training to take needed actions there). Robots were used to a limited extent way back at the Three Mile Island cleanup. Do Japanese nuclear plants have any remote operated robots which could go in and do work such as extending a firehose to a spent fuel pool, or opening a valve? The authorities are now, in desperation, asking for helicopters to fly above a hazardous radiation zone and drop water on a spent fuel pool which had previously boiled away water allowing the burning of spent fuel. There are search and rescue robots and firefighting robots which could be introduced into a high radiation building and controlled from a safe distance, to extend a hose to a spent fuel pool from which the water is boiling away. Edison (talk) 15:58, 15 March 2011 (UTC)

Nuclear experts in the 1970's and 1980's noted weaknesses of this design, said there was a high probability of the vessel and containment bursting soon after a core melt, and said the concrete containment structure was not strong enough in the event of a cooling failure. Edison (talk) 18:11, 15 March 2011 (UTC)

Ah, the experts speak, per CNN at 22:37 GMT, March 15: "Plant managers were considering removing panels from the buildings housing those reactors in an effort to prevent the hydrogen buildup that officials believe caused the other explosions, the IAEA said. Edison (talk) 23:48, 15 March 2011 (UTC)

The optical properties of ptfe (teflon)

I am trying to find optical properties/ transmittance data for virgin (opaque) PTFE. Many web sites have mechanical properties but no optical. I wish to use PTFE sheet as a diffuser to measure solar radiation. Is this data available? It is not included in http://en.wikipedia.org/wiki/Polytetrafluoroethylene_(data_page)#Spectral_data.Fredthemuffin (talk) 05:06, 14 March 2011 (UTC)

Characteristics of crab nebula

i read in "astrophysical concepts "by (martin harwit) that the cloud which we see there in crab nebula containes pieces in volume some cube meters . thus it cannot be dust , is it so in other references?[ that was in last my question replyed it is such as oven and low density dust] akbar mohammadzade march 2011 --78.38.28.3 (talk) 06:45, 14 March 2011 (UTC)

I can't find that in my copy of Harwit (4th edition). In which section did you find that statement? --Wrongfilter (talk) 08:53, 14 March 2011 (UTC)

that is third edition 1988 chapter nine 9-1 page420 mohammadzade(cicular and about some ten cube meter ) —Preceding unsigned comment added by 78.38.28.3 (talk) 10:53, 14 March 2011 (UTC)

Third edition is on google books, but page 420 is in Chapter 10. The relevant bit in 9.1 should be here but this doesn't mention grain size. Are you sure that the number you mention doesn't refer to a density? --Wrongfilter (talk) 11:41, 14 March 2011 (UTC)

Evolution of the solar core?

The solar core is currently about 150 times denser than water, at 15 million kelvin. Over the next five billion years the Sun will gradually get hotter and larger, which I assume means that its core must get hotter and denser. As I understand the Wikipedia articles, eventually the Sun becomes a red giant following the asymptotic giant branch, until the core consists of degenerate matter and undergoes a helium flash that drives it out on the horizontal branch, but only temporarily. Apparently multiple ? helium flashes at the end of the process end up converting these huge outer red giant layers into a planetary nebula, leaving behind the degenerate core as a white dwarf.

What I wonder is, how does the solar core evolve over this process? How does its heat and density change over the billions of years before the sun becomes a red giant? How quickly does it collapse to degenerate matter as the red giant phase sets in?

Last but not least, for a sci-fi story I'm writing, I'm curious whether it is possible to save the core of sun-like star once it starts to become denser and/or hotter. For example, if you could somehow make a red dwarf star collide with the sun, would that provide fuel and abort the red giant stage in some semi sane period of time (by which I mean, less than 10⁵ years, which I think is what it would be...^[5]) If you could somehow inject the hydrogen from the star all the way to the core could it help? (though my favored hyperdrive would be hard to use that way...) Wnt (talk) 08:04, 14 March 2011 (UTC)

Regarding "...its core must get hotter and denser", getting hotter would cause it to expand, reducing density. As for adding more hydrogen, that sounds like it could work, if you can mange to carry another star there. I would think the hydrogen would find it's way to the core on it's own. StuRat (talk) 11:52, 14 March 2011 (UTC)

Stellar structure is a good place to start. StuRat's understanding of the hotter/denser issue is correct over short time scales, but fails to take into account the change in stellar core composition as the star ages. In stars similar to our Sun, the core never quite gets hot and dense enough (while it is on the main sequence) for it to start burning appreciable amounts of helium; this helium accumulates in the core, increasing the core's density. Because of this increased density, there is increased gravitational compression of the fusing material at the core, and the core gradually gets hotter as the star ages.

On the issue of how to get fresh hydrogen to the core, I'm afraid that dumping it on the surface won't work for a star like our Sun. While there is significant convective transfer of material in the Sun's outer layers, there's actually very little exchange down into the core. (Note that adding hydrogen at the surface could work for very small stars, less than 0.4 solar masses. In such stars there is convective transfer all the way down to the core—though I don't know how rapidly that exchange of material takes place.) TenOfAllTrades(talk) 13:54, 14 March 2011 (UTC)

Wow. I just read that the Sun is expected to go red giant when just 12 percent of its hydrogen is used up.^[6] Yet according to red giant, I have the impression that all of the hydrogen in the core is used up. Which I think means that the core, like Tantalus, is surrounded by a near endless sea of compressed hydrogen, but in 10 billion years it never gets to drink. Which kind of kiboshes the red dwarf idea, unless maybe if it's moving really fast... Wnt (talk) 22:33, 14 March 2011 (UTC)

StuRat got it wrong. Stars actually get hotter when they get denser and get cooler when they expand due to gravitational potential energy released during the compression (or taken away during the expansion). Also, it is true that a sun sized star becomes an iland of helium surrounded by a lake of hydrogen and that the hydrogen of the added star wouldn't reach the central part, but it would increase pressure and temperature at the boundary between the core and the envelope allowing more hydrogen to burn. The island would expand at the expense of the surrounding lake, so to speak. I like the Tantalus analogy. Dauto (talk) 00:30, 15 March 2011 (UTC)

They get hotter when they get compress, yes, but then this increased heat makes them expand, reducing density. Thus you can get short term cycles of expansion and contraction as these two forces battle each other. StuRat (talk) 01:47, 15 March 2011 (UTC)

Cycles can happen in some situations but it is much more common to reach an equilibrium where higher densities correspond to higher temperatures. Stars are somewhat counter intuitive thermodynamic systems because they have negative heat capacity. Dauto (talk) 01:51, 15 March 2011 (UTC)

To expand on my earlier comment, the core gets denser and hotter as its helium content increases. The correspondingly increased energy output causes the expansion of the star's outer layers, increasing the star's overall diameter but also decreasing its surface temperature. Even while still on the main sequence, stars like our sun get slightly larger, slightly more luminous, and slightly redder as they age. TenOfAllTrades(talk) 12:25, 15 March 2011 (UTC)

It should also be said that lack of hydrogen in the star in general is not the issue with the "running out of fuel" because the driving fusion is really only happening in the core. When the core hydrogen runs out, the star begins to break out of the Main Sequence and swell, but there's still plenty of hydrogen outside the core - it just doesn't get in there - the core finds a more profitable fusion into higher elements, all the way up to iron, but the problem is that in doing this the energy release is much much lower, so the star cools.

As for the sci-fi, it's an interesting question, but as explained you can't just pump in hydrogen. Colliding it with a red dwarf will destroy the Solar System, first by gravity and then by big explodey thing, but it may actually get things mixed around the extend the fusion process in the star quite well. However, stars are very beautiful, very uniformly-behaved things, and messing with their structure to that extent will have largely-unpredicted consequences (i.e., fiction fodder?). My suggestion: if you have all that energy available, use it to push Earth's orbit back away from the Sun as it expands.

Oh wait, one more solution - you might be able to extend the star's lifespan stably if you can get it to accrete material off of a more-massive structure that you place in orbit. The problem is still that the new structure's gravity and heat (it's a star) will also destroy the Solar System. Keep us updated if you get any ideas. SamuelRiv (talk) 08:47, 15 March 2011 (UTC)

These people live inside the star, so the solar system isn't an issue. ;) Wnt (talk) 15:14, 16 March 2011 (UTC)

My BS detector ...

[During the Gulf War of 1991] ... Lieutenant Commander Michael Riley was monitoring the radar screens onboard the HMS Gloucester ... he noticed a radar blip off the Kuwaiti coast. ... He couldn't explain why, but the blinking green dot on the screen filled him with fear; ... [It was heading for USS Missouri ] ...

... The radar blip was located in airspace that was frequently traveled by American A-6 fighter jets, ... It looked exactly like an A-6 on the radar screen. ... the A-6 pilots had gotten into the bad habit of turning off their electronic identification on their return flights. ... the pilots opted for the cloak of silence over Iraqi-controlled airspace. ... [The only way to tell], they could determine the altitude of the blip. ... the type of radar that Riley was using didn't provide him with any altitude information. If he wanted to know the height of a specific object, he had to use a specialized radar system known as the 909 ... Unfortunately, the 909 radar operator had entered an incorrect tracking number shortly after the blip appeared, ...

... Riley issued the order to fire; two Sea Dart surface-to-air missiles were launched into the sky. ...

[The target was shot down.] ... the captain of the HMS Gloucester entered the radar room. "Whose bird is it?" he asked Riley, wanting to know who was responsible for destroying the still unidentified target. ... The results of the investigation were in: the radar blip was a Silkworm missile, ... Riley had single-handedly saved a battleship.

... [The British naval officers could not distinguish between the Silkworm and a friendly A-6. based on the records, until] ... the summer of 1993, when Gary Klein started to investigate the Silkworm affair. ...

... Because Riley's naval radar could pick up signals only over water -- after a signal went "wet feet" -- he was accustomed to seeing the fighter jets right as they flew off the Kuwaiti coast. The planes typically became visible after a single radar sweep. ... Unlike the A-6, the Silkworm didn't appear off the coast right away. ... it wasn't visible until the third radar sweep, which was eight seconds after an A-6 would have appeared. Riley was unconsciously evaluating the altitude of the blip, even if he didn't know he was doing it.

... There was something strange about this radar blip. It didn't feel like an A-6. Although Riley couldn't explain why he felt so scared, he knew that something scary was happening. This blip needed to be shot down.

-- How We Decide (2009) by Jonah Lehrer, pages 28 to 32

This story turns on my BS detector. I find following points very suspicious:

• How could a radar operator fire two Sea Dart missiles and the captain did not know it?
• Could he be in a room other than the bridge?
• The Sea Dart's homing radar is exactly the 909 mentioned in the story. How could he know nothing about the altitude?
• If I were an A-6 pilot and I turned off my IFF for whatever reason, why don't I turn it on if I am being locked by a British targeting radar?
• Now, if a British radar operator used the 909 radar to lock on an unknown target, would the target turned on its IFF if he's a U.S. A-6?

The author only cited two of Gary Klein's books in his bibliography, The Power of Intuition. New York: Doubleday, 2004. and Sources of Power. Cambridge: MIT Press, 1999. I have neither of them. I checked Amazon.com for the index of the first book. It probably does not talk about Riley's instinct.

The author also cited Finlan, Alastair. The Royal Navy in the Falklands Conflict and the Gulf War. London: Routledge, 2004. This book mentioned Riley's story. However, it quoted The London Gazette that reads: "the ship's operation room team swiftly assessed the contact as a Silkworm missile". And it also said the missile's target was another ship beyond USS Missouri. (page 147) And the HMS Gloucester's phalanx (close-in defense system) sprayed several rounds on the USS Missouri even though no one was injured. (Now I added links!) -- Toytoy (talk) 14:30, 14 March 2011 (UTC)

The book is yet another example of the avalanche of pulp-non-fiction comming from America - very verbose quasi-textbooks that are based on dubious reasoning. They often tell things as a folksy story focused on personality. Bin them. 92.15.11.100 (talk) 12:53, 14 March 2011 (UTC)

Without dredging up a full technical explanation, I'll offer something a little more substantial than 92.x's response.

• "How could a radar operator fire missiles without the captain knowing?" First, the officer in question isn't the radar operator; a lieutenant commander is much too high a rank for that position (the operator likely isn't a commissioned officer). Rather, he's probably the second- or third-ranking officer on the ship. It's entirely reasonable that he could be the officer presently in charge. The captain can't be on duty all the time, and his subordinates will regularly give orders in his name (though they'd better not be orders that the captain needs to countermand, else those subordinates won't have a long career). Destroying an inbound missile is the sort of thing that requires a response too quickly to summon the captain if he's not presently on duty.
• "Could he be in a room other than the bridge?" The combat information center (CIC) is another logical possibility, depending on how the Gloucester is laid out. But I think this is tied to the above, and so the particular physical locations aren't really important.
• "The Sea Dart's homing radar is the 909..." You appear to be conflating the radar on the missile (used after launch) with one of the radars on the warship (used before launch).
• "If I were an A6 pilot, wouldn't I turn on IFF?" You're an A6 pilot who's running under EMCON to avoid detection in enemy airspace. Your IFF is off, and all mission long you've been picking up enemy radar signals. Now you're headed home, and you're apparently lazy about turning your IFF back on -- what's one more indication of a radar signal? Your aircraft doesn't report "US radar" vs "British radar" vs "Soviet radar", it just reports "radar". Additionally, you're flying in a corridor that has undoubtedly been designated as "this is where A6s fly back; don't shoot the A6s".
• "If a British operator locked onto an unknown target..." See above. Additionally, IFFs are generally left in an "on" or "off" setting. Pilots are usually not in the habit of fiddling with the settings on accessory electronics while flying in a combat zone. There are certainly going to be rules of engagement to reduce friendly fire beyond whether or not an IFF switch is in place (note also: what if the IFF has sustained battle damage? It's not a magic fix-friendly-fire box that never fails).

While I can't vouch for the veracity of the thing, it's not overtly a "verbose quasi-textbook based on dubious reasoning". Hope that helps. — Lomn 13:56, 14 March 2011 (UTC)

Sorry, after looking at the pages available on Amazon, it looks that way to me. It certainly is a folksy story based on personality, and is written in a very verbose manner. And, unless the author was sitting or standing there witnessing events in the command room or whatever, or is paraphrasing a witness stement, then the details must be from the author's imagination. If these things had all the uninformative padding cut out, I'd be more inclined to read them, and they'd provide a better service for the world. 92.15.11.100 (talk) 14:08, 14 March 2011 (UTC)92.15.11.100 (talk) 14:02, 14 March 2011 (UTC)

According to "The Royal Navy in the Falklands Conflict ..." (p. 417), the incoming Silkworm missile was spotted by a "junior seaman". This book says HMS Gloucester's Phalanx CIWS gave USS Missouri a couple of rounds. On another web page (http://www.gulflink.osd.mil/du_ii/du_ii_tabh.htm, see section I. Ship-to-Ship Incident), it was USS Jarrett (FFG-33)'s Phalanx that was having a good time shooting at a chaff from USS Missouri. Wikipedia's article also said so. Anyway, all the ships in that area were engaging that missile. And they knew it. This book is crap. -- Toytoy (talk) 14:47, 14 March 2011 (UTC)

Again, with reasonable speculation:

• "Junior seaman" vs "lieutenant commander": The seaman is actually operating the radar. He says "Commander, there's an unidentified contact." Pretty simple discrepancy.
• "Just Gloucester engaging" versus "all ships engaging": The Sea Dart has an engagement range of miles, the CIWS an engagement range of (admittedly lots) of meters. There's plenty of time for Gloucester to engage the target, alert the other ships, and those ships activate their close defenses before the missile is destroyed -- but the rough overview I see never indicates that Jarrett's CIWS was in position to engage the missile before Gloucester destroyed it. "All the ships were engaging that missile" is a somewhat different statement from "Gloucester was engaging that missile, and the other ships were alerted to its presence".
• "Gloucester's CIWS hitting Missouri": based on other stuff, I think this is a typo for Jarrett's. We note at the Sea Dart article that Gloucester's engagement was tail-end, that is, after the missile passed Gloucester en route to Missouri. I can't think Gloucester's CIWS would have been in range. — Lomn 19:15, 14 March 2011 (UTC)

The USS Missouri article seems to say that the Silkworm and Jarrett incidents occurred on different days. But it may just be poorly written. 75.41.110.200 (talk) 23:30, 14 March 2011 (UTC)

Here are the three pages from "Royal Navy in the Falklands Conflict and the Gulf War: Culture and Strategy" (2004):

• http://piczasso.com/i/0bipo.jpg (p. 146)
• http://piczasso.com/i/avcpp.jpg (p. 147)
• http://piczasso.com/i/xyicp.jpg (p. 148)

FYI -- Toytoy (talk) 01:48, 15 March 2011 (UTC)

I used to work with the Chief Gunner that launched those weapons, and the description above doesn't really reflect the decision process. But to respond to the specific points.

• The question from the CO applied to whose bird took down the Silkworm, GLOU wasn't the only potential shooter. The launch would have been noted by the CO, but he wouldn't know whether they were the only ones in the air.
• The CO had been in his cabin, two decks up from the Operations Room. The Lieutenant Commander would have been the Anti Air Warfare Officer on watch. ships of that class carry two, and the on watch AAWO is responsible for fighting the air battle. It's a while since I discussed it by I also think he was Anti-Air Warfare Co-ordinator.
• The T909 is a pointing radar and can be used to determine altitude, but it needs to be allocated to the correct track. It does strike me as odd that it could be allocated to the wrong contact yet the birds engaged the correct one. The Sea Dart rides a reflection from the target back. It's not out of the question that the narrative conflates the decision process with the launch process that assures the correct target prior to launch.
• Can't comment on IFF as it would have depended on the protocols in force at the time. Nowadays IFF is required at all times, but there were changes in the 90s after a number of fratricide incidents during Granby.

ALR (talk) 10:38, 15 March 2011 (UTC)

Thank you for you input. My educated guess is that the British 909 radar caught the right target immediately. Possibly Riley's radar operator first noticed the suspicious blip and his suspicion was confirmed by 909's correct reading on the correct target. Based on radar operator's correct decision, Riley (very likely the AAWO on duty) gave the order to shoot down that bird. However, he was not sure. He was afraid that he killed a U.S. pilot. In the end, he was proven right.

The author distorted many vital parts of the story to make his point. There is no way the 909 radar would point at the wrong target and then the Sea Dart could hit the Silkworm. And there were two Silkworms instead of one. The U.S. boats also knew it and opened fire. I will never buy a book by this author.

Now, why didn't the Iraqis set their Silkworms to fly at the A-6s' altitude? Since these A-6s tend to turn off their IFFs all the way, these Silkworms could easily fake it into the fleet if they flew just a little higher. Why didn't they do this?

I think if Riley had the power to fire, he was not supposed to read the radar by himself. The radar operator was not supposed to be the decision maker. It was the nameless radar operator who noticed the strange-looking blip. Maybe he asked Riley to see it. But it's very unlikely that Riley was the radar guy. The observer and the decision maker shall not be the same person. Either Riley was the radar guy, or Riley was the AA guy. I think it is against any navy's policy to let the observer make the decision. -- Toytoy (talk) 18:08, 15 March 2011 (UTC)

The T909 doesn't "catch", it's a pointing radar rather than surveillance so needs to be allocated to a specific track number in the combat system. Also the air picture involves three individuals, although there are more than that. There are three Air Picture Compilers, an Air Picture Suprvisor and the AAWO. There is then the missile team.

In terms of process the AP team support the AAWO to identify the target, that's then prosecuted by the weapons team. The T909 can be used in picture compilation, but it's intended to be the weapon direction radar. Given that the processes are well documented it's entirely reasonable that one of the two T909s was used to identify altitude, and the other one was used to direct the missiles.

ALR (talk) 22:18, 15 March 2011 (UTC)

nuclear plant questions

Two questions from the incident at Fukushima. That BWR has a torus shaped pool, any reason it is in that shape? Why is zirconium used as cladding when it will produce hydrogen in accidents? F (talk) 11:15, 14 March 2011 (UTC)

Zircaloy's major advantage over other cladding options is that it has a very low neutron absorption cross section. TenOfAllTrades(talk) 13:21, 14 March 2011 (UTC)

A torus is a reasonably pressure-resistant shape that fits nicely around the bottom end of a sphere (the reactor containment vessel). --Carnildo (talk) 02:16, 16 March 2011 (UTC)

Sound of the Japanese earthquake

I'm not happy with this http://soundcloud.com/micahfrank/earthquakes-off-the-east-coast as it says nothing about how speeded up it is, or how it has been treated or created. It also appears to be a compilation of different things.

While I appreciate that the "sound" could be the seismology record rather than actual noise, is anything better available? Thanks 92.15.11.100 (talk) 12:48, 14 March 2011 (UTC)

They do say that it is based USGS XML feed, I figure they have converted acctual seismic readings to sound. Not sure, if ground vibration has any particular sound in reality ~~Xil (talk) 13:59, 14 March 2011 (UTC)

Seismic wave says they travel at a maximum of about 2 km/s. Human hearing's low end is about 20 waves per second. So it seems unlikely one could hear an earthquake itself. Of course there could be all kinds of other sounds one might hear. Pfly (talk) 07:41, 15 March 2011 (UTC)

Some earthquakes make a lot of noise, such as the 1929 Murchison earthquake, which was heard more than 250 km away. Mikenorton (talk) 13:16, 15 March 2011 (UTC)

Largest earthquake in human history

Within human history - say, looking at the period since the Toba eruption - is there any evidence of earthquakes having occurred which are larger than the 1960 Valdivia earthquake, which is the largest one listed at the Richter magnitude scale article? I am thinking of cases where there might be geological evidence of major sudden earth movements, which are interpreted as having been of greater magnitude than the ones recorded over recent centuries. Ghmyrtle (talk) 12:49, 14 March 2011 (UTC)

Given that the article dosen`t list any such theory, while listing other pre-historical catastrophes, I would doubt it. ~~Xil (talk) 13:25, 14 March 2011 (UTC)

Any what such theory? Matt Deres (talk) 13:39, 15 March 2011 (UTC)

Given the question below, I wasn't treating Xil's response as authoritative.  ;-) Ghmyrtle (talk) 14:05, 15 March 2011 (UTC)

That`s somewhat unfair - there is no connection between earthquakes and electricity ;) My point, though, is based on logic, not knowledge - if there was a reason to suspect such an earthquake, authors of that article would know, if not every geek who watches discovery - apparently it would cause global devistation. Given that it states that there is no known magnitude 10 quake, you would need 9.6-9.9 magnitude, which seems too small diffrence for estimiated magnitude. Yucatan meteorite strike seems to be closest thing to what you are looking for ~~Xil (talk) 13:29, 16 March 2011 (UTC)

I think the problem is that such quakes don't leave good geological evidence. The reason is that the fault typically continues to be active, and thousands of years of subsequent quakes right on top of the original obscure any record. Just from a statistical perspective, the chances of there having been a larger quake than one in 1960, since Toba, is well over 99%. StuRat (talk) 06:46, 15 March 2011 (UTC)

However, you can look at the earthquake record along subduction zones, which is where you get the largest continuous fault surfaces on earth, and try to estimate what is the largest area that could conceivably rupture all at once, the magnitude of an earthquake is mostly a function of the slipped area. Along all subduction zones there is evidence of asperities (areas of excessive fault 'roughness') that earthquake ruptures never cross, so it should be possible to predict the largest likely magnitude. Mikenorton (talk) 14:37, 15 March 2011 (UTC)

What would happen, if wet hair would get into contact with electricity?

I just washed my hair, and pluged in blowdryer, being carefull not to get my hair tangled around it the plug. Now what would happen, if it did - is it a freak death scenario, a light shock or maybe nothing to worry about? ~~Xil (talk) 13:26, 14 March 2011 (UTC)

To be electrocuted, you would need to have a complete electrical path from your hairdryer, through you, to ground/earth. If your wet hair got all the way to the heating elements inside the hairdryer, and tied in a knot around them, somehow, and if your wet, naked leg was held firm against a pipe under the sink, then you might get a shock, but I doubt if wet hair would conduct well enough to kill you. StuRat (talk) 13:37, 14 March 2011 (UTC)

Sorry, I should have paid more attention to what I wrote, I meant, if they got tangled around the plug and pushed into the outlet ~~Xil (talk) 13:49, 14 March 2011 (UTC)

The results would be the same. Hair isn't an electrical conductor, and the small amount of water on the surface would likely only conduct electricity well enough to give you a bit of a shock, before evaporating. StuRat (talk) 14:03, 14 March 2011 (UTC)

Wouldn't the addition of a thin layer of chemicals present in conditioner, shampoo, etc. to hair significantly increase its conductivity? Like adding a bit of salt to water? It probably wouldn't make much of a difference, it still needs moisture to conduct. Plasmic Physics (talk) 23:34, 14 March 2011 (UTC)

Well, absolutely pure water is an insulator, but only a small amount of impurities make it into a good conductor. I had already assumed this to be the case, and that the water was a good conductor. However, the small quantity on wet hair still seems insufficient to cause a fatality. StuRat (talk) 00:04, 15 March 2011 (UTC)

Is there any way it could be fatal? I mean here we assume smalla mount of hair gets into contact with electricity. Imagine an unrealistic scenario - let`s say very long and very wet hair get blown by wind onto power line? ~~Xil (talk) 02:07, 15 March 2011 (UTC)

I have a hard time seeing how. Perhaps, if you're writing a story that features electrocution death due to long hair, a better set-up would be if the person gets their hair caught in a dangerous area, say in a chain-link fence with a downed, but non-energized, power line draped over it, and are thus unable to escape before for the electrical system switches to a back-up transformer and re-energizes the downed line, killing them. Be sure to have both of their hands in contact with the chained-link fence, and them standing in a deep puddle in the rain, to explain how they would make good contact with the ground. StuRat (talk) 06:39, 15 March 2011 (UTC)

Thirsty nuclear reactor

At the Fukushima I Nuclear Power Plant, the source of their problems appears to be an inability to keep the core filled with water, due to it boiling off quicker than they can refill it, because the pumps won't work, due to lack of electricity. Is there any reason why such a water-front nuclear plant can't have the core built below sea-level, so that gravity can then be used to flood the reactor with sea-water, in an emergency ? StuRat (talk) 14:01, 14 March 2011 (UTC)

I already suggested undersea nuclear plants above. I expect the reason is that it would cost more and be more difficult to run and maintain. 92.15.11.100 (talk) 14:13, 14 March 2011 (UTC)

They can flood the reactor with sea water (and boric acid) and are already doing so. The problem appears to be more complicated than that. --Mr.98 (talk) 14:27, 14 March 2011 (UTC)

They are trying, but, according to the article I linked to, they are unable to keep the reactor cores submerged. This is due to lack of electricity from the shut down reactors themselves, the grid, and the backup diesel generators. Unlike electricity, you don't have to worry about a lack of gravity in a quake zone, so having a gravity backup seems like a good idea, to me. StuRat (talk) 20:44, 14 March 2011 (UTC)

StuRat, reactors are already horribly expensive. As 92.15.11.100 mentioned, the (I expect) extra cost of building "below sea-level" would very likely, be prohibitive, plus in all likelyhood not a good idea operationally. Many/most reactors are already near lakes or ocean for a good supply of water for cooling (see page 8), and it would thus likely require constant pumping to keep the facility dry. The cooling needs to be done in a very controlled manner, otherwise you may end up with a cloud of radioactive steam or an explosion as has happened in Japan. - 220.101 talk^\Contribs 16:28, 14 March 2011 (UTC)

I can't imagine sump pumps being a major expense, relative to the cost of a nuclear reactor. The cooling could still be done in a controlled manner, by opening and closing valves that provide gravity-fed water. The explosions they had in Japan are apparently due to the build-up of hydrogen gas, as a result of the cores not being covered with coolant. StuRat (talk) 20:52, 14 March 2011 (UTC)

I wonder if 92.15's enthusiasm for undersea nuclear plants is warranted. Imagine the crisis if a reactor had a minor technical glitch, such as a leaking valve. Recent events been demonstrated that deep sea repairs are prohibitively difficult. Of course, we could put the nuclear reactor somewhere more accessible - such as on land - and just pump in the seawater as needed.

