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August 22

How Often Do Hurricanes Hit Puerto Rico Redux

How often do hurricanes hit Puerto Rico? Redux Tropical Storm Irene barrels toward Puerto Rico DANICA COTO, Associated Press Updated 10:24 p.m., Sunday, August 21, 2011

http://www.chron.com/business/article/Tropical-Storm-Irene-barrels-toward-Puerto-Rico-2134551.php

μηδείς (talk) 03:35, 22 August 2011 (UTC)

According to our last discussion, I think several people brought up some convincing data that it was once every three years or so. --Jayron32 11:47, 22 August 2011 (UTC)

Three was my subjective guess, I think it was less often. The editor who posted the question was going on Sept 1, so this is good news, since it's highly unlikely a secon storm will so quickly follow the same path. μηδείς (talk) 16:17, 22 August 2011 (UTC)

I bet somewhere there's a map of the hurricane frequency for the whole hemisphere or more - if someone could get or make such a thing for Hurricane it would be absolutely awesome. We have some maps there of all the hurricane tracks, but it's hard to convert that mentally to frequency; yet that data could be used directly to infer frequency if we make the somewhat unreasonable approximation that it is "frequency of being within X miles of a hurricane track". Obviously a map based on the actual extent of each hurricane would be better if we could. Wnt (talk) 16:51, 22 August 2011 (UTC)

Jeff Masters at http://wunderground.com has the historical data set and (almost all?) the code to make such a map if he doesn't already have such a map, and I'm sure he'll be willing to share it, but you probably want to catch him next week. 208.54.5.213 (talk) 04:48, 23 August 2011 (UTC)

It looks like Beeblebrox has missed the boat, although he could still go to Florida later this week. Count Iblis (talk) 23:08, 22 August 2011 (UTC) ''Italic text

Weak interaction

This is based on a question I had asked around a year ago, and have been thinking about since. From the standard formulation of QM, ${\langle \chi |\psi \rangle }^{*}={\langle \psi |\chi \rangle }$. So $|\langle \chi |\psi \rangle |^{2}=|\langle \psi |\chi \rangle |^{2}$. This is another way of expressing time-reversal symmetry: if a particle is in a certain state ψ, it has a certain probability of being found in the state χ at a later time. If we reversed the situation, the probability that the particle goes from χ to ψ is the same. But weak interactions aren't symmetric in time. I was wondering how this is accommodated in the mathematics of QM. 74.15.137.168 (talk) 05:26, 22 August 2011 (UTC)

${\langle \chi |\psi \rangle }\neq {\langle \chi |\psi \rangle }^{*}={\langle \psi |\chi \rangle }$. which means that QM requires time reversal but doesn't require time symmetry. Dauto (talk) 14:23, 22 August 2011 (UTC)

Life Expectancy After Surviving Childhood?

Is there any data showing the average life expectancy of someone in the United States after surviving to adulthood? My understanding is that childhood deaths really bring down the average. Historical data going back to the 70s would be great. --CGPGrey (talk) 09:07, 22 August 2011 (UTC)

WHO have a mass of data by age range by country by year etc., but their site seems to be having problems right now. [1]--Aspro (talk) 11:47, 22 August 2011 (UTC)

Here (page 7) is a life table for the total US population for the period 1999-2001. It says the life expectancy at birth was 76.83 years, which the life expectancy at age 18 was 59.70 (which corresponds to an age of death of 77.70). So, people dying in childhood drag down the average by about a year. The probability of dying before your 18th birthday, according to that table, is 1.178% (the chance of dying before your first birthday is 0.695%). That's very low, which is why the effect on the average is also very low. It would have been much greater 100 years ago, say. --Tango (talk) 19:51, 22 August 2011 (UTC)

You want to take a look at the article life table. Quest09 (talk) 19:58, 22 August 2011 (UTC)

I'm an actuary, so no, I don't really want to take a look at that article. The OP might though. Please see WP:INDENT! --Tango (talk) 21:03, 22 August 2011 (UTC)

Killing the brain while keeping the body alive

Is this possible? Can you give a person brain death but then keep their body alive, functioning, and growing? Kind of like an empty shell so to speak? ScienceApe (talk) 16:11, 22 August 2011 (UTC)

Brain death covers some of this. --Jayron32 16:18, 22 August 2011 (UTC)

Also organ harvesting. 76.254.20.205 (talk) 16:32, 22 August 2011 (UTC)

A) If the brain was totally dead, the rest of the body couldn't be kept alive long. This is because the brain stem regulates breathing, heartbeats, etc. These functions can be temporarily replaced by machines, but not over the long term.

B) On the other hand, it's quite common for the higher brain functions to cease while the brain stem continues to function. In this condition, the body can be kept alive indefinitely. StuRat (talk) 16:42, 22 August 2011 (UTC)

In vitro meat may be of interest. Comet Tuttle (talk) 17:37, 22 August 2011 (UTC)

iceberg

How close to the equator was the most tropical iceberg sighted (drifting south from Greenland or drifting north from Antarctica)? Googlemeister (talk) 16:42, 22 August 2011 (UTC)

For an answer to the first participial phrase in your parenthesis, see this page, under "What is the extreme range of iceberg locations?" Deor (talk) 17:30, 22 August 2011 (UTC)

From the supplied map in that link, it seems that one iceberg got as far south as about 28 degN. How about coming from the other way? Googlemeister (talk) 18:48, 22 August 2011 (UTC)

Mass of all the sunlight...

What's the mass of all the sunlight that strikes Earth in one second? Comet Tuttle (talk) 17:35, 22 August 2011 (UTC)

Per solar energy, the Earth receives 174 petawatts of incoming solar radiation, so 174 petajoules per second. Per e=mc², that's about 2 kg per second. — Lomn 17:47, 22 August 2011 (UTC)

Fascinating - does that mean that the Earth's mass is increasing by around a thousand tonnes a year? Quintessential British Gentleman (talk) 18:14, 22 August 2011 (UTC)

Much of that light is reflected back away from the Earth. Note that the Earth also gains mass each year due to meteors, micrometeors, and the solar wind, and loses mass in the form of hydrogen and helium which bleed off into space. I wonder if there's a chart which compares all these quantities.StuRat (talk) 18:20, 22 August 2011 (UTC)

If I recall correctly, meteors, micrometeors, and space dust lead to an accretion of about 50,000 metric tons per year. (Which is isn't nearly as much as it sounds like once you spread it out across the entire Earth's surface). Dragons flight (talk) 22:51, 22 August 2011 (UTC)

(ec) More to the point, the "increased mass" due to sunlight would really only be increased temperature. Photons have zero rest mass (probably; if it's nonzero it's not enough to make a difference in this discussion). So it's not like they can stick to the planet and increase its mass. The only way the Earth's invariant mass would be increasing as a result is as an increase in thermal energy.

But the temperature is not increasing. Well, OK, it's increasing some (climate change) but not the way it would be if the energy from the sunlight just stayed.

What happens is that the Earth radiates the energy back into space, as approximately black body radiation based on its temperature. --Trovatore (talk) 18:28, 22 August 2011 (UTC)

In principle, it could also be stored as chemical energy. However, the size of the biosphere isn't increasing at any particular speed, and I don't know of any inorganic light-driven chemistry that's particularly active either. --Tardis (talk) 13:01, 23 August 2011 (UTC)

Thank you! Comet Tuttle (talk) 18:45, 22 August 2011 (UTC)

Radiation pressure can be used to quantify the momentum transfer due to incident electromagnetic waves. Use caution: the math and physics involved is subtle, and it is very common to apply the formulas incorrectly, resulting in non-physical conclusions. A good example is the Crookes radiometer: there are an abundance of incorrect physics-esque explanations for the apparent momentum-transfer. The same conceptual problems exist with regard to solar radiation incident on the Earth - and the experimental challenges of measuring planet-sized objects are much more difficult. Nimur (talk) 18:52, 22 August 2011 (UTC)

Looking at photon it looks like E=pc=mc^2, so p=mc as expected. 2 kg/s * 299,792,458 m/s = (5.9736 E+24 kg) (1E-16 m/s^2). Not a huge acceleration, despite the remarkable whack. Wnt (talk) 02:49, 23 August 2011 (UTC)

You should not use that formula. First of all, it's incorrect, relativistically - because, whether you realize it or not, you have taken a first-order derivative with respect to time (in other words, you are using "dm/dt", the rate of incident "mass" of photons). That's not a relativistically invariant value. You should properly compute the radiation pressure by dividing the Poynting vector by the speed of light, to obtain an expectation-value for the radiation-pressure, in units of pressure. Nimur (talk) 17:01, 23 August 2011 (UTC)

Hmmmm... I'm not very familiar with that concept, but the article calls it an energy flux in W/m^2. Taking it times however m^2 the Earth gets gives us watts, or energy per second. Dividing energy by c gets us mc, which is what I used above. I don't see any relativistic correction. Originally I ignored relativity, being satisfied to use a clock on Earth, but truly if your clock ticks as some different rate you should count a different number of photons and get the same answer, I'd think. Wnt (talk) 16:58, 24 August 2011 (UTC)

Yeah, that would be applying the lorentz transform to the "dm/dt". You can relativistically correct any formula by applying the appropriate Lorentz transform (if you can remember how to do it correctly, which I can rarely do); but, if you just use a relativistically invariant formula, you never need to do that. S / c is always valid. Nimur (talk) 22:29, 24 August 2011 (UTC)

Galaxies, solar systems and planets systems

Is the speed of a star around a black hole and the speed of a planet around a star and the speed of a moon around a planet all based on the same formula of mass and the distance apart or are there differences between each system? --DeeperQA (talk) 20:23, 22 August 2011 (UTC)

They are all due to the same property of the universe, gravitation. In the case of a moon/planet system, we can use the equations defined as Newton's law of universal gravitation to model the interaction. In the other cases you mentioned, more sophisticated mathematical equations are needed in order to accurately describe the interaction, but they are based on the same physics. You can, if you want, apply the identical formulation of gravitation to the planet/moon system, but the math is more difficult, and you obtain the same result as the Newtonian formula, out to several decimal-places. Nimur (talk) 20:43, 22 August 2011 (UTC)

If other objects are sufficiently small and far away, you can treat any of these three scenarios as a two-body problem and use Kepler's laws of planetary motion to get a very good approximation. Your star around the black hole would also need to be sufficiently far enough away that the BH is not tearing pieces off of the star. Googlemeister (talk) 20:53, 22 August 2011 (UTC)

Well, there are several relativistic corrections to Newton's laws that may be quite a bit larger for the black hole scenario, because the black hole will produce a much larger curvature of space-time in its vicinity. Looie496 (talk) 21:16, 22 August 2011 (UTC)

Only particularly near to the black hole. A black hole with a mass equal to the sun, say, will have exactly the same gravity as the sun as long as you are more than one solar radius away from it (ie. as long as you wouldn't be inside the sun if it were actually the sun). --Tango (talk) 22:58, 22 August 2011 (UTC)

Is the solar equivalent radius the black hole's event horizon? --DeeperQA (talk) 06:59, 23 August 2011 (UTC)

electricity and light?

do electricity and light travel at the same speed or is light slightly faster? Thornydevil ^Munchies? 21:11, 22 August 2011 (UTC)

It's potentially important to specify the medium, as both light and electricity travel at different speeds through different substances. That said, if we consider that electrons are particles with rest mass, it's clear that they cannot be accelerated to c (the speed of light in vacuum) -- thus, it's reasonable to make a general statement that electricity does not travel as quickly as light. For practical numbers, the propagation of an electrical signal through a copper line travels at about 2e8 m/s, as contrasted with light's 3e8 m/s. — Lomn 21:17, 22 August 2011 (UTC)

It's misleading to bring up the speed of the electrons. Nothing you said is actually wrong, but it could lead a naive reader to think that the speed of the electric signal is the same as the speed of the electrons in it.