The problem is not a shortage of coolant - that is a gross oversimplification of the serious multiple-system-failure that is currently occuring in Japan. A trivial solution is to flood the reactor with thousands of tons of coolant-water, and vent the resulting steam into the atmosphere. The fission reactor will rapidly cool, but a massive cloud of possibly radioactive steam will form - and it's not easy to estimate whether that is a safe action to take.

Many things are currently broken in the reactor, not just the coolant system. The problems could be better described in the following brief way: how do we maintain nuclear radiation containment while exchanging thermal energy rapidly enough to cool the reactor? More to the point - how do we perform the needed maintenance in a safe way, under the assumption that certain critical safety-systems might be malfunctioning? Nimur (talk) 18:02, 14 March 2011 (UTC)

I believe that the lack of coolant in the reactor cores was a critical point in the chain of failures leading to the current problems. As for underwater repairs, I believe any reactors (like the current ones) that need to be flooded with seawater are then decommissioned. Release of radioactive steam is a concern, but is preferable to a melt-down. StuRat (talk) 20:59, 14 March 2011 (UTC)

This discussion has been closed. Please do not modify it.
The following discussion has been closed. Please do not modify it.
It's so unfortunate, StuRat, that you're over here, playing armchair reactor engineer on Wikipedia, rather than over there in Japan, where you could tell them what to do and how easy it could be. Amazing how much talent is on here for designing and operating reactors! Who knew? --Mr.98 (talk) 21:04, 14 March 2011 (UTC) I do have an engineering degree. It's mechanical, rather than nuclear, but simple mechanical problems, like how to move water, do seem to be at the core of this situation. Also, your reply seems to be saying "leave it all to the experts, they know what they are doing". Unfortunately, blind reliance on "the experts" can lead to all sorts of problems, like the current one. If they are certain that the public isn't paying attention, then they can cut corners and nobody will know, until the inevitable accident, by which time they will likely be retired. Lack of public oversight, like absolute power, corrupts absolutely. You might think that Japan's equivalent to the Nuclear Regulatory Commission would ensure that the plants are safe, but the same issues also apply to them. If the public isn't monitoring them, and forcing them to do their jobs correctly, then they won't, via regulatory capture, bribery, and other means of corruption. StuRat (talk) 06:33, 15 March 2011 (UTC) And now you're an expert in regulation, and on Japan's nuclear industry! Please, StuRat, soapbox away! Who cares if you're just making it up as you go along... My reply does not say "leave it to the experts", it says, "you are way out of your depth"! I contend you understand neither 1. nuclear reactor engineering in general, 2. these reactors in particular, 3. the current accident except in the most superficial of terms, and 4. the Japanese nuclear industry not at all! The experts may occasionally get it wrong, but their track record is infinitely better than people on the internet who make it up as they go along! --Mr.98 (talk) 03:00, 15 March 2011 (UTC) And what qualifies you to judge my level of expertise of nuclear reactors ? Do you have a degree in nuclear engineering ? Or are you doing the exact same over-reaching you accuse me of ? StuRat (talk) 06:33, 15 March 2011 (UTC) Guys, nobody's challenging your qualifications. I'm sure both of you could, with sufficient specialization, be qualified to work on a nuclear reactor, with or without the on-paper "nuclear engineering" degree. The real issue is that none of us have good, complete information about the current situation. As much as our 24-hour internet-news deludes us, the actual event is very far away - and every piece of information we receive is probably funneled through a journalist who mangles up the "unimportant technical details." Unless anyone has a schematic of the particular plant, with an up-to-date assessment of the exact systems that fail, it's moot for any of us to debate the "best solution." For better or worse, we have no option except to "trust the experts" at this point. If any of you guys think you'd be well-qualified to fix the disaster, you should have pursued a full-time career as a nuclear engineer, and further specialized in crisis-response, and then sought a position with the appropriate commercial contractors or government institutions; then you could be involved in the on-the-ground technical response to the current disaster. But since none of us have done that, the best we can do is try to parse through the mangled web of misinformation that the CNNs of the world trickle back to us - understand that there are technical, language, cultural, and time barriers that all severely inhibit our ability to correctly understand the actual problem at the nuclear plant. With due respect to involved parties, I'm hiding this discussion, in the hopes that we can cool off and apply whatever technical qualifications we do have to help provide reliable reference-information for other concerned readers of the Science desk. Nimur (talk) 14:41, 15 March 2011 (UTC) This has been my point the entire time. It is one thing to ask, "why is it so," or "what is going on?" It's another to assert things that are simply not true, and to grandstand about things one knows nothing about. And StuRat, it is obvious from your assertions that you know nothing about the details on which you are holding forth. It is trivial to tell when someone is making stuff up as they go along, far easier than actually coming up with technically informed conclusions. I do not know how to design a reactor — but I know enough to tell that you don't know anything about it either! I have no problem with you discussing the topic — I do have a problem with you claiming all sorts of things that you assume must be true (e.g. that the Japanese public must not have known what the earthquake tolerance levels were for those plants) that in fact you have not bothered to learn anything about at all. --Mr.98 (talk) 21:34, 15 March 2011 (UTC) I'm still waiting with my $10 for you to come up with any actual proof of your claims. Put up or shut up. StuRat (talk) 07:32, 17 March 2011 (UTC)

You could put the relevant part in a dry pit that was below sea level, and in an extreme emergency open a sluice gate to flood them. I'm not sure if just cooling the outside of the pressure vessel would be sufficient. 92.15.31.3 (talk) 18:57, 14 March 2011 (UTC)

How many serious nuclear incidents have occurred at sea? And what fraction of the world's nuclear power plants are seaborne? Hcobb (talk) 18:32, 14 March 2011 (UTC)

There have been 3 fatal nuclear incidents at sea, all on Soviet submarines (in 1961, 1968, and 1985). There are several other naval nuclear incidents noted, all Soviet, without deaths listed. There have been approximately 500 nuclear subs, with give or take 100 in service presently, plus 30-50 nuclear surface ships or so. There are, for comparison, 436 nuclear reactors presently used in power plants worldwide. So naval usage makes up 20%-30% or so of active reactors, and no current operator nations have experienced significant nuclear accidents. — Lomn 19:28, 14 March 2011 (UTC)

Of course, a few nuclear subs have sunk for reasons other than a nuclear reactor malfunction, but that still leaves a nuclear reactor at the bottom of the sea. See the category Lost nuclear submarines. Jc3s5h (talk) 19:38, 14 March 2011 (UTC)

If the reactor core was below water level, that would allow cooling water to initially flow into the core, even if the pumps were inoperative. But if the pumps were inoperative, how would the water flow out of the core? Dolphin (t) 21:26, 14 March 2011 (UTC)

It boils off, and leaves as steam. As stated previously, this can be somewhat radioactive, but it's usually less of a problem than a nuclear melt-down. StuRat (talk) 21:54, 14 March 2011 (UTC)

A simple problem of being unable to pump water due to lack of power just makes no sense to me. It's so easy to solve that I am certain it's not the actual problem they are having. I read they brought portable generators but the plugs wouldn't fit?? That can't be real, you either cut the wire and attach it directly - or go get a plug, it's been 4 days! I suspect the quake broke cooling lines and they are having to jerry rig something. Also, I suspect the rods are not fully inserted, because if it's just residual decay, by now the heat should have faded. Ariel. (talk) 22:09, 14 March 2011 (UTC)

Actually, I think a common problem in disasters is that things which are normally so easy to obtain that we don't think of them suddenly become an issue. Another example is communications. Land lines can go down and cell phone networks can be overloaded, both of which also interfere with the Internet. An additional case would be basic medical care. You can't just drive to the hospital to have broken arm set, since your car is flooded and upside down, the road is washed out and covered with debris, and the hospital is closed due to structural damage and a lack of power. StuRat (talk) 23:04, 14 March 2011 (UTC)

As for the problem with the plugs (I hadn't heard of that before, but trust your source is reliable), just getting new plugs might be difficult if the stores are all closed and the roads are impassible. Also, different sized plugs likely indicate that the power source is not appropriate for that device, due to different voltages or A/C versus D/C. StuRat (talk) 23:13, 14 March 2011 (UTC)

The "plug story" is complete hogwash! The scale of machinery and energy we are dealing with here is a whole different ball game. Forget about silly stories about "the plugs being different".Bigredtoe (talk) 19:38, 30 March 2011 (UTC)

Even so, after 4 days they could have any type of generator or plug they could possibly need. They have helicopters and Tokyo is undamaged. (I don't actually know if the plug story is true - I read it on the news once, and not again. Half the stuff that comes out at the beginning of an emergency turns out not to be true.) Now I read they have a stuck valve - that strikes me as more believable than not having power to run pumps. I'm still surprised at the heat though, see Decay_heat#Power_reactors_in_shutdown. It seems to me after 4 days it should basically be over. Ariel. (talk) 00:19, 15 March 2011 (UTC)

It has not been 4 days of controlled shutdown, with the fuel consistently cooled. News reports indicate the zirconium cladding has split and the fuel has melted, at least partially, while the cooling water had dropped, exposing at least several feet of the fuel rods. Japanese government officials have admitted to at least a partial meltdown, amongst backtracking, parsing and prevarication, while wishing the problem would just go away, or maybe they would wake up and it was all a bad dream. Edison (talk) 02:11, 15 March 2011 (UTC)

Human actions make no difference to decay rates. After 4 days residual decay should be pretty low, cooling or no cooling. It's pretty obvious we don't know the whole story. Ariel. (talk) 03:30, 15 March 2011 (UTC)

A 500 MW_electrical Mark I reactor has an operating thermal load of about 1500 MW due to inefficiencies. Immediately after shutdown that falls to about 100 MW_thermal, and after 5 days, it would be about 5 MW_thermal. That's a large drop-off, but 5 MW is still a significant amount of heat to dissipate, roughly equivalent to boiling 7000 kg of seawater per hour. Of course, if you have a decent pump, you can provide that much water through a large firehose, so it isn't a ridiculous amount of water. But the numbers are large enough that you don't have a ton of margin of error for things breaking and blowing up, which seems to be happening a lot at Fukushima. Dragons flight (talk) 10:58, 16 March 2011 (UTC)

Science Fiction Detachable Fingertips

Does anyone remember this story? I don't know much about it, my friend was talking of it last night, she mentioned she wished she owned it still, but she doesn't remember where she read it. There's a guy with detachable fingertips. He can point them at people, shoot them off, there's a thin coiled up wire that keeps them connected. I guess he can shoot his fingers towards people, wrap around their necks, and vuala, murder them. Cheers, --i am the kwisatz haderach (talk) 15:03, 14 March 2011 (UTC)

I think you must mean the short story Johnny Mnemonic. Specifically, it was a removable thumb tip. Gibson described the wire as a 'monofilament', and we even have an article on that: Monomolecular_wire, see the 'uses in fiction' section for other works you may be thinking of. SemanticMantis (talk) 17:06, 14 March 2011 (UTC)

p.s. I think you mean "voilà". As a word often heard but seldom read, it's easy to spell it wrong ;) SemanticMantis (talk) 17:09, 14 March 2011 (UTC)

p.p.s. I was going for the AMERICAN TRUCK DRIVER FRENCH Spelling Edition. Kushti Bok!, Good Luck in Romani --i am the kwisatz haderach (talk) 21:04, 14 March 2011 (UTC)

p.p.p.s. In Switzerland the Romani would never spell it that bad, and they're even more hick than American truck drivers! SamuelRiv (talk) 08:31, 15 March 2011 (UTC)

We don't have an article about Sixfinger. I'm shocked, just shocked. See here it was before my time but I thought there was a TV show about a guy who used one. 75.57.242.120 (talk) 10:17, 16 March 2011 (UTC)

What is the difference between convection and conduction

After reading the respective articles, I'm still not really sure what the difference is. In laymans terms, what's the difference? ScienceApe (talk) 16:58, 14 March 2011 (UTC)

Conduction is heat moving between two "objects" (could be masses of air or whatever). Convection is an object moving and taking its heat with it (where it then might conduct it into some object that had been too far away). --Tardis (talk) 17:10, 14 March 2011 (UTC)

Well said Tardis, yours is the ONLY "answer" on this page that is correct! ScienceApe doesn't quite grasp it (he needs a little more illustration) but the poor sod will be totally confused and misled after reading the rest of this page.

Csmiller and StuRat both fail to understand the difference between two distinctly different uses of the word convection and therefore have confused you in the process of sidetracking themselves.

The other contributors appear to be only semi literate at best and therefore unable to understand a simple question properly, but just able to quote textbooks or lectures they don't really understand.

Take heart SciencApe it's not really that hard. Firstly just remember that the word convection is used in a couple of different ways and does not mean the same thing in every context, the word conduction more straight forward.

The fact that you have asked the question the way you have indicates you are thinking of convection in its more correct meaning, what it means when used in the same context as conduction. That is the transfer of heat.

Tardis referred to "objects", we could talk in terms of atoms and/or molecules but lets not. If you pick up a cold fireplace poker and stick the tip in the fire and hold on to the handle at the other end, the metal at the tip will absorb heat from the fire. After a while the other end of the poker (that you are holding) gets hot! The heat has traveled 2 feet (600mm is you must)by conduction. The "object" did not move but the heat did. The heat keeps moving - into your hand (ouch) because your hand is in contact with the poker. Once again conduction.

Your hang up the poker (and blow on your hand). A log in the fire place spits a glowing hot ember straight at you and you catch it in your other (cold) hand -more ouch. The heat from the ember (the object) transfers into your hand by conduction once again. HOWEVER convection occurred when the ember moved 2 feet out of the fireplace and onto your hand BRINGING THE HEAT WITH IT!!!!!

It is that simple. Yes it is that simple at its root. Don't get distracted and confused like Csmiller and StuRat by thinking of convection in terms of fluid dynamics ("hot air rises" (it doesn't aways!) etc etc) that is a whole different thing (and in as much as there is a connection they have it arse about.

So talking in molecules; if there is a continuous line of molecules (or atoms) between point A and point B and heat moves through the line (gets passed along) that's conduction. Any time a molecule (or atom) gains some heat in one place and then moves to another location carrying the heat with it That is convection. It does not matter whether the direction is up, down or side ways, it does not matter whether the object is a gas, liquid or solid. Bigredtoe (talk) 21:07, 30 March 2011 (UTC)

(edit conflict) Hot molecules vibrate faster than a colder ones. In conduction, the hot molecules bumps into their neighbours, transferring speed (heat) into them. This occurs in solids, liquids (and to some extent) in gases. In convection, hot parts are less dense than cooler parts, so in gases and liquids (but not solid) they rise (if there is gravity). CS Miller (talk) 17:13, 14 March 2011 (UTC)

Can I have an example of the two? ScienceApe (talk) 20:40, 14 March 2011 (UTC)

Sure:

When you heat a pot of water on the stove, conduction moves the heat along the surface of the pot itself, and there is also some conduction of heat to the water and within the water. Within the water, you also have convection, where the hottest water at the bottom rises to the top, and cooler water drops to the bottom and then heats up, repeating the cycle.

You always have some conduction, except for when there's a vacuum between the objects. Convection, on the other hand, generally requires a fluid (liquid or gas) and enough of a temperature difference to drive it more than the currents which would otherwise prevail. For an example of where convection is almost the only method of transferring heat, look at how heat is redistributed in the atmosphere. There the distances and low density of air mean that conduction is very slow, but convection can happen quicker, with winds being the result of convection currents in air. You may have noticed that rapid temperature changes are almost always accompanied by winds. A third type of heat transfer, radiation, is also present, but, at the temperature differences between adjacent air masses, it has a very minor contribution within our atmosphere. (It is, however, pretty much the only way the air is heated from the Sun, due to the vacuum of space preventing both conduction and convection. StuRat (talk) 21:11, 14 March 2011 (UTC)

Conduction: the transfer of heat, due to the thermal equilibrium principle.

Convection: the transport of heat, due to a pressure differancial in a dynamic medium. Plasmic Physics (talk) 23:28, 14 March 2011 (UTC)

Those aren't laymen's terms. StuRat (talk) 23:55, 14 March 2011 (UTC)

Wait, I thought *advection* was the movement of the particles in space, with convection being a combination of both conduction and advection? 169.232.190.22 (talk) 09:34, 15 March 2011 (UTC)

Any time a gas or fluid is convecting, it's fair to say that heat is also being transferred through conduction and radiation. "Advection" is really ultimately the same concept as "convection" - except that it can also be used to describe transfer of things other than heat. I'd use the following rough definitions:

• Advection - bulk movement of fluid particles to transport something (heat, salinity, dissolved chemicals...)
• Convection - bulk movement of fluid particles to transport heat
• Conduction - transfer of heat by direct contact
• Radiation - transfer of heat via blackbody radiation

Now, if we zoom the scale length way up or way down, we kind of break this "clear-cut" set of definitions. At the most microscopic level, there is only conduction. (Or, only radiation, depending on how you want to look at it). Energy is exchanged via scattering and collision between microscopic fundamental particles. If we zoom all the way out to astronomical scales, we again find that radiation is the most significant form of heat transfer. In day-to-day physics scenarios, like a room with a hot-air radiator, we have all the types of heat transfer: the radiator conducts heat from the iron bars to the air by direct contact. The hot air right next to the radiator starts flowing around the room (convecting). And, the radiator also emits infrared radiation, warming any object within its "line-of-sight" via electromagnetic heat transfer. Because the line of sight includes the room air (which is flowing convectively), some radiative heating is spent interacting with the convection pattern; and every individual air molecule that is part of a convective flow is also both re-radiating heat and also conducting heat to anything it's in contact with (walls, other air molecules), and so on - it's a giant muddled mess of "details" and coupled systems - which is one reason why fluid dynamics is so difficult to solve with formal mathematical treatment. Nimur (talk) 14:53, 15 March 2011 (UTC)

I wouldn't expect much direct heating of the air by radiation, since a few feet (or meters) of air absorbs a very small percentage of infrared light. Most will heat room surfaces, instead. StuRat (talk) 20:16, 15 March 2011 (UTC)

Silicon boiling point

Most places I've read give this as 2355 degrees C, but our article (Silicon) says 3265 degrees. Why the difference? Or is it a mistake? Grandiose (me, talk, contribs) 17:20, 14 March 2011 (UTC)

Made in this revision to Template:Infobox silicon (in mid-2008). Grandiose (me, talk, contribs) 17:32, 14 March 2011 (UTC)

Such infobox parameters are very hard to enforce against intentional vandalism and honest editing-errors. I always defer to a reputable source, such as the CRC Handbook of Chemistry and Physics, if I need a chemical parameter. Unfortunately I don't have a CRC handbook handy to check this number, but your lab or library almost certainly has one. Nimur (talk) 17:53, 14 March 2011 (UTC)

SI Chemical Data states 2680°C but that is fairly old. Wolframalpha gives 2900°[7]. Other random sources from google scholar give 2878°C[8], 3514K 3504K (and 3267° in a patent). Graeme Bartlett (talk) 21:02, 14 March 2011 (UTC)

Webelements has 3173 K (matching wolframalpha's quote). The German wikipedia article de:Silicium strangely cites webelements but uses 2628 K instead. -84user (talk) 23:57, 14 March 2011 (UTC)

when diesel power failed why not restart one of the reactors & it's generator?

I wonder whether they considered restarting one of the main generators after the diesels failed and while they still had enough battery power. Haven't seen this question posed, considered or commented on anywhere. Would be sad if it was a case of "just let your tires down mr truck driver"! Bigredtoe (talk) 20:04, 14 March 2011 (UTC)

Starting up a damaged nuclear reactor doesn't sound wise to me... --Tango (talk) 20:41, 14 March 2011 (UTC)

There is no evidence to suggest that the reactors themselves were damaged at all when the generators failed. The damage to the reactors only occurred some time AFTER the generators failed because without power they could not manage the reactors properly. You have missed the point of the question!Bigredtoe (talk) 15:36, 30 March 2011 (UTC)

Starting up a reactor, even under normal conditions, is not as easy as just hitting a switch and having power come out. It takes time to work them up to peak levels, make sure everything is working correctly, etc. --Mr.98 (talk) 21:00, 14 March 2011 (UTC)

Agreed. There is the question, though, of whether the decision to shut down all nuclear reactors was wise, considering the lack of reliable backup sources of electricity. Perhaps the least damaged reactor (2 ?) should have continued to be run at low levels, to provide power for the pumps, until a reliable electricity backup could be established. StuRat (talk) 21:03, 14 March 2011 (UTC)

Mr.98 (and StuRat) you are completely wrong! Hot starting a reactor IS in practice pretty much as simple as hitting a switch. Further down this page Mr.98 said to someone "You make an awful lot of assumptions about things you know very little about...!" Mr.98 should take his own advice. For further FACTS about restarting a reactor see further comments later.Bigredtoe (talk) 15:49, 30 March 2011 (UTC)

Generally it takes more power to start up a reactor than the emergency diesels can provide. It needs grid power to startup. Lots of big pumps must be operating, for instance. The emergency diesels are only sized for operation of shutdown for cooling pumps and controls.Edison (talk) 21:13, 15 March 2011 (UTC)

"Generally" you are wrong. Single reactor Nuke subs & ships are fully capable by design to COLD START their reactors using on-board secondary power systems (diesel and/or steam driven generators & pumps). In Fukushima's case by far the largest single pumping load would be the primary "cooling" circuit, (those of you that actually understand NPPs will know why I have used the quotes) however adding together all the load of the secondary and emergency cooling systems would tally to a capacity somewhere near capable of running the primary pumps. Given that Fuk No1 has six diesel gensets each one capable (by design) of fully supporting the entire secondary and emergency systems load; if several or all of the reactors were cold or even cool, you would have more than enough on site power to start a dead cold oven, let alone a hot one, and spin up an alternator. That of course assumes that your aux power supply switching has been designed and built with flexibility in mind. As for the "..diesels are only sized.." PLEASE state your source! or are you just guessing and/or assuming? I know of at least one other NPP, with larger reactors and turbines than Fuk No1, that can do a "black grid" start if needed. In any event your comments indicate you have not properly understood the question. The question specifically addresses the circumstances AFTER THE DIESELS HAD FAILED.Bigredtoe (talk) 16:20, 30 March 2011 (UTC)

SCRAMing the reactor is the default action when you are unsure whether it is going to work correctly. It's the right action. What you want to avoid is anything that will keep you from shutting it down in the future, which is essentially what happened at Chernobyl (it got too hot and they couldn't re-insert the control rods). It is far, far safer to rely on diesel or something else in that period. If the diesel doesn't work, you can always get more diesel. If the reactor won't shut down, you're in real trouble. --Mr.98 (talk) 21:20, 14 March 2011 (UTC)

Mr.98 not following his own advice again.

Your comment shows that you clearly do not understand one of the fundamental characteristics of a SCRAM. For your education the shutdowns at Fukushima were not done because anybody was "unsure whether" it was going to work. If that were the case it would not have been a SCRAM!! The shutdowns at Fukushima were initiated and fully carried out by the control system (computers). The human operators at the plants had no say in it. The control rods were fully inserted in a matter of seconds after the readings from ground acceleration sensors, at the plant connected directly to the control system, exceeded a pre-programmed level.

Your summation of the chernobyl event is also quite misleading and indicates an ignorance of the unique keys to that event. These two events have virtually nothing in common. There was a particular behaviour characteristic of the Chernobyl reactor that was not "in the instruction manual" but was inherent in its design which was key to that event.

As far as your waffle about getting more diesel fuel and the safety of relying on diesels? You appear to be blissfully ignorant of the situation on the ground at Fukushima at the time (didn't bother reading the question properly?), and I suspect you have no idea of the scale of machinery we are talking about here.Bigredtoe (talk) 17:55, 30 March 2011 (UTC)

By most reactors, the control rods system isn't linked to the emergency Diesel generators and cannot be operated without external power. If external power fail they are automatically driven in a safe position to shutdown the reactor.--Franssoua (talk) 14:54, 14 April 2011 (UTC)

(edit conflict)Against that you have to weigh the risks involved of running the reactor without an external power supply for emergencies. This article about a different Japanese BWR says the control rods must be inserted from beneath, and mentions the possibility that an earthquake may have shifted the structure such that a single control rod could not be moved. The article also suggests that the standard response to a moderate earthquake was to shut down the reactors. Actually running the reactor in this compromised circumstance carries the risk that a subsequent aftershock will shift the pile such that many control rods can't be inserted (and/or kill the hydraulics that insert the control rods); if that aftershock also knocks out the circulation system, you have what they have now, but with the reactor generating several times as much heat. Given that no-one can predict aftershocks, and plant operators have a necessarily imperfect view of what equipment in their plant still works after an earthquake, all things being equal a control-rods-fully-in posture seems to be the safest. -- Finlay McWalter ☻ Talk 21:29, 14 March 2011 (UTC)

The scramming I understand, but... if the reactor continued to stay hot, or reheats itself, as it did, why can't the cooling systems continue generating electricity? Wnt (talk) 21:33, 14 March 2011 (UTC)

I must say I was surprised by this, i thought NPPs were much more fail safe since Chernobyl. Vespine (talk) 22:02, 14 March 2011 (UTC)

They are, in that the total failure mode is much less catastrophic than Chernobyl. Even in the event of a total core meltdown, the most radioactive material (the uranium core) will remain trapped in the containment vessel, rather than catching on fire, exploding (rupturing the containment vessel), and sending burning radioactive matter up into the sky and all over the countryside. Buddy431 (talk) 22:46, 14 March 2011 (UTC)

The news reports keep suggesting otherwise. We'll see soon enough. Wnt (talk) 22:51, 14 March 2011 (UTC)

Long experience has convinced me that news reporters have no clue about anything, ever. Certainly not about anything scientific and certainly not about any rumors circulating in the immediate wake of a major disaster. -- BenRG (talk) 00:19, 15 March 2011 (UTC)

Agreed. This is not an analogous situation to Chernobyl at all. It is much more similar to Three Mile Island in its technical respects. But they are having a heck of a time getting it under control. The news reports which incessantly say, "worst since Chernobyl" are technically true, but comparing it with Chernobyl is itself quite misleading — it is not like Chernobyl at all, but it is the worst problem at a nuclear plant that has occurred since Chernobyl. --Mr.98 (talk) 02:56, 15 March 2011 (UTC)

However, the fact that all 3 active reactors are having similar failures implies that there are fundamental design flaws and/or inadequate procedures. If the reactors are only designed to withstand quakes up to X magnitude and tsunamis of up Y meters, then the Japanese public should have been told that, so they could either demand greater protection or choose to live farther from the reactors. StuRat (talk) 22:59, 14 March 2011 (UTC)

What makes you assume that the information was not a matter of public record? I'd be willing to be you $10 that the earthquake rating of those reactors is easy to come by if you read/write Japanese. You can only secure a given reactor (or dam, or chemical plant, or whatever) against certain types of risks. In many modern countries (the US in particular), exactly what those risks are is part of the environmental impact report and is part of its public documentation. You make an awful lot of assumptions about things you know very little about...! --Mr.98 (talk) 02:56, 15 March 2011 (UTC)

Well, it's possible, but then again, they may have claimed they were safer than they really were, as happened with the levies in New Orleans when Hurricane Katrina hit. I'd be interested to see any documentation you can come up with. Note that you are making the assumptions that this information was released, and was correct, so I could make the same charge that you "make an awful lot of assumptions about things you know very little about". If you can come up with proof that there were publicly available records that said that the plants could not withstand this level of quake and tsunami, then you win the bet and I will wire you $10. StuRat (talk) 06:26, 15 March 2011 (UTC)

The current US standard is that a nuclear plant should be designed to survive with no major damage from the worst natural event that is predicted to occur within 1000 years at its location, and with no hazardous release of radiation against a once in 10000 year event. I don't know what standards Japan applies, or what standards might have been in use 40 years ago when the reactors were being built. Of course, given that we don't have thousands of years of history to go on, estimating the 1000-year flood / earthquake / tsunami / tornado / etc. is decidedly something of a guessing game. Dragons flight (talk) 11:09, 16 March 2011 (UTC)

While I can't comment on the relative safety or merits of the General Electric designs used at Fukushima I compared to those at Chernobyl, I will observe that the Japanese reactors are actually slightly older than the ones in the Ukraine. Construction of reactors 1, 2, and 3 at Fukushima began between 1967 and 1970, and they entered service between 1971 and 1976. Construction of the Chernobyl facility began in 1970, and the fourth (catastrophically-failed) reactor at that site entered service in 1983. (From what I gather from our article on void coefficients, however, the boiling-water reactors at Fukushima aren't vulnerable to the same type of runaway failure suffered at Chernobyl.) TenOfAllTrades(talk) 23:07, 14 March 2011 (UTC)

Age was not the problem with Chernobyl. The problem was poorly trained operators mixed with a very dangerous reactor design. I don't know the specifics of the Japanese designs, but the fact that they have full containment buildings automatically makes them much safer than Chernobyl, even ignoring the different nuclear setups. --Mr.98 (talk) 21:40, 15 March 2011 (UTC)

Wnt's question above is the important one. Is it possible to restart just the steam plant of a scramed reactor to generate power from the decay heat, and in the process cooling that very reactor. I suspect that it is possible as long as emergency power is available during the start-up, but that without such power you might not be able to bootstrap the system. Are the condensate & feedwater pumps and sea water cooling pumps to the condenser all driven by steam or by electric power? Even if they are all steam driven, start-up without external power might not be possible depending on conditions such as condenser water level and temperature. -- 119.31.126.67 (talk) 00:58, 15 March 2011 (UTC)

I don't think they can. The steam turbines are designed for lots of steam. The small amount produced here can not run them. However they do have steam powered pumps which were used to directly pump water to cool the plant. Ariel. (talk) 01:14, 15 March 2011 (UTC)

There are multiple reasons why this wouldn't work. Big generating plants aren't designed to run at a low fraction of maximum power. If you don't have nearly full output from a reactor, the generator isn't going to run right. The generating system may already be damaged from the earthquake and tsunami. Even if there were no damage and the generating system were happy to run at a fraction of full power, running a generation system on its own output is mathematically unstable; you can't keep it running easily without an external power source. Finally, clearly power is not the problem. If their only problem was how to power the cooling system's pumps, they would not be in the mess they are in. Something else is wrong: damage to the cooling system, damage to the core, etc. It's unlikely that running the steam plant would be any help at all.--Srleffler (talk) 04:25, 15 March 2011 (UTC)

Srleffler -where do I start? You have let the cat out of the bag that the automotive industry has been defying the laws of mathematics for decades!!!! and the rotten sods have sold us millions of cars that are mathematically unstable! It is just a con man's trick that we have to pay for alternators etc. When our cars electrical system dies it really is that secret chip inside the car getting triggered by a secret message from the car factory to turn off the secret (invisible) power system inside our car!!! (and then they send another secret message to the invisible "real" power system in our car at the same time as we pay for a new alternator?)

As far as big not being able to run at "low fraction of max power" - nonsense.

The real screamer though is "If you don't have nearly full output from a reactor, the generator isn't going to run right." You obviously have no idea of the elegant beauty of a large steam turbine alternator!

And finally, CLEARLY POWER WAS THE PROBLEM. Until they lost their diesels they were IN CONTROL. Contrast No1 to No2!!! Daini did NOT lose their diesels, (they did loose grid power too) and they achieved full cold state without significant damage or leakage.

And finally finally (and for about the tenth time) UNTIL AFTER THE DIESELS FAILED THERE WAS NO CORE DAMAGE. soooo frustrating when people blabber before reading properly.Bigredtoe (talk) 17:15, 30 March 2011 (UTC)

I doubt they would have been able to restart the reactor so soon after a SCRAM from full power. From a reactor physics perspective, even if the plant operators had full confidence in the reactor following the earthquake and had wished to restart it, they would have had the problem of reactor poisons. These are fission products (such as xenon-135) which act as strong neutron absorbers and remove reactivity from the core. Often, reactors have to wait several days in order for sufficent posions to decay before they have a sufficient reactivity margin to restart. HighOrbiter (talk) 09:35, 15 March 2011 (UTC)

Not true! The only time reactor poisons would prevent a restart after a SCRAM (or any shutdown) even very shortly after, is if your reactor was very near the end of its fuel cycle and therefore you had close to zero "reserve" power in your pile. There is one fully documented case I recall where a full sized commercial power station reactor was restarted inside 3 minutes of a SCRAM. Wrists were slapped some time later but the reactor and power station suffered ZERO negative effects or technical complications.

It is SOP for reactors in nuke subs to complete a restart within 7 minutes of a SCRAM. Bigredtoe (talk) 16:34, 30 March 2011 (UTC)

Has one or more transmission lines had power restored to the Fukushima 1 switchyard, so there is offsite power? The tsunami flooding the basements and shorting out the reactor controls and aux power is a separate issue from having grid power available. I would expect there to be high voltage transmission in 2 or 3 directions from the transmission yard,as is typical for any nuclear plant, and it is unlikely every line would have suffered complete disruption beyond what a day or 2 orf repairs could correct. If the transmission was restored, when did that happen? Edison (talk) 21:19, 15 March 2011 (UTC)

As I understand it, the reactors are in an area hit by the tsunami. I would not be surprised to find that the power lines are destroyed for tens of miles in all directions. --Carnildo (talk) 02:25, 16 March 2011 (UTC)

"Tepco sounded a rare optimistic note by saying engineers would soon restore an electrical connection from the national grid - which should allow them to re-start water pumps, provided they have not been damaged by the tsunami or the hydrogen explosions." 16 March 2011 20:16 GMT BBC

Mattress

So, I flipped over my mattress yesterday and started using the other side, because a spring was sticking out and poking me in the back. I noticed that it feels much, much harder on the flipside (the side I've been using for years had a nice, comfy and me-shaped indentation), which I guess is how the thing felt when it was new (though I don't really recall).

Question - what's the current thinking with regards to buying the best mattress? Does the medical profession still advise that one should buy a really hard mattress, for improved spinal health? Personally, I've always purchased the hardest one that I could bear lying on - figuring that it will take longer to go soft and thus last longer. --Kurt Shaped Box (talk) 23:21, 14 March 2011 (UTC)

A mattress which is too hard can also lead to medical problems, as pressure points can lead to bed sores, or wake you up often, causing a lack of sleep. If the flipped mattress is too hard, I suggest putting more fabric between you and it, such as comforters. Another option is to buy a pillow top mattress pad: [9]. Either should work until the mattress softens back up. Note that the spring poking through could also be repaired. However, if the mattress is on it's last legs in other ways, it may not be worth the trouble. StuRat (talk) 23:53, 14 March 2011 (UTC)

Na, it's not too hard. Just feels harder than the side I've been sleeping on. One side seems like new, the other is completely knackered and beat-up. Just wondering in general what the current thinking was, re: mattress firmness. Years ago, 'they' (as 'they' do) used to say that it was best to get the hardest one that you could manage on... --Kurt Shaped Box (talk) 00:44, 15 March 2011 (UTC)

Modern mattresses usually have a defined "up" side. Even when new, the side you are intended to sleep on is softer than the other side. Older mattresses could be used on either side, and in fact the manufacturers recommended flipping them over every few months so they would wear evenly.--Srleffler (talk) 04:38, 15 March 2011 (UTC)

This indicates that medium-firm and firm mattresses allow better spinal alignment, but did not indicate that spinal alignment had any affect on the body (in patients with no back problems). Effect of firmness of mattress on chronic non-specific low-back pain: randomised, double-blind, controlled, multicentre trial (F Kovacs et al., 15 November 2003, The Lancet, 362:9396, p.1599-1604) mentions in the introduction that 95% of orthopaedic surgeons surveyed believes "that mattresses played a part in the management of low-back pain, with 76% recommending a firm mattress. However, evidence supporting this advice is lacking." due to few studies and poor methodology. That study found that replacing an old mattress with a firm, or especially a medium-firm mattress, lead to patients with chronic lower-back pain having less pain and reduced drug usage. There are several other studies which produces similar results. As for very hard mattresses, I did come across a couple of pieces of research which found that sleeping on a wooden board was not as good as using an actual mattress (shocking, I know!) --Kateshortforbob _talk 16:53, 15 March 2011 (UTC)

What you should also test is if the mattress you intent to buy does not depress a lot more when you push a lot harder on it. If you lie on your back on the mattress, it will depress a certain amount around the hip area. Then, if you flip over and lie on your side, it will depress a bit more because the exerted pressure increases, but it should not depress a lot more. Count Iblis (talk) 17:03, 15 March 2011 (UTC)

Do you mean, it should follow Hooke's law? — Sebastian 19:51, 15 March 2011 (UTC)

If your matress follows Hook's law, it will depress perhaps 4 times more when you flip on your side, which would be very bad. Count Iblis (talk) 15:11, 16 March 2011 (UTC)

Since this is the Science desk, I'd recommend experimenting. Select Comfort makes mattresses that allow you to change their firmness. (I usually avoid commercial external links, but I feel differently about them for reasons that would be off topic here.) So you could experiment and see at which firmness you feel best the next day. — Sebastian 19:51, 15 March 2011 (UTC)

March 15

Were Neanderthals more intelligent?

I recently found out that the cranial capacity of a Neanderthal(being 1400) is larger than our cranial capacity of modern humans(being 1350). This led me to think more cranial capacity will provide room for a larger, more intelligent brain to develope. A larger brain developing makes me ponder over whether they wouldv'e advanced quicker than we had. Well I mean if they never became extinct. I'm just not entirely sure. Matthew Goldsmith 02:43, 15 March 2011 (UTC) — Preceding unsigned comment added by Lightylight (talk • contribs) 02:42, 15 March 2011 (UTC)

The real thing you'd want to know is not the brain size, which doesn't tell you much, but the encephalization quotient — which is related to the ratio of brain size to body mass. The latter gives you a better understanding of whether a given species is fairly "intelligent" (broadly defined) than raw brain size alone. (If raw brain size was all that was necessary, whales would be hunting us for oil, rather than the other way around!) --Mr.98 (talk) 02:51, 15 March 2011 (UTC)

If whales had opposable thumbs we'd be in trouble. PЄTЄRS J V ►TALK 14:42, 15 March 2011 (UTC)

Well, the real thing you'd want to know is how intelligent Neanderthals were. We have pretty close to zero specific information about that. Presumably at some point we'll be able to draw conclusions from the Neanderthal DNA sequence, but we're a long way short of that right now. Looie496 (talk) 03:03, 15 March 2011 (UTC)

We are not entirely clueless. For one thing, they are extinct and we are not. It is impossible to know for sure why that is so, but our intelligence may very well have played a role. May be our warfare skill is what did them in... Dauto (talk) 03:21, 15 March 2011 (UTC)

Its also not just encephalization quotient alone, there are also structural difference between brains unrelated to size directly, such as the complexity of the Cerebral cortex which plays a major role in intelligence. --Jayron32 04:30, 15 March 2011 (UTC)

Hooray for pedants! Yes, of course I meant the encephalization quotient as a proxy for intelligence, lacking other information about their anatomy and behavior. And Dauto, the fact that they are extinct does not tell us very much about their intelligence. They may have just had a bad run of things, or not been clever enough in some areas as opposed to others. Perhaps they just happened to be exceptionally tasty to certain large predators. My overall point was, in any case, that raw brain size by itself is no anatomical indicator of intelligence at all — if you want to make sense of raw brain size, you have to compare it to raw body mass, and even then that is a crude (albeit not unhelpful) metric. --Mr.98 (talk) 14:40, 15 March 2011 (UTC)

There are things we can infer from the Archeological record about Neanderthal intelligence, and that's a much safer indicator than trying to guess intelligence using anatomy (generally a poor indicator). The Wikipedia article on Neanderthals mentions a burial with flowers that was found; I can recall a much stronger example of Neanderthal culture from my archeology professor (maybe someone can help me out with a specific name of this find) where a pair of Neanderthals were found buried beside each other, face up, but with the head of one next to the toes of the other. Their spears were on either side. Why would they bury valuable spears if they did not believe in some abstract significance of the event? Religious cermonies and especially beliefs in an afterlife (if that's what this burial shows) require "visualizing ahead" and long-term planning, some of the most rare and important skills of critical thought.

Since they interbred and co-existed with modern humans (see the Neanderthal wiki article), that's the strongest evidence we towards them having negligible differences in intelligence compared to us; if they had vastly different brain structures, the interbreeding process would not have gone well at all, because complex information processors (such as computers) can't just be mashed together to get a functioning result. Since most modern humans are descendents from this interbreeding, we know it went well. Their extinction was thus probably not due to them being dumber or anything, but probably due to something like starvation during the most recent ice age. They were huge and thus required a lot of food; we were small and could jog for long distances to run down prey, giving us more food options. Their leg bones do not show the "teardrop" shape that indicates long-distance running; Homo Sapiens is one of the only animals out there that can actually run cross-country because of our unusual bodies (near-hairlessness, efficicient bipedal gait, awake during the day but having stereoscopic vision, etc).

They are believed to have hunted in groups, which requires communication (and obviously language), co-ordination, and more planning. These account for pretty much all of the features we define as intelligent, so they were probably very similar to us in capacity. One could perhaps be raised to adapt to the modern world if it was alive today.—Preceding unsigned comment added by 169.232.190.22 (talk) 05:36, 15 March 2011 (UTC)

Some other indicators of intelligence are art (such as cave drawings), trade (indicated by the presence of items in their camps not native to the area), sophisticated weapons and tools, a varied diet (determined by fecal analysis and animal bones), cities, and writing. I don't believe we've found any Neanderthal art, am certain we haven't found any writing or cities, do believe their weapons and tools were less sophisticated and their diet was less varied, and I'm unsure about Neanderthal trade. However, most of these would indicate that Neanderthals were less intelligent than modern humans, and humans may also be significantly more intelligent now than they were then, particularly with respect to use of language and symbolic logic. StuRat (talk) 06:20, 15 March 2011 (UTC)

I guess the counter-argument to that would be that intelligence isn't all biological; biologically they may have been equally intelligent (and they probably were, if my logic above holds about brain structures and interbreeding, an argument borrowed from Stephen Pinker) but culturally, perhaps they did not have as many good ideas floating around and accumulating over generations, and so were less intelligent because of social conditions rather than biological. Maybe that would explain the two having the same intelligent behavior on the small-scale (mystic beliefs, tool use, group hunting) but vastly different behaviors on the large scale (ie. trade, cities, advanced tools, art when it's construed as more of a learned meme rather than innate) that would involve more organized, refined societies. I'm certainly no expert on this stuff though, not being in a related field; just hypothesizing/generating discussion since the existing answer had left some things unexplored.[Special:Contributions/169.232.190.22|169.232.190.22]] (talk) 07:01, 15 March 2011 (UTC)

I think a general difference is that modern humans are "generalists", meaning we can adapt to many different environments and niches, while Neanderthals, like most species, were specialists, designed for a single niche. Being a generalist requires far more ability to learn, while instincts can serve a specialist well. StuRat (talk) 07:10, 15 March 2011 (UTC)

Neanderthal's use of tools and creative (not hard-wired) methods of hunting, however, were a form of generalism. They adapted to and solved the real-time environmental problems they faced. If they had been a specialist species, their hunting techniques would been programmed in as sort of an automatic routine, like a wasp building a nest, for greater computational efficiency and quicker reflex speed. Varied, special-purpose tools would suggest forethought; forethought about such things as how to get around a hunted animal's specialized natural defenses. I think all early human species filled the "generalist niche"; their hunting niche was "surprise them with something new", that is, coming up with techniques on the fly in real time that evolved defenses could therefore not keep up with.

Now, perhaps Homo Sapiens were somehow "more generalist" than Neanderthals were; but that again runs into the problem of, how did they interbreed successfully with different brain structures? Unless there is an easy way to interpolate between a more generalized mind and more specialized one (ie. a single chemical's concentration gets varied), it seems like the genes would clash and produce an unusable result.—Preceding unsigned comment added by 169.232.190.22 (talk) 07:33, 15 March 2011 (UTC)

Regarding interbreeding, I was aware that this was one theory, but am not aware that it had been proven. Do you have a source for this ? StuRat (talk) 07:45, 15 March 2011 (UTC)

Yes, what I'm referring to is a recent find and you can read about it near the top of the Neanderthal wikipedia article. To both you and to SamuelRiv below, what I'm referring to is not a particular specimen that was found, but rather a genetic discovery made in 2010 (and featured on Wikipedia's front page for a while) asserting that "1–4% of the genome of people from Eurasia" was contributed by Neanderthals. So basically, that would mean that for everyone who is not African, we are part Neanderthal; the only "pure Homo Sapiens" are those of African descent. Obviously this is a very huge assertion and stands to change a lot of what we know, and people interested in science made a pretty big deal about it when it was announced. (It's also kind of an ironic find considering how it makes white-supremacist groups' rhetoric about being a "pure" race backfire. I also wonder if it explains how so many of the best long-distance runners are from Africa, since Homo Sapiens were evolved for endurance running.) Anyway, since then even another hominid species that apparently was just genetically found to have interbred with us was featured on Wikipedia's front page (edit: Found it on the Human Evolution Page: "the recently discovered Denisova hominin may have contributed 6% of the genome of Melanesians.").

This mixing of the DNA of various species that we can now find in the human genome tells us a whole lot, and allows us to infer that we were at least compatible enough as species to share brain parts and also co-exist (assuming it was an amicable co-existence and not interspecies rape or something). It seems that perhaps the final truly significant iteration of human intelligence may have spanned across a few different species with highly different bodies and hunting styles. 169.232.190.22 (talk) 08:38, 15 March 2011 (UTC)

To StuRat and Unsigned: I believe you are referring to the debate over the Lagar Velho hybrid child. That link is extensive on the scientists' arguments, rebuttals, and counters for at least the first period after publication, but I'm not sure what consensus is, though it looks like they critique got the last word in solid by showing that the skeleton was within expected bounds of human morphology (comparable to northern Finns). So there is no clear hybrid, and question to biologists: do we have confidence that a hybrid would even show extensive morphological difference, that those skeletal traits wouldn't just prefer one side or another in hybridization? SamuelRiv (talk) 08:21, 15 March 2011 (UTC)

I just added a reply up above 169.232.190.22 (talk) 08:50, 15 March 2011 (UTC)

Their crainal capacity was only 3.7% larger from the numbers given. This tiny difference may have been due to all sorts of reasons and is not sufficient to suggest they were more intelligent. 92.15.5.217 (talk) 14:00, 15 March 2011 (UTC)

I've read somewhere some time ago that Neanderthals are believed to have grown into adulthood much faster than modern humans. And this is strongly indicative of "being less intelligent", at least in the following sense: If we could clone Neanderthals back to life and raise Neanderthal children, they would not be able to become professors. The flip side here is hat they they could be "more intelligent" when it comes to solving ad-hoc problems for which no established knowlege is of help.

This is similar to why, on the one hand, Chimps have the overall intelligence of a two year old or so, but there are certain intelligence tests in which they routinely outperform ten year olds. In one such test children and chimps were shown a box and shown a complicated set of actions, supposedly needed to open the box. Thing is that almost all of these actions are completely irrelevant and most adults will immediately see this. So, if you want to open the box, you will just open it in the obvious straightforward way. Children below the age of ten will, however, typically go through the entire routine of performing all the irrelevant actions. Chimps, however, won't and will open the box just like adult humans open it. Count Iblis (talk) 15:12, 15 March 2011 (UTC)

There's a much older reference about Neanderthal milk teeth, but a current one is [10](open access)(also see [11] for commentary). I should say that I have a problem with their plot showing that Neanderthals reach effectively age 16 by age 12, because if you look at the line they draw through the Neanderthal samples crosses the human at age 3. If you assume linear development it should start from birth, and if you assume variable development then there's only one sample which is more than a year or two ahead of the humans, so that straight line is overly bold. So I think they overstate the case a little, though I don't deny there's something of a separation.