In fact, the signal travels much much much faster than the so-called drift velocity of the electrons. The usual help to intuition is to imagine a pipe full of tennis balls. If you push a tennis ball in one end, another one pops out the other end, and the delay in that happening is much smaller than the time it would take the tennis ball to get to the other end at the speed the tennis ball itself is moving. --Trovatore (talk) 22:14, 22 August 2011 (UTC)

Sorry, I should have specifid in the air. Thornydevil ^Munchies? 21:31, 22 August 2011 (UTC)

We have an article, speed of electricity, that deals with this. The basic answer is that light is faster but sometimes not much faster. Looie496 (talk) 21:18, 22 August 2011 (UTC)

Thanks for the help! Thornydevil ^Munchies? 02:52, 23 August 2011 (UTC)

Ball screw

A diagram of a Recirculating Ball mechanism

How does a recirculating ball nut and lead screw achive zero backlash?--92.28.71.6 (talk) 21:58, 22 August 2011 (UTC)

In a regular "geared" system, the tighter the gears are meshed the more friction there is, the looser they are the more slack there is, so inevitably you'll have some friction and some slack. It seems to me that due to the reduced friction of the Ball screw design, the mechanism can just be made within much tighter tolerance. I'm not sure it's correct to say "zero" backlash, it might be so small as to be insignificant, but even at 80% or more efficiency, it's not technically "zero" backlash. Vespine (talk) 23:48, 22 August 2011 (UTC)

The balls sit in the 'V's of the threads of both the ball nut rack & the worm gear. Thus there is no play.--Aspro (talk) 23:56, 22 August 2011 (UTC)

(EC)Ok, thought about if for one minute and that's incorrect (My 1st post). In a single gear system it's impossible to have zero backlash... With a ball screw it IS very possible to get zero backlash, all you need to do is have SOME of the balls mesh with ONE side of the thread and some of the balls mesh with the OTHER side of the thread. This is easily acheived just by making the ball nut rack pitch very slightly different then the shaft worm gear. That way, the balls on one end of the rack mesh on one side of the worm gear and the balls on the other side meshes the opposite side, there's your "zero backlash". As for Aspro's comment, gears are normally "v" shaped, I don't think that actually has anything to do with reducing the "play". Vespine (talk) 00:02, 23 August 2011 (UTC)

You seem to be guessing as you go! The balls ensure there is all ways contact on all surfaces (four point contact) – no gaps, no play.--Aspro (talk) 00:09, 23 August 2011 (UTC)

Hmm, i disagree. I'm not an engineer but I used to fix power tools so have a bit of experience with gears... You're neglecting the fact that this is a three dimensional shape. There is a RING of balls, so the 4 points of contact you talk about has an OPPOSITE 4 points of contact on the other side of the shaft, so there obviously has to be SOME play in the system, or else the thing won't move at all. The "trick" here is to minimize play along the functional axis. The way to do this is to have "mesh" that opposes it self along that axis. If you imagine the ball nut rack has a very slightly narrower thread then the shaft worm, along the top of the worm, the left most ball will be getting pulled towards the centre of the nut toward the right, therefore meshing the LEFT side of the "groove" in the nut and the RIGHT side of the groove in worm. By the time you get to the RIGHT most ball, it too will be getting pulled towards the centre, which is to this ball's left, it will be meshing the opposite sides of the nut and worm cancelling out the "play" along that axis. Vespine (talk) 00:24, 23 August 2011 (UTC)

Look at the diagram.--Aspro (talk) 00:31, 23 August 2011 (UTC)

Ok, I am full of it, opposing mesh is used as an "anti-backlash" measure, but it seems not in recilculating ball designs, not that I can find in any of our articles anyway. It makes sense in my head;). The article DOES say however that recilculating ball gears are made to very high precision because of the low friction of the design, up to 90% efficiency. I think this still means that "no gap, no play" is a far too simplistic answer, as is "4 points of contact". You'd be hard pressed to find a "gap" in any geared system with half decent precision, but it doesn't mean there's no play or backlash. A seized gear has NO play. In the real world there's things like wear, lubrication, heat expansion, etc. The very fact that tension in one direction means slack in the OTHER direction on the opposite side of the shaft should be enough to show that the groove or the ball are not the only factors, or even one of the main factors, in the reduction of backlash, otherwise, why not use just ONE rotation around the shaft? I think the main factors in the practical elimination of backlash in this design are the firstly the high precision and secondly the number of turns around the shaft. Vespine (talk) 01:20, 23 August 2011 (UTC)

I don't know anything about this, but that gear at the bottom of the picture looks much like the gear used as an example in the Backlash article. Shouldn't there be some backlash there? And when looking at the other part, the worm gear part, isn't a worm gear part generally supposed to be effectively irreversible, and thus not able to backlash past that point anyway? Wnt (talk) 00:34, 23 August 2011 (UTC)

The question was about ball screws, the sector gear is an addition (as found on say a car steering control). A recirculating ball nut and lead screw assembly (on say a large motor car with five and a half turns of the steering wheel between lock and lock) gives a lot of mechanical advantage without the backlash inherent in other gearing systems such a rack and pinion. A little play after this assembly has much less effect on over all directional control. An yes, as you say, because of the mechanical advantage of the worm gear (to the driver) of this configuration, the torque coming the other way has this mechanical advantage working against it but the lack of backlash refers to the lack of play on the side of the steering wheel as well. --Aspro (talk) 01:23, 23 August 2011 (UTC)

The absence of backlash is indeed due to the inability to circulate the balls by movement of the steering rods due to torque ratio. However, the absence of play is due to the compression of the balls against the walls and one another. --DeeperQA (talk) 09:17, 27 August 2011 (UTC)

August 23

How good is Scientific Learning Corporation's Reading Assistant?

Scientific Learning Corporation currently redirects to one of their products in which I am not interested. I need independent evaluations of the 'Reading Assistant' product they acquired from Soliloquy Learning some years back. Where can I find those? 208.54.5.213 (talk) 05:14, 23 August 2011 (UTC)

From http://www.scilearn.com/products/reading-assistant/ under "Q&A":

Is Reading Assistant research-based? Yes. According to the report of the National Reading Panel, "classroom practices that encourage repeated oral reading with feedback and guidance leads to meaningful improvements in reading expertise for students—for good readers as well as those who are experiencing difficulty." With Reading Assistant, the computer becomes the supportive listener that ensures all students can regularly practice oral reading while receiving immediate, individual feedback from Scientific Learning's advanced speech verification software.

Is Reading Assistant research validated? Yes. The impact of Reading Assistant on fluency growth was evaluated with mainstream students in Grades 2-5. Half of the classrooms in two schools used the software in thirty-minute sessions, once or twice a week over 17 weeks. Across all four grades, fluency gains were significantly greater for students who used the software than those who did not, averaging 43% (E.S.=0.91) greater than normative expectations over grades. Project sponsored by the Carlisle Foundation and NICHD.

76.254.20.205 (talk) 08:24, 23 August 2011 (UTC)

What does "E.S.=0.91" mean? 76.254.20.205 (talk) 09:31, 25 August 2011 (UTC)

tomato, hot pepper - why are they toxic?

Tomatoes and hot peppers are flowering plants, and thus designed to attract animals and insects to feed of them and so disperse their seeds. In this case, why were tomatoes, or some species of them, poisonous (being related to the deadly nightshade family)? How would being poisonous help a plant to disperse it seeds? Then too, I've read that the toxicity of tomatoes was highly overrated, and that no one was seriously in danger. With hot peppers, most animals would not be able, or want to, eat fruits such as these. I've read in WP, that because birds do not have pain receptors to the capsaicin which causes the burn, then they become the preferred carriers of the seed. Why would this plant discourage other animals from eating its seed, and leave it to the birds? Do the birds help to pollinate the plants? And in any case, if so, why do no other plants encourage birds but discourage non-birds to eat their fruit? Myles325a (talk) 07:01, 23 August 2011 (UTC)

Apparently mammals like mice will digest the seeds if they eat hot peppers. Birds will not digest the seed, and will pass it through, transported to a new location! Graeme Bartlett (talk) 07:07, 23 August 2011 (UTC)

Birds can't taste the capsicumcapsaicin in chilli peppers. Assuming Graeme is right (I have no knowledge either way, but it seems sensible), then it is in the plants' interests that only birds eat its seeds. CS Miller (talk) 10:11, 23 August 2011 (UTC)

The missing piece seems to be, why is it that mammals keep the 4-vanilloid receptor that responds to capsaicin? If it's not harmful intrinsically, then it's odd that the receptor that causes the pain wouldn't be selected out.

The vanilloid_receptor_subtype_1 receptor is activated at well over normal body temperature (43°C), and seems to part of the the thermal homoeostasis mechanism in mammals. Capsaicin interferes with the calcium channel in it, and causes it to activate at around body temperature. So, mammals will need to develop another thermal regulation system before they can remove the receptor. Until the major source of food are capsicums there is not enough selection pressure for this. CS Miller (talk) 10:57, 23 August 2011 (UTC)

Thanks; that seems reasonable. --Trovatore (talk) 20:42, 23 August 2011 (UTC)

Then you get the paradoxical cases of humans who eat the stuff deliberately for the endorphin glow that comes with it. I wonder if that happens with mammals in the wild, as well. --Trovatore (talk) 10:27, 23 August 2011 (UTC)

Do you have a reference for any cultivar or variety of tomato being toxic? Yes, they contain small amounts of toxic substances, as do most foods, but as far as I'm aware their reputation for toxicity was never anything but a flat mistake. Calling it an "exaggeration" is too mild; it was just wrong. --Trovatore (talk) 07:34, 23 August 2011 (UTC)

Op myles325a back live. Yes, I've checked up and you are right. Tomatoes are related to, and look like, deadly nightshade, and apparently ALL parts of it including the leaves and roots are indeed poisonous, except for the fruit. This makes sense, as the fruit is the only part of it that the plant needs to have eaten. Myles325a (talk) 07:48, 23 August 2011 (UTC)

Members of Solanaceae are just naturally very rich in alkaloids. And alkaloids are usually used as the anti-herbivore chemical defenses of plants aimed at indiscriminate feeders (animals who will eat the whole plant if they can), most notably insect and mammalian grazers. Birds are obviously not usually indiscriminate feeders. So yes, that's why concentrations of different alkaloids can vary in different parts of the plants and why they sometimes exclude specific groups of animals. It's not only birds though, some fruits of poisonous Solanum are only poisonous (or at least far more poisonous) when unripe.

And for what it's worth, other plants do have the same kind of targeted toxicity. It's actually fairly common when it comes to berries, especially the brightly colored ones. Pokeweed, Mistletoe, Baneberry, and Holly for instance have berries or seeds poisonous to mammals, but not to birds. Elderberry are also toxic only when unripe. Poison ivy is another good example, they have contact toxins in their vegetative parts but their fruits are perfectly edible for birds. Cashews also have edible fruits but the seed shells are protected by contact toxins even if the seeds themselves are also edible. Milder examples of this kind of repulsion/attraction mechanisms for seed dispersers also includes the extremely sour unripe fruits of some plants and plants with edible berries that are covered with specifically anti-mammalian defenses (like spines). All of them are not members of the nightshade family. Some plants also use different classes of chemical compounds like saponins which are toxic to insects and unpalatable for livestock, even when their fruits are quite edible. Also seed dispersal, while important, is usually less so when compared to the need for fertilization and sheer survival. The bulbs of members of Liliaceae (lilies) for instance are highly poisonous to mammalian grazers and they don't exactly need other species to disperse their seeds.

It's also an ongoing war, so some animals have circumvented those defenses or even coopted them (ragworts and cinnabar moths for instance), others are specifically targeted or excluded (as discussed above, and birds and capsaicin), others have actually evolved with it (the mutualistic relationship between Manduca hawkmoths and Datura is one fascinating example).

All in all, you could simply say that in the plant kingdom, nightshades are armed to the teeth.-- Obsidi♠n Soul 10:56, 23 August 2011 (UTC)

For what it's worth, it's not clear that the indirect allergic reaction of most humans to the urushiol in poison oak, poison ivy, and the like, is adaptive for the plant. Most animals don't seem to react that way, or at least not as strongly (deer, for example, will eat poison oak branches). The twenty-four-hour-or-so delay before the reaction shows up is not ideal as a chemical defense, and there are similar chemicals in the skin of the mango fruit, which would seem to have no objection to mammals (or indeed humans) as seed dispersers.

Also, urushiol polymerizes into a strong lacquer (in fact, lacquer in the original, strict sense is polymerized urushiol oops, from the lacquer article it appears this is not the original sense) so it's plausible that its function for the plant is simply to close up wounds. --Trovatore (talk) 21:07, 23 August 2011 (UTC)

Hm didn't know that. Scratch Anacardiaceae then :P At least the contact toxins defense theory, urushiols are also resins and thus might still function as plant defense against insects. -- Obsidi♠n Soul 02:14, 24 August 2011 (UTC)

Aside from digestive issues, some plants may favor birds as seed dispersers for other reasons. Birds generally can disperse seeds to farther and more varied locations than mammals can (e.g. mountain tops, islands, etc.), and this can aid in long-term persistence of a population. SemanticMantis (talk) 14:30, 23 August 2011 (UTC)

I'll mention in passing that there have been experiments in the past where tomatoes have been grafted on to jimsonweed root stock, with the intention of producing a tomato plant with the inherent frost and insect resistance of the jimsonweed: [2]. Such experiments were abandoned when it was found that toxic concentrations of (hallucinogenic) alkaloids migrated into the tomato fruit. The experiment has occasionally be independently repeated by farmers and gardeners who don't know better, often with unpleasant and dangerous results: [3]. TenOfAllTrades(talk) 14:54, 23 August 2011 (UTC)

Op myles325a back live. You pay a lot more for a tomato like that. This is a case where if you cook it, YOU get stewed, not the tomato. Myles325a (talk) 10:23, 25 August 2011 (UTC)

From what I've heard about jimsonweed, it's not a good trip. Basically you're sick and delirious. I don't think many people do it for pleasure. --Trovatore (talk) 09:50, 26 August 2011 (UTC)

(I'm a layman). It occurs to me that since birds don't chew their food the seeds have a much better chance of making it out the other end intact, aside from other digestive issues. --Sean 16:54, 23 August 2011 (UTC)

Myles325a back live. That makes excellent sense. Also, the digestive tract of a bird is very much shorter than that of most mammals. Myles325a (talk) 10:23, 25 August 2011 (UTC)

Take a read of Bugs put the heat in chili peppers for a reference on the topic. Graeme Bartlett (talk) 11:15, 25 August 2011 (UTC)

event horizon

Is the solar equivalent radius the black hole's event horizon? --DeeperQA (talk) 13:06, 23 August 2011 (UTC)

I only find the term "solar equivalent radius" used with respect to describing galactic evolution, which is unrelated to an event horizon. For the basic case of a nonrotating black hole, the event horizon is the Schwarzschild radius, a value proportional to the mass of the object in question. — Lomn 13:34, 23 August 2011 (UTC)

if the mass of the Sun and the mass of a Black Hole were the same would the event horizon of the Black hole be the same radius as the solar radius? --DeeperQA (talk) 14:28, 23 August 2011 (UTC)

No, it would be significantly smaller. --Goodbye Galaxy (talk) 14:41, 23 August 2011 (UTC)

Goodbye Galaxy is correct. If the Schwarzschild radius of a solar-mass black hole was the radius of the Sun, then the Sun (being of solar mass) would be a black hole. Obviously this is not the case. Our SR article, linked above, notes that the SR for a solar mass body is 3 km; the Sun has a 700 000 km radius. — Lomn 15:51, 23 August 2011 (UTC)

So... Obviously the surface of the star is not the radius of the black hole it would make, other wise nothing from beneath the surface would ever be able to escape... Our sun is not large enough to MAKE a black hole, but on a star that CAN make a black hole, say it makes a black hole that's 10km wide, it's going to have similar gravity to the original star right? (minus any matter that's lost in the nova or whatever)... Does that mean, that in the original star, there was essentially already a black hole in the middle 10km? As in no material would have ever been able to escape from that region? Vespine (talk) 23:10, 23 August 2011 (UTC)

How would such a region avoid growing if things could enter it but not leave? The substitution of a point mass at an object's center of mass is only valid when considering the effects outside the body (and is also only strictly valid for spheres, though at large distances it is approximately true regardless of the shape). --Tardis (talk) 04:37, 24 August 2011 (UTC)

Duh! Of course, the star has to collapse 1st... Thanks. Vespine (talk) 01:25, 25 August 2011 (UTC)

What would happen if you injected fat into a vein?