Even so, it's hard for me to take this case all that seriously, because I know that by the time I was 15, I'd gone off to college, stopped growing, and had all four wisdom teeth mostly into their right positions. While I don't think I delivered on early estimates of future mental or physical development (some of my precocity was, indeed, just precocity), I'm not a troglodyte either. My guess is that the development time is some simple trait, probably controlled by a relatively small number of genes, which varies under selection or random drift in any species of humans. Wnt (talk) 19:34, 15 March 2011 (UTC)

I see, so things are more complicated :) Another thing that came to my mind was that Neanderthals are known to have hunted animals by attacking them from close range. This requires good eye-hand coordination and there was certainly a lot of selection pressure for that, as many Neanderthal bones show evidence of injuries. So, perhaps the brain areas involved in eye-hand coordination were far better developed than in us. This suggests that Neanderthals would likely have been better Formula 1 drivers or figher pilots than modern humans. Count Iblis (talk) 15:27, 16 March 2011 (UTC)

Someone please tell the military this right away, so we can get some Neanderthals spliced up and ask them directly. ;) Wnt (talk) 21:18, 16 March 2011 (UTC)

On the other hand, hand-to-hand combat might require more strength and less precision, making them less well-suited to the mentioned tasks.149.142.48.73 (talk) 00:06, 17 March 2011 (UTC)

atomic structure

can electrons shift dimensions i have a theory on it please help.. — Preceding unsigned comment added by Genius1109 (talk • contribs) 06:06, 15 March 2011 (UTC)

What does "shift dimensions" mean? Ariel. (talk) 06:09, 15 March 2011 (UTC)

I imagine "shift" means to translate; and dimension has a specific meaning in physics; I usually choose to say that the word "dimension" is synonymous with "generalized coordinate" in physics. So, yes, an electron can "shift dimensions" insofar as it can move along the x,y,z, axis. Such movements are subject to constraints imposed by proper solution of the position operator on a wave function that must be a solution to the Schrödinger equation. I think the OP should learn existing theory and review (or repeat) prior experiments before proposing a new theory. The theoretical solution for the electron position in the atom is the basis of modern atomic theory and has been very carefully validated by experiment for more than a century. Nimur (talk) 15:09, 15 March 2011 (UTC)

Are you perhaps referring to double-slit experiments ? One interpretation of this experiment's results is that the electrons are interfering with those in a parallel universe (under the many worlds hypothesis). Therefore, such electrons must at least pass information about themselves between these universes, which could be called "shifting dimensions" (although physicists don't call alternate universes "dimensions", this is more of a laymen's term). StuRat (talk) 07:23, 15 March 2011 (UTC)

If you look at a simple theory of the hydrogen atom, you may think that the electron orbits in a circle, in two dimensions. However using quantum mechanics you can show that the electron is not just found in a circle, but takes up 3 dimensions. Graeme Bartlett (talk) 11:26, 15 March 2011 (UTC)

And it would be better to say that the electron does not actually "orbit" as we imagine a planet to orbit a star; even if we consider it to do so in three dimensions. Instead, the better models consider the electron to exist across a probability distribution of locations (i.e. as measured over an arbitrarily long time, the shape of space that the electron may be found in with some arbitrarily high probability) without any concern for its mode or pattern of travel within that space, or we can consider the electron to be modeled as a standing wave in three dimensions organized around the nucleus; much as a guitar string represents a standing wave in two dimensions. These two concepts are nicely combined into a mathematical single concept, known as the Wave function, whose general shape and behavior is described mathematically by the Schrödinger equation. The image of a smaller ball (the electron) revolving around a larger ball (the nucleus) in some describable pattern, as we would expect it to look if it were large enough to see, is very limiting and does not actual work well to accurately model actual atomic behavior. --Jayron32 13:22, 15 March 2011 (UTC)

Sorry to nitpick the otherwise excellent response: a guitar string is a model of a standing wave in one dimension (not two). Constructing the standard wave-equation for a taut string requires an assumption of "negigibly small" deviations, such that the displacement and propagation terms are only a function of the position along the string. A 2-D model of a guitar-string would be a non-linear wave equation. A web search turned up this very nice student-report, Guitar String Tension Experiment; page 2 includes the mathematical reduction to 1 dimension (note the absence of an F_x term due its very small magnitude). Nimur (talk) 17:01, 15 March 2011 (UTC)

Space colonization

Not telling to predict anything, just a curious question. Is there any possibility of space colonization in the next 50 years that will have SIGNIFICANT impact on world economy, as opposed to extraterrestrial human presence (such as the ISS, which is year round human presence in the space for research purpose rather than economic activities)? Is it a possibility from the current state of technological progress in space exploration? Thanks! --Reference Desker (talk) 08:42, 15 March 2011 (UTC)

We could have a lot grander things than that happening in the next 50 years if the Technological Singularity (see the huge Wikipedia article) happens as early as Ray Kurzwiel predicts (using a bunch of trends like Moore's law). Any prediction of "where technology will be by XXXX year" using the current advancement rates is rendered moot if that happens.169.232.190.22 (talk) 09:10, 15 March 2011 (UTC)

Likewise, much grander things could happen if Christ returns to start his thousand-year reign of peace, or if people finally manage to tap the latent psychic powers hidden in the unused 90% of their brains. -- BenRG (talk) 22:30, 15 March 2011 (UTC)

Are you parodying me? (edit: yep, he was. You won't be laughing when I set my future robotic brain to work on destroying your logic! >:( 149.142.48.73 (talk) 02:07, 16 March 2011 (UTC)

Most scientists will readily admit that there is essentially no economic benefit to space colonization - certainly not in the next 50 years. Don't take my word for it: here's some high-quality reading material for the pragmatic space enthusiast:

• Science in NASA's Vision for Space Exploration, a 2004 report by the National Research Council of the National Academies;
• The Space Operations Mission Directorate at NASA, including their most recent Mission Statement and Vision for Space Exploration
• NASA Headquarters Library bibliography of scientific publications on Space Colonization.

If you're lazy, just search these readings for the phrase "economics" or "profit" - such discussion is noticeably absent in any realistic discussion of the near- and mid-term future of space exploration. For the "layman", here's How much will Space Colonization cost? from NASA Ames.

Read a lot of different sources - draw your own conclusions - but you will notice a recurring theme. Despite the vast reservoir of public enthusiasm for space colonization, expert astronauts, scientists, engineers, bureaucrats, and politicians all know that space colonization is not profitable in the sense of "extracting resources" from other worlds. Space travel is a very expensive "luxury hobby" for our planet; and the laws of physics (particularly, gravitation and the need to launch faster than escape velocity) are not in favor of interplanetary commerce. No conceivable hypothetical technology or engineering solution will make gravity go away.

Still, space exploration has a massive economic impact: the space industry is constantly improving Earth technology, pushing the frontier of human knowledge, developing new materials, technologies, software, and scientific understanding that makes life on Earth much more efficient and sustainable. Nimur (talk) 15:43, 15 March 2011 (UTC)

• Thanks man! --Reference Desker (talk) 17:21, 15 March 2011 (UTC)

You might enjoy Marshall Savage's The Millennial Project: Colonizing the Galaxy in Eight Easy Steps -- Finlay McWalter ☻ Talk 17:28, 15 March 2011 (UTC)

That appears to have no more connection to reality than Kurzweil's technological singularity. -- BenRG (talk) 22:30, 15 March 2011 (UTC)

There are fans of helium 3 extraction from the Moon (though I never got how that was supposed to work in practice), and space-based solar power (in that article I read a fascinating description of an H.G. Wells style space launch from a gun, supposedly for 10% the current price ... and people thought Saddam Hussein was crazy. ;) [12]) Wnt (talk) 21:40, 15 March 2011 (UTC)

Helium-3 mining is only useful if someone invents a viable nuclear fusion reactor. There is no way to know how long that will take. --Tango (talk) 22:04, 15 March 2011 (UTC)

Wikipedia has an article on space guns. -- BenRG (talk) 22:30, 15 March 2011 (UTC)

Hormones

This may sound a bit stupid..... I'm a 21 year old male and I find myself sexually attracted to females. What I mean by sexual attraction is the desire to @#$%... Now I don't want that, if I'm attracted to a girl I only want to love her nothing more. I learned from wikipedia this is due to new hormones developing, so is there any way to remove these hormones? My body thinks very differently from my mind. Money is tight (talk) 14:24, 15 March 2011 (UTC)

Unless you feel like getting injected with female hormones or have certain parts permanently removed, I suggest you start with a cold shower. PЄTЄRS J V ►TALK 14:48, 15 March 2011 (UTC)

I'm having trouble understanding why you would want to do this! Despite what you may have been told, sexual intercourse is entirely natural and pleasurable. It's also not inevitable: see Platonic love. Advice on how to chemically castrate yourself would probably constitute medical advice, which we're not allowed to give. --TammyMoet (talk) 15:03, 15 March 2011 (UTC)

Chemical castration, perhaps? 93.95.251.162 (talk) 15:59, 15 March 2011 (UTC) Martin.

Hormone therapy is another relevant article. In case the OP hasn't already surmised, these hormone treatments are extremely serious medical procedures with numerous physiological and psychological consequences. They aren't something that should be considered lightly on account of "social awkwardness." If the OP really wants to pursue hormone treatment, they should speak with a physician. There are many options for less-severe treatment, ranging from medication to counseling to simply "taking a cold shower" as mentioned above - we really aren't able to determine what the OP's actual needs are. Nimur (talk) 16:52, 15 March 2011 (UTC)

If it poses danger to my health, I don't think I'm that desperate. I just want to feel pure without any materialistic desires. Money is tight (talk) 18:37, 15 March 2011 (UTC)

The Refdesk does not offer medical advice. We can't reliably tell you what is safe and what isn't (even if it's nucking futs...). And you'd probably get better information on the purity of love, with or without the wet work, at the Humanities desk. Wnt (talk) 18:39, 15 March 2011 (UTC)

Though I suppose, provided that this is clear, it does no harm to mention monk's pepper, in a purely platonic sense. Wnt (talk) 21:55, 15 March 2011 (UTC)

I think you need to fix your mind, not your body. Everyone belongs to everyone else.

Ben (talk) 18:59, 15 March 2011 (UTC)

The fact you think this makes you somehow "un-pure" makes me think this is an ideological issue, if I had to guess probably a religious one. Religions just love to make people feel guilt for perfectly normal and natural feelings especially concerning physical desire. As the post above states, I think you need to work on your mind not your body. HOWEVER that's not to say people can't have objectively unhealthy obsessions or desires which lead them to commit criminal acts or leave them unable to function in social situations, if you believe this might be the case then you really need to seek the help of a relevant professional, like a doctor or therapist. Hormone therapy might be one of the solutions if there is indeed a problem, but you need to strat from the problem not from the solution. Vespine (talk) 22:28, 15 March 2011 (UTC)

It's worth remembering that unless they're straight out of a Victorian novel, females have hormones too. The object of your affections might be more than a little disappointed if your interest turned out to be purely non-physical. APL (talk) 00:21, 16 March 2011 (UTC)

Since you were born a human being, you will never get rid of materialistic desires. Becoming an adult means learning to manage those desires in a healthy way. What you're feeling is what virtually every heterosexual male feels to some degree, and there's nothing impure about it. thx1138 (talk) 22:58, 15 March 2011 (UTC)

The original post sounds like stupid trolling, but in case it's sincere, the best cure is the one nature intended: get yourself a girlfriend and $*&^!@# away. You'll love it. 75.57.242.120 (talk) 06:08, 16 March 2011 (UTC)

I am being sincere. Why would I troll on an account with these many edits? I'm not under some regligious influence. Maybe I just have something wrong with my way of thinking, seeing as how everyone responded negatively. But if it helps I went through years of suffering from a loss and only recently have I felt like I'm beginning to recover. Sorry I didn't know medical advice weren't allowed here. Money is tight (talk) 11:09, 16 March 2011 (UTC)

It seems you have some very basic questions about what we are, how we got here, and why we behave the way we do as humans. Get on Amazon and pick up the book "How the Mind Works" by Stephen Pinker (Cognitive Scientist from MIT) for a very satisfying answer of those questions, including your questions about why sexuality works the way it does - that book has entire chapters devoted to the biological "economics" and the psychology of sex. So much of what I understand about science and about mankind was turned upside down by reading that book in particular.

Also, if you are actually 21 years of age, your social and emotional development as indicated by what you have typed here would suggest a sheltered upbringing. I am guessing you were raised by a religious single mother as I was. Either way, there are a lot of surprising and wonderful things that you're about to find in the world now that you are older that you may not have been aware of before, if you throw off your blinders and explore it passionately, and look into science in particular. Best of luck! 149.142.48.73 (talk) 00:21, 17 March 2011 (UTC)

Yikes guys, some people legitimately want to understand and separate blind sex from love. Some people do not separate the two. It doesn't mean either one is religious or sheltered or let loose or criminal, so stop insulting the poster or making fun of him like a bunch of jr. high preteens!

Modern media outside of Hollywood seems to understand that there is an identity crisis in the Western world over free sexuality vs. traditional human monogamy, both of which obviously are evolutionarily relevant. I link to a scene from Torchwood where a character, in talking with someone from the 50s, awkwardly dances into the contradiction, and to an SMBC comic on the arbitrariness of the human reproductive act.

To OP - from what I've seen (and what Alfred Kinsey said), everybody on this planet experiences sexuality differently, so you have to pick and choose from what people might say. Sex is not without consequences, emotional and physical, until after you're 40, so discipline is an important skill, particularly against 50-year-old flower-children giving bad advice. SamuelRiv (talk) 05:30, 17 March 2011 (UTC)

Simple chalk oscillator

In this video, at 1:38, how does Prof. Walter Lewin make the dotted line on the blackboard? If I tried that, it would only screech miserably. — Sebastian 20:09, 15 March 2011 (UTC)

Lol, lot's of practice. WikiDao ☯ 20:48, 15 March 2011 (UTC)

That's some mad blackboard skills. Very nice. (I suppose the secret of the dotted line has to do with having exactly the right angle, force, and the right elasticity in how you hold the chalk). He gets less careful later in the lecture, though -- at about 15:50 there's a very releaxed rendering of $2\pi$. Hmm, it is just formulas versus figures -- there's really good drawing from 29:09 again. –Henning Makholm (talk) 21:27, 15 March 2011 (UTC)

No doubt history will mourn the loss of these skills to the march of technology. I wonder if there's some way to preserve the dead sport for posterity - maybe give it an event at the Olympics? Wnt (talk) 21:32, 15 March 2011 (UTC)

Does he explain his easy-access banana? Admittedly, it's right there when you need it, but surely putting it in a pocket would be more convenient while sacrificing very little in draw time. APL (talk) 00:17, 16 March 2011 (UTC)

BTW he has an article: Walter Lewin. Also Walter Lewin Lectures on Physics. You could probably email him and ask - the article says he replies to emails. Ariel. (talk) 01:05, 16 March 2011 (UTC)

Good suggestion; I'll do that! — Sebastian 11:31, 16 March 2011 (UTC)

Drawing a dotted line with chalk is indeed easy. One additional variable is the distance from the board you grip it. I've found it easier with long pieces (I guess greater "bounce" per skip?). For angle, close to perpendicular is a way...it's almost as if the dotted line is a low-frequency version of the sqeeking. Sometimes even going a little beyond perpendicular ("pushing" at an angle instead of "dragging") works. I can't do it often because I usually lean hard when doing a chalk-talk and then forget to ease up...nearly-perpendicular + long chalk stick between hand and board + high pressure against the board + crappy quality (soft and dusty) chalk == lots of broken chalk and a face-full of colored powders:( DMacks (talk) 01:35, 16 March 2011 (UTC)

There was a big mathoverflow thread[13] about some deluxe chalk from Japan that mathematicians like to use. Maybe that has something to do with it. Then again, I also don't know if physicists like Prof. Lewin are in on such secrets. 75.57.242.120 (talk) 07:29, 16 March 2011 (UTC)

I just noticed that we already had a related discussion at WP:Reference_desk/Archives/Science/2009_April_9#Noisy_chalk_holders. — Sebastian 11:31, 16 March 2011 (UTC)

Grains of salt/sand/sugar in a cup

Hello all! Today in class we did a rather unimpressive activity in which we were challenged to find the number of grains of sand/salt/sugar in a cup. We were free to use anything in the lab (which was pretty well-equipped, but obviously excluding corrosive chemicals and flame) but we had nothing that could measure the mass of a single grain. The expected solution was that we count out grains until we got enough that we could measure on the scales provided. I think there was a better solution though, but unfortunately I was too busy counting the grains to figure it out :) It might have to do with volume. DOes anyone have any ideas? (PS: Rest assured this is just idle curiosity, the activity was completed in class and not homework). Thanks 72.128.95.0 (talk) 22:16, 15 March 2011 (UTC)

You could have tried photographing the grains in a known volume to get a digital image, used some software to count the grains in the image, and weighted that. Graeme Bartlett (talk) 22:46, 15 March 2011 (UTC)

(ec): Not very different from your suggested solution, but you might go the other way: Using a balance, divide the cup into halves of equal weight. Divide the half-cup into quarter cups. Continue, until you have reached the limit of what can be balanced with your equipment. You could then try to continue the division process manually, by dividing the sugar into heaps of equal size, visually, on a dark surface. When the heaps are of managable size, count the grains (or take a photograph, as Graeme Bartlett suggested), and multiply to get the approximate number in the original cup. --NorwegianBlue ^talk 22:52, 15 March 2011 (UTC)

A different approach: count as many grains (assuming NaCl) as you can manage. Dissolve them in a small volume of destillated water. Measure the Na+ concentration. Calculate the number of micromoles/L of Na+ in the solution, multiply by the volume, get the number of micromoles in the grains that went into the solution, and get the number of micromoles per grain. Repeat with a larger quantity of salt, and calculate the number of micromoles of Na+ in the cup. Divide, and get the number of grains per cup. --NorwegianBlue ^talk 23:16, 15 March 2011 (UTC)

Or just walk into the building superintendent's office and say: "I will give you this fine cup of salt if you can tell me ..." –Henning Makholm (talk) 23:20, 15 March 2011 (UTC)

A microbiologist would get something with a big grid on it, like a paper cutter, and scatter the salt (or a smaller volume as is reasonable) over its entire surface. Then count a few grid squares until the standard deviation looks alright... Wnt (talk) 23:30, 15 March 2011 (UTC)

Another variation on the photographing method, but less onerous to count because it is a linear measure: photgraph the surface of the cup of salt with a digital camera. Magnify to a scale you can count the number of grains occuring in a 1mm interval. Cube to get the number of grains in 1mm³. Multiply by 1000 to get grains in 1ml. Multiply by 250 to get grains in a cup. SpinningSpark 23:44, 15 March 2011 (UTC)

Different method: Weigh your cup of sugar. Expose it to ants and count the ants as they take away grains of sugar. Ants are a lot easier to count than grains. Weigh the cup again and take the difference to the original weight. Divide this into the original weight and multiply by the number of ants counted. SpinningSpark 23:44, 15 March 2011 (UTC)

How about an hourglass approach? Make a paper cone with a small hole at the tip and put the sugar in it, count how many grains fall out in, say, five or ten seconds, depending how fast it's falling out, then time how long it takes it all to drain. Vespine (talk) 01:12, 16 March 2011 (UTC)

Going back to volume, how accurately can you measure the dimensions of a single crystal? Better do a few to account for different sizes. I bet you could convert the average volume of the crystals into their average mass pretty easily, using some known physical constant of...whatever chemical you think salt mainly is. DMacks (talk) 01:20, 16 March 2011 (UTC)

Volume is no good in this case. The listed density for sugar would be the density of the sugar itself, but the cup has a combination of sugar and air. You don't really know what part of the cups volume is air, reliably... --Jayron32 02:29, 16 March 2011 (UTC)

Volume of a crystal is a route to mass of a crystal. If you then know the total mass of some uncountably large number of crystals, what does the mass of a single crystal allow you to calculate? DMacks (talk) 03:39, 16 March 2011 (UTC)

Now if the crystals are sand, a cell biologist would find some sugar in the lab, dissolve it, and pour it into tubes in a sucrose gradient, or at least, a goopy mass of melted sugar. Then dump lots of grains into the tubes from a large height, so he can see what the average distance is that the grains travel into the sugar. The grains at the average distance are average grains, so by aspirating this band of grains, washing them and drying them, and weighing them in aggregate, he gets to the average weight of a grain. ;) Wnt (talk) 21:27, 16 March 2011 (UTC)

But a molecular biologist, presented with a cup of sugar, would simply add a little water, perhaps flour, egg, a few spices... Then knead the mixture until it is homogeneous, and roll it up into ten little balls. Cook them if desired, put them back into the cup, and answer - "ten". Wnt (talk) 21:33, 16 March 2011 (UTC)

A chemical engineer would find the appropriate documentation for that particular variety of sand/salt/sugar sold by that specific company, and look up the 'average mass per grain' entry in the specifications. If it's a standard product, there may be an entry in a standard reference book, and you may be able to bypass mass and look up the average volume and packing volume ;) 86.164.66.59 (talk) 22:44, 16 March 2011 (UTC)

after effects of radiation in india

what are the possible after efeects of 2011 radiactive radiation in japan to asian countries including india —Preceding unsigned comment added by 220.225.96.217 (talk) 22:41, 15 March 2011 (UTC)

Because the air moves generally from west to east around Japan, any radioactive material would have to go all the way around the world to reach India, or most other parts of Asia. It astonishes me that so many people think there is a risk to other countries -- even the US west coast, which is in the direct path of atmospheric flow, is 8000 miles from Japan, a third of the way around the world. Looie496 (talk) 22:51, 15 March 2011 (UTC)

(ec) At the moment, nothing. The amount of radiation is too low to be of significance to India or China. Even if there were a Chernobyl-style catastrophe (which is highly unlikely), the fallout plume probably wouldn't affect India in a substantial way. At its maximum, the problematic radioactive material from Chernobyl was dispersed some 2,800 km away. That's enough so that if it was going due West (highly unlikely), it would potentially end up in China or the Koreas (or the edge of Russia). Definitely not enough for India, and that would be a worse-case scenario. More problematic would be the effect on the food supply — whether it would end up in the fish sold in Asian (and world) food markets. I don't know enough about that to comment. But the current levels of radiation, though hardly ideal, are not of a level that should have any consequences as far India. Unless they sharply rise, they should not have consequences even in Japan, as I understand it. But the situation has not played itself out yet. --Mr.98 (talk) 22:54, 15 March 2011 (UTC)

The news I'm hearing is that they have four reactors and who knows how many pools of spent fuel rods all about to cook off, and the place is so radioactive they've cut 700 workers down to a skeleton crew of 50, and abandoned the control room.^[14] It seems reasonable to be talking about a Level 8 nuclear disaster here. Wnt (talk) 23:26, 15 March 2011 (UTC)

There doesn't seem to even be a level 8 on the International Nuclear Event Scale... They are struggling to control the situation, but at the moment it is under control. Radiation levels outside the evacuated zone are negligible and have been throughout the incident. --Tango (talk) 00:19, 16 March 2011 (UTC)

Not yet there isn't. Wnt (talk) 00:41, 16 March 2011 (UTC)

The current situation is either a 4 or a 5 on the INES scale (depending on who you listen to), with the worst-case scenario (all three reactors undergoing complete meltdown, combined with uncontrolled fires in all the spent-fuel pools) being an INES 6. --Carnildo (talk) 02:28, 16 March 2011 (UTC)

This was a declared a level 4 by Japan when only two reactors were involved. Since then they have said nothing (3 reactors and 3 spent fuel tanks involved now). France, Finland(?) and a number of private organizations have called it a level 6 now. The IAEA apparently will not rate it yet. 75.41.110.200 (talk) 04:31, 16 March 2011 (UTC)

March 16

Possible causes for temporary blindness due to car crash

Rest assured I`m not asking for the dreaded medical advice, it is for short story I`m writing for school. I need to know if there is any kind of traumatic injury (after say crashing car head on in a tree or a metal pole) that would cause temporary blindness and doctors would be almost certain the induvidual will recover fully stright away ~~Xil (talk) 03:51, 16 March 2011 (UTC)

It would be possible, impact to the optic nerves or part of the brain. Graeme Bartlett (talk) 04:42, 16 March 2011 (UTC)

Yes, but why - hemorrage (I suspect that would rather cause something similar to stroke), inflamation or what? ~~Xil (talk) 06:45, 16 March 2011 (UTC)

This paper cites a study into 10 patients with blunt trauma injuries (mostly caused by crashes) that caused blindness (14 eyes in all, I assume some suffered blindness in both eyes, other only in one). It says that in most cases the blindes was caused by swelling of the optic nerve, but also stated that in three cases a fracture in the optic canal wall was the cause of blindness. [15]. I must admit that I have only read the brief summary, but that alone seems to provide a useful basic insight into your question. Darigan (talk) 12:35, 16 March 2011 (UTC)

Judging by the summary those aren`t cases of temoprary blindness (it makes it quite clear that patients needed medical intervention to spare their vision). For this case, I need patient to expierience emotional trauma, which makes him rethink purpose of life, not have lasting damage. Just something that would sound pausible, I don`t want to write about something that would kill him in reality ~~Xil (talk) 14:17, 16 March 2011 (UTC)

Anything that could cause blindness is likely to have a high chance of being fatal without medical treatment. Having his eyesight restored by medical treatment should work for your story. --Tango (talk) 01:43, 17 March 2011 (UTC)

It is not question of receiving medical help or not, it`s just that I don`t want major brain surgery in the story. I need doctors saying that the problem will sort itself out in few weeks and patient freaking out at chance that doctors might be wrong. Such conditions exist outside of realm of soap operas? ~~Xil (talk) 13:52, 17 March 2011 (UTC)

Which salt water, with a lot of salt or little salt, absorbs heat more quickly?