I guess the subject is basically the question. I assume different types and amounts of fat will have different answers too. Egg Centric 17:51, 23 August 2011 (UTC)

I expect it would cause a nasty embolism and probably kill the person if we are talking about more then a microscopic amount. Googlemeister (talk) 18:59, 23 August 2011 (UTC)

See fat embolism. Dragons flight (talk) 19:06, 23 August 2011 (UTC)

Total amount of platinum

What's the total amount of platinum in/on Earth, including both what's already been mined and what's still in rocks somewhere? --75.10.48.39 (talk) 17:53, 23 August 2011 (UTC)

Well, our article says "Platinum is one of the rarest elements in the Earth's crust and has an average abundance of approximately 0.005 mg/kg" The crust is about 0.5% of Earth's mass, which is 6x10²⁴kg. So that's about 3x10²²kg; or 1.5x10²⁰mg of platinum, 1.5x10¹⁷g, 1.5x10¹⁴kg. This is, of course, rather a guesstimate, I wonder if there are any other estimates out there. Grandiose (me, talk, contribs) 18:00, 23 August 2011 (UTC)

I'd expect there to be substantially more in the core, and also a bit in the oceans, although those sources may be unavailable to us for quite some time. StuRat (talk) 01:46, 24 August 2011 (UTC)

The total mined is about 180 million toz according to http://www.howstuffworks.com/question213.htm. Googlemeister (talk) 18:57, 23 August 2011 (UTC)

Online seismograph reports?

It feels like we just had an earthquake (in Connecticut). Is there an online seismograph report for the region that I can check? RJFJR (talk) 18:03, 23 August 2011 (UTC)

Oh, USGS NEIC at [4] RJFJR (talk) 18:06, 23 August 2011 (UTC)

5.9 in Virginia, time seems right. That's pretty far away but this building may be particularly susceptible to sway. RJFJR (talk) 18:07, 23 August 2011 (UTC)

I felt it also in Syracuse, New York, on the ground floor.. It's not unusual for earthquakes of that magnitude to be felt very far away. —Akrabbim^talk 18:21, 23 August 2011 (UTC)

On the US East coast anyway. If a 5.9 hit in California, it probably wouldn't be felt 100 miles away. Different geology knocks them down quick out there. Googlemeister (talk) 18:53, 23 August 2011 (UTC)

A 5.9 is big enough to be felt 100 miles away even in California -- that's a big quake. This is really remarkable: this quake comes just hours after a series of pretty large quakes in Colorado, which also gets very few. Looie496 (talk) 20:14, 23 August 2011 (UTC)

In the most literal sense, this is a "coincidence" - a "near-simultaneous" incidence of an earthquake in two unusual places. Before we jump to calling it "really remarkable," though, we should do a thorough statistical analysis to determine how improbable a coincidence this really is. There's no shortage of research into remotely triggered earthquakes, or induced seismicity, teleseismic interactions, etc. Here's a few: Remotely Triggered Earthquakes Following Moderate Mainshocks (or, Why California Is Not Falling into the Ocean), from the US Geological Survey; Seismicity Remotely Triggered by the Magnitude 7.3 Landers, California, Earthquake, from the journal Science (1993); and Remotely Triggered Seismicity on the United States West Coast following the Mw 7.9 Denali Fault Earthquake. It's difficult to produce convincing evidence that distant earthquakes are causally related, and this is an active area of research subject to scientific dispute. But it's at least within the realm of possibility that two earthquakes in unlikely, not-very-seismically-active areas, might be linked. I'm sure in the next weeks and months, seismology journals will be hosting a flurry of research papers into this fairly large earthquake in an otherwise seismically-quiet area. Nimur (talk) 03:02, 24 August 2011 (UTC)

@Louie & Googlemeister: According to a Berkeley Seismologist, quoted here: [5] an earthquake of the size that hit Virginia would "rarely" be felt farther than 30 miles from the epicenter; the very different geology of the Eastern U.S. compared to California explains the difference in travel. --Jayron32 03:38, 24 August 2011 (UTC)

lizards

What is the best place and time of year in Ireland to find Lizards that are native to Ireland and also legless lizards. — Preceding unsigned comment added by 86.45.169.42 (talk) 18:37, 23 August 2011 (UTC)

As you probably know there are only two reptile species in Ireland, the Viviparous lizard (Zootoca vivipara) and the legless lizard, better known as the slow-worm (Anguis fragilis). The lizard is widely distributed across the island and can be found in dry heathland, dunes, grassland, bogs and even gardens. The slow-worm is confined to The Burren. The best time to see them is during the warmer weather of spring and summer when they are more active. I'm sure there must be a Natural History Society or club around the Cork area that could offer you local advice. Good luck. Richard Avery (talk) 22:21, 23 August 2011 (UTC)

Required muzzle velocity of a cannon to shoot any target on Earth

What would be the minimum muzzle velocity required for a projectile fired from a cannon to be capable of hitting any target on the planet? Lets say it's being fired from some kind of futuristic cannon like a railgun or a massdriver. ScienceApe (talk) 19:17, 23 August 2011 (UTC)

About 70% of earth's escape velocity which is about 7.9 km/s, assuming no air friction. Dauto (talk) 19:45, 23 August 2011 (UTC)

(ec) Ballpark, ignoring air resistance, you need orbital velocity which, at sea level, is about 8 km/s. Technically you don't need quite this much, as (assuming you can rotate your cannon) you only need to get a projectile halfway around the world, but that won't change the final answer by more than a percentage point or two. — Lomn 19:54, 23 August 2011 (UTC)

If you don't ignore air resistance, then only needing to get half-way round is a big advantage. It means you can reach the opposite side of the planet at ground level, rather than needing enough altitude to counter the drag on the second half of the trip. --Tango (talk) 22:03, 23 August 2011 (UTC)

Project Babylon?--92.28.71.6 (talk) 20:53, 23 August 2011 (UTC)

Just because an object circles the Earth once does not mean that it is in orbit, see Space shuttle abort modes#Abort Once Around (AOA) for an example of this. Whoop whoop pull up ^{Bitching Betty | Averted crashes}`

With an AOA, they do achieve orbit. The orbit is just too low so the drag from the atmosphere is too high and the orbit decays before they can get around more than once. You still need orbital velocity to AOA. --Tango (talk) 21:57, 23 August 2011 (UTC)

They do not. With an orbit, it will circle the Earth forever neglecting air resistance. With an AOA, even without air resistance, it will come down where it was launched. An AOA is basically just a suborbital trajectory where the distance traveled downrange is equal to the Earth's circumference. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:33, 27 August 2011 (UTC)

• Can I butt in with a follow-up question? To hit a target on the exact opposite side of the earth using minimum muzzle velocity, what direction would you fire in? Ignore air resistance. 86.179.3.58 (talk) 22:18, 23 August 2011 (UTC) PS: I was assuming that the target could be attained with some muzzle velocity in numerous directions, but actually I'm not even sure if that is correct.

Ignoring air resistance, possible obstacles such as mountains, and earth's rotation, a very low shot in any direction will do the trick. Dauto (talk) 22:38, 23 August 2011 (UTC)

I wonder if this is actually possible... I mean, wouldn't there be an "upper limit" to how fast you can shoot an "un-powered" projectile in the atmosphere? and how quickly it would decelerate? I remember reading something about theoretical mass driver naval guns and they still said the range would only be in the order of hundreds of miles. Vespine (talk)

Slightly pedantic, maybe, but such a cannon would not be possible, as it would be unable to shoot down its own barrel, and would therefore not be capable of hitting any target on Earth, whatever the speed of the projectile. Likewise with the 'other sides' of mountains, etc.

What do you mean by shoot down its own barrel? Dauto (talk) 23:39, 23 August 2011 (UTC)

@Dauto, are you saying that a very low shot in any direction would be the optimum shot in terms of minimising muzzle velocity? I ask again because on a level surface, a given distance is achieved at minimum velocity by firing up at 45 degrees, isn't it? So, when the whole round Earth is considered this changes and a low shot is best? 86.179.3.58 (talk) 23:43, 23 August 2011 (UTC)

Combine the Vis-viva equation $v^{2}=G(M+m)\left({\frac {2}{r}}-{\frac {1}{a}}\right)$, The standard equation of an elipse in polar coordinates from Kepler's laws of planetary motion $r={\frac {p}{1+\varepsilon \,\cos \theta }},$ and the relation between the Semi-major axis and the Semi-latus rectum $a={\frac {p}{1-\varepsilon ^{2}}}.$ to get $v^{2}={\frac {G(M+m)}{a}}\left({\frac {1+2\varepsilon \,\cos \theta +\varepsilon ^{2}}{(1-\varepsilon ^{2})}}\right)={\frac {G(M+m)}{p}}(1+2\varepsilon \,\cos \theta +\varepsilon ^{2})$ where $p\,$ is the semi-latus rectum which is the radius of the orbit half way between apogee and perigee (90 degrees away from each). In our problem that coincides with the radius of the earth $R\,$. Setting theta to 90 degrees (0 degrees is the perigee while 180 degrees is the apogee) we get the equation $v^{2}={\frac {G(M+m)}{R}}(1+\varepsilon ^{2})$. Clearly the speed is minimized by choosing the eccentricity $\varepsilon =0$. That's the eccentricity of a circular orbit. Dauto (talk) 03:18, 24 August 2011 (UTC)

Why do you want the semi-latus rectum to be the Earth's radius? Assuming your target is on the surface, you want the radius of the orbit when it's above the target to be equal to the Earth's radius. I can't see why you would need to have the apogee and perigee be 90 degrees away from that point. The simplest method (from a mathematical, not engineering, viewpoint, and ignoring air resistance) is to fire horizontally at a speed between zero and circular orbital velocity (which makes the firing point the apogee). If you fire at zero speed, you'll hit yourself. As you increase the speed, you'll go further and further around until you reach the opposite side of the Earth at circular orbital velocity (actually, you would be in a circular orbit and wouldn't hit at all, but that's just the limiting case). By varying the angle you fire at, you can move the agogee (and make it higher, obviously). I would need to do some maths to work out whether another angle would allow a slower launch speed, so I'll leave that to someone else. --Tango (talk) 11:45, 24 August 2011 (UTC)

You don't need to leave the math to someone else. I already did the math in the post right above yours. My post is correct. read it carefully. The apogee is actually the half way point of the trajectory, not the initial point as you stated. Remember that we are assuming that the canon is at the surface of the earth - not at the top of a mountain. That puts the canon and the target at the same level. Obviously, the solution to this problem is a degenerate one because the circular orbit, as pointed out by others, skims the surface of the planet all the way around. Dauto (talk) 15:07, 24 August 2011 (UTC)

As far as I can see (and I'm by no means 100% sure), the only way to reach the antipodean point is by firing exactly horizontally. Any other trajectory headed for the antipodean point would inevitably hit some other part of the Earth first. The lowest velocity horizontal-firing case would be a circular orbit, which would skim the antipodean point, but also skim all other points on the Earth's circumference, so would not in practice be achievable even if the Earth was a perfectly smooth sphere. 86.183.4.36 (talk) 12:02, 24 August 2011 (UTC)

There is clearly an infinite family of elliptical orbits that pass through a point and its antipodes, with one focus at the Earth's center. 69.234.120.192 (talk) 13:00, 24 August 2011 (UTC)

Sure, but show me one that doesn't hit another part of the Earth first. 86.183.4.36 (talk) 13:21, 24 August 2011 (UTC)

Um, none of them do. Each ellipse crosses the earth's surface exactly twice (only at the two points of interest). In general, an ellipse might intersect a circle in four places, but none of those ellipses has a focus at the center of the circle. 69.234.120.192 (talk) 13:51, 24 August 2011 (UTC)

Sorry, I realised later that I made a silly mistake. I was making the centre of the ellipse coincide with the centre of the earth, not the focus. 86.181.200.231 (talk) 17:03, 24 August 2011 (UTC)

If air resistance is included, I'd think you'd want to minimize that by firing at a steep angle, over 45 degrees. You might still have a problem with your projectile burning up in the atmosphere even then. StuRat (talk) 01:38, 24 August 2011 (UTC)

The trajectory needs to be similar to that of an ICBM:

...the flightpath is part of an ellipse with a vertical major axis; the apogee (halfway through the midcourse phase) is at an altitude of approximately 1,200 km; the semi-major axis is between 3,186 km and 6,372 km; the projection of the flightpath on the Earth's surface is close to a great circle, slightly displaced due to earth rotation during the time of flight; the missile may release several independent warheads, and penetration aids such as metallic-coated balloons, aluminum chaff, and full-scale warhead decoys. reentry phase (starting at an altitude of 100 km): 2 minutes—impact is at a speed of up to 4 km/s (for early ICBMs less than 1 km/s); see also maneuverable reentry vehicle.