I may be not looking at answers — Preceding unsigned comment added by Like sushi (talk • contribs) 04:16, 16 March 2011 (UTC)

At a given temperature, the thermal conductivity of salt water decreases with increasing salinity.[16] Red Act (talk) 17:55, 16 March 2011 (UTC)

Thank you.Like sushi (talk) 02:42, 17 March 2011 (UTC)

Real E.T. or Hoax

Is this news real ?  Jon Ascton  (talk) 04:39, 16 March 2011 (UTC)

Yeah, right. 75.57.242.120 (talk) 04:54, 16 March 2011 (UTC)

Mierda del toro... --Jayron32 05:18, 16 March 2011 (UTC)

My poor uncle. -- Toytoy (talk) 05:57, 16 March 2011 (UTC)

Yes, that's really "news" (unfortunately). But you don't really think it's about a real baby alien, do you? WikiDao ☯ 16:16, 16 March 2011 (UTC)

remote controlled helicopter

Is there such a thing as a remote controlled helicopter, basically a regular helicopter with servos connected to the controls? Could they rig some up in a hurry over there in Japan, to overfly those reactors and dump stuff on them without irradiating human pilots? Just wondering. 75.57.242.120 (talk) 04:50, 16 March 2011 (UTC)

Dumping stuff on them wouldn't do much, it would just roll off. The outer container is not very hot, it's the internal one that is, so they need to pump water inside. That said, they certainly can do it remote if necessary. But it's not necessary - the radiation is still pretty low, so a regular fire-fighting helicopter could overfly, dump, and continue and be exposed to almost nothing. Ariel. (talk) 06:04, 16 March 2011 (UTC)

Could they rig some up in a hurry? No, aircraft modifications are not undertaken lightly, and especially not the sort of modification required to convert a conventional heavy-lift helicopter into an un-manned helicopter. A modification project of this kind would involve design, manufacture of parts for the modification, installation of the parts, and then extensive testing and fine-tuning, mostly at light weights. Then there would need to be testing and fine-tuning at heavy weights. It couldn't be done in the sort of time-frame that would interest the people grappling with the Japanese reactor problems. Dolphin (t) 06:24, 16 March 2011 (UTC)

They would use these: Helicopter bucket, they already exist (if Japan doesn't have any I'm sure they could be brought). No need for any time consuming design. Ariel. (talk) 09:31, 16 March 2011 (UTC)

Thanx. I know that Chernobyl liquidator helicopter pilots (they dumped concrete over the burning reactor) got considerable radiation exposure and I think some of them died of related illnesses. That's why I asked about remotes. The R/C helicopter article is about little tiny models that don't count for this, though they might be good for photography, sensors, etc. Also I wonder if the USS Reagan (aircraft carrier off Japan) has any UAV's (Predators or whatever) on board. Yeah, Dolphin51 is probably right about modification, even though there is a 30 km no-fly zone around the reactor right now, so I'd think they could suspend normal aviation rules. I wasn't thinking of any fancy stuff designed specially for the helicopter, just some servos or off-the-shelf industrial robot arms, bolted into the pilot's seat and operating the controls. This doesn't seem terribly hard to do with automobiles but I can see how aircraft could be more complicated. 75.57.242.120 (talk) 07:21, 16 March 2011 (UTC)

Re dumping stuff: they are talking about using fire hoses to shoot water into the hole in the roof of the building that exploded, to refill the spent fuel pool which has been boiling from decay heat. Apparently it is exposed from above. 75.57.242.120 (talk) 07:23, 16 March 2011 (UTC)

Actually they are dumping stuff already (can't find a RS but it was on the news in the past 30 mins or so and also mentioned on BBC's twitter [17]) even if they ruled it out a few hours ago [18] [19] perhaps a reminder in an ongoing crisis where things can change rapidly it's wise to be carefully when saying something like 'they won't do that' or 'that won't happen'. Note on BBC it does according to NHK TV "the helicopter can't stay too long over the plant because of the risk of radiation to the crew" Nil Einne (talk) 08:20, 16 March 2011 (UTC)

Well, remotely operated helicopters seem potentially useful for firefighting and other unsafe activities, so even if they can't be built soon enough to deal with this nuclear incident, maybe they're something the aircraft makers could work on. 75.57.242.120 (talk) 10:30, 16 March 2011 (UTC)

There are already helicopter-style UAVs such as the Northrop Grumman MQ-8 Fire Scout. However, they don't seem to have the lifting capacity of manned helicopters yet. --Colapeninsula (talk) 11:15, 16 March 2011 (UTC)

Latest news now of course is that the plans were abandoned due to fears of radioactive contamination for the crew Nil Einne (talk) 12:01, 16 March 2011 (UTC)

The radiation levels are rising and falling as things change at the plant. You might see a burst of radiation as a steam vent opens, causing the crew to evacuate, then have the wind blow the steam out to sea, causing the radiation levels to fall and letting the crew return. --Carnildo (talk) 20:12, 16 March 2011 (UTC)

I haven't read anything suggesting the helicopters will be back. Edit: Should have taken my own advice [20]. (I admit even when posting the first time I was suprised no one was talking about trying again later but since I still never heard anything I decided there must have been something I was missing.) Even so it still demonstrates the idea that there was no reason to use a remote controlled helicopter seems to have been incorrect. Nil Einne (talk) 21:56, 16 March 2011 (UTC)

I'm disappointed. I would have thought that sometime during the Cold War the U.S. military would have thought up a way to radiation-proof a helicopter. I suppose we're probably just as badly prepared for a nuclear war as we would be for a disaster like this. Wnt (talk) 00:06, 17 March 2011 (UTC)

Radiation-proofing a helicopter would basically involve lining it with thick sheets of lead. That is very heavy - not a good thing in an aircraft. You would also need to make it air-tight and fit appropriate ventilation systems. While all of that could be done, it would make the helicopter extremely inefficient when operating away from radiation. Building helicopters for use only in high-radiation situations would be very expensive for fairly small gain. The gain right now would be quite big, but situations like this one are extremely rare. --Tango (talk) 01:39, 17 March 2011 (UTC)

Hmmm - so you think the limits on the helicopter are truly from direct radiation exposure and not from the contamination of personnel through the air? I'd assumed otherwise (I was just thinking you could seal it and filter the air thoroughly) but I don't actually know. Wnt (talk) 06:53, 17 March 2011 (UTC)

Thanks,the Fire Scout is the kind of thing I was wondering about. I wonder why they're not using them. It does look like they've sent some fixed-wing drones.[21] 75.57.242.120 (talk) 00:47, 17 March 2011 (UTC)

Because as per Colapeninsula they're puny things which couldn't deliver significant amounts of water presuming they could be reliable fitted to lift any water? (Probably because they weren't intended to lift things.) It also sounds like they don't have many and are still basically in testing. Nil Einne (talk) 04:46, 17 March 2011 (UTC)

According to the link you provide, the drone in question is the Northrop Grumman RQ-4 Global Hawk. It's got a payload capacity of 3000 pounds, but it's entirely internal storage. Even if you could refit it to carry a water bucket, that's only about 300 gallons, which would have essentially no impact. --Carnildo (talk) 23:19, 17 March 2011 (UTC)

Question about light clocks/ time dilation?

Let we have the following three clocks in a spaceship which is moving close to the speed of light.

Clock 1 is AB long which is perpendicular to the direction of ship. Clock 2 is CD and Clock 3 is EF long. Both 2 &3 are along the direction of spaceship such that 3 is just above No.2. Distance between A&B, C&D and E&F is L = distance covered by a light in one second. 

Now in order to analyze time dilation for one second a pulse is fired at the same time from 

From A towards B in Clock 1

From back of the ship "C" to it's  front "D" in Clock 2

From the front of the ship "E" to it's  back "F" in Clock 3 

For inside observer: 

Clock1- experienced a perpendicular of the right angle triangle of time dilation diagram. 

Also a pulse fired from the back of the ship to the front would take the same amount of time as a pulse fired from the front to the back. 

For outside observer:

Clock1-observed  a hypotenuse of right angle of time dilation and hence experienced more time than inside observer for the same clock.

Clock2- observed a very small fraction of distance covered by a pulse due to the high speed of ship in the same direction. Thus experiencing more more more and more time than inside observer for the same clock.(so slow even if length contraction is ignored)

Clock3- notice a very short time due to the rushing of back of ship and hence experienced a less time as compared to inside observer. This means time is contracting in this case for him (so fast even if length contraction is added)

So are their differences wrong?74.198.150.229 (talk) 06:34, 16 March 2011 (UTC)khattak#1-420

The one-way times are all different, as you noticed, but the round-trip times are all the same. -- BenRG (talk) 08:57, 16 March 2011 (UTC)

(ec)You hit onto one of the fundamental consequences of the Theory of Relativity, namely that there is no global simultaneity. The order of events (and hence, possibly, causality!) depends on the frame of reference of the observer. Our article on relativity of simultaneity has more. In other words, an observer in the middle of the space ship who shoots light beams at mirrors in the front and the back will observe them hitting the walls at the same time. A outside observer not co-moving with the ship will see the front and the back beam hit at different times. --Stephan Schulz (talk) 09:01, 16 March 2011 (UTC)

Here's a link to that article: Relativity of simultaneity Red Act (talk) 09:33, 16 March 2011 (UTC)

I don't want discuss it further because I know the wikipedia rules but sounds like I didn't explain things clearly enough for you understand my question therefore it behooves me to try it the other way.

Let we have the following arrangement.

Mirror at the back of ship is B, Mirror at the middle of ship is M, Mirror at the front of ship is F

For on board observer pulses are back and forth in between BM and FM at the same time. Each cycle is same for him. Cycle means back and forth distance covered by pulse in either BM or FM.

Let study the two cycle of aforementioned pulses for outside observer not co- moving.

Cycle 1

Between B&M- pulse would hit B very early and then reflected very very slowly towards M

Between M&F- Pulse would be moving very slowly towards F and will be reflected towards M when it hit F. 

Since for onboard observer, cycle 1 is completed earlier than outside observer and for him pulses are ready again towards B &F while for outside observer cycle1 is yet to be completed. So here is my question?

Why would outside observer see two pulses in between B&M (one which is lag behind for him in cycle1and other from cycle2 of onboard observer) and similarly two pulses between F&M. 

This means number of pulses increases per cycle ( of on board observer) for outside observer if he had the opportunity to observe all.  So is this parallax for out side observer who is not co-moving? 74.198.150.229 (talk) 18:38, 16 March 2011 (UTC)khattak#1-(ec)

It seems to me that you are failing to distinguish the time as measured by one observer from the time as measured by the other observer when you say "Since for onboard observer, cycle 1 is completed earlier than outside observer". These are different times measured by different observers and it makes no sense to say that one happens earlier than the other. Dauto (talk) 19:53, 16 March 2011 (UTC)

The reasons why I'm thinking eccentrically is that if we fired a pulse from the back of spaceship towards its front then onboard observer will see a pulse leave a ship through it's front in one second (if the length of the ship is one light second) while an outside observer will find it in very slow motion inside ship because both a pulse  and a ship are moving almost at the same speed. Therefore for him a pulse would take hours hours ...... to reach the front of ship.

Therefore to me it sounds like round trip wouldn't be same for both observers because ship and a pulse are almost at the same speed if traveling in same direction. This is my last reponse to this question therefore pls don't consider this for warning. Thanx —Preceding unsigned comment added by 74.198.150.213 (talk) 22:44, 16 March 2011 (UTC)

The round trip won't last the same for both observers. It will be time dilated for the external observer. I don't think the wikipedia police will come knocking at your door if you chose to post one more response to that question. Dauto (talk) 23:39, 16 March 2011 (UTC)

With respect to the moving frame, the distance between the mirrors is L/γ, where γ is the relativistic gamma factor ($1/{\sqrt {1-v^{2}/c^{2}}}$). The time for the light to cross this distance moving with the ship is ${\frac {L}{\gamma \,(c-v)}}$, which is large if v ≈ c. The time for it to cross in the other direction is ${\frac {L}{\gamma \,(c+v)}}$. The sum of these is

${\Bigg (}{\frac {L}{\gamma }}{\Bigg )}{\frac {(c-v)+(c+v)}{(c+v)(c-v)}}={\frac {2L}{\gamma \,c\,(1-v^{2}/c^{2})}}=\gamma {\frac {2L}{c}},$

which is γ times the round-trip time in the rest frame. -- BenRG (talk) 00:58, 17 March 2011 (UTC)

Cooling the inside of the building

About Japanese nuclear accident.

Wouldn't it help to cool it down with liquid nitrogen and oxygen?

If the supression pool is broken, though hopefully not, it would work more.

I may not be looking at answers. — Preceding unsigned comment added by Like sushi (talk • contribs) 07:30, 16 March 2011 (UTC)

Liquid oxygen is best kept away from nuclear reactors - or, for that matter, barbeque grills!^[22] Supposedly, if you soak the charcoal with oxygen before lighting, you can even get a sizeable explosion. Liquid nitrogen would be very cold, but it doesn't actually have as much heat capacity as water, so there's not so much of an advantage ... though it would put out a fire. Wnt (talk) 08:00, 16 March 2011 (UTC)

Sorry, I seem to have forgotten to write the most important.

I would say the air inside the building to be replaced with mixture of liquid nitrogen and oxygen. — Preceding unsigned comment added by Like sushi (talk • contribs) 08:30, 16 March 2011 (UTC)

I mean, in evaporated form. — Preceding unsigned comment added by Like sushi (talk • contribs) 08:42, 16 March 2011 (UTC)

Er you mean oxygen and nitrogen gas? Nil Einne (talk) 09:01, 16 March 2011 (UTC)

I fail to see how it would be diffrent from mix of oxygen and nitrogen 84.52.26.118 (talk) 09:06, 16 March 2011 (UTC)

I suppose so.

If it is generated from liquid nitrogen and oxygen, it would be still very cold, I think. — Preceding unsigned comment added by Like sushi (talk • contribs) 09:05, 16 March 2011 (UTC)

In case it's not clear, the air inside the building, not the pressure vessel. — Preceding unsigned comment added by Like sushi (talk • contribs) 09:41, 16 March 2011 (UTC)

On second thought, if the suppression pool is broken, the water in the pool may freeze, and the effect of it, I do not know. — Preceding unsigned comment added by Like sushi (talk • contribs) 09:58, 16 March 2011 (UTC)

I don't think that is likely. I don't actually understand what you think is going to happen but you still have the problem Wnt mentioned of little heat capacity. It's even worse now since you don't even have much of it. It seems a bad idea to try to have a highly pressured mixtured in the containment vessel for many reasons. So presuming you're keeping it atmospheric that means you end up with ~ 1.3kg/cubic metre. I don't know the volume of the containment vessel but even if it's 1000 cubic metres that's only 1300kg you're putting in, a relatively tiny amount of a lower heat capacity then water substance. Plus the heat isn't even going to transfer well. Not to mention if you're talking about the spent fuel storage pond isn't one of the problems that they're now exposed to air? Are you planning to replace the earth's atmosphere with 'evaporated liquid nitrogen and oxygen'? Nil Einne (talk) 10:58, 16 March 2011 (UTC)

Looking at Heat capacity#Table of specific heat capacities,

although columns for Volumetric heat capacity are left blank,

in "mol"-related columns, which seems to have something to do with volume,

"Water at 100C (steam)" is, in value, only less than 1.5 times than that of nitrogen and oxygen.

Heat transfer#Convection says "Convection is usually the dominant form of heat transfer in liquids and gases.",

and mentions Newton's law of cooling, "The rate of heat loss of a body is proportional to the difference in temperatures between the body and its surroundings."

If the temperature of 'evaporated liquid nitrogen and oxygen' is so close to absolute zero,

I think we can assume at least additional 300C difference in temprature

(, assuming steam of water to be over 100C),

and if (the body's temperature - temperature of steam of water) is smaller than

2/3 of (the body's temperature - temperature of 'evaporated liquid nitrogen and oxygen')

I don't think there isn't a chance.

And I don't know if the buildings' state is so bad to let the vapor

(of water or of nitrogen and oxygen) easily out. — Preceding unsigned comment added by Like sushi (talk • contribs) 13:42, 16 March 2011 (UTC)

It seems like you intend to replace air with very cool air? Perhaps using liquid nitrogen in air conditioner would work somewhat better - probably you can keep it from evaporating that way ~~Xil (talk) 13:56, 16 March 2011 (UTC)

I don't know what suggestion "using liquid nitrogen in air conditioner" is,

but if it is to bring a lot of air conditioners to the site, it seems to take a lot. — Preceding unsigned comment added by Like sushi (talk • contribs) 14:18, 16 March 2011 (UTC)

I think the point you are missing is that the objective is not just to cool the fuel rods, but to *keep them* cool - they are continually generating heat. So you need a constant supply of coolant. Water is a good coolant because it has a high heat capacity by volume, good thermal conductance and is readily available in large quantities - which, ironically, is why reactors are often built near the coast. Gandalf61 (talk) 14:09, 16 March 2011 (UTC)

I think keeping the temperature of the air (or vapor) inside the building as low as 0C,

wouldn't hurt, except for ones working in it,

because water doesn't freeze at 0C, if containing a little salt. — Preceding unsigned comment added by Like sushi (talk • contribs) 14:57, 16 March 2011 (UTC)

No matter how much salt you add, you can only lower the freezing point a dozen or two degrees...LN2 temperatures will quickly freeze it either way, during which the volume will expand for a while and likely break various vessels containing it. That's...bad. I think you are missing the truly enormous scale of the situation. Even though LN2 temperature is very low, a gas at that temperature is simply not good at cooling the huge amount of solid and liquid high-temperature materials. And once it does warm up, it no longer helps--in fact it would have to be continually replaced because the reactor components are not just "hot" but are "continuously generating more heat". If you put ice cubes in a pan in a hot oven, they will melt and cool the pan. But if the oven is on, the pan will still get hot, boiling away the water (heating the coolant solid -> liquid -> gas -> hot gas) and now you have...nothing except the same hot pan where you started. DMacks (talk) 15:31, 16 March 2011 (UTC)

The last comment was not about cooling the air (or vapor) to near absolute zero,

but to 0C.

I didn't think in a way that just inside the building is as highly pressured as the inside of the pressure vessel,

so, at least then, didn't have reason to think pushing away the air (or vapor) with colder (or cooler) one hurts. (Again, except for ones who are working in it.) — Preceding unsigned comment added by Like sushi (talk • contribs) 16:08, 16 March 2011 (UTC)

No, that is not what I meant, you may want to explore how air conditioner works, but esentialy my idea is that you would have pipes filed with liquid nitrogen, rather than releasing it in the buliding where it would evaporate and escape the building (unless it is hermeticaly sealed, which seems unrealistic) ~~Xil (talk) 16:33, 16 March 2011 (UTC)

This seems bold, but do you mean by "pipe", the pipe in which primary coolant is?

(I do not know if there is secondary coolant)

No, I mean, instead of filling room with nitrogen and oxygen (note that it is what air is made of, so once it evaporates all you will get is somewhat cooler air), you would have piping filled with constantly liquid nitrogen, which would cool the air around it ~~Xil (talk) 01:11, 17 March 2011 (UTC)

Would it transfer heat, I mean, coldness as quickly as by making it a vapor?

If the pipe is directly made in contact with the body, it would work very well.

Making it in vapor can be done from relatively far from the body, for the safety,

and doing both, though with less efficiency, would work more

Like sushi (talk) 01:40, 17 March 2011 (UTC)

Pipes, can they be soaked into glue-ish substance for making it possible to stick to the body, even if thrown from far apart?

(It may be a silly idea, though)

Like sushi (talk) 01:56, 17 March 2011 (UTC)

Per the above discussion, one of the plans was to try to dump water from a helicopter. Another one is/was? to shoot water from a police or fire water canon. I think it's clear such a structure is not going to keep air/oxygen/nitrogen/water vapour/whatever in very well... Nil Einne (talk) 21:55, 16 March 2011 (UTC)

At least at the time it was constructed, the building seems to have been meant to serve as one of the sealing in emergency.

Like sushi (talk) just before 23:42, 17 March 2011 (UTC)

I'm confused now. Are you suggesting they should have kept it with an evaporated liquid nitrogen/oxygen atmosphere all the time? I thought the question was how to cool it right now since they were clearly not having a problem cooling it before the current problems and you specifically mentioned the nuclear accident and in the specific post I was replying to you said 'And I don't know if the buildings' state is so bad to let the vapor' (which was in reply to me saying 'they're now exposed to air' although I admit now exposed to the atmosphere was what I was intending). BTW can you please sign your posts with four tildes ~~~~ to avoid confusion. Nil Einne (talk) 23:42, 16 March 2011 (UTC)

I just don't know how much the building is damaged, and if all the buildings are damaged, I mentioned the intention at the time of construction to suggest, if the damage is not all over, it may still serve for a little goodLike sushi (talk) 00:35, 17 March 2011 (UTC)

There are pics in the article on the accident, quite obviously walls and roof are gone ~~Xil (talk) 01:14, 17 March 2011 (UTC)

Most of the relevant buildings have recently exploded, so I think it is safe to say they are significantly damaged! --Tango (talk) 01:32, 17 March 2011 (UTC)

It looks at least 3 and 4 plants have no roof nor wall, by the picture.

Like sushi (talk) 01:40, 17 March 2011 (UTC)

I may be just becoming so desperate, so take this with a bunch of salt.

Would berrying the reactors in a lot of (presumably iron or steel) pachinko balls help?

As iron or steel seems to have high thermal conductivity,

and it would still leave (small, but not no) room for water to enter,

and would enlarge the surface area of matters with relatively high temperature

(because heat capacity of iron or steel is small),

which may make it easy for pumped water to deprive heat.

(Even if it seems so nice, do not jump on it, everyone,

it wouldn't take many people to check this idea.)

Like sushi (talk) 05:34, 17 March 2011 (UTC)

Explanation: I am thinking in a way like,

pachinko balls may "take away" heat

from relatively small surface area of container vessel (?)

to relatively large suface area of the balls

more quickly than air (or vapor) does.

(Though air is gas and flows freely, so I am losing hope in it,

and anyway, I don't have a way to even personally judge which is better)

Like sushi (talk) 05:59, 17 March 2011 (UTC)

what happens if signal peptidase malfunctions and fails to cleave the signal sequence?

Does it usually hinder the function of the produced protein? John Riemann Soong (talk) 08:38, 16 March 2011 (UTC)

Well, it depends by what you mean "function". The (endoplasmic reticulum) signal peptide is a transmembrane domain, and the protein isn't going anywhere without some kind of cleavage. (I should add, though, that signal peptidase has quite a few homologues, and the options for cleavage by various enzymes at various points can become complicated - things like amyloid precursor protein can be cut in many ways, with significant effects) But if you just want protein activity, it isn't uncommon for a tethered protein to work the same way as an untethered one. But any individual protein may have its own quirks. Wnt (talk) 15:10, 16 March 2011 (UTC)

Flocking birds in SE England

A large flock of European starling in England

In the last couple of days I've noticed at least two large flocks of birds wheeling about the sky, here in south-east england.

Would they be flocking because they've just arrived (from Scandinavia, Europe, Africa?) Or are they preparing to leave (to Scandinavia, Europe, Africa?) Or is it impossible to tell? Is it possible infer anything else about these flocks or birds? Thanks 92.29.117.90 (talk) 13:02, 16 March 2011 (UTC)

Any bird species in particular? Given that it is spring they probably were wintering in England and now are prepering to migrate to north ~~Xil (talk) 13:39, 16 March 2011 (UTC)

Sorry I was too far away to identify them. How can you telling they are departing rather than arriving? Thanks. 92.29.117.90 (talk) 13:48, 16 March 2011 (UTC)

I believe there is no need for them to flock when arriving, they would rather spread out once they are close to the destination. Assuming, of course, that they flock because of migration, not some other reason ~~Xil (talk) 14:08, 16 March 2011 (UTC)

Perhaps European starling - see image. Although the sight is becoming less common as bird numbers decrease, this is a well known but poorly understood feature of starling behaviour. More information here. Ghmyrtle (talk) 13:49, 16 March 2011 (UTC)

PS: Starling flocking has nothing to do with migration. Ghmyrtle (talk) 14:55, 16 March 2011 (UTC)

Here in south central UK starlings are still wheeling about in huge murmurations before settling to roost for the night. If memory serves they will reduce in size pretty soon as they start nesting but will be back at it again in the autumn. Richard Avery (talk) 16:24, 16 March 2011 (UTC)

Does that mean they are not preparing to migrate, but are British starlings who behave like that during the winter? Dosnt flocking make it difficult for them to find enough food? Thanks 92.15.26.91 (talk) 20:49, 16 March 2011 (UTC)

Flocking in birds etc, and similar behaviours (schooling in fish and other marine organisms, herding, swarming - I notice our articles on these subjects could use some improvement) is thought to some extent (and variably with each case) to be a protection against predators. Each individual flock member decreases its chances of being predated by surrounding itself with many other targets, and some predators are confused by an over-profusion of targets.

Starlings and similar birds tend to exhibit this behaviour more in the winter months when food is scarcer and 'following the flock' may increase the chances of finding at least some food, which may also tend to be concentrated in small areas like recently harvested, ploughed or sown fields, of stands of seeding trees etc, and when they are not competing for nesting places. In the spring and summer the wider and more plentiful availability of food enables them to disperse and stake their own more individual nesting and foraging territories. Other bird species pursue other strategies, there being several viable niches in the environment. {The poster formerly known as 87.81.230.195} 90.197.66.165 (talk) 22:38, 16 March 2011 (UTC)

Arrow of time

I was watching a BBC programme (Wonders of the Universeand the presenter was talking about the arrow of time. He seemed to say that time goes in one direction but nobody knows why. How would you know if time was reversed and if time doesn't continually head in one direction would it even matter? --BlackberryPicking (talk) 13:03, 16 March 2011 (UTC)

If direction of time reversed, the entropy of the universe will tend to decrease with time. i.e. heat will flow from cooler bodies to hotter bodies. Generally the energy of the universe(which is conserved regadless of the direction of time) will be concentrated in fewer particles over time. Diwakark86 (talk) 13:54, 16 March 2011 (UTC)

That's a silly program. There is really no mystery about the time's arrow. It is a tricky thing but it is well understood. To answer your question, don't you think you would notice a river flowing up river and then raining backwards into the sky while you got younger over the years like Benjamin Button? Dauto (talk) 13:46, 16 March 2011 (UTC)

Entropy is the reason for the arrow of time I believe. That programme, like so much on evening TV, seems designed for kids or young teenagers in its vocabluary, intellect, slow delivery, and its new-information/waffle quotant. (Television presenters should model themselves upon Patrick Moore in my opinion). I don't think you would notice any theorectical reversals in time as your brain would be reversing as well. 92.29.117.90 (talk) 13:52, 16 March 2011 (UTC)

I watched the program in question and it was actually reasonably good. (Brian Cox has appeared on The Sky At Night, if that improves his credibility with you!) It is a difficult concept to get your head around, so it isn't surprising that someone wouldn't understand it the first time it was presented to them, however good that presentation would be. --Tango (talk) 15:17, 16 March 2011 (UTC)

Agreed. There is no great mystery about the arrow of time. Percieved time goes in the direction of increaisng entropy, by definition. You cannot remember the future because memory (either biological or non-biological) involves observing a current state (which includes the memory) and infering another state which we call the "past" - but the inferred state must be one with lower entropy than the present, otherwise there are too many "choices" to make an inference. Therefore the perceived past must, by definition, have a lower entropy than the present. In a universe with constant entropy there could be no memories, and hence no perceived past or direction of time. In other words, asking why time never goes backwards is like asking why things never fall upwards. See Entropy (arrow of time) for more details. Gandalf61 (talk) 13:59, 16 March 2011 (UTC)

The arrow of time considered in isolation doesn't make much sense. Time doesn't really have a direction. Time just is. When people talk about the arrow of time, they are relations between different things that give time a direction. The most obvious one is human memory. We remember the past, we don't remember the future ("the pyschological arrow of time"). You then try and explain why other things go in the direction they do, relative to the psychological arrow. For example, why, when we see a broken egg do we often remember it when it was intact but, when we see an intact egg we never remember it when it we broken? It all comes down to the concept on entropy, which is what Brian Cox spent most of that program talking about. The universe started out in a highly ordered state (we don't really know why) and statistics tells us it must be becoming steadily more and more disordered. Both storing memories and breaking eggs increase the disorder in the universe, so they happen in the same direction.

The idea of reversing the direction of time doesn't make much sense. You can change all the t's in your equations to -t's, but that won't actually change much (see T-symmetry). You can define time to be going in the opposite direction, but that just means you would remember what you define to be the future rather than what you define to be the past, so your perceptions wouldn't actually change (you would still remember intact eggs, not broken ones).

--Tango (talk) 15:17, 16 March 2011 (UTC)

The arrow of time article (distinct from entropy (arrow of time) covers the various definitions. Musing over the arrow of time became popular with Stephen Hawking, I think his A Brief History of Time. Wnt (talk) 15:26, 16 March 2011 (UTC)

The best exposition of what reversing the arrow of time would look like, IMHO, is the episode "Backwards" from Red Dwarf. --TammyMoet (talk) 16:16, 16 March 2011 (UTC)

That episode was completely unscientific (of course, it wasn't intended to be otherwise). They had people in the same universe with some remembering the past and some the future. That violates the 2nd law of thermodynamics. --Tango (talk) 17:02, 16 March 2011 (UTC)

Merlin in The Once and Future King lived backwards in time. He was getting younger as everyone else got older. 92.15.26.91 (talk) 20:53, 16 March 2011 (UTC)

Just to note...I watched this episode of the Wonders of the Universe series last night ('destiny') and I was not left in the slightest with the impression that nobody understood 'why' time went in one direction. There was a good 15-20 minutes dedicated to describing Entropy. (or have I misunderstood the question/show?) ny156uk (talk) 21:16, 16 March 2011 (UTC)

Energy Catalyzer

Is the Energy Catalyzer a hoax, or just bad science? 148.177.1.210 (talk) 13:23, 16 March 2011 (UTC)

If it was just bad science, the authors would at least try to get their work published in a real peer-reviewed journal. Instead, they created a blog entitled "Journal of Nuclear Physics" to seem like they're publishing their work in a reputable place. I'd call that behavior unethical and hoax-like. Nimur (talk) 13:53, 16 March 2011 (UTC)

Their patent application looks like it will fail because the inventors didn't adequately describe their device's construction, nor did they present appropriate evidence that it works as claimed: [23]. The difference between a 'hoax' and 'bad science' is, I would say, down to whether or not the inventors really believe their own claims. (A similar distinction exists at the fringe of the medical profession when one distinguishes a 'quack' from a 'fraud'.) TenOfAllTrades(talk) 15:12, 16 March 2011 (UTC)

How effectively can control rods stop fission?

It might be yet another question about the Japanese reactor malfunction, but I can't find any article which addresses this issue: as far as I know, if the control rods are fully inserted, they stop the reaction by capturing the neutrons which cause the fission. Weren't the control rods inserted in the case of the current accident? I assume they were, as most the news sources say the reactors were stopped at the first warning, before the quake hit. So, if the reaction is stopped, what causes the overheating? I know it might not be an instantaneous stopping of the fission, but what exactly is generating heat even after many days after the malfunction? I know the reactors are hot and don't cool themselves quickly, but something is generating heat, doesn't it? --87.169.20.137 (talk) 15:33, 16 March 2011 (UTC)

Yes, the reaction is stopped. (The residual neutrons that avoid the control rods are of little consequence for the total energy balance.) The problem is that nuclear reactor generated a lot of unstable radioactive isotopes during its run. It is the decay of these isotopes that generates the heat after the control rods are inserted. This heat is known as decay heat, and there is really nothing one can do to avoid it. All you can do is wait for the various fission fragments and such to decay to a more manageable level. Dragons flight (talk) 15:41, 16 March 2011 (UTC)

The heat is generated by spontaneous decays of the radioactive material. That is, a nucleus in an atom sends out a particle at high energy, which heats the surrounding material. This is as opposed to fission, where a neutron from outside hit and shatter a nucleus. As Dragons flight says, you just have to wait for this to cool down. Interestingly this means that the severity of the situation is slowly but steadily decreasing. This must feel like gratingly bad choreography for the news media, which wants the perceived risk to increase, so as to keep our attention. EverGreg (talk) 15:47, 16 March 2011 (UTC)

In Japan, with one new nuclear reactor exploding or burning down each day and increasing radiation levels and evacuations, the media are doing fine for stories. See also Timeline of the Fukushima nuclear accidents. The government coverups, company misdirections and simple lack of understanding at Chernobyl and 3 Mile Island provided plenty of news fodder as well. 75.41.110.200 (talk) 16:07, 16 March 2011 (UTC)

(ec) That is not the only source of heat - remember the rods are filled with uranium and, in one reactor, a bit of plutonium, that is constantly fissioning all on its own. The "chain reaction" is stopped by the control rods but natural radioactive decay will persist for thousands of years. 75.41.110.200 (talk) 16:02, 16 March 2011 (UTC)

Although it will only be acutely quite dangerous and hot (e.g. require being kept in a spent fuel pool) for a few decades. The heat is not caused by plutonium spontaneous fission (which is not that much), but all of the fission products that are in there. --Mr.98 (talk) 16:24, 16 March 2011 (UTC)

Even the MOX fuel reactor has only a couple percent plutonium; its almost all Uranium. 75.41.110.200 (talk) 16:37, 16 March 2011 (UTC)

I was under the impression you were referring to the plutonium content of the spent fuel. It is only 1% or so. The spent fuel is itself some 96% uranium. Most of the heat and immediate radioactivity, though, comes from that 3% or so of fission products, really nasty stuff that is very unstable. That's the stuff that mostly burns itself out after 20 years or so, leaving only the stuff that is radioactive in the very long term, but not as "hot". --Mr.98 (talk) 18:32, 16 March 2011 (UTC)

The danger of the current situation is not that they are unexpectedly hot, but that the reactor cores have at various times been exposed (without coolant). That allows the spent fuel in them (chock full of fission products) to get dangerously hot and dangerously radioactive. If it gets too hot and causes parts of the core to melt (the "meltdown") that can create new problems, e.g. spent fuel pooling on the bottom of the reactor vessel, which can create its own criticality problems. If there wasn't a coolant problem, the reactor would still be "hot" but not hot enough to cause any trouble. The problem is the coolant, not that the reactors are "out of control" in the chain reacting sense. --Mr.98 (talk) 16:27, 16 March 2011 (UTC)

"and dangerously radioactive" - exposed rods are not more radioactive. They may release more radiation or radioactive compounds in places where you don't want them but they don't increase in rate unless there is a criticality event. High temperatures, in fact, make criticality harder to achieve. See Critical mass#Changing the temperature 75.41.110.200 (talk) 16:37, 16 March 2011 (UTC)

Well, pedantically: the rods are dangerously radioactive as it is. The coolant water shields quite a lot of that. The removal of coolant means your radioactivity is going to be higher in places it wouldn't otherwise be. The relationship between temperature and criticality is not entirely germane here — it's not a question of trying to create a critical mass deliberately, but the mechanical action of melting the spent fuel or its containment. Which is bad for a number of reasons, criticality included. --Mr.98 (talk) 16:49, 16 March 2011 (UTC)

I don't think the difference is unimportant. The amount of misinformation increases with every news report - most of the "science experts" are getting things wrong as well. And I think you just agreed with everything I wrote. 75.41.110.200 (talk) 17:01, 16 March 2011 (UTC)

Yes, we agreed with each other. It was just clarification on both of our parts, in the end. :-) --Mr.98 (talk) 18:32, 16 March 2011 (UTC)

The possible melting of the fuel rods due to the secondary decays is sometimes referred to by china syndrome, but in that case Brazil syndrome might be a more appropriate moniker. Dauto (talk) 19:39, 16 March 2011 (UTC)

Well, the term China syndrome never did make much sense, given that it was implicitly meant to talk about reactors in the United States. No antipodal point of the United States is anywhere near China (easiest way to see this: Both the US and China are entirely in the Northern Hemisphere). If you take the United States and project it over to its antipodes, your projected image is mostly in the middle of the Indian Ocean.

(Does anyone know where this "straight through to China" meme originates?) --Trovatore (talk) 00:42, 18 March 2011 (UTC)

It's covered in the china syndrome article. --Tagishsimon (talk) 00:46, 18 March 2011 (UTC)

Well, not really. The article says that the name comes from the fictitious notion that "the other side of the world" is China. But my parenthetical question was where that notion (which is certainly much older) comes from.

It froze clean through to China

It froze to the stars above

At a thousand degrees below zero

It froze my logger love -- old song

--Trovatore (talk) 01:15, 18 March 2011 (UTC)

Strictly speaking, the melting of fuel is just a meltdown. The China syndrome is a specific subset of meltdowns where the material actually burns through the containment dome. --Mr.98 (talk) 21:38, 16 March 2011 (UTC)

Bird ID help...

So, my 4-year old asked for the name of a bird we saw today. We live in Raleigh, North Carolina. Sadly, I didn't get a picture, but I'll try to describe it the best I can. It was a passerine bird, shaped and sized like a Blue Jay, except it didn't have the tuft on top of its head, the head was perfectly round. The coloration was more like a Carolina Chickadee, i.e. all black and white and gray, but it wasn't shaped or sized like a chickadee, and it didn't have a chickadee's call. Two of them were fighting in my front yard, and they made sounds like a raspy back-of-the-throat sound, almost like the german or scottish 'ch' sound, but a longer in duration. If I can get a pic, I will take one and upload it, but right now does that sound familiar to anyone? To sum up, a bird roughly the same size and shape as a Blue Jay, with a round head, black and white coloration, which makes a distinctive "back-of-the-throat hiss" sound when agitated. Location: Raleigh, NC. Thanks to any help anyone can give... --Jayron32 17:57, 16 March 2011 (UTC)

Wild guess—do the pictures at Northern Mockingbird look anything like it? Deor (talk) 18:08, 16 March 2011 (UTC)

The shape is about right, but the neck on my bird was a bit longer, and the coloration is wrong. This one had more black around the head, and more sharply defined bands on the wing. Perhaps another kind of mockingbird? I'll follow that thread... Any other suggestions out there? --Jayron32 18:17, 16 March 2011 (UTC)

Magpies are corvid like blue jays, and have black and white markings. They tend to be a bit larger than jays, and are known to bicker and fight. (I'm not sure what species might be in the Carolinas at present) SemanticMantis (talk) 18:51, 16 March 2011 (UTC)

Yeah, I looked at Magpies, and that wasn't it either... Those have too much black, and the bill is too crow-like; these had a more jay-like or mockingbird-like bill. In fact, if the magpie fucked the mockingbird, you might imagine that offspring would look more like this bird. This one had a black stripe on the head, or maybe a black head, but the neck itself was more slender than the magpie, and the black did NOT extend to the neck. --Jayron32 19:32, 16 March 2011 (UTC)

Another clue: In my searches, the closest I can find (and it is pretty close in appearance) is the Gray Jay, which looked very much like my bird, but that bird doesn't have a range anywhere near North Carolina; and I have seen enough of these birds this year and in years past to indicate that this was not an accidental; these birds are common enough around here. So: does anyone have any clues on a bird which looks a lot like a Gray Jay but which lives in North Carolina at this time of year, and which makes the sound I noted above? --Jayron32 19:38, 16 March 2011 (UTC)

The problem is, you know what the critter looks like and we don't. Your mention of a "black stripe on the head" above made me think of the Loggerhead Shrike, but that's just another guess. We have a List of birds of North Carolina; you may want to peruse that. Deor (talk) 20:07, 16 March 2011 (UTC)

When you say that the colouration was like a chickadee, do you mean that it contained the same kind of colours or that the patterning was similar (i.e. with distinctive black cap and throat patch)? I'm going to chime with Hairy Woodpecker (and other woodpeckers) as something to check out, if only because it's technically not a perching bird and so might get overlooked, but is still shaped much like a passerine bird. Matt Deres (talk) 13:43, 17 March 2011 (UTC)

For another resource, whatbird.com has a great interface to its database, and an expert forum, so you might have better luck there. (can't link direct, it's on the spam list for some reason) SemanticMantis (talk) 13:54, 17 March 2011 (UTC)

Thanks for all your help guys! Unfortunately, my memory of the bird is fading, and all of these pics are starting to run together for me. Lesson learned: next time I'll get a pic. But I really do appreciate everyone that chimed in with suggestions! --Jayron32 18:18, 17 March 2011 (UTC)

Speed of WiFi

Would it be terribly incorrect to suggest that wireless signals — for cellphones, computers, what have you — travel through the air at roughly the speed of light? I know that this is not the speed of information transmission, and that I am speaking of the speed of light in atmosphere (not a vacuum). --Mr.98 (talk) 18:28, 16 March 2011 (UTC)

They travel through the air at exactly the speed of light in atmosphere, not just roughly. Note that while the signal travels at that speed, that isn't necessarily the speed at which information can be exchanged along WiFi signals; such information throughput is limited by things like bandwidth, both Bandwidth (computing) and Bandwidth (signal processing) are relevent to the idea. So, yes the speed at which the signal travels is exactly the speed of light, but the speed at which information can be exchanged between nodes in a network is significantly slower than that. --Jayron32 18:31, 16 March 2011 (UTC)

Thanks, that's what I thought, but I was afraid I might be being a dope if I were to say such a thing. --Mr.98 (talk) 18:33, 16 March 2011 (UTC)

You can't compare the speed of light (dimensions: distance/time) with the speed of information exchange (dimensions: bits/time). The time it takes for signals to travel from A to B affects the latency, not the throughput. Latency is, of course, caused by a lot of other things as well, which will usually have a greater impact - speed of light issues are relevant when you are going via a satellite, but that's about it. --Tango (talk) 18:36, 16 March 2011 (UTC)

Jayron, can you explain why the atmosphere has no effect on wave speed, as opposed to a tiny/negligible effect, as implied by Electromagnetic_radiation#Wave_model? — Preceding unsigned comment added by SemanticMantis (talk • contribs) 18:40, 16 March 2011 (UTC)

I assume by "They travel through the air at exactly the speed of light in atmosphere" he meant light and wireless signals go at the same speed in the atmosphere - but less that the "speed of light" (in a vacuum). Grandiose (me, talk, contribs) 18:43, 16 March 2011 (UTC)

Thanks, I will now read more carefully before posting follow-up questions :) SemanticMantis (talk) 18:54, 16 March 2011 (UTC)

(EC x 3) In short, no, that would not be terribly incorrect--Radio_waves says "Like all other electromagnetic waves, they travel at the speed of light." However, Electromagnetic_radiation#Wave_model says "speed of the wave (c in a vacuum, or less in other media)", which is an apparent contradiction. My understanding is that, in the atmosphere, EM waves 'effectively' propagate at the speed of light, but if you measure carefully, the speed is less, e.g. 0.999999999999999999999999c SemanticMantis (talk) 18:37, 16 March 2011 (UTC)

According to the 2nd paragraph of speed of light it's about 0.9997c. --Tango (talk) 18:50, 16 March 2011 (UTC)

I'm highly skeptical that radio waves travel at exactly the same speed as light in the atmosphere. That assumes that the atmosphere has the same refractive index for all wavelengths. Even over the visible spectrum, this is demonstrably false: we have rainbows. --99.237.234.245 (talk) 19:14, 16 March 2011 (UTC)

Radio waves are light. They are not visible light, but the sensitivity of the cells at the back of your retina to them doesn't make the light itself fundementally different. Yes, as you note, the speed of a light wave through a medium, like the air, is dependent on the wavelength of that light, it's why the different colors of the rainbow are split by a prism; as white light passes through the prism, the different wavelengths slow down to different rates of speed, which causes them to seperate out. However, such an effect is mathematically predictable; and if you know the refractive index of the medium and the wavelength of the light in question, you can calculate the actual speed of that specific wavelength. A discussion of how to do so is covered at Refractive_index#Speed_of_light. This calculation works whether you are doing it on light at 600 nanometers (yellow) or 125 millimeters (2.4 GHz WiFi). So, while the speed of the light waves carrying the Wifi signal do travel slower than, say, the speed of yellow light waves in the same atmosphere, the speed of the Wifi signal travels at exactly the same speed as all light waves of that frequency in that medium. So to answer the OP's question, pretty much exactly as I answered it, but with less ambiguity: The speed of the WiFi signal through the atmosphere is exactly the speed of that wavelength of light through the atmosphere. --Jayron32 19:28, 16 March 2011 (UTC)

No, Jayron. That effect cannot be mathematically calculated and the article you site describes un important relation which cannot by itself be used to predict the effect from first principles. A detailed model of how the electrons in the matter interact with the light must be used as well. Or it can be experimentally measured which is much easier. Dauto (talk) 22:41, 16 March 2011 (UTC)

OK, so that part's a bit wrong. But the radio portion of the light spectrum is still light and signals travel at the "speed of light" in whatever medium it is, regardless of what that speed is, and what complicated calculations or experiments you need to determine it. Our ability or inability to do the calculation doesn't change the fact that it is still 100% accurate to say that the WiFi signal, being itself light, will travel at the local speed of light, whatever it is... --Jayron32 15:39, 17 March 2011 (UTC)

Down here at sea level (and in fact, at all altitudes that humans normally go to), it's safe to say that radio frequencies, ranging from the low-frequencies (ULF, VLF, and so on, at 300 - 30 kHz), up to High Frequency (10 MHz) up to VHF, UHF, microwave, and so on, (essentially, all frequencies from ~ 300 Hz to 30 GHz) travel with the same speed in atmosphere. Their attenuations depend highly on frequency, but their speed in air is essentially the same as the speed in a vacuum (at least, let's say, to "several decimal places"). As has been pointed out, this is something like 0.9995 c (in other words, for many practical purposes, equal to the speed of light in a vacuum). This is mostly because at such long wavelengths, the wave "doesn't even see" the neutrally-charged atoms of the atmosphere. If you send the wave through non-atmospheric conditions, especially if there are free electrons and ions, (like when you're beaming signals through the ionosphere, about 100 kilometers above sea level), then you start getting neat frequency-dependent wave propagation speeds, because the air molecules interact with the radio signal. This causes the skywave effect, among numerous other electromagnetic phenomena.

Also, once you get past the millimeter-wave / micro-wave band, and start hitting long infrared and visible light, regular sea-level atmosphere does actually behave non-ideally. This is, of course, because the wavelength of infrared and visible light is very close to the scale-lengths for atmospheric molecule interactions. So, if you get to higher frequencies (like infrared, visible light, ultraviolet), then molecular interactions and scatterting cause frequency-dependent index of refraction. Hence, blue sky, red sunsets, seeing light bend over-the-horizon at dusk, and so on.

So - briefly summarized: in Earth atmosphere, all waves between ~300 Hz to 30 GHz travel at the same speed, which is very close to speed of light in a vacuum. In other conditions, or at other wavelengths, various non-trivial interactions cause frequency-dependent wave speed. Nimur (talk) 16:31, 17 March 2011 (UTC)

What substance has the highest known melting point?

What substance has the highest known melting point?

Our article Tantalum hafnium carbide stakes its claim, but its source is the Encyclopedia Britannica, and even the EB article only says it's "one of the most refractory" chemical compounds.

(I was looking this up out of curiosity because of the ongoing meltdown, of course, and then wanted to add a mention of the record-holder to our melting point article.) Comet Tuttle (talk) 18:45, 16 March 2011 (UTC)

Well, some substances can't assume a liquid state at any temperature, and even for those that can, the melting temperature is a function of pressure. Basically there are three ways for a solid to change state: (1) melting; (2) sublimation; (3) breakdown of internal structure. Since even atomic nuclei will break down at sufficiently high temperatures, I would guess that the substance at which a solid-to-liquid transition occurs at the highest temperature would be neutronium (at extremely high pressure). Looie496 (talk) 21:09, 16 March 2011 (UTC)

I'd throw in my vote for the ultra-high temperature ceramics, which are an entire class of materials. These include hafnium diboride, zirconium diboride, and some similar materials. These materials usually ablate before melting; their phase transition characteristics are complex (sort of entering a "glassy" amorphous phase which might be considered fluid-like). Here's a NASA report on their material properties - they sort of "melt" (braze) in contact with certain metallic lattice faces, but never actually "liquify." Nimur (talk) 21:18, 16 March 2011 (UTC)

I'm not sure it's really meaningful to talk about neutronium as being a solid; our article on degenerate matter describes it as a degenerate neutron gas, but 'fluid' might be suitable as well. TenOfAllTrades(talk) 00:14, 17 March 2011 (UTC)

Sorry, I should have clarified that I was curious about materials' melting points under "normal" conditions, say, at 1 atm. Comet Tuttle (talk) 06:01, 17 March 2011 (UTC)

Maybe what you really want is the substance that remains solid and holds its strength through the highest temperature, at one atmosphere. That gets around all the quibbling about things that sublime or decompose rather than melting. --Trovatore (talk) 06:13, 17 March 2011 (UTC)

When evaluating materials also pay attention to what happens to them under neutron bombardment. Ideally you want to use elements that can't become radioactive for long (so zirconium is out). You also want materials that don't become too weak (or that can be annealed easily). Ariel. (talk) 09:11, 17 March 2011 (UTC)

Tungsten and Platinum have long been valued as non-exotic and non-theoretical metals with fairly high melting points. Edison (talk) 05:14, 18 March 2011 (UTC)

Where are the robots?

Japan appears to be the world leader in robot technology. So why arent remote-controlled robot things being sent in to fix the nuclear reactors? 92.15.26.91 (talk) 21:50, 16 March 2011 (UTC)

Because robots take a while to be planned and built. And I don't think it's quite as easy as just sending a robot in and fixing it. --T H F S W (T · C · E) 21:54, 16 March 2011 (UTC)

You're right it wouldn't fix the problem but I guess robot/s may be helpful to continue to try and cool the reactor when there are temporary radiation spikes which require the removal of workers if they had them (which they don't). Just don't use ones with most types of lithium ions batteries... Nil Einne (talk) 22:07, 16 March 2011 (UTC)

You'd think at least we could have some of those bomb robots from Iraq in there, just keeping an eye on the fires. Wnt (talk) 00:10, 17 March 2011 (UTC)

Rest assured, the robots are being put to work in disaster recovery any way they can. See e.g. this blurb from IEEE Spectrum: [24]. SemanticMantis (talk) 00:09, 17 March 2011 (UTC)

But as far as the reactors are concerned, Asimo Asimov taught us that positronic brains are even more susceptible to damage from sufficiently intense gamma radiation than humans are. -- 110.49.241.128 (talk) 00:55, 17 March 2011 (UTC)

Robots tend to have to be designed for a specific purpose. I guess no-one anticipated the current problems or thought them likely enough to design robots to deal with them. --Tango (talk) 01:10, 17 March 2011 (UTC)

I certainly hope they do after this incident. ScienceApe (talk) 03:21, 17 March 2011 (UTC)

One thing worth noting about robots: even if we have exactly the prototype to churn out, having complex self-powered joints move around substantial amounts is extremely sensitive and prone to breakdown. The director of Death and the Powers gave a seminar here and noted, when asked if robots would take over the world, that he'd be happy if he'd have one week when a robot didn't break down on stage. SamuelRiv (talk) 04:37, 17 March 2011 (UTC)

Nuclear power is no more dangerous today than it was two weeks ago. If it wasn't worth it to develop such robots two weeks ago, it isn't worth it today. --Tango (talk) 22:21, 17 March 2011 (UTC)

Would you like to be at a nuclear plant that might meltdown and is leaking dangerous radioactive material into the environment? If you would, I'm sure Japan would love to have your assistance at Fukushima to help prevent a catastrophe. Personally I think investing in robots that can handle dangerous work like this is worth it. ScienceApe (talk) 22:38, 17 March 2011 (UTC)

Its a pity that no-one appears to have a remote control device that you can just clip into a standard vechicle such as a bulldozer or tractor, or even a tank or riot-control water-cannon wagon, in place of the driver. Even something crawling along at 1mph would be very useful. Wouldnt a tank offer the crew protection against radiation? 92.24.180.239 (talk) 15:15, 17 March 2011 (UTC)

Well steel is better then nothing, and I suppose you could always upgrade it with some lead additions, but after a while, you have a radioactive tank that you need to stash somewhere away from people, but I am not really sure what a couple people in a tank are going to be able to help anything without leaving the tank. Unless it is like a bulldozer engineering unit tank. Googlemeister (talk) 19:04, 17 March 2011 (UTC)

BoingBoing covered this very issue today. Main conclusion: "robots and power plants have to be designed with each other in mind. Fukushima Daiichi, which dates to the 1970s, may simply not be navigable to newer nuclear helper 'bots." --Tagishsimon (talk) 22:24, 17 March 2011 (UTC)

There should be proper robots built for the purpose but they will need very good protection from radiation. As far as I know any electronics they tried to use at Chernobyl failed very quickly indeed in the order of minutes. It's quite horrifying that they used humans for instance to look at things where video cameras wouldn't work. Dmcq (talk) 23:56, 17 March 2011 (UTC)

It was apparently cheaper for the Japanese power company involved to do little in regard to providing remote operated equipment, in favor of letting workers injure their health by large radiation exposure. For instance: a boom truck, remotely operated, could have used a demolition tool to cut a hole in the masonry panels surrounding the top of the reactors. This would have allowed air circulation and prevented the hydrogen explosions that demolished the tops of the buildings. Then, guided by a TV camera, a water spray could have been used to refill spent fuel pools thought to have little or no water. Instead, there was a silly attempt to use helicopters to drop seawater on the roofs of the buildings, with only a tiny fraction even hitting the roofs, with radiation exposure to the flight crews such that the efforts were suspended. Then police "antiriot water cannons" were used to spray water in the general direction of the buildings, but the radiation levels were too high to get very close for very long, and it did little good. (Does Japan have lots of riots where water cannons are needed, like Soviet satellite states used to?) It all evokes images of trying to fix an overheated car radiator by throwing a bucket of water at the car, with the hood only slightly ajar. There are bomb disposal robots and firefighting robots aplenty, with remote control and remote TV viewing. If a wall panel were removed, such a tracked device could have been inserted via a boom truck. We have had remote operated devices on Mars for years, for pity's sake, going around and sending back 3D color pictures, and cutting into things. We have seen teleoperated submersibles in the Titanic. There are even teleoperated robotic soldiers, which can shoot at the enemy or retrieve wounded soldiers. We have had the Darpa Challenge, with true autonomous robotic vehicles driving all over a town, obeying traffic signals, and in and out of parking garages. Google has operated autonomus cars for over 100,000 miles on California highways. The Space Station has teleoperated devices to assist the astronauts, with the ultimate aim of maintaining the station when no humans are on board.How much easier where all that is needed are teleoperated devices to send back pictures and thermal images, and aim hoses. How much progress has the nuke industry demonstrated since the post-Three Mile Island robotics developments? Why must they call on humans to "make the supreme sacrifice" rather than showing some initiative in developing and applying robotics and remote operated devices? Yeah, Japan has lots of cute little Asimo robots which dance around, but no apparent development and deployment of anything useful in a situation like the Fukushima 1 mess. A remote operated crane and a remote operated cutting torch on a boom truck could clear away the twisted structural steel overlaying one of the reactors after the hydrogen explosion, so that the concrete of the containment would be exposed, allowing better viewing and access to the spent fuel pool. Edison (talk) 04:56, 18 March 2011 (UTC)

March 17

How often does Sansevieria trifasciata bloom?