Count Iblis (talk) 02:05, 24 August 2011 (UTC)

Unreal Creatures in Cave paintings

1. How often did our ancestors draw imaginary creatures in cave paintings (e.g. dragons, gods, etc.)? Where can I find such paintings' images on the web?
2. Is this painting a fake?

Thanks, Oh, well (talk) 19:59, 23 August 2011 (UTC)

Although [6] is supposed to teach you that humans walked the Earth with dinosaurs, which is absurdly false, it does have a nice collection of ancient dragon depictions. And, that FSM painting is almost certainly a fake. Authentic cave paintings almost never use separate full outline and full fill color pigments as is popular with drawing and painting today. 76.254.20.205 (talk) 20:20, 23 August 2011 (UTC)

A recent feature movie about cave paintings, "Cave of Dreams," portrayed drawings of what appeared to be "Monkeys on Wheels," a type of creature which never was manifest tens of thousands of years ago. Three members of my family watched the movie and agreed that some of the cave drawings appeared to be monkeys on wheels. Maybe it was just inept and unskilled drawings of mammoths. Or maybe the ancients dreamed of monkeys on wheels and drew them accordingly, thousands of years before they put any practical device on wheels. I seriously considered changing my Wikipedia name to "Monkey on wheels," so it is no idle observation. Edison (talk) 04:25, 24 August 2011 (UTC)

I assume you're referring to Werner Herzog's Cave of Forgotten Dreams --George100 (talk) 08:25, 24 August 2011 (UTC)-

Our article: Cave of Forgotten Dreams -- 110.49.235.213 (talk) 12:15, 24 August 2011 (UTC)

Some anthropologists, such as David Lewis-Williams, have theorised quite persuasively that some rock paintings depict hallucinatory visions seen in dreams or trances deliberately induced by drugs, extreme exhaustion caused by ritual dancing, etc. In such dreams and trances the shaman (or whatever equivalent term one might use) likely saw/sees imaginary entities, often composite animals (bird-headed men are I believe common in African rock paintings) as well as realistic ones. {The poster formerly known as 87.81.230.195} 90.197.66.45 (talk) 07:38, 24 August 2011 (UTC)

Because all the races of man diverged long before recorded history, we should be confident that ancient humans possessed the same capacity for art, imagination, delusion, hallucination, and guesswork as those who live today. Because so many of our own artworks are made with ephemeral materials, it seems reasonable to suppose that what survives on cave walls is only a tiny and probably a low-quality subset of what was available. But it's also worth mentioning that the ancients sometimes had a penchant for paleontology (such as the Greeks who hunted for "giants' bones" to display as local relics - see e.g. [7]) Of course, they had fewer scientists, much poorer communications and archives - they couldn't develop the kind of comprehensive insights that people take for granted nowadays. But I would not rule out the possibility that a well-preserved skeleton led to a dinosaur artwork on more than one occasion in prehistory. Wnt (talk) 22:53, 24 August 2011 (UTC)

vehicle skid marks

could a car travelling 10-15 km/hour leave 5-10' skid marks that end 10-15' behind the vehicle's final stopping point on dry pavement? 24.69.118.194 (talk) 21:37, 23 August 2011 (UTC)

I don't see why not. There are loads of factors that determine things like that. The weight of the car, the type and condition of the tyres, the type and condition of the brakes, what the driver does, etc.. I can't see why there couldn't be a combination that results in what you describe. --Tango (talk) 22:26, 23 August 2011 (UTC)

here is a stopping distance calculator. Having a bit of a play around with that, and having done a few skids myself, I think 10-15' skid sounds extreme for going only 10-15km/h. As the above says, it's not "impossible" if you plug in appropriate variables (over loaded car, bald tyres, loose surface), but with a normal weight car, road worthy tyres and a sealed dry road, I think you'd be lucky to get 2-4' skid, even if you tried to break very violently. To get 10-15' skids, I think you'd need to be going more like 20-30km/h. Another factor to consider is that a lot of cars these days have Anti-lock breaking so it's quite hard to actually skid in them, especially at such a low speed. Vespine (talk) 22:44, 23 August 2011 (UTC)

Just because you have ABS does not necessarily mean that it will work. Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:35, 27 August 2011 (UTC)

That sounds like you need to consult an appropriate forensic specialist with expertise in vehicular accident reconstruction. TenOfAllTrades(talk) 23:24, 23 August 2011 (UTC)

Sounds like the skid marks are too long for that speed, unless another vehicle then pushed it along, which can happen in multiple vehicle accidents. StuRat (talk) 23:32, 23 August 2011 (UTC)

You you were stopping on a steep downhill grade. Googlemeister (talk) 14:49, 24 August 2011 (UTC)

Yes, yes. Right, right. StuRat (talk) 22:08, 24 August 2011 (UTC)

rainfall and earthquake

We've had extreme rainfall on the East coast of the United States this summer. Could large quantities of water entering the ground contribute to the triggering of an earthquake? Links: [8], [9]. Bus stop (talk) 21:45, 23 August 2011 (UTC)

Large bodies of water created behind dams can produce some seismicity, injecting fluids deep into the crust can also trigger earthquakes, but it's hard to imagine that rainfall (however intense) would have such an effect - most of the rain will simply run of into rivers, rather than end up in the ground. Mikenorton (talk) 22:23, 23 August 2011 (UTC)

It might be relevant that the depth of today's earthquake was 1km. I'm not geologist but it seems awfully deep for rainwater to have an effect. Dismas|^(talk) 02:51, 24 August 2011 (UTC)

The focal depth has been recalculated to 6 km, so not that shallow - I should have linked to our article on induced seismicity. Mikenorton (talk) 07:07, 24 August 2011 (UTC)

There's an article in Tectonophysics that looked at this issue.

"Correlations between streamflow and intraplate seismicity in the central Virginia, U.S.A., seismic zone: evidence for possible climatic controls"

Sean.hoyland - talk 13:35, 24 August 2011 (UTC)

Well I've never heard of hydroseismicity before, but always something new out there. This study found an effect at Mt. Hood in Oregon, but note that there was a delay of 151 days between the spring melt and the peak in the seismicity, as it takes time for the pressure change to reach the level at which earthquakes initiate. Mikenorton (talk) 19:11, 24 August 2011 (UTC)

We've been having a severe drought on my part of the east coast. We hoped we'd get some rain from Irene, but no. Bubba73 ^{You talkin' to me?} 02:53, 27 August 2011 (UTC)

Pressure sores

Is it possible to get pressure sores just by remaining seated for too long on a regular basis?--92.28.71.6 (talk) 21:49, 23 August 2011 (UTC)

Our article says "A simple example of a mild pressure sore may be experienced by healthy individuals while sitting in the same position for extended periods of time" bit this is unsourced. Grandiose (me, talk, contribs) 22:03, 23 August 2011 (UTC)

http://www.foxnews.com/health/2011/03/31/obese-ohio-man-dies-fused-chair-2-years/ μηδείς (talk) 22:51, 23 August 2011 (UTC)

I'm not sure the Fox News link has anything to do with pressure sores. It smells of hoax - among other things! Richard Avery (talk) 07:16, 24 August 2011 (UTC)

Not just from remaining seated, no. You have to not change positions, either. Even a slight change in position can allow any pooling blood to move on. StuRat (talk) 01:28, 24 August 2011 (UTC)

Identical Universes

Would it be possible in principle to create another Universe identical to ours (at some instant of time)? Would such a Universe inevitably evolve in exactly the same way as ours, and, if not, what would be the cause of the divergence? I'm not sure whether things at a quantum level (or whatever) may exist unknowably or happen randomly in the sense that they are not even in principle replicable or determined by a replicable "state of the Universe"... 86.179.3.58 (talk) 22:12, 23 August 2011 (UTC)

I don't know what you mean by creation of an universe in principle, but there is a general theorem called No-cloning theorem which forbids the creation of a clone of an unknown quantum state. Bell's theorem states that no hidden variable theory can reproduce QM so whatever randomness is provided by QM must be really random since any unknowable internal variable producing the apparent randomness would violate Bell's theorem. Dauto (talk) 22:28, 23 August 2011 (UTC)

Creating universes is obviously not within our abilities. However, the article determinism will help answer the rest of your question. --Tango (talk) 22:31, 23 August 2011 (UTC)

Thanks. In case it is unclear, "in principle" means ignoring all practical difficulties, and the fact that it is of course not actually within our abilities. Kind of like a thought experiment. 86.179.3.58 (talk) 22:39, 23 August 2011 (UTC)

Whether the universe is deterministic at the quantum level is unknowable. Even in principle, we can not recreate the conditions of the big bang (e.g., there is no principle which could reverse the metric expansion of space.) If we could, the aforementioned unknowability prevents us from saying whether it would turn out the same. 76.254.20.205 (talk) 02:21, 24 August 2011 (UTC)

If you could create a universe identical to our own that would evolve in the same way, then your copy in that universe would necessarily have to create another such identical universe etc. etc. All your copies are identical, so you cannot locate yourself at one particular level in this infinite hierarchy of universes. Count Iblis (talk) 03:54, 24 August 2011 (UTC)

Sorry, I should have mentioned that the new Universe is created instantaneously. If it takes time to build then the question gets much messier, in a way not relevant to the question I wanted to ask. 86.183.4.36 (talk) 12:17, 24 August 2011 (UTC)

"Instantaneously" is difficult to support if you have to take relativity into account. Sounds as if your universe creation scheme requires the suspension of so many physical laws as we understand them that you might as well call it magic, in which can anything is possible. Gandalf61 (talk) 14:04, 24 August 2011 (UTC)

Yes, you can imagine many aspects of this universe creation to be magic that "just happens". Although I didn't originally know the terminology, my question was really about determinism and the theoretical possibility of cloning of quantum states, rather than any ancillary issues. 86.181.200.231 (talk) 17:08, 24 August 2011 (UTC)

The definition of a universe is a deep philosophical question, but as a barbaric supposition it seems fair to say that anything that exists which is subject to the laws of physics as we know them is part of our universe. So the creation (and generally, I'd say, the contents) of another universe is outside our laws of physics. This makes it either impossible or meaningless (probably the latter) for us to say any operation you propose in this realm is possible or impossible. Wnt (talk) 20:31, 27 August 2011 (UTC)

August 24

Dark side of a planet

Is it possible for a planet to be habitable all the way around when it is locked into an orbit where only one side ever faces its star? And by habitable, I mean that the extremes aren't any more extreme than what is present on the Earth now. Dismas|^(talk) 04:37, 24 August 2011 (UTC)

If it had an extremely thick atmosphere, as in a gas giant, then the heat from the sunlight could be effectively redistributed to the other side. However, this would mean you couldn't see the Sun from the surface and you'd have thousand mile per hour constant hurricanes, like the Great Red Spot, and the atmosphere would be largely hydrogen, helium, and methane. So, this doesn't sound very habitable to humans, but I can imagine something evolving there which thrives in such conditions. StuRat (talk) 04:46, 24 August 2011 (UTC)

The tidally-locked world is a staple of science fiction. The earliest account I can find (with some admittedly very brief searches) is in Olaf Stapledon's 1937 novel Star Maker, which describes a tidally-locked world in orbit about a red dwarf star; the habitable region is limited to region along the terminator. (More often than not, science fiction treatments generally assume a civilization occupying the terminator, along the boundary between the day and night side of the planet.) In reality, under conditions of planetary mass and atmospheric density like Earth's, tidal locking leads to runaway glaciation (as water precipitates and freezes on the dark side), followed by atmospheric collapse (as atmospheric gases eventually condense on the cold side). In principle, one could stabilize such a system at least temporarily (on geological time scales) through extensive vulcanism (replenishing atmospheric greenhouse gases).