How often does Sansevieria trifasciata (snake plant) bloom? My mother has one that is blooming now and she says that it is rare. Bubba73 ^{You talkin' to me?} 01:04, 17 March 2011 (UTC)

When grown as a houseplant, the period between blooms is highly variable, based on sun exposure, and how root-bound it is in its container. I'm sure you could not see a bloom for several years in some cases, especially if starting from a small clone in a large pot. Under 'average' houseplant conditions for a mature individual, expect a bloom every 2-4 years. They are more likely to bloom the more root-bound they are, because this is when they have reached the limit of vegetative growth. Note that it spreads rapidly through clonal growth in its natural environment, so sexual reproduction every year is not critical for long-term population success. Also, as a side note they have nectaries on the base of each flower on the raceme, which each produce a large drop of sweet nectar. Your mother may enjoy trying some; it tastes much like honey :) SemanticMantis (talk) 02:32, 17 March 2011 (UTC)

This one is in a small pot but it gets plenty of sunlight (next to a picture window). Mother says that she has never seen one bloom. She had me take photos to show the women in the beauty shop to prove that it does bloom. Bubba73 ^{You talkin' to me?} 02:58, 17 March 2011 (UTC)

I should have flagged (OR) above, maybe 2-4 years is a bit optimistic, as it is in the same family as the century plant, which is known for its long bloom interval. The bloom definitely feels special when it happens. SemanticMantis (talk) 14:00, 17 March 2011 (UTC)

That helps explain it, thanks. Bubba73 ^{You talkin' to me?} 15:37, 17 March 2011 (UTC)

Scent

I'm a hunter and I know how good an animals sense of smell is. My question is, all else considered, does hair make it easier for an animal to smell you? I heard it helps to vaporize it, which sounds bad, as that odor no doubt travels.

Any help would be appreciated, and if you know of any odor blockers (not stuff that leaves you smelling like perfume, but true blockers) I'd be much obliged. —Preceding unsigned comment added by 148.61.220.214 (talk) 01:08, 17 March 2011 (UTC)

Body odour is increased by the presence of pubic hair. That has even been proposed as the reason we have pubic hair. --Tango (talk) 01:24, 17 March 2011 (UTC)

Maybe for our naked cave-dwelling fore-bearers, but wouldn't the clothing of a hairless human absorb and hold odors just as well as, if not better than, body hair?

I assume he's not talking about shaving his body and then going out into the woods nude. APL (talk) 02:11, 17 March 2011 (UTC)

Here's a blog called ArcheryTalk that discusses this issue from a bowhunter's perspective. The author discusses five main strategies in further detail there:

1. Cleanse – Your body……..
2. Neutralize – Odor causing Bacteria…….
3. Maintain – Clean clothing/footwear…….
4. Mask – We’ll talk about this one……
5. Play the wind – Enough said………

He "neutralizes" by scrubbing down with an antiseptic like Betadine, and claims that a product called 'Bob’s “Skunk Essence”' works as an effective mask for him.

Also, as far as hair-odor-blockers, here's a plug for the product Invisible Hunter Shampoo^tm:

"Sometimes overlooked, human hair carries odors from not only one’s own body but from other environments that one has visited. A good practice of shampooing with Invisible Hunter’s Scent–Removing Shampoo is all you need to eliminate dirt and odors. Invisible Hunter’s Scent-Removing Shampoo will leave your hair clean and soft while providing you the extra scent control the serious hunter seeks."

WikiDao ☯ 04:20, 17 March 2011 (UTC)

Just curious, how do you get rid of the skunk essence smell. Great in the woods, real bad at home! Richard Avery (talk) 12:00, 17 March 2011 (UTC)

Real hard-core hunters wouldn't care about that. Real hard-core hunters are also probably single. (If not, see No true Scotsman) :-) . {The poster previously known as 87.81.230.195} 90.197.66.165 (talk) 01:48, 18 March 2011 (UTC)

Thanks, all. I like your comment though that clothes themselves would be a big issue...Do you know some products specific to cleaning your clothes, but not leaving it smelling like Tide, either? Thanks again. —Preceding unsigned comment added by 148.61.220.214 (talk) 03:25, 18 March 2011 (UTC)

More examples of millisievert doses?

I am skeptical of Sievert#Yearly_Dose_Examples-- for example, how could "some parts of Iran" naturally have half the carcinogenic dose? Can anyone find a good source for this kind of information? Shii (tock) 01:10, 17 March 2011 (UTC)

What you are calling the "carcinogenic dose" is the dose at which the probability of you getting cancer is measurably higher than normal. It isn't much higher, though. It is still an insignificant dose as far as individuals are concerned (other factors, such as diet and lifestyle, affecting cancer cause far more variation from person to person). When you look at a large number of people, it becomes significant, but only just. --Tango (talk) 01:21, 17 March 2011 (UTC)

Seems reasonable to me. Why do you find that so surprising? Dauto (talk) 03:01, 17 March 2011 (UTC)

The figure "Background radiation in parts of Iran, India and Europe: 50 mSv/year" sounds somewhat high to me, even though it comes from a BBC source - a value that high must be very localised. Our article on Ramsar, Mazandaran says "Some areas around Ramsar have the highest level of natural radioactivity in the world, due to the presence of radioactive hot springs ... the medium value in the Ramsar area is 10.2 mSv/year" - although background radiation levels in and around the springs themselves can be much higher. Gandalf61 (talk) 07:12, 17 March 2011 (UTC)

Full meltdown?

According to this, http://www.cnn.com/interactive/2011/03/world/interactive.nuclear.japan/index.html?hpt=C2

Three mile island and Chernobyl were only partial meltdowns. What's a full meltdown? This never happened? I always thought Chernobyl was a full meltdown. How far deep can a meltdown melt through stuff? ScienceApe (talk) 02:50, 17 March 2011 (UTC)

Nuclear meltdown refers to the heating of the Nuclear reactor core to the point where it melts; i.e. turns to a liquid. In a partial meltdown, parts of the core would melt, and other parts would remain intact. In a total meltdown, the entire core would be a pool of liquid at the bottom of the reactor; AFAIK this has never yet happened. In Chernobyl, the problem wasn't no much a meltdown, which is a serious but managable event, it was the excursion (i.e. the fissile material reached criticality) which damaged the containment security in the plant and allowed radioactive material to be sent into the atmosphere. Indeed, our article on the Chernobyl disaster doesn't even mention a meltdown, except briefly in passing. Indeed, an excursion (basically the reactor turns into a bomb) is a far more serious event than a meltdown; once the reactor core exploded, whether or not it melted is somewhat moot. --Jayron32 03:01, 17 March 2011 (UTC)

Side-questions: I'm kind of kidnapping this question, but the questions about nuclear reactors are a hot (sorry for the pun) topic this week. So, here for the questions: (1) if we let it meltdown, wouldn't this bore a hole and let the atomic material slip through this hole, and in the same process, cover it with other molten substances? Sounds pretty optimistic, I know. (2) Have anyone let a small core meltdown to test the question (1)? (worse experiments indeed happened) Quest09 (talk) 18:15, 17 March 2011 (UTC)

1. Probably not. I mean if you put a pile of melted nuclear fuel it might burn down into the earth, but unless the nuclear pile is actually vaporizing everything it touches, how is the dirt and rocks and such going to get out of the hole? Plus all the stuff you are melting is becoming radioactive at the same time. 2. I would really, really hope not. That sounds like a very expensive experiment with potential to cause enormous environmental damage and large negative impacts to human health and for what real purpose? Googlemeister (talk) 19:00, 17 March 2011 (UTC)

See corium. Once the fuel melts, you get a radioactive slag of fuel oxides plus everything else the fuel encounters. If the molten corium encounters water (say, the suppression tank underneath the reactor) you get a steam explosion that spreads a radioactive dust over a huge area. --Carnildo (talk) 23:29, 17 March 2011 (UTC)

Earths axis

Does the 6.5 inch shift in the earths axis from the earthquake create any changes, such as change in seasonal patterns or tides? —Preceding unsigned comment added by 68.36.96.146 (talk) 03:02, 17 March 2011 (UTC)

The circumference of the earth is roughly 40,000,000 meters. 6.5 inches is .1651 meters. .1651/40,000,000 = 0.0000000041275 or 4 parts per billion variation. That's pretty imperceptible. --Jayron32 03:08, 17 March 2011 (UTC)

In a related note, I've been trying to find out which way it's shifted. Here in Connecticut, am I closer or farther from equator? APL (talk) 07:36, 17 March 2011 (UTC)

It means Mrs. Claus is yelling at Santa to get his fat ass off that Nintendo game and go out there and move that pole! Wnt (talk) 17:14, 17 March 2011 (UTC)

Jayron, thanks for enlightening us on the imperceptibility of 6.5 in. in relation to the circumference of the earth. Does someone else care to answer the straightforward question? it obviously is different that before, so what does that difference equate to in more or less sunlight each day for the northern hemisphere? —Preceding unsigned comment added by 165.212.189.187 (talk) 17:28, 17 March 2011 (UTC)

The Earth's axis already shifts seasonally (at a greater magnitude than caused by the Earthquake, I believe), due to the rearrangement of mass caused by the weather (mostly the redistribution of water, I believe). Here are a couple articles on it, though they relate more to the change in day length than the axis shift [25], [26]. As these articles point out, pretty much every earthquake redistributes the mass at least some, but you can also see that the changes are on par with the yearly variation that is experienced anyway, regardless of earthquakes. The answer is definitely "no", this Earthquake will not have a noticable effect on seasonal patterns or tides. Buddy431 (talk) 18:03, 17 March 2011 (UTC)

Addendum: Here's a source that explicitly addresses the axis shift issue: the Earth's axis shifts about 3.3 ft seasonally, about 6 times the shift caused by the quake. Richard Gross, a Geophysicist, says "These changes in Earth's rotation are perfectly natural and happen all the time. People shouldn't worry about them." [27] Straight from the mouth of a real scientist. Buddy431 (talk) 18:07, 17 March 2011 (UTC)

This shift is in addition to the regular shift of the seasons. Who said anything about worrying, what did he say about curiosity, that it killed the cat? That is why this desk exists - to inform and enlighten not easy worrys of. —Preceding unsigned comment added by 165.212.189.187 (talk) 18:24, 17 March 2011 (UTC)

And it's doing a great job - who knew that the Earth's axis moves? Or that there was both an axis and a figure axis to keep track of? Wnt (talk) 23:32, 17 March 2011 (UTC)

Storing electricity via “counterbalance” batteries?

Some time ago, I asked about the viability of using dams to augment sporadic electricity production via windmills and solar panels. The method is used in Sydney. When more than enough power is being produced, the power not needed is used to raise water to storage dams, where it can later be used to create hydroelectric power. This is, in effect, a battery, and I was surprised that it returned about 70% of the power it took to raise the water. Now, there are other ideas for batteries, as not all that many sites have big dams nearby.

My idea is: when the wind is strong and more power than is needed is being produced, why not have the mill raise a heavy weight chained below the vanes? When power is needed later, the weight can be slowly lowered, turning the vanes via gears and generating electricity.

I did read in New Scientist, years ago, in one of their historical featurettes, that in the early 20th Century, there were at least some English farmhouses which had a wind mill such as I have described on their thatched roofs. When the vanes turned, they could raise a weight, enclosed by a cylindrical cage located in the main room. When the wind died down, that weight could be allowed to slowly descend, generating electricity. I can’t find that source now, and I am wondering if someone knows anything about such an ingenious contraption. Myles325a (talk) 03:57, 17 March 2011 (UTC)

The idea's good - but the "engineering details" are hard. Gravitational potential energy is usually approximated as mgh - so pick some reasonable numbers for a mass (let's say, 10 tons), and a tower height (say, 100 meters); how much energy is that going to actually store? About ten megajoules of gravitational potential energy - about 3 kilowatt-hours. And that's a huge weight, and a really tall tower! Now, consider that one single barrel of oil contains (in the form of chemical energy) about one-thousand times as much energy as our massive 10,000kg, 100-meter-tall contraption!

To store a lot of energy in the form of gravitational potential energy, you need a lot of mass - which is why pumped storage hydroelectric is the only practical way to do it. Nimur (talk) 04:29, 17 March 2011 (UTC)

Myles325a's suggestion was used in practice for a couple of centuries in the longcase clock. I agree with Nimur that the attraction of using water is that vast amounts of it are available, and can be pumped into elevated storage. Solid components that could be used for storage of energy are miniscule compared with the mass that is available as water. Dolphin (t) 04:34, 17 March 2011 (UTC)

The use of such dams is not fondly regarded by environmentalists. Realize that such a system creates a large body of water without a shoreline, but just a large muck zone that is irregularly covered by water. Wnt (talk) 04:51, 17 March 2011 (UTC)

What exactly is the reason for the radioactivity?

I'm a little confused after having read Fukushima I nuclear accidents. If the containment vessels are indeed all intact, what exactly is the source of the radiation that has been detected? Is the problem that water within the containment vessel is being made radioactive as it flashes into steam and gets vented (as an emergency measure) because the pressure within the containment vessel is high enough? Wouldn't this mean the vented steam is riddled with decay products? I'm not very clear on whether this reactor design has water pumped directly at the fuel rods so there's essentially direct contact between the fuel rods and the water that gets flashed into steam and then spins the turbines. On reflection, I suppose it must. Doesn't this mean that these "containment vessels" aren't actually able to be sealed? Comet Tuttle (talk) 06:26, 17 March 2011 (UTC)

The main thing is that spent nuclear fuel is kept in open ponds with very little containment. That's where most of the radiation has come from - there's a lot more to be released from there than from the reactors themselves. This is mostly slovenliness - there are other countries which have moved largely to dry cask storage. It is well known that in any natural disaster (such as a major pestilence or all-out civil war) anywhere in the world, which would cause nuclear reactors to go unattended, eventually the reactor will shut down, the diesel backup will run out, and the spent fuel pools will go Chernobyl at every unattended site. In addition, the containment for #2 is cracked.^[28] Wnt (talk) 06:46, 17 March 2011 (UTC)

I only know of the Pebel bed reactors not using Spent fuel pools for the first few months or years. The heat generated for the first few half lives of the fast decaying isotopes is in an order of magnitude that all other methods are impractical. Most reactors store the spent fuel close to the reactor, this might change after the disaster.--Stone (talk) 07:22, 17 March 2011 (UTC)

I don't think it is "slovenliness" that dictates whether one uses wet storage. For one thing, Japan reprocesses — that usually dictates against dry storage. In any case, you need to store it in wet storage for awhile (at least a year) before you do anything else with it, so the really nasty stuff burns itself out. It's unclear to me how "old" the fuel in the wet storage is (you could calculate it if you knew the time between refuelings and the amount of spent fuel in there). --Mr.98 (talk) 15:01, 17 March 2011 (UTC)

Would someone more reliable than Wnt on physics-related subjects please confirm or deny what (s)he wrote above? Especially the claim that active cooling is the only defense against a Chernobyl-like disaster at any nuclear plant with a spent fuel pool? The article seems to say that this is false, but I don't know what to believe any more. -- BenRG (talk) 08:20, 17 March 2011 (UTC)

Yah I don't think he's right about that. Even if you left the reactor completely alone it wouldn't go Chernobyl. Especially once the control rods are in place a real catastrophe is pretty much impossible - and those rods are designed to fall into place at any disruption. It may melt down, but it will stay inside the containment. And the urnanium in storage can't go Chernobyl either. However it does seem that the containment pools are a weak spot. People paid a ton of attention to reactor design, and it looks like their designs worked. However the pools did not receive as much attention and most of the current problems (fires) are from those. Spent fuel pool#Status implies that someone noticed the problems and new designs are better. I have to assume that the Japanese fuel is not designed this way. Ariel. (talk) 09:03, 17 March 2011 (UTC)

To clarify, I used "go Chernobyl" to mean "produce all kinds of radioactive smoke and fire", not "break the reactor containment". I thought I was being clear there that the radiation would be coming from the pools. Wnt (talk) 10:34, 17 March 2011 (UTC)

Fukushima I nuclear accidents says:

"The nuclear fuel requires 1–3 years of constant active cooling (by flowing water) before the decay heat production gets low enough that effective passive cooling becomes sufficient to avoid excessive heating up to temperatures where the integrity of the fuel is at risk."

"At the time of the earthquake unit 4 had been shut down for maintenance and refueling since 30 November 2010. All fuel rods had been transferred in December 2010 from the reactor to the spent fuel pool on the top floor of the reactor building where they were held in racks containing boron to damp down any nuclear reaction. These recently active fuel rods were hotter and required more cooling than the spent fuel in units 5 and 6."

and mentions speculation "that the Fukushima management could have been engaged in an unsafe industry practice of re-racking spent rods in the pool well beyond its rated capacity, in effect heightening danger of melting and pool boil-off". Gandalf61 (talk) 09:51, 17 March 2011 (UTC)

So, the with problem with the spent fuel pools is that they are not contained . Also the fuel rods are still relatively rich in fissionable fuel and the racks that should hold them upright and provide some necessary separation to prevent criticality coming about, have been subjected to several server shakeings. If some off these racks (and any other safety devices like boron separation sheets) have been badly damaged or collapsed by the quake, then the evacuation of the local population seem like a very sensible step to take. The fuel may not be combustible but it can possible go critical again, given the right circumstances and until they can dump a lot of boric acid into the pool, there may still be enough water to facilitate this.--Aspro (talk) 10:13, 17 March 2011 (UTC)

I suspect, but do not know for sure, that criticality is not the major concern with the spent fuel at this point. I suspect that they would need to really be in a very poor state (e.g. melted sludge) for that to be an issue. The bigger problem is that they are very hot and full of very nasty things, and could catch fire, vent, melt, etc. --Mr.98 (talk) 15:31, 17 March 2011 (UTC)

Radiation is still being released by the venting of steam from reactors 1 and 3 (and 2 which may not even be contained). This radioactivity was observed before any issues arose with the spent fuel pools at 3 and 4. However, this radioactivity was a lower level (didn't require removing plant workers) and was blowing out to sea at that time. 75.41.110.200 (talk) 14:42, 17 March 2011 (UTC)

Thank you all for your responses. A followup question: Is it known whether the spent fuel at the site is recently spent fuel, or has some of it been sitting there in a swimming pool for a couple of decades? Mr.98 mentioned that Japan reprocesses their fuel, so it sounds like it's probably recent; but do we have an article on the lifecycle of fuel uranium and plutonium in Japan? Comet Tuttle (talk) 16:25, 17 March 2011 (UTC)

I doubt we have an article on it. It should be information that is "out there" though — it's the kind of thing the IAEA would know definitely. My mangled German + Google Translate of this article seems to indicate that there are 50, 81, and 88 tons of fuel rods in the three pools, but that this is not their full capacity, and in fact they are relatively empty. (By comparison, the spent fuel at some US reactors is around ten times that amount — because we don't reprocess, and we don't have any long-term waste disposal options worked out.) This suggests to me that they are pretty recent, but I'm not sure. --Mr.98 (talk) 17:31, 17 March 2011 (UTC)

The most resent rods were removed in November and December. These two pages out line the problems. Danger of Spent Fuel Outweighs Reactor Threat . I guestimate that a 13 foot long rod must weigh about 5 or 6 2½ to 5 hundredweight. Zirconium alloy is a wondrous material and hopefully it will resist the contents of the rods or the pellets themselves from forming a 'pile' on the floor. If not, then it wont just be the cherry bosoms glowing in the sunset this spring and Japan will be off my itinerary for the foreseeable future. Came across this handy little chart showing the current state of play at a glance. Status of nuclear power plants in Fukushima as of 16:00 March 17--Aspro (talk) 18:18, 17 March 2011 (UTC)

I don't think you need to be flip about the risks (cherry "bosoms" and etc.) — there are real people's lives here at stake. We are not quite in the "joke about it" stage yet. --Mr.98 (talk) 19:59, 17 March 2011 (UTC)

And if I had worded the possible out come more accurately would you have then accused me of over exaggeration and scaremongering? --Aspro (talk) 21:09, 17 March 2011 (UTC)

In fact, no. I think your comment was in extremely bad taste. That's a different category from whether I think it was accurate or not. --Mr.98 (talk) 21:34, 17 March 2011 (UTC)

Iodized salt instead of iodide tablets

I have seen recent news stories about paranoid people hoarding potassium iodide tablets. I know that iodized salt is widely used for cooking, and contains either potassium iodide or sodium iodide (the two shouldn't really matter, right, since they all just disassociate to iodide ions in solution), couldn't one achieve the same effect by eating a lot of iodized salt? Or is there insufficient quantity of iodide in iodized salt? --98.210.210.193 (talk) 06:55, 17 March 2011 (UTC)

Right! My salt contains 0.0025% of potassium iodate. 1g would than be 2.5mg. Somebody said that a dose can be above 100mg of potassium iodate. This would be 40g of table salt. This is a deadly dose of salt for children and very unpleasant for adults. --Stone (talk) 07:33, 17 March 2011 (UTC)

The concentration apparently varies in iodized salt in important ways. I just read that Switzerland raised its concentration to 20 mg/kg from 15 mg/kg - your container appears to be just 15 mg/kg. Fortunately the article Thyrosafe I started is still knocking around, despite being deleted last December :( :), so I can see that the tablets are 130 mg for adults or 65 mg for children. So a child's dose of iodized salt required would be just, 8.6 kg?! Hmmm, I think you missed the % up there when you did the math before, unless I just fouled up.

Right! I missed the %. --Stone (talk) 13:52, 17 March 2011 (UTC)

Ooops, I messed up myself - the pills are labeled for 130 mg of KI, not 130 mg iodine, so it's only equivalent to 6.6 kg of iodized salt. If you pace yourself.... ;) Wnt (talk) 16:00, 17 March 2011 (UTC)

Anyway, since it's not needed in the U.S. where the crazy rush is, tossing a pinch of iodized salt over your shoulder would do no harm. And maybe that 8.6 kilogram figure will make people think twice about hammering their poor thyroids with that kind of iodine for no reason. Wnt (talk) 07:44, 17 March 2011 (UTC)

Can we react Tincture of iodine with something commonly available (baking soda?) to make sodium or potassium iodide? Ariel. (talk) 09:17, 17 March 2011 (UTC)

Just don't react it with ammonia or you'd get a pill with a kick to it. No, scratch that, I would say don't try this at all! Who knows what kind of impurities you'd choke down, not the least of which being iodine itself. But as you know, I'm not giving medical advice here. Wnt (talk) 10:30, 17 March 2011 (UTC)

"Japan radiation fears spark panic salt buying in China" -- Finlay McWalter ☻ Talk 15:08, 17 March 2011 (UTC)

Would eating some tinned fish or other seafood be of any use in an emergency situation? (Seafood - contains iodine). 2.97.215.199 (talk) 23:42, 17 March 2011 (UTC)

Well, for edible seaweeds e.g. kelp: "12 different species of seaweeds were analyzed for iodine content, and found to range from 16 microg/g (+/-2) in nori (Porphyra tenera) to over 8165 +/- 373 microg/g in one sample of processed kelp granules (a salt substitute) made from Laminaria digitata.";^[29] "Edible seaweed contained I levels of between 4300 and 2,660,000 micrograms/kg";^[30] (summarizing these two) "the average iodine content of kelp of 1,500 to 2,500 μg/g".^[31] So we're looking at roughly 2 mg of iodine per gram of kelp (I assume these are all dry weight), if you happen to get an average sample, with a just ridiculous amount of variation. So eating 65 grams, a plausible dose, would be equivalent to the 130 mg tablet - though you might end up getting four times as much if you are unlucky. Or you might get less than a mg. Wnt (talk) 02:38, 18 March 2011 (UTC)

Why does the World suffer from nuclear phobia?

Ever since Chernobyl, people have had a strong irrational fear of nuclear power. The public prefers coal fired power plants over modern ultrasafe nuclear powerplants, even though the dangers of global warming are far, far worse than that of a Chernobyl-type disaster. People are now fleeing Tokyo in airplanes, when merely being aboard the airplane at 40,000 feet altitude will expose people to 100 times more radiation than they would get if they were to stay in Tokyo. How can we explain this irrational behavior? Count Iblis (talk) 16:45, 17 March 2011 (UTC)

Just because the reading on a Geiger counter is the same doesn't mean the exposure is the same. In an airplane, you get off and the exposure ends. But in Tokyo the counter would be clicking due to various isotopes in the air, water, environmental surfaces which you might inhale or ingest and become exposed to for years to come.

Still, I think it is reasonable to assume many of the people fleeing are convinced that the radioactivity will become much worse, or that basic necessities will become even harder to find than they are now. After all, many people would have left the tsunami-disrupted country even without a nuclear situation. Wnt (talk) 16:52, 17 March 2011 (UTC)

Your premise is that people's fear of the ongoing nuclear crisis is irrational, but you would have to cite a source for that. What makes you think it is irrational? The actual situation at the site is very unclear; right now, nobody in the world, including you, can even assess the probability of Tokyo becoming increasingly irradiated, or of a criticality accident, in the coming week; and the Japanese government's and Tokyo Electric's shameful avoidance of disturbing the public with the scary details they do have only exacerbates the (rational, I'd argue) fears that already exist. Comet Tuttle (talk) 17:07, 17 March 2011 (UTC)

(ec) A better question would be why people have an irrational belief in the safety of nuclear power. Put simply, nuclear power isn't safe and it never has been. Even when operating correctly, nuclear power plants produce radioactive waste that will be dangerous for the next 10,000 years. A Quest For Knowledge (talk) 17:08, 17 March 2011 (UTC)

I think the question is why people seem to be more afraid of a rare leak of radioactive carcinogens from a nuclear plant than they are of the routine dumping of radioactive carcinogens into the air by coal plants; and seem to be more upset about a 1% increase in lifetime cancer risk for the nuclear workers than about the horrible lung diseases and fatal accidents that routinely afflict coal miners; and seem to be more afraid that a nuclear plant will render a hundred square kilometers uninhabitable than that coal plants will stop the gulf stream and render all of Western Europe unsuitable for agriculture. People do worry about those things, but I'm not sure that will stop them from demanding the closing of nuclear plants after this disaster, which will inevitably (as far as I can tell) lead to an increased demand for fossil fuels at a time when we desperately need the opposite. That's my fear. -- BenRG (talk) 20:15, 17 March 2011 (UTC)

There is quite an advanced literature on risk perception, esp. in relation to nuclear power. In particular you might find the work of Paul Slovic quite interesting — he charts out how fears of technology generally chart onto two axis: "unknown risk" and "dread risk". "Unknown risks" are things that are invisible hazards, with delayed effects, or exceptionally new. Think contamination, poisoning, irradiation. "Dread risks" are global, uncontrollable, catastrophic, involuntary. Think big disasters, or small disasters that you feel like you can't control. If you plot out how people judge various hazards on this scale, you get a nice graph of risk perception. On the bottom left (low dread, low unknown) are actually some quite dangerous things: bicycles, home electrics, automobiles, smoking (all things with very local effects, where you feel "in control", where by itself, one "accident" isn't going to kill more than a person or two). On the top right (high dread, high unknown) sits all of the radioactive fears (waste, weapons, meltdowns) — they trip up our psychological systems in a big way, and we've always viewed them (even before nuclear power) in rather mythological terms. Humans have ancient stories about evil rays, contaminated lands, and deformed children — the nuclear threat fit into these fears quite nicely. (On this point, my favorite book on the subject, though it is now a few decades out of date, is Spencer Weart's Nuclear Fear: A History of Images.) Note that I have generalized quite a bit regarding that chart. Weapons actually are somewhat less "unknown" than waste/power related things.)

None of this is correlated at all with what we might call actual risk (which can be tricky to calculate, but let's assume it exists). (This is not to say that all things considered dangerous are safe, or vice versa. Just that there isn't necessarily a meaningful correlation here in any individual case.) It is psychological. It is not a straightforward case of people not being "educated" enough on actual risks — that can itself backfire quite heavily (if you say, "it's safe, it's safe, it's safe!", and you're wrong in a BIG WAY one time... then your credibility is shot, and it's worse than if you hadn't said anything). Anyway, it is an interesting field. Whether people's risk perceptions are "rational" or not is entirely beside the point: human beings are not "rational" when it comes to our fears, and wishing they were will never make that so. --Mr.98 (talk) 17:15, 17 March 2011 (UTC)

An excellent way to assess risk in a rational way is to attach a price tag to it and see what a free market does with it. It's called the insurance industry and they're pros at weighing the cost of paying a claim versus the likelihood of having to do so.

When private companies in the USA wanted to start operating nuclear plants they asked insurance companies to take on some of their risk. The pros at the insurance companies looked at the payout vs. likelihood equation and said "no thanks". The industry should have ended there, but unfortunately it was important enough to national self-esteem that Uncle Sam stepped in and said "you guys just stash away a little money for minor accidents and if shit ever hits the fan my taxpayers will pick up the tab".

When the nuclear industry can cover its own risks then you can fairly claim that its skeptics are irrational. --Sean 18:12, 17 March 2011 (UTC)

Sean, nobody wants to insure against rare, large losses because that's risky. Insuring against many frequent, small (at the scale of the insurance company) losses is safe; you can build a business on that. The market is great at some things, but it's terrible at pricing rare, long-term risks. The actual, scientific cost of nuclear power versus the alternatives is such that we have to keep building nuclear power plants. The government steps in in these situations because that's why governments exist: to do the things that the market does badly. I know there are people who believe that the market does everything well and governments should be abolished, but those people are wrong, just like the people who think that homeopathy works, etc. This is the science desk. -- BenRG (talk) 20:15, 17 March 2011 (UTC)

I'm pretty sure those people fleeing Tokyo are actually at a greater risk of being injured getting to the airport or the train station, than they are of being injured by a small amount of radiation. Astronaut (talk) 18:15, 17 March 2011 (UTC)

At the moment, maybe yes. But the situation is fluid, and if shit goes bad, which it can very quickly, it can go very bad. Thousands and likely millions of people had measurable and sometimes drastic health outcomes from the Chernobyl disaster, and while right now things are not Chernobyl bad, people may not want to be around when it does. To get back to answering the first questions, the real reason is that there is something in the general human psyche that fears disaster and catastrophe, that is events where dramatic and large damage occurs in the very short term, but does not really fear small, incremental, or common dangers which only show their harm in the long term after many years. Thus, people really fear plane crashes, but car crashes aren't that scary, since plane crashes, though rarer, are more dramatic and catastrophic. And people fear being fat even less than getting in a car crash, even though being fat is going to kill many more people, and cause much more measurably bad health outcomes than car wrecks will, if only because not many people die or get hurt instantly from being fat. It's the same deal with nuclear power vs. coal power. What worries people is not nuclear waste (even though THAT is the real danger), what worries people is their local nuclear power plant blowing up like a bomb and killing all of them isntantly. Coal power, which has very little danger of blowing up and spreading instant death around the country side, feels safer because of that reason, even though we know that it is actually worse for our health, and for the health of the earth, than Nuclear. --Jayron32 18:42, 17 March 2011 (UTC)

I'm not sure why you think waste is "the real danger." It is a difficult technical problem only because we'd like to be able to say that it will be totally containable for thousands of years. In the short term, dry storage of waste is extremely safe, providing you don't live right next to it. (Wet storage is a different question, of course.) The political difficulties of waste siting are vastly overblown compared to the technical risks. (Which is not to say there aren't technical risks, but they are very minor. You can see this when you look at the actual engineering assessments of the hazards — it's things like, "will 100 people get cancer in the next 100 years" — not great, but hardly public enemy #1.) --Mr.98 (talk) 19:04, 17 March 2011 (UTC)

It's relative danger, again. In the long term, in accumulative effects, more problematic outcomes are likely to occur from nuclear waste than from power plants blowing up. Nuclear waste may be more safe than say, coal slag or greenhouse gas emissions from ordinary cars, but it is also probably the more problematic part of the nuclear equation picture, when compared to the dangers of catastrophic nuclear plant failure. But because it is cumulative and slow moving, it tends to get ignored. The point is not that nuclear waste is either perfectly safe, or the worst thing ever to have occured to humanity; people want to paint the world in dichotomies like that, much as you just charactized my arguement. Its that, taken in comparison, we can say that nuclear waste is more problematic than some stuff (like say, plant failure) but less so than other stuff (like, say, smoking cigarettes). --Jayron32 19:41, 17 March 2011 (UTC)

I think I read (a WP article?) about the over-reporting of train crashes (rare, kill more, overall death rate lower) and car crashes. Seems to be similar here. Can't find it now, though. Grandiose (me, talk, contribs) 18:53, 17 March 2011 (UTC)

The world needs energy, and all have environmental impact. You decide:

• Oil: Greenhouse-gas pollutant, limited amount to drill safely, Deepwater Horizon and Exxon-Valdez.
• Coal: Dirtiest greenhouse gases, over 20,000 miner instant deaths per year (most in China, fewer in US, but major long-term health impact), and more radioactive than nuclear waste.
• Nuclear: only three major accidents in 60 years, extremely expensive start-up, but so far the only "wasteland" area is in Chernobyl - atmospheric radiation accidents disperse quickly.
• Hydroelectricity has major ecosystem impact and is not universally available or unlimited, as with renewables like solar, wind, and wave.

So indeed, take your pick. SamuelRiv (talk) 19:32, 17 March 2011 (UTC)

I disagree about the nuclear waste impact you've given, as we are still experiencing effects in the UK, hundreds of miles from Chernobyl: Chernobyl_disaster_effects#24_years_after_the_catastrophe. I also notice you refrain from mentioning the environmental impacts of renewable energy. --TammyMoet (talk) 21:27, 17 March 2011 (UTC)

I don't see that data on coal miner instant deaths in the article cited. Yes, it's dangerous, both in the ground and downwind, but would it be if we spent the kind of money we spend making nuclear plants "safe"? Wnt (talk) 23:41, 17 March 2011 (UTC)

If you spent that kind of money on coal, it would no longer be cost effective. Nuclear energy is far more cost effective, to start, allowing you to add lots of safety precautions and still have it be competitive. StuRat (talk) 00:23, 18 March 2011 (UTC)

I have never seen an economic justification for nuclear that includes the real cost to future generations of managing the waste. HiLo48 (talk) 07:06, 18 March 2011 (UTC)

Well, then, you'd have to compare that with the real cost to future generations of the alternatives. In the case of fossil fuels, that would include moving the populations of major cities on the oceans inland some 50 miles to deal with rising sea levels from global warming, or building massive dikes around them. I think that's several trillion dollars right there. Then there's the increased damage from hurricanes and tornadoes to consider. StuRat (talk) 07:31, 18 March 2011 (UTC)

The data regarding yearly international coal miner deaths is taken from the "China" section. Official China Labor Bulletin statistics cite 6000 deaths per year, and the number is adjusted to reflect the vast number of mines with few or no records (particularly those of accidental deaths). Additionally, I get sources for 400 deaths/yr in the US from black lung disease, which of course is an immediately-identifiable etiology (as opposed to cancer). I don't mention environmental impact of renewables, just that they can't be tapped wherever and whenever you want and thus will not replace all power, but you're right that like anything else they have environmental impact as well. Regarding long-term Chernobyl effects outside of the immediate area, fair enough. I will note, though, with respect to the compare-two-evils fallacy, that the amount of atmospheric fallout from Chernobyl is negligible to that of the above-ground nuclear tests. Regarding investment, in the US where coal is king we invest heavily in safety, which is why miner deaths per year has gone from thousands 50 years ago to 30 today. SamuelRiv (talk) 00:45, 18 March 2011 (UTC)

I am skeptical that China really has ~13000 deaths a year from coal mining that they don't know about; [32] sounds like a confident source. Obviously 6000 deaths is already intolerable, and perhaps the question of nuclear power in China might go a different way. Then again, Nuclear power in the People's Republic of China is only 1% currently, and who knows how it will work out for them (especially in the same poor regions of the country)? Wnt (talk) 01:51, 18 March 2011 (UTC)

The answer to the OP's question is quite simple. People display irrational behavior because people are irrational. Does that really surprise anybody? Dauto (talk) 23:57, 17 March 2011 (UTC)

Displaying an irrational fear takes a lot less effort than learning the science so that you can display a rational fear. HiLo48 (talk) 00:04, 18 March 2011 (UTC)

That's just a tautology. It fails to explain why the nuclear fears touch off such irrationality in particular. --Mr.98 (talk) 02:08, 18 March 2011 (UTC)

Some thoughts as to why nuclear power feeds irrational fears:

1) Radiation is invisible. Thus, people don't believe when politicians and "experts" tell them everything is safe. If radiation was visible, they would know if an area was safe or not. Perhaps if everyone had Geiger counters, they would feel safer, both because they would know if radiation levels went up, and would realize that there's background radiation everywhere, and it's nothing to worry about. Maybe portable pollution detectors would also be a good idea, so they would know when they are in an areas of (fossil fuel) air pollution, and would see how much worse that problem is.

2) Nuclear waste is concentrated, versus fossil fuel pollution, which is widely distributed. It's easier to point to a barrel of nuclear waste and think "that's dangerous" than to point at the sky and think "that's dangerous". If, at some point, fossil fuel pollution is also concentrated into barrels of toxic waste, then this difference may disappear, when people compare millions of barrels of FF waste with a few of nuclear waste. StuRat (talk) 00:32, 18 March 2011 (UTC)

I think of several things:

• Nuclear power is very expensive if you calculate the absolute cost. Reprocessing is extremely expensive. Storage for 10000 years is also very expensive. It only works when the military and the government pays for the expenses.
• I like to imagine a conflict like that in Libya in a country with a lot of nuclear power plants. All people leave and one after the other explodes. Or in like in Yugoslavia. When one party shells the nuclear power plant instead of a bridge. Or like in Egypt. When after an election a fundamentalist government Israel bombs the power plants as a friendly first gesture.--Stone (talk) 08:15, 18 March 2011 (UTC)

Elastic - is it okay to keep it stretched?

I need to know how bad it is for elastic to be kept it in its stretched state for a very extended period of time. Thanks. 71.220.225.153 (talk) 19:49, 17 March 2011 (UTC)

I'm not sure if that would effect how long it will last, as, for many elastomers, "aging" is due to mainly exposure to UV light or evaporation of volatile components. However, one concern is that when it does finally give way, it may injure somebody, say by snapping them in the eye or dropping whatever it was holding. Can you tell us what you had in mind as far as the type of elastic and load ? StuRat (talk) 00:09, 18 March 2011 (UTC)

I recently bought a bandoleer to hold a bunch of shotgun shells. The holders for the shell are made out of elastic and I was going to store the bandoleer with shells loaded in it unless it would wear out the elastic and make it unusable. As of right now I'd say the elastic is far too tight. It is fairly difficult to get shells in and out of it. 71.220.225.153 (talk) 05:43, 18 March 2011 (UTC)

Well, then you want to stretch the elastic, right ? I think that might work. However, certain types of elastic might also leave residue on the shotgun shells, as the elastic deteriorates, and this could interfere with performance when the shells are used. A safer approach might be to remove the shells, and replace them with something as large or larger, like rolled up newspaper bits, to do the stretching. A similar method is often used to help shoes in storage keep their shape. StuRat (talk) 07:22, 18 March 2011 (UTC)

Virgil C. Summer

who was Virgil C. Summer? a nuclear plant is named after him?? — Preceding unsigned comment added by Timc321 (talk • contribs) 20:01, 17 March 2011 (UTC)

He was a president of the South Carolina Electric and Gas Company, see [33] for a very brief statement as such. Since they built and own said nuclear plant, it makes sense they would name it after a former president of the company. --Jayron32 20:16, 17 March 2011 (UTC)

And this Google Books search turns up a few more scanty refs: [34]. --Jayron32 20:19, 17 March 2011 (UTC)

I've added a reference (from SCANA's own website) to that effect to the Virgil C. Summer Nuclear Generating Station article. Unfortunately there's no more worthwhile info, beyond what Jayron32 has found already, there. -- Finlay McWalter ☻ Talk 20:27, 17 March 2011 (UTC)

High oxidation numbers: above 8?

Is there any reason why transition metals' oxidation numbers always seem to cut out at eight (in group 8 elements)? For instance, why can't you get nine on a group 9 element (I'm thinking rhodium, iridium, possibly also americium where the d electrons are replaced with f) to make it d⁰? Like say iridium(IX) hydride (IrH₉), which is isoelectronic with the real complex ReH₉^2–. Or I could certainly imagine a hyper-periridate anion IrO₅^–. Os(VIII) forms readily and it's nearly identical. (Feel free to get really in-depth; I'm three years into a chemistry masters degree.) 137.205.222.209 (talk) 20:40, 17 March 2011 (UTC)

Might if have to do with the geometry of 9-ligand complexes? Once you get over 6 ligands, the Octahedral molecular geometry, things get weird. There are occasional higher order bonding schemes, like Pentagonal bipyramid molecular geometry but they are quite rare. You almost never find bare transition metal ions in solution or in crystal networks, especially with the higher oxidation number metals; even low-oxidantion number metals like copper-(I) and copper-(II) form complexes very regularly. Admitedly, my chemistry is a bit older than yours, since you are in it, and it's been 15 years or so for me since I studied this stuff in depth. There's probably some combination of electrostatics and orbital geometry that makes high oxidation number transition metals to be highly unlikely. The article Ligand field theory hints on some of the problems with considering what happens in d-orbitals; at first approximation, and under normal circumstances, all 5 d-orbitals are degenerate, which is true energetically, but in real bonding situations, the three d(xy), d(xz), and d(yz) operate differently than do the d(z²) and d(x²- y²) orbitals. Making a WAG, my guess is that due to these differences in d-orbital organization, there's some barrier towards, say, removing all 9 electrons from the 6s and 5d electrons in Iridium; in other words theres something in the way that the d-orbitals are organized that presents a large jump in ionization energy between the 8+ state and the 9+ state. f-electrons are so deep, I doubt they participate to any great end in hybridization, in bonding, or in ion formation in the way that s, p, and d orbitals can. Again, this is just me riffing on my admittedly underused 1990's era inorganic chemistry knowledge... --Jayron32 02:32, 18 March 2011 (UTC)

More than just that they "seem to cut out at eight" (emphasis mine), that is citedly the actual highest known (at least as of a little over a year ago), although there are groups studying that limit. See for example doi:10.1002/cphc.200900910. DMacks (talk) 03:05, 18 March 2011 (UTC)

Deliberate meltdown

Lets say some psycho wants to create a doomsday device. What would happen if someone made a reactor that had no coolant, turned it on full power, and deliberately let it meltdown. Could this have global effects or would the effects be relatively localized near the point of meltdown? ScienceApe (talk) 20:41, 17 March 2011 (UTC)

Basically what you are describing is a type of dirty bomb. Looie496 (talk) 20:57, 17 March 2011 (UTC)

There are two hugely relevant variables. How large is the device, and where is it located. Googlemeister (talk) 20:58, 17 March 2011 (UTC)

A meltdown would certainly be no worse than a nuclear bomb with the same amount of material. The nuclear bombs used, either for wars (hiroshima) or for Nuclear weapons testing, do not appear to have had global effects. 83.134.176.57 (talk) 21:08, 17 March 2011 (UTC)

You really cannot compare reactor meltdowns and nuclear weapons. (What do you even mean by "the same amount of material" in such a comparison? Reactors use tons of fissionable materials; nuclear weapons use kilogram quantities.) The comparison is highly misleading in every way. They are very different types of events. The only similarity is that both involve distributions of fission products. And there is some dispute as to whether the years of atmospheric nuclear testing did have global effects (e.g. increased thyroid cancers, etc.). They certainly had national effects. But again, this is kind of irrelevant, because it tells you very little about meltdowns. --Mr.98 (talk) 21:28, 17 March 2011 (UTC)

This is essentially what happened at Chernobyl, albeit not "mad men" so much as "fools." The acute effects are "regional" — not global, but certainly not just "local". There are some "global" effects, but they are very hard to measure (statistical up-tick in cancers, for example — hard to figure out what the causes of those are). --Mr.98 (talk) 21:28, 17 March 2011 (UTC)

The cobalt bomb was proposed as a similar device; one could translate its principles into a reactor, but a bomb would be more effective at creating and distributing the fission products. I believe (the article doesn't mention it, but its references do) that one advantage of such a device would be that it would not have to be transported to the target and could be arbitrarily large, providing, of course, that the device is understood to be a "doomsday weapon." Acroterion _(talk) 21:37, 17 March 2011 (UTC)

After encountering cobalt bomb, I ran across some unusual claims that the Russians had actually built a Doctor Strangelove type device. These emanate from Bruce G. Blair. I encourage anyone to take a look at the evidence and try to figure out if this is plausible or not; I've added a brief mention of what I found in the article. Wnt (talk) 00:28, 18 March 2011 (UTC)

He's referring to Perimetr, the so-called "Dead Hand" system. It's not really the same thing as the doomsday device. It was a command and control system that would allow the top Soviet leaders to say, "we're in a very tight time, and nuclear war could start any minute, so if you need to, launch the bombs." Then the Soviet army heads could, if they felt things were really bad, could say to a specific base, "look, if you lose contact with us, assume we're toast, and launch the nukes." Then the specific base would send up a special ICBM that had a radio transmitter on it that would say to all of the other ICBM bases, "go ahead and launch 'em, boys!" and then they'd all launch at the USA or whomever. So it's that last bit that makes it sound Strangelovian — it's a one-way trip at that point if a bomb goes off (or if for other reasons they lose contact). But it's a few more steps than that. The reason to make it was not some sort of MAD pact; it was due to the fact that in the 1970s the Soviet army realized their leaders were a bit dotty (Brezhnev and Chernenko being the obvious ones) and might not be able to order the nuke attack if it came down to it, and also they realized that a very weak point in the Soviet ICBM system was the communication system between individual missile bases. (For more information, I heavily recommend David Hoffman's The Dead Hand, which came out a year or so ago, and is pretty well-researched. --Mr.98 (talk) 01:28, 18 March 2011 (UTC)

Ach! I got hit by the oldest trick in the book that time. The first 'sources' I came across in the blogosphere made it sound like the system set off cobalt bombs automatically, but the ones closer to the source I actually cited didn't actually make that link, even though they talk about both things. (They're just both reminiscent of Doctor Strangelove. That one catches me more than any other. Wnt (talk) 01:41, 18 March 2011 (UTC)

I've run across references (don't ask me where, it's been a while) to a similar last-ditch American system, going by the codename Last Dance. Acroterion _(talk) 02:09, 18 March 2011 (UTC)

Breast milk and iron

According to this site: [35], human breast milk is almost devoid of iron, and many other vital nutrients. So then, how do babies which are exclusively breast fed get their iron, and those other nutrients ? StuRat (talk) 00:40, 18 March 2011 (UTC)

They store it before they are born. Especially non-c section babies get filled with extra blood from the placenta by the contractions (sometimes causing jaundice when the extra blood is broken down). The iron in blood is almost completely recycled, and the store of iron lasts them till they start eating solids. Ariel. (talk) 00:44, 18 March 2011 (UTC)

Where is this "excess blood" stored ? Even with perfect recycling, they would need more iron to account for their growth. And, if babies can recycle iron so well, why can't adults (especially men, most of whom don't menstruate :-) )? Why do adults need dietary iron ? StuRat (talk) 03:32, 18 March 2011 (UTC)

(edit conflict)Two things:

1. When reality seems to be in conflict with "experts", trust reality. In this case, since humans for millions of years fed their infants breast milk, and yet we as a species survived; and since today, still, the majority of humans still feed their infants breast milk, and those babies keep growing into healthy adults, there must be something right about breast milk. Regardless of what the "label" says, or the list of ingredients or anything else, its not that breast milk is deficient, it must be that what you are presupposing to be necessary OR what you are presupposing to be actually in breast milk, per that label, is really there, that is what is deficient. Breast milk is not deficient, obviously, so we need to figure out what is going on here.
2. Read the label again. The % of iron is the % of the daily requirement an adult eating a balanced 2000 calorie diet would get out of taking in 172 of those calories in breast milk. Instead what you have is an infant, who is eating much less (say 500 calories or less), and getting all 500 of those calories from the breast milk. In that case, the infant may be getting 100% of their daily requirment for iron, since a) their iron requirements are likely different b) American food labels are rounded somewhat, so what might be, say 0.44% for an adult would still show up as zero. That doesn't mean there is no iron, just a small amount when compared to an adult requirement, but likely suffient for what an infant needs. And that is all dependent on the fact that you can trust what that website is telling you...

That's how I read the situation. (post EC extra stuff) what Ariel said makes sense regarding how infants work out their iron situation. Makes sense. I knew it had to work out, because of point 1.--Jayron32 00:54, 18 March 2011 (UTC)

To your point 1, if a baby has only 1/4 the calorie requirements, and also only 1/4th the iron requirements, then 0.44% of an adult RDA would become 1.76% of a baby's RDA, still grossly insufficient. And I suspect that more iron is needed, proportionally, when growing, than as an adult. StuRat (talk) 03:28, 18 March 2011 (UTC)

Apparently not; again your assumption that small babies need, proportionally, the same amount of iron as adults is not borne out by the fact that breast fed babies aren't all dead, and are perfectly healthy, even with regards for the kinds of reasons that, you, as an adult, need iron. Breast milk is empirically not deficient, so either a) that "nutritional facts" label is wrong or b) babies need a lot less iron in their diets than adults. Ariel, above, provided ample evidence that the real answer is b, though I have my suspicions that there may be some option a at play as well. Again, you can't start with the supposition that breast milk is deficient when there's ample empirical evidence (nearly all of humanity for all of history; indeed even more than that, we have nearly all of mammalia for even longer). The experiment has been run trillions upon trillions of times and milk works. So we have to rephrase the question: What in your supposition is wrong, or what is it about how babies need iron that is different than adults? Ariel answered that succinctly: they don't need dietary iron during their first several months because of the massive iron boost they get during normal birth. --Jayron32 03:50, 18 March 2011 (UTC)

It's patently obvious that it has to work out somehow, so stating that over and over doesn't help much. I want to know HOW it works out. The only assumption I made in my initial post is that the nutrition site I listed has correct info. If you have another site which disputes that info, then that would be useful. If babies are born with "excess blood", I'd like to see a site which supports and describes that. Also, I believe some cultures have babies who are exclusively breast fed for years, so how can the iron last that long ? StuRat (talk) 07:11, 18 March 2011 (UTC)

How the following time dilation senario in three frames of reference can be explained?

Let we have A and B transparent spaceships such that B is inside back of A as the size of A is greater than B. Also there is an observer at the middle of A who is stationary for B.

Now both spaceships ignited and set out at same time (with speed close to the speed of light) for space journey. The front of A is open so that B may leave A if want. The reading of speedometer of B may or may not be the same with that of A. Light clocks installed in each ship with top and bottom mirrors,  is also starts automatically with ignition.  

We have following three reference frames

1-  within B (with light clock LC2)

2- within A (with light clock LC1 and moving spaceship B in which LC2 is installed)

3- for outside observer who is not co moving on asteroid

Now

1- LC2 is making time dilation triangle for (a) for observer at the middle of A who is stationary for B (b) for outside observer who is on asteroid.

2- LC1 is making for (a) for outside observer on asteroid (b) may be for onboard observer B.74.198.150.213 (talk) 02:48, 18 March 2011 (UTC)Eccentric Khattak#1

I think I understand the setup, but what is the question? You only asked "how can it be explained?", which is not specific enough. -- BenRG (talk) 03:25, 18 March 2011 (UTC)

Then you understand more than me. The explanation above about the setup is quite confused in my opinion. Dauto (talk) 03:48, 18 March 2011 (UTC)

I don't understand what the point is of making the spaceships transparent or allowing one to enter the other. Couldn't they simply be normal spaceships that pass by one another? More to the point, can't you just say that A is the surface of the Earth and only look at B (i.e. usual twin paradox?) But I don't understand the acceleration that A and B might undergo. Wnt (talk) 05:34, 18 March 2011 (UTC)

I don't know what it is that you want to know or you have trouble understanding, but maybe you should have a look at Bell's spaceship paradox. If you are asking whether 2 spaceships, initially at rest, and starting at the same time with the same acceleration, are moving relative to each other while they are accelerating, then the answer is yes (specifically, in the reference frame of an observer at the position of one spaceship with the velocity of this spaceship at any point in time while they are accelerating, as we only look at non-accelerating reference frames). Icek (talk) 08:07, 18 March 2011 (UTC)

Efficiency of nuclear reactor

Hello, What % of the heat generated by a nuclear reactor is converted to electricity?(whats the efficiency of the turbine-cooling circuit i mean)

TY DST DSTiamat (talk) 08:53, 18 March 2011 (UTC)