On the other hand, this paper discusses simulations of Gliese 581 d: a real exoplanet orbiting a real red dwarf star. The paper's simulations suggest that there could be liquid water (indeed, the planet could be ocean-covered) if it had a dense atmosphere (at least 10 times Earth's atmospheric pressure at the surface) rich in carbon dioxide and water vapor. Their simulations of a fully-locked, water-covered world with a 20-bar carbon dioxide atmosphere predicted temperatures as low as 280 K (a cool day, but above freezing) in the middle of night side, and a high of 305-310 K (a heat wave in most of the Western world) in the middle of day side. Whether you would consider that 'habitable' depends on your definitions. TenOfAllTrades(talk) 05:05, 24 August 2011 (UTC)

Wouldn't a pressure of 20 bar crush you like a bug? 67.169.177.176 (talk) 05:57, 24 August 2011 (UTC)

That pressure is like being under 200 m of water. Sure it would be bad for unprotected humans (cause we aren't designed for it), but fish have evolved to be happy at that pressure and much higher pressures. Life is certainly possible at such pressures. Dragons flight (talk) 06:36, 24 August 2011 (UTC)

Once the pressure equalizes, you wouldn't feel it. For example, if the same pressure air is inside your lungs as outside, you wouldn't feel any pressure on your chest. However, the behavior of gases changes a bit under higher pressures, so that a normal oxygen-nitrogen atmosphere doesn't work. Specifically, the nitrogen must be replaced by other gases. StuRat (talk) 08:42, 24 August 2011 (UTC)

And more importantly, the oxygen percentage must be reduced. -- 110.49.235.213 (talk) 13:58, 24 August 2011 (UTC)

You would also have to be careful of the CO2 you mentioned because CO2 is toxic at around 5% at atmospheric pressure, so you couldn't have more then 0.25% CO2 in the atmosphere of a 20bar planet unless that is something humans could adapt to. Googlemeister (talk) 14:47, 24 August 2011 (UTC)

Okay, I guess I should have been more precise. I wasn't referring to fish. I meant habitable by humans. Present day humans. So, judging by the answers thus far, I guess the answer is "no". Thanks, --Dismas|^(talk) 09:03, 24 August 2011 (UTC)

You can use Mercury as an example. It rotates about 1.5 times for every Mercury year (88 days). So, it gets about 1.5 days per year. It isn't locked, but it is very close to being so. On the light side, the temperatures are over 400°C. The dark side is below -180°C. The big problem isn't really the temperatures - it is the wind. Mercury has no noticeable wind because there is no noticeable atmosphere. But, if it were habitable, there would be monstrous storms due to the constant conflict between the two temperature extremes. -- kainaw™ 12:58, 24 August 2011 (UTC)

But, of course, then the temperatures wouldn't be so extreme, since the atmosphere would redistribute the heat. StuRat (talk) 21:15, 24 August 2011 (UTC)

Maybe not 500K extreme, but still pretty extreme. Googlemeister (talk) 13:11, 25 August 2011 (UTC)

Carrot overdose

What level of carrot consumption would lead to hypervitaminosis A ? According to that article, "Betacarotene, a precursor of vitamin A, is selectively converted into retinoids, so it does not cause toxicity." So, does that mean that carrots don't cause toxicity, or are there other forms of carotene or vitamin A present in carrots which do cause toxicity ? (Note that this question isn't about carotenosis, another problem from excess carrot consumption, leading to orange skin.) StuRat (talk) 05:06, 24 August 2011 (UTC)

Carrots contain beta- and alfa-carotene, neither of which can cause hypervitaminosis A. Only retinol can cause this type of overdose. 67.169.177.176 (talk) 05:51, 24 August 2011 (UTC)

Carrots can cause liver damage (cirhosis) etc. according to [10]. The term is apparently "carotenosis". Collect (talk) 13:12, 24 August 2011 (UTC)

I'm suspicious about carrots causing cirrhosis. [11] suggests such a thing, with help from alcohol, but I'm still not convinced. A rabbit caught hypervitaminosis A from eating too many carrots (PMID 11702930), but this is because they convert beta-carotene into retinol, which carrots do not possess. Excessive use of vitamin A supplements has caused liver cirrhosis requiring transplant [12] but their contents were unspecified in the publication. People who have turned yellow from eating too many carrots carotenosis had slightly elevated vitamin A levels but were otherwise healthy. (PMID 8449701). Apparently carrot overconsumption is not so uncommon (PMID 1764358) and was even claimed by a few patients to be addictive like tobacco! (PMID 1511232). Wnt (talk) 17:46, 24 August 2011 (UTC)

Carotenosis is NOT the same as cirrhosis! What happens in carotenosis is that the excess carotene deposits in your skin and turns it orange -- it DOES NOT CAUSE LIVER DAMAGE OR ANY SERIOUS HEALTH EFFECTS! And FYI, vitamin A supplements all contain retinol rather than beta-carotene. 67.169.177.176 (talk) 00:24, 25 August 2011 (UTC)

Agreed - I wasn't suggesting otherwise. Wnt (talk) 00:50, 25 August 2011 (UTC)

Our Beta-carotene#Side effects and briefly Vitamin A#Toxicity notes possible side effects from chronic excessive consumption of beta-carotene. It's not clear to me that this is likely to be a concern from consumption of carrots. Nil Einne (talk) 12:01, 25 August 2011 (UTC)

Only in people who smoke. 67.169.177.176 (talk) 05:59, 26 August 2011 (UTC)

Hand propping

At what point does an aero-engine become too powerful to allow starting by hand? More specifically, is it possible to start an engine in the 500-to-600-hp range by hand-propping? I know that it is possible to swing the prop by hand with a 500-hp engine (most notably on the Winnie Mae), but what about even bigger engines? Is it possible, for example, to hand-prop an Electra 10-E (550-hp engines)? How about a DC-3 (as much as 1200 hp)? Or does it become too hard to pull the prop through with such high engine power (and/or too dangerous when the engine does catch)? What's the most powerful engine that has ever been hand-propped? 67.169.177.176 (talk) 06:14, 24 August 2011 (UTC)

I suppose you could hand-start much larger engines, provided the energy was stored up and then all used at once in the starter. Early phonographs worked in this way, by winding a spring prior to playing the record, as do hand-wound watches. An alternative to winding up a spring would be charging a capacitor. The first generation of telephones worked like this, and some military walkie-talkies. An external "starting unit" could be used to contain either the spring or capacitor, so this doesn't add to the weight of the plane. However, I'm not sure why this would be better than using an electric on-board starter. StuRat (talk) 08:17, 24 August 2011 (UTC)

No, I meant actually pulling the prop through by hand, either with just your hands or with some kind of device to give you a mechanical advantage (like a rope). Yes, some early aircraft used to have inertia starters which used a hand-powered flywheel to store the energy and release it at once, but that's not what I meant. Just FYI, the scenario I envision is a failure of the electric starter and/or the main battery. 67.169.177.176 (talk) 00:15, 25 August 2011 (UTC)

I see what you mean. I've often thought the same thing about cars. Yes, you can push-start a manual transmission car, but with an automatic, you're out of luck. StuRat (talk) 00:19, 25 August 2011 (UTC)

It isn't reasonable to talk about "such high engine power" because when the engine is being started it isn't producing any power. The significant parameter is the compression ratio. Hand starting quickly became impractical with larger and faster aircraft because of their higher compression ratios, higher displacement (eg cubic inches) and greater height above the ground. It was quickly recognized that hand starting an aero engine is a hazardous activity!

Major improvements in storage batteries helped hasten the end of hand starting. Between hand starting and modern electro-mechanical-pneumatic starters there was a "mechanical hand starter" called the Hucks starter. Dolphin (t) 08:32, 24 August 2011 (UTC)

So is it only the compression ratio that determines how much physical effort you have to make to pull the prop through, or does displacement also play a role? (Seems to me that both of these would be equally important.) Also, what is the practical limiting factor to hand-propping -- is it only the effort required, or is it the danger of getting chopped up when the engine catches? 67.169.177.176 (talk) 00:28, 25 August 2011 (UTC)

Costly military technologies

Many military technologies are beneficial to the civilian world -- at least according to those big military companies. Radar, jet engines, nuclear energy, composite materials, they all have great use in the peaceful world.

Now how does stealth technologies find their ways to benefit civilian lives?

Certainly there are short paths and long paths to civilian use. May be the way they build stealth fighters may be used to cut costs or increase reliability in civilian factories. But that's quite a long way to go from military to civilian and also marginal.

I mean how do we use radar-absorption materials or radar-reflection configurations technologies to make money in the civilian world? -- Toytoy (talk) 07:00, 24 August 2011 (UTC)

1) Radar-reflecting materials, if they can be adapted to work at other wavelengths, might be helpful on tall buildings which otherwise would tend to block cell phone transmissions, etc.

2) Similarly, such material might have application in space, to protect astronauts and equipment from various wavelengths of radiation.

3) If this technology is applied to microwave frequencies, it might be useful with microwave ovens.

4) Reflective materials might also have applications in reflector antennae.

5) People who are sensitive to EMFs (or think that they are) might appreciate a way to block such fields. StuRat (talk) 08:22, 24 August 2011 (UTC)

The stealth fighter uses its own geometric shape to reflect radar waves. It then uses some highly classified materials to absorb remaining EMF. The outer coating shall only absorb EMF at a number of limited frequency ranges.

Reflection of microwave is ancient technology. It has been available since the Iron Age. Though cooking-grade microwave may take a few more years to develop. In the mean time, we have forgotten most of the knowledge about fine cooking.

The only legitimate radar-absorbing material in my microwave oven shall be the CHICKEN!!!. I don't want to see my microwave oven heated to smoking by itself while my chicken remains frozen, just because someone used a radar-absorbing material inside the oven. -- Toytoy (talk) 10:44, 24 August 2011 (UTC)

You want the sides of the microwave oven to reflect microwaves, and perhaps the plate underneath the food should absorb them to cook from underneath. This is important if you want to simulate grilled food, for example. StuRat (talk) 06:33, 25 August 2011 (UTC)

A few days ago, I have seen a short article somewhere that argues that the U.S.S.R. failed because they could not use military technologies to improve their living while the U.S. usually have good civilian use for their military technologies. As a result, the U.S. could earn back a part of its military spending.

Now the stealth technology as a whole is extremely costly and it has to be highly classified. Even the allies can hardly know anything about it not to mention using it for any civilian product (if it can be used by the people). Does it mean that the investment to create this technology can be difficult to recover even in the distant future? -- Toytoy (talk) 10:52, 24 August 2011 (UTC)

Arguably and allegedly it might be recovered by providing military superiority in a conflict, with all the advantages which may follow from such superiority. Allegedly. --Ouro (blah blah) 12:10, 24 August 2011 (UTC)

How about cop defeating sportscars? Granted, just paying for your speeding tickets would probably be cheaper then a stealth car. Googlemeister (talk) 14:41, 24 August 2011 (UTC)

There is zero reason to believe that every military technology necessarily leads to useful civilian technologies, or that any spinoff technologies will actually be comparable in terms of their return on the investment. Even the most positive source of military R&D doesn't believe it is a substitute for civilian R&D, or that the economic returns are anything related. One should not confuse the two. It's true that military R&D can have, and has had, some civilian return. But expecting military R&D dollars to universally translate directly into civilian outputs is foolish and false economics.

This is a separate issue, mind you, from the possibility of boosting contractors who in turn use some of that boost to fund loss leaders and speculative R&D in other sectors, or manage to take the expertise in one field and apply it to others (military funding of transistor research, for example, didn't necessarily lead to lots of direct civilian applications, but it did increase the transistor industry's abilities and capital, which could then allow them to pursue other projects on the side). --Mr.98 (talk) 15:35, 24 August 2011 (UTC)

I think it has become more and more difficult for the top end military R&D to find its way into the civilian world. As a result, you spend more and more money to develop a weapon for making a weapon's sake. It is now less and less likely that the military R&D would help the civilian world and generate future tax money.

The stealth technology can be neutralized if some vital secrets are disclosed. Back to 1 million BC, an ape man who invented to use rocks would have become the king of the world if other ape men only fight with their bare hands. Now if a second ape man learned to use rocks, it did not make the first ape man's rock useless. Rocks are always fatal. The second ape man's rock only makes the first ape man more difficult to conquer the world.

However, if you have knowledge about any country's stealth fighter, you can probably invent a way to defeat it. Plus you can build one for yourself if you are capable. As a result, much of the technologies cannot be disclosed even to an ally. And on the other hand, the U.S., fearing that allies' stealth technologies can be uncontrollable, used its own power to get most of the allies to get on the F-35 wagon.

I think this is unlike before. The spread of jet engine technologies did not make existing jet fighters useless. -- Toytoy (talk) 16:53, 24 August 2011 (UTC)

I can't believe that nobody thus far has even mentioned the numerous ancilliary technologies required to make a successful stealth fighter, many of which have important civilian applications. Like for instance the new structural materials (composites, super alloys, etc.) from which the stealth fighter is made, which can also be used both in the civil aircraft market (lighter, faster passenger jets) and in other civil applications. Or the advanced forming/fabrication technologies used to give the airframe components their complex shape, which are also useful for manufacturing a wide variety of other products. Or the advances in engine technology which allow the same aircraft to supercruise at Mach 1+ without the use of gas-guzzling afterburners and also to take off and land vertically, and which might well be used in a future supersonic VTOL passenger jet. Or the top-of-the-line electronics used in the plane's fly-by-wire system, which could soon make their way into the next generation of PCs and Macs. It takes a lot more R&D to build a stealth fighter than just the radar-defeating technology, you know! 67.169.177.176 (talk) 03:07, 25 August 2011 (UTC)

Harrier Jumpjets with VTOL capabilities existed before the earliest functional stealth aircraft and the Concorde had supercruise ability well before any stealth aircraft as well. Googlemeister (talk) 13:09, 25 August 2011 (UTC)

True, but the Harrier couldn't break Mach 1 OR carry passengers, and the Concorde needed a three-mile runway to take off and land. With the new generation of engines developed in connection with the F-22 and F-35 programs, a future "super-Concorde" might be able to supercruise at Mach 2+ AND take off from any small-town airfield, AND burn less fuel per payload carried than either the Harrier or the Concorde. And besides, what about the advanced materials developed for the stealth program, not to mention the processing tachniques developed for those materials? These are also important technological advances with civilian applications. Same thing with the onboard electronics. 67.169.177.176 (talk) 06:09, 26 August 2011 (UTC)

Classification of TNOs: SDO vs. Detached TNO

CalRis (talk) 07:38, 24 August 2011 (UTC): Hello, I'm not sure whether this is the right place to ask this questions. I'm wondering about the orbital classification of Eris as a SDO-object (and the general classification scheme adopted by Wikipedia for TNOs). I am aware that the MPC lists it as an SDO. I'm only an astronomy aficionado, but the MPC's classification seems not entirely reliable. For example, according to the minor planet center, Sedna has the orbit type "Centaur", which is of course absurd (according to JPL's Small-Body Database Browser perihelion is 76 AU, aphelion is 995 AU). If you look at its "Centaur" list and briefly check its orbital elements (q, Q, a), you will find that there are other objects the classification of which seems rather doubtful (far too large q).

Anyway, which classification system/nomenclature is used by Wikipedia? Even the orbit classification of Eris in various scientific papers is varying (SDO, detached). Gladman et al. published (as part of the TNO-Bible The Solar System Beyond Neptune) a Nomenclature in the Outer Solar System which restricted SDOs to those objects which are currently scattering actively off Neptune (as indicated by 10 million years numerical integrations). They list both Eris and Sedna as detached TNOs.

The final verdict about what TNO-classification/nomenclature is going to be adopted by the scientific community is still out. So shouldn't Wikipedia be a bit more circumspect? One might include, for example, a respective hint by including a statement in the Eris-article that Eris is variously listed as an SDO and a detached TNO, according to the classification scheme used. What do you think? Salvete! CalRis

Wikipedia uses whatever scheme(s) are supported by "WP:reliable sources". We don't form general policies about whose ideas to prefer over the others, if both are out there in the available literature. It sounds like you know quite a bit about this topic, and you're welcome to edit these articles. By all means, please add the best sources you know about. (but do mind WP:V/WP:OR - we want data published elsewhere, not arguments that you come up with on your own, even if they're right). Wnt (talk) 02:06, 26 August 2011 (UTC)

Moon

1. Is there any difference between tempreture of the surface with underground of Moon?
2. Is there any Volcano on Moon?
3. What kind of Gases are find on Moon?
4. Is it applicable if you install a refinery in Space Rocket and inject the needed returning fuel of Orbiter by one of gases , in which are fine on Moon? Then, you need to deliver only the launching fuel in the orbiter and the weight of Space Rocket would be lighter.
5. Is it applicable to attach the fuel tank with Electrical Magnet to Space Rocket? And with turning off electricity, empty tank detaches the Orbiter.
6. Is it applicable if you launch Space Rocket only with sufficient fuel to reach the space. After a while send another fuel tank to space. n the returning way, at a meeting point, the Orbiter attaches itself to the fuel and returns home.
7. To manufacture Space Rocket lighter ,is it applicable if you fix Talc or Isinglass for the widows of Orbiter instead of Glassware?
8. Is it applicable if you withdraw making buildings in the surface of Moon?
9. Instead build the main part of the city in closed circle underground tunnels with adequate Oxygen and immune against storms and space stones?
10. Since the ground of the Moon is precious and it took years Human reached there, did you predict making cemetery on Moon? Or just organize sorrow ceremonies for the passed away people and let them be thrown to the orbit?
11. What are the seasons on Moon?
12. What are filled into the tiers of Moon Walkers?
13. Since Moon has lesser gravitational pull than earth, what technique did you applied that the Moon walker move without being thrown up?
14. In the first decades of Human permanent residing on Moon, they don't need cars. I gone suggest that you build a few parking lots on Moon , then install Cable Cars for getting to parking areas. Residents, would be transferred to miles by Cable car and they choose their way to minor districts they wish. — Preceding unsigned comment added by 2.144.220.32 (talk) 10:51, 24 August 2011 (UTC)

formatting fixed CS Miller (talk) 11:57, 24 August 2011 (UTC)

Were these questions meant for us humans of 2011? There are some answers in our article Moon, as for the volcanism and seasons and such, but with regard to the first decades of permanent human residence on the Moon - you'll have to wait a while, we don't have an answer to that one yet. --Ouro (blah blah) 12:07, 24 August 2011 (UTC)

1. Yes
2. No
3. See Atmosphere of the Moon
4. No
5. Yes
6. Yes
7. Can't help.
8. Don't understand.
9. Don't understand.
10. Can't help.
11. See Moon#Physical characteristics#Seasons
12. See Lunar Roving Vehicle#Features and specifications#Wheels and power
13. None required.
14. Can't help.

Plasmic Physics (talk) 14:12, 24 August 2011 (UTC)

Is that a homework question?Quest09 (talk) 14:39, 24 August 2011 (UTC)

I'd say yes to question 4. There has been work on extracting oxygen and hydrogen from the surface of the moon, which could be used to power a rocket[13]. More hypothetically, Helium-3 extracted from the moon could be used to power a nuclear fusion propulsion unit[14].

"What are filled into the tiers of Moon Walkers?" I assume you mean tires. The lunar rovers used by the Apollo missions had wire mesh tires, which contained no gases but were open to the vacuum.[15] --Colapeninsula (talk) 15:15, 24 August 2011 (UTC)

2) There may be long extinct volcanoes on the Moon. StuRat (talk) 20:37, 24 August 2011 (UTC)

5) When using an electro-magnet, you'd need to be careful to avoid damaging sensitive equipment with the magnetic field, or possible distorting readings. StuRat (talk) 20:57, 24 August 2011 (UTC)

6) It might be better the send up the fuel tank first, so the main launch can be aborted if the fuel tank doesn't make it. StuRat (talk) 20:44, 24 August 2011 (UTC)

7) Why not eliminate all windows and use cameras instead ? Yes, a power failure would mean they'd be blind, but they would likely be dead soon, in any case. StuRat (talk) 20:44, 24 August 2011 (UTC)

8 and 9 seem to suggest building underground instead of on the surface of the Moon. This is a good idea for the reasons you listed, and also because the ground would provide some protection from the radiation (which is provided by the thicker atmosphere on Earth) and temperature extremes. Also, underground construction on Earth is limited due to problems with ventilation, water infiltration, and the weight of the Earth to be supported. These problems either don't apply or are lessened on the Moon. However, Moonquakes do occur, due largely to tidal forces from the Earth, thus any structures would need to be able to withstand those, so don't use materials like unreinforced concrete. StuRat (talk) 20:23, 24 August 2011 (UTC)

10) Burying dead lunar colonists would work well, as they would become mummies and wouldn't require embalming to prevent the spread of disease. Launching them into space would be more problematic, as it would require a great deal of energy to launch their bodies into the Sun, and any other location would leave the body as space debris which would pose a hazard to future space exploration. StuRat (talk) 20:48, 24 August 2011 (UTC)

13) To clarify, the added weight of space suits keeps people from bouncing too high, when walking. However, the force upon landing is still the same, whether on Earth or the Moon, so it's not really an issue. Astronauts can walk the same as on Earth, by taking slower steps, but it isn't normally necessary. Hopping tends to be more efficient there. StuRat (talk) 20:35, 24 August 2011 (UTC)

14) Cable cars only work for short distances. For longer distances you need taller towers, or a series of towers. Lunar dust might also be rather abrasive on moving parts. StuRat (talk) 20:53, 24 August 2011 (UTC)

@7) Neither isinglass nor talc would have the strength to withstand the pressure differential between the space rocket fighter's cockpit and the vacuum of space, not to mention the thermal stress encountered during reentry -- or damage from enemy weapons! Indeed, not even ordinary glass can provide sufficient damage resistance for combat operations. Other, better materials like polycarbonate would have to be used for the fighter's windows. 67.169.177.176 (talk) 00:39, 25 August 2011 (UTC)

Just out of curiosity: Is this for some kind of futuristic sci-fi novel that you're working on? 67.169.177.176 (talk) 00:42, 25 August 2011 (UTC)

Oops -- I just noticed that I misread your question; you asked for suggestions to make a space rocket lighter in weight, while I thought you were trying to design a space rocket fighter like the ones in Star Wars. So in this case, combat operations are obviously not relevant. Still, I stand by the assertion that neither talc nor isinglass meet the structural or thermal requirements for a space rocket's windows (not the "widows" you mentioned in the original question -- the phrase "widows of Orbiter" refers to the spouses of crewmembers of the Challenger and the Columbia, and might even be considered offensive toward said spouses). Mica might do from a structural point of view, but it's also heavier than glass and less transparent, as well as hard to make into large panes. Polycarbonate, either alone or in some combination with pyrex glass, is prob'ly the best material for lightweight space rocket widows (I mean, windows...) 67.169.177.176 (talk) 03:47, 25 August 2011 (UTC)

Space tourism

The WP article on Space Tourism lists 7 Space tourists. Were not Malaysian Shiekh Shokor and South Korean lady astronaut Il So Yoen also Space tourists? Plus, I think that Simonyi went up twice. Am I not correct? Thanks. John: [e-mail address removed for personal sanity] — Preceding unsigned comment added by 220.137.67.189 (talk) 12:04, 24 August 2011 (UTC)

Dear John, I've removed your e-mail address, as these pages are frequented heavily by bots and the like, which might harvest your address and include it in some spam mail lists or whatever. Expect any and all answers right here. --Ouro (blah blah) 12:08, 24 August 2011 (UTC)

Sheikh Muszaphar Shukor isn't classed as a space tourist because he went up as part of a deal between Russia and the Malaysian government, rather than paying personally, and he performed scientific research while he was there. Russia, and the USSR, have a long history of repaying allies by sending people from their nations up into space.

Yi So-Yeon was chosen by the Korean astronaut program to fly in Soyuz, has a doctorate in biotechnology and is a legitimate astronaut. I don't know why you would question her status. --Colapeninsula (talk) 15:22, 24 August 2011 (UTC)

Not Russian? Not American? So, you must be a tourist if you go to space. 88.9.108.128 (talk) 21:06, 24 August 2011 (UTC)

I think Yang Liwei and a number of participants of the Chinese space program make that questionable no matter how strict you are. Nil Einne (talk) 11:43, 25 August 2011 (UTC)

You may be interested in Talk:Sheikh Muszaphar Shukor#re: Link to Space Tourism, Talk:Space tourism and Talk:Spaceflight participant. NASA and sometimes possibly the RKA did use the term Spaceflight participant (which is the same one they use to refer to people listed as space tourists) to refer Sheikh Muszaphar Shukor and Yi So-Yeon. I believe both trained as whatevernauts but didn't have many or any? official crew responsibilities on their respective missions (but did undertake research), and were considered whatevernauts by their countries and Russia at least on occasion. Note that it's been questioned why other then Christa McAuliffe, other people in the past both on NASA (including it sounds like Barbara Morgan) and the earlier RKA and Soviet missions have not been similarly deemed spaceflight participants (instead mission specialists or payload specialist) despite seemingly greater similarity of circumstances. In any case, neither seem to fit with the definition given in space tourism. Nil Einne (talk) 10:18, 25 August 2011 (UTC)

Flying submarine

So I was looking at Flying submarine and I was wondering if it's possible to have a dual purpose jet engine that can work both in water and in the air? ScienceApe (talk) 13:10, 24 August 2011 (UTC)

Seems unlikely. Jet engines typically rely on compression to operate, and while air is highly compressible, water is not. — Lomn 13:55, 24 August 2011 (UTC)

Water is also not very supportive of combustion compared to air. Googlemeister (talk) 14:38, 24 August 2011 (UTC)

On the other hand nuclear aircraft have been proposed.--Colapeninsula (talk) 16:03, 24 August 2011 (UTC)

And have some severe issues. The two major ones off the top of my head is that both coolant and shielding is heavy, and aircraft need to be light. The other issue is that you will have a lot of potential issues with containment in the event of a crash. Googlemeister (talk) 18:42, 24 August 2011 (UTC)

Nuclear aircraft have been built, they just haven't been flown under nuclear power. The Convair X-6 was a bomber that carried an operating nuclear reactor and all relevant shielding; the project was abandoned because it became unnecessary, not because it wouldn't have worked. Project Pluto, a nuclear cruise missile/unmanned bomber, was deliberately unshielded to increase its effects as a weapon; it was abandoned for political reasons. --Carnildo (talk) 02:16, 25 August 2011 (UTC)

(unindent) IMO, the most fundamental problem with the idea of a flying submarine (or underwater aircraft) is the contradiction in structural requirements, even more than the choice of propulsion. An aircraft must have a very lightweight structure in order to get off the ground, which would severely limit its submergence depth; a submarine, on the other hand, needs a very strong (and therefore heavy) pressure hull in order to withstand the water pressure, and so would not make a good aircraft. In other words, trying to build a flying submarine inherently requires designing it to meet two opposing requirements, which in practice always means that it will not perform either task well. 67.169.177.176 (talk) 03:19, 25 August 2011 (UTC)

I'm surprised the flying submarine page doesn't include Supercar (TV series). ←Baseball Bugs ^{What's up, Doc?} carrots→ 00:04, 25 August 2011 (UTC)

Fly me to the moon ............. and then?

In the highly realistic movie 2001: A Space Odyssey, Dr. Floyd took a space ship to the moon and then from the moon base, he took another moon surface ship to the monolith.

Since there is practically no air on the moon, you can't use a winged aircraft on the moon. You have to provide all the lift by yourself.

It looks like that the surface ship would use much fuel and oxidant to fly on the moon surface for every second of flying. A hovercraft or a ground effect vehicle may be a good idea. However, in the vacuum, the gas cushion would be gone in a matter of seconds.

I think there's a new sci-fi movie about Hitler's moon base (when the Nazi was defeated, they went to the moon ...). I saw a Nazi-style sidecar motorcycle running on a moon highway in their Youtube trailer. Sorry I can't remember the movie's name. Is it a good idea to build a road on the moon surface for cars and bikes (assume that they have fuel and oxidant)? Since the moon can only provide 1/6 of earth gravity, friction force on the road surface can be a big problem.

The Apollo moon car was useful because it was better then walking or hopping. How do we travel on the moon? I mean travel in an efficient and practical manner. -- Toytoy (talk) 14:41, 24 August 2011 (UTC)

Once on the moon, a "hopping craft" would be a reasonable mode of travel (in fact, it has already been designed by multiple groups). You can have a craft hop great distances without requiring much energy to do so. The problem is that there is very little atmosphere for steering. So, you would want to hop short distances, correct the trajectory, and hop again. Because of the low gravity, it wouldn't feel like hopping does on Earth. Instead, it would feel driving down a road that goes up a bit and down a bit in a cyclic manner. As for driving on a road - the road itself would be a bad idea unless you are in the pothole repair business. The Moon doesn't have the atmosphere to block micro-meteors. They would likely tear up the roads faster than you could build them. The only safe place to consider roads would be as close to the side of the moon facing Earth as possible since there is far less meteor activity there. -- kainaw™ 15:03, 24 August 2011 (UTC)

I suspect you're seriously overestimating the 'impact' of micrometeors. Yes, the Moon's surface is covered with impact craters, but it's worth remembering that it took billions of years to get that way. (It's not as though the International Space Station is getting a fist-sized hole in it every day.) And millimeter-to-centimeter sized craters aren't really going to affect the function or performance of a road by much. Plus, lunar roads aren't going to be affected at all by the two big Earth-based forces that destroy roads: erosion by water (either of the road itself or the underlying road bed) and frost heaving. The low lunar gravity also lessens the wear and tear caused by heavy vehicles. I'd be interested to know if someone has some real numbers on the rate of crater formation on the Moon...? I strongly suspect that any road on the Moon would last far longer than a similarly-constructed, similarly-used Earth road. TenOfAllTrades(talk) 16:13, 24 August 2011 (UTC)

There are regular meteor showers that we see hitting the Earth's atmosphere. They also pelt the Moon without the atmospheric benefit of burning them up before they hit the surface. It isn't just the meteor strike that is a problem on the Moon. Because of the low gravity, the ground explosion travels much farther and with far less resistance than on Earth. So, a single meteor becomes a shower of smaller meteors over a very wide range. -- kainaw™ 17:09, 24 August 2011 (UTC)

Yes, I am aware of those facts, but I still think that you're overestimating the severity of the problem. The moon collects something like 1 ton per day of material (mostly dust), over its surface area of about 40 million square kilometers. If we assume a two-lane roadway 10 meters wide, that's 0.01 square kilometers of road surface area per kilometer of road length. Per year, we're looking at about 91 mg of meteor material per kilometer of road. If we assume 100 mg of meteor arriving at 50 km/s, that's 125 kJ deposited energy per kilometer of road: equivalent to about 30 grams (one ounce) of TNT. If you put that in one spot on the road, then yes—it will do some damage; probably enough to close a lane of traffic until a patch crew gets out to it. If that hits as a hundred 1 mg particles (much more likely), there will just be some scoring and chipping of the surface. If they're finer dust, you won't even see the effect without a microscope.

If we consider the ejecta and generously assume that the dust kicked up by an impact exceeds the mass of the original meteor by a factor of one million, we're looking at just 100 kg of dust spread on each km of road; call it a nearly-negligible 10 grams of fresh dust per square meter, per year. Finlay McWalter's excellent source below further strongly supports such a conclusion. TenOfAllTrades(talk) 19:20, 24 August 2011 (UTC)

We can gain some insight as to the wear on artificial objects from the Lunar Laser Ranging experiment. In the 40 years these have been on the Moon, they're still sufficiently intact and reflective for bouncing lasers off them to be effective (one project was, it seems, defunded in 2009, but not for want of mirror). This paper quotes another paper saying micrometeoroid damage to such objects as having "the fill-factor of craters on an exposed surface to be ∼ 10⁻⁴ after 40 years, dominated by craters in the 10–100 µm range." Both of these factors suggest that the micrometeoroid damage to something insensitive like a precast concrete slab would be trivial, and surely dwarfed by the wear from vehicles. -- Finlay McWalter ☻ Talk 16:44, 24 August 2011 (UTC)

The Nazis-in-space film you mentioned is probably Iron Sky. -- Finlay McWalter ☻ Talk 15:55, 24 August 2011 (UTC)

I would vote for driving rather than hopping around (losing one's lunch in a spacesuit would be a problem). I wonder just what the effect of micrometeorites would be over say a 40 year period. The impressive crater collection on the Moon is the result of billions of years, with no rain or wind to soften or obscure them. The Surveyor 3 probe was exposed on the Moon for 31 months before the Apollo 12 crew visited it, and brought back portions of it, and it did not appear to have been hit by micrometeorites, although the Wikipedia article says little about the surface of it. A book says "There are no definite impacts of micrometeorite origin found on the returned Surveyor 3 equipment." A website however says some of the microscopic craters might have resulted from micrometeorites, among the many from the Apollo landing 160 meters away and kicking up dust, creating a sandblasting effect. There were some particles kicked up by the Apollo landing. All the retroreflectors left on the moon in the 1960's and 1970's are reportedly still functioning, so meteorites have not knocked them out. If space is full of micrometeorites, one would expect them to frequently damage satellites. How often does that happen? I expect that it a lunar road were bulldozed, or paved with concrete (lunar soil plus water makes concrete), it would look much the same decades later, with potholes not being much of a problem in a road many miles long. Edison (talk) 16:23, 24 August 2011 (UTC)

I think you're right. It would be a pain in the whatever to build roads or tracks on the moon. They could be destroyed by any Act of God at any moment. Otherwise, I guess Maglev (transport) would be a nice idea. Very little need for fuel and oxidant. You only need electricity (powered by the sun). Given the low gravity, it would be more fuel efficient then on earth.

Is it a good idea to use the hopper craft to transport a great amount of materials and products? I mean something like our cargo ship. Or can we build a very big moon truck to crawl on the moon surface?

Yes, Iron Sky. Thank you. I just love the moon highway idea. If only I could ride an old-fashioned bike on the moon ..........

http://www.youtube.com/watch?v=4KEueJnsu80 (1:12) -- Toytoy (talk) 16:11, 24 August 2011 (UTC)

According to NASA, the first footprints on the Moon will be there for a million years.^[16] Compared to the vicissitudes of Earth, the Moon should not be harsh on roads. Of course, wheeled vehicles themselves can still tear up dirt roads like anywhere else, and the expansion/contraction issues with pavement must be pretty nasty, but I'm sure you can work out something.

On the other hand, with 1/6 the gravity, I suppose ideas like monorails are easier to implement - the main appeal being that if you have a perfectly straight rail and a near frictionless pivot, and no air, you can go as fast as you dare. Wnt (talk) 16:44, 24 August 2011 (UTC)

The footprint is a point but the road is an area. Today's space around earth is a much safer place then it was billion years ago. I still think that from time to time, a very small meteor may hit the road surface and cut it off. I think the inner planets have already "vacuumed" the space clean enough. But there are still meteor showers on earth. -- Toytoy (talk) 17:11, 24 August 2011 (UTC)

Right, but even on earth, roads are only a tiny fraction of a % of the surface, and we have billions living here who use them. A few roads on the moon are an incredibly small target which would be unlikely to sustain significant damage from extralunar impacts for centuries. Googlemeister (talk) 18:35, 24 August 2011 (UTC)

I have a suggestion:

1) Use a "road", but of an unconventional design. Instead of being paved, have it be full of lunar sand (although you might want concrete barriers at the edges to contain the sand). This road should withstand micro-meteors quite well, although the sand may need to be replenished from time to time.

2) Have the vehicles be solar/electric powered snowcats. That is, they would have deep treads that dig into the sand and move it, to provide forward motion. I wouldn't expect such a vehicle to be very fast on the Moon, but hopefully quite reliable.

3) Since the turning radius would be quite large, you would want the roads to be relatively straight, between bases. Also, design the vehicles to be reversible, so they can just pivot the seats around and drive in the opposite direction, either once they reach their destination or if they need to "turn around" mid-trip. Note that such a vehicle could also operate where there are no roads, provided there's a path through the boulders. StuRat (talk) 19:29, 24 August 2011 (UTC)

A second suggestion, for longer distances, is a flying vehicle, with a launch device which would shoot it into near orbit from the ground and thus greatly reduce the requirements for on-board fuel, perhaps only using the rockets when landing. A large gun could be used to launch into space, although the g-forces involved would likely make this method inappropriate for passengers or sensitive cargo. Also note that such a ballistic trajectory should be aimed to miss the target base by a safe distance, in case the retros failed to fire, so the base wouldn't be damaged by the impact. StuRat (talk) 20:04, 24 August 2011 (UTC)

A cable car would possibly be easy to implement.It also is probably more energy efficient than a road or some flying vehicle propelled by rockets. 88.9.108.128 (talk) 22:08, 24 August 2011 (UTC)

I like the cable car idea. Given the low gravity nature, you may not need very thick cables. However, the moon is still likely to have moonquakes. You may need very specialized lubricant oils and moonquake-resistant structure to build a cable car on the moon. Otherwise, the view can be truly amazing! -- Toytoy (talk) 16:42, 25 August 2011 (UTC)

Why do flies hit windows repeatedly without realizing they can't get out that way?

Perhaps nobody knows. But I'll ask anyway.

Jonathan ^talk 18:29, 24 August 2011 (UTC)

That is a great question. I hope you get a good answer because I also do not know and would love to find out. Googlemeister (talk) 18:31, 24 August 2011 (UTC)

Just a guess: they are relying on visual cues, absent due to the transparency. Memory and/or learning may just be insufficient, reasoning may be present but reaching the wrong conclusion—that another try might work.

Do they hit the same spot each time, or a slightly different point on the pane of glass? If they hit the same spot—how much time elapses between strikes?

Obviously I don't know the answer to the question posed. But I think these factors may be applicable. Bus stop (talk) 18:40, 24 August 2011 (UTC)

I find it most useful to think of insects as very sophisticated robots. They don't "realize" things, they execute programs. Their visual-navigation programs have evolved to work well in situations that they commonly encounter, but don't work so well when they encounter glass, which doesn't occur in nature. Looie496 (talk) 18:43, 24 August 2011 (UTC)

Footnote: see sphexishness for Daniel Dennett's way of explaining this. Looie496 (talk) 18:45, 24 August 2011 (UTC)

I'll add a related puzzling question. How can a House Gecko simultaneously walk on a glass window and repeatedly bang its head on the glass trying to eat the bug on the other side ? This is odd because as far as I can tell, they have to learn that they can walk on glass and yet they never seem to learn that they can't eat things through it or fight other geckos through it. This also seems to be the case for the Gekko gecko too. Sean.hoyland - talk 18:54, 24 August 2011 (UTC)

I second the notion of animal instincts being like simple computer programs. In this case, it's like two subroutines, one with the logic "if you can feel it with your foot, then try to walk on it" and another with the logic "if you can see food with your eyes, then try to eat it". These two subroutines do not interact. Higher animals have intelligence with true learning, but there is very little learning in the lower animals. StuRat (talk) 19:09, 24 August 2011 (UTC)

An applicable factor as simple as the deficiency, relative to the human counterpart, of the visual mechanism, could also be a heavily contributory factor. What it would have to learn is that a plane was impenetrable, but that is a difficult problem when the knowledge that the barrier is planar is not known. If it cannot see the glass—how can it know that it exists as a "pane"—that is, in the planar geometric configuration? This is why I am concerned with whether it is hitting the same spot on the glass each time. Bus stop (talk) 19:13, 24 August 2011 (UTC)

I observe that they don't hit in quite the same spot on subsequent attempts for the most part, they hit a few inches away each time in what looks like a random fashion. Googlemeister (talk) 20:34, 24 August 2011 (UTC)

House flies (and many flying insects) display positive phototaxis when trapped or stressed. Thus a tried and true method to get flies to exit is to close and shutter all windows, turn off all lights, and open one window completely. The flies will happily leave in an hour or so, unless they are otherwise attracted to a food source or oviposition site. Basically, the flies' instincts are tuned such that (more light)=(more freedom). This is a good rule, but windows mess it up. SemanticMantis (talk) 20:53, 24 August 2011 (UTC)

But, unfortunately, there are other insects, such as wasps, which see dark places as a good spot to build nests, so they might fly right in. StuRat (talk) 22:04, 24 August 2011 (UTC)

Blowflies, when trapped in a room will indeed fly in circles around it and bat their heads on windows repeatedly as they try to get out. I notice that house flies never exhibit this type of behaviour. That's why they call them house flies: your place is home. Myles325a (talk) 10:12, 25 August 2011 (UTC)

Hurricane Irene on Weather Underground: computer models much scarier than 5-day forecast

Why is Weather Underground's 5-day forecast so much further East than its computer models? Given the path and intensity projections, and the flooding potential for a coast-hugging path, I am wondering whether Irene has the potential to rival Katrina's damage.

"If the core of Irene stays offshore, the mid-Atlantic and New England may escape with a few hundred million dollars in damage from flooding due to heavy rains and storm surge. If Irene hits Long Island or Southeast Massachusetts, the storm has the potential to be a $10 billion disaster.... I'll be discussing Hurricane Irene on a special edition of our Internet radio show, the Daily Downpour, today (Wednesday) at 4:30pm EDT. Fellow wunderground meteorologists Shaun Tanner, Tim Roche, and Angela Fritz will also be there. Listeners can email in or call in questions. The email address to ask questions is broadcast (at) wunderground.com." -- Jeff Masters[17] 76.254.20.205 (talk) 19:16, 24 August 2011 (UTC)

The two pages look approximately the same to me -- tracking near Cape Hatteras, then landfalling around New England. What particular discrepancy are you looking at? As for damages, Hurricane Katrina caused $81 bn in damages (an order of magnitude higher than Masters' $10 bn estimate quoted) and struck an area that sits largely at or below local water level, geography that isn't found much along Irene's projected track. — Lomn 19:22, 24 August 2011 (UTC)

Huh! I wonder if they just updated the 5-day. About 15 minutes ago it looked at least 100 miles East of all but one of the computer models, with the center projection not intersecting the Connecticut coastline. I wish the models had shifted East instead of the forecast shifting West, but that is the order in which you'd expect them to update. I would take the consensus advice of the wunderground blog commenters and not wait to buy preparations (plywood, etc.) Please see http://www.nhc.noaa.gov/HAW2/english/disaster_prevention.shtml and http://www.aoml.noaa.gov/hrd/shutters/index2.html for more information. 76.254.20.205 (talk) 19:30, 24 August 2011 (UTC)

It seems about right to me. The models are within the track forecast cone for Irene. Titoxd^{(?!? - cool stuff)} 20:02, 24 August 2011 (UTC)

I will be in Washington on Sunday and Monday. What should I expect? I do know thunderstorms but Hurricane is word only associated to news films. --Stone (talk) 20:36, 24 August 2011 (UTC)

If you have a flight landing in Washington D.C. Sunday, it could easily be delayed or even cancelled. What time Sunday? 76.254.20.205 (talk) 21:34, 24 August 2011 (UTC)

New York is not exempt from being struck by major hurricanes, capable of doing catastrophic damage Count Iblis (talk) 20:53, 24 August 2011 (UTC)

Sunday lat in the afternoon.--Stone (talk) 19:13, 25 August 2011 (UTC)

Let me give a pointer to NOAA's hurricane page. In the material for each storm you can find a section called "Forecast discussion", that explains what each important model predicts, and how the information is combined to reach a forecast. It is pretty much always a judgement call to some degree. Looie496 (talk) 21:42, 24 August 2011 (UTC)

Thanks! "THE NEW ECMWF SHOWS MUCH MORE AMPLIFICATION OF THE TROUGH...WHICH HAS RESULTED IN ITS TRACK SHIFTING OVER 100 MILES TO THE WEST"[18]. I guess that is the change I was noticing above. Someone should explain to NOAA and NWS about the caps lock key, although in this case I suppose it's appropriate. 76.254.20.205 (talk) 21:52, 24 August 2011 (UTC)

If I remember correctly, they are constrained to use all caps for backwards compatibility for older receptor equipment. Titoxd^{(?!? - cool stuff)} 07:26, 26 August 2011 (UTC)

August 25

Bladder Cancer

Is there any evidence that the human papilloma virus can cause bladder cancer? Ref. an article in the UK "Daily Telegraph" newspaper on 19 August 2011 about a woman academic, a non-smoker, who had a successful operation.Pensioner.bsc (talk) 00:30, 25 August 2011 (UTC) — Preceding unsigned comment added by Pensioner.bsc (talk • contribs) 22:59, 24 August 2011 (UTC)

Single cases are really almost never meaningful. The idea has been around for a long time and a number of studies have been done yielding a mix of results, summed up in an authoritative 2008 review, PMID 18815920, as "The possibility that infection by human papilloma virus (HPV) is a risk factor contributing to bladder cancer has been investigated but no definite conclusions have been drawn.". Looie496 (talk) 23:13, 24 August 2011 (UTC)

Thanks for the reference.Pensioner.bsc (talk) 00:46, 25 August 2011 (UTC)

The question I would have is: "how does the HPV get to the bladder" ? Does it travel up the urethra ? Bacteria causing bladder infections can do so, especially in women, where the urethra is shorter. However, the bacteria can presumably grow in the urethra, using urine for it's nutrient supply, and slowly spread, while a virus would need to find living cells to infect, in order to spread. This would cause rather noticeable warts in the urethra, causing pain and or urine blockage, wouldn't it ?

I suppose the other alternative is the virus traveling via the circulatory system, but, in this case, why would it only go to the bladder ? StuRat (talk) 23:26, 24 August 2011 (UTC)

I agree, if the urine flow is always outwards from the bladder there would be no problem, but one might speculate that the flow could be briefly backwards when the bladder relaxes after urinating.Pensioner.bsc (talk) 00:29, 25 August 2011 (UTC) — Preceding unsigned comment added by Pensioner.bsc (talk • contribs) 00:27, 25 August 2011 (UTC)

I believe there are valves in place to prevent that. StuRat (talk) 06:28, 25 August 2011 (UTC)

Thanks, from the articles I have looked at on HPV eg Viral disease there is just an "association" with urinary problems. It could certainly get into the circulation via cuts and abrasions (eg in sex and dentistry) and thence to organs vulnerable to it, but the common cause of HPV infection and bladder cancer I would conclude is an impaired immune system.Pensioner.bsc (talk) 00:03, 27 August 2011 (UTC)

I can think of another way they could be related: Perhaps people who have lots of unprotected sex with multiple partners both tend to be exposed to HPV and (bacterial) urinary tract infections, and those are what cause the bladder cancer ? StuRat (talk) 06:03, 27 August 2011 (UTC)

Well in the case mentioned in the "Daily Telegraph" I think she was just unlucky, the immune system deteriorates with age, making you more vulnerable to carcinogens of all types, eg burnt toast, barbecued food. Also in women thyroid deficiency hypothyroidism is more common than in men and that may impair the immune system, but this is getting way beyond my expertise!Pensioner.bsc (talk) 20:05, 27 August 2011 (UTC)

Total value of precious metals

What's the total value of all silver, gold, and platinum in Earth (in USD)? --75.10.48.39 (talk) 00:29, 25 August 2011 (UTC)

According to this place, there were an estimated 800 million ounces of silver as of 2009 or 2008 at let's say $40 an ounce, so about $32 billion. Gold reserve says there were 165,000 tonnes of gold mined in total as of 2009; at the current price of roughly $1750, that's $9.2 trillion, again according to that article. I'm having trouble finding the figures for platinum. Clarityfiend (talk) 03:03, 25 August 2011 (UTC)

Something seems very wrong with those silver figures. If there are only 800 million ounce divided by some 7 billion people, then there's just over a tenth of an ounce for every person on Earth. Silver's not that rare. Many people have silverware sets, for example. I think what you have there is the yearly production of silver. Here's a source which claims the total silver supply is about 43 billion ounces: [19]. StuRat (talk) 06:18, 25 August 2011 (UTC)

Our article on silver mining gives an estimate for 2010 total silver production as 735 million ounces, so yes - the 800 million ounce figure is an annual production number rather than a grand total. TenOfAllTrades(talk) 12:14, 25 August 2011 (UTC)

This is the mined metals. Based on the earlier question #Total amount of platinum by the same IP, the question may include the unmined. There is no meaningful answer to the total value in that case. If the current price was multiplied by the total amount then the result would be a meaningless number far greater than the total assets of all humans. But prices in a competitive market depend on supply and demand. If we imagine that all the metals were available then value would depend on who had possession of what. If all people had an equal share then there would be no reason for anybody to buy. If one company controlled everything then they couldn't get people to carry it all away if they gave it away for free, but they could earn a fortune by setting a significant price and only sell a small part. PrimeHunter (talk) 03:45, 25 August 2011 (UTC)

http://www.gold-eagle.com/editorials_05/zurbuchen011506.html gives an estimate based on multiple sources and comes up with approximately 45 billion toz of silver mined in human history, at a rough value of $1.8 trillion. Combined with $9.2 trillion for gold and about $325 billion for platinum (based on 180 million toz I referenced in the earlier question by this OP), the total is $11.3 trillion. Googlemeister (talk) 14:10, 25 August 2011 (UTC)

It should be noted that these dollar values are just for the raw metal. Something like Tutankhamun's gold mask or the 1794 silver Flowing Hair dollar coin would be worth far more. Clarityfiend (talk) 18:47, 25 August 2011 (UTC)

Perhaps, but I doubt that the metals that happen to be in antiquities would make much of an impact when we are talking about an amount this size. I mean 11 trillion is roughly on the order of the US national debt. Googlemeister (talk) 20:23, 25 August 2011 (UTC)

... and, of course, the figures above are all for the metals that have been recovered (mined) from Earth. The amount still there is at least thousands of times the largest figure mentioned above, possibly millions of times, but if there were an easy way to obtain the metals then they would not be valuable (as explained by PrimeHunter above). Dbfirs 08:26, 27 August 2011 (UTC)

What makes the difference in weight gain/loss?

I did some figuring of nutritional information of what I ate today. It came out roughly like this:

• 1800 Calories
• 640 Calories from Fat
• 71 Fat - Total (g)
• 18 Saturated Fat (g)
• 2 Trans Fat (g)
• 145 Cholesterol (mg)
• 5050 Sodium (mg)
• 243 Total Carbohydrates (g)
• 9 Dietary Fiber (g)
• 88 Sugars (g)
• 56 Proteins (g)

Given that this is below the 2000 calories that's the daily value, roughly at the upper end of daily value of fat calories, and spot on for protein (according to this), but given that it is off the charts for carbohydrates and cholesterol, if I kept up this type of diet (assuming that there was no deficiency in vitamins or minerals) for an extended period of time, 1. would I be more likely to gain weight or lose weight, and 2. why? Note that I don't necessarily want the response specific to me...I'd be happy if it were more along the lines of if a person went an extended period of time on a diet like this and assuming they had no vitamin and mineral deficiencies (say if they took a multivitamin), would they be more likely to gain or lose weight and why? Thanks, Ks0stm ^(T•C•G) 01:15, 25 August 2011 (UTC)

I am not going to be popular with anyone else for saying this, but this is clearly the sort of question you need to ask your doctor or similar professional about. We in no way know your medical history, current physical condition, or anything else about you, and so there is no way to tell if the diet you outline above is appropriate for you, or what its effects would be on you. If it isn't you you are asking about, it is impossible to answer for ANY individual, and so saying "you will lose weight" or "you will not" is irresponsible for anyone to answer. Any individual who wishes to know the correct answer should have the diet, and their own condition, looked at by a professional and not assholes like me. --Jayron32 02:38, 25 August 2011 (UTC)

It is totally impossible to give a generic answer. The answer depends on whether you are male or female, how much you presently weigh, how old you are, and how active you are. Some people can eat 1500 calories per day and gain weight, others can eat 4000 calories per day and lose weight. Those are extremes, but with zero information there is no way to rule out that those extremes apply to you. Looie496 (talk) 02:40, 25 August 2011 (UTC)

243 g/day of carbohydrates isn't really "off the charts". The 130 g/day listed for carbohydrates in the DRI is a recommended minimum, not a maximum. Protein and carbohydrates both have about 4 cal/g, so if someone were to only eat the 130 g/day of carbohydrates and 56 g/day of protein listed in the DRI for an adult male, and limit fat to no more than 35% of calories as the DRI recommends, the person would be eating at most 1145 cal/day, which wouldn't be sufficient for most adults to maintain a healthy weight.

Under your assumption of "if I kept up this type of diet", the only nutritional information you listed above that's pertinent to your question as to whether you'd be likely to gain or lose weight if you ate similarly every day is pretty much just the calories. If you consume more calories each day that you expend, you'll gain weight, and if you consume fewer calories each day than you expend, you'll lose weight. (Saying "digest" rather than "consume" in that sentence would make it more accurate, but that's pretty much a minor quibble.) Diet fads come and go as to whether emphasizing high protein, low fat or low carbohydrates sells the most diet books, but the scientific reality is that whether you'll lose weight or not basically just depends on how many calories you eat, not how those calories are divided among the three macronutrients.[20] This is basically a statement of conservation of energy, since a calorie is a unit of energy. To a very high degree of accuracy, within any given period of time, energy that enters your body, which is mainly in the form of chemical energy stored in food, minus the energy that leaves your body in one form or another, must equal the difference in how much energy is stored within your body. Your body creates fat as a way of storing excess energy.

As pointed out above, you have given insufficient information above to determine if you will gain or lose weight by eating 1800 cal/day. The missing information is how many calories you expend each day, which depends primarily on your gender, age, weight, height and activity level. The Wikipedia article discussing this matter is Energy balance (biology), which refers you to this rather rigorous paper on the topic[21] as well as the commonly used and fairly easy-to-use Harris-Benedict equation. There are also numerous calculators on the internet for calculating your energy requirements, such as this one[22], but those unfortunately tend not to explain whether they're using Harris-Benedict or what. Red Act (talk) 04:27, 25 August 2011 (UTC)

Actually, you gave exactly the information I was looking for. I didn't really need it related to me...I was just using what I ate today as an example of the type of situation I was inquiring about, and you gave me all I needed to answer my questions in your second paragraph. Sorry my question was so strangely asked...it was a very hard question for me to phrase. Thanks for taking the time to answer. Ks0stm ^(T•C•G) 05:20, 25 August 2011 (UTC)

Just out of curiosity, did you have any brazil nuts? 208.54.86.157 (talk) 07:35, 25 August 2011 (UTC)

And I can tell you that I would gain weight rapidly on such a diet. The carbs in particular seem to pack on the weight for me. That much sodium would also make by blood pressure spike. StuRat (talk) 06:04, 25 August 2011 (UTC)

I see you are getting one third (33%) of your daily calorific intake from fats. This can't be healthy, whatever diet you're on! I suspect you will lose weight a lot quicker if you bring this down to around 20% as recommended by this site.--TammyMoet (talk) 14:54, 25 August 2011 (UTC)

You'll lose weight a lot faster by exercising instead of dieting. Muscles always burn energy, even if they aren't used. So, the more muscles you build, the faster you can lose weight. Count Iblis (talk) 00:18, 26 August 2011 (UTC)

But then you'll be hungrier and eat more. There's no amount of exercise which can't be undone by a bad enough diet. So, diet is definitely important, and exercise is nice, too. StuRat (talk) 03:27, 26 August 2011 (UTC)

I agree, but if you do a lot of exercise, you won't be able to overeat easily. E.g. I run for about 35 minutes at a pretty fast pace 5 times per week, and I eat quite a lot (more than 3000 Kcal per day). But my weight is very stable, the weekly average has been constant to within 1 kg for over 3 years now (between 62 and 63 kg). To gain weight, I would have to eat a lot more, but I'm already eating huge amounts of foods all day long. The fact that my weight is stable over long periods of time, means that my metabolic rate is compensating for excess energy intake or excess energy use (eating just 7.3 kcal more per day would lead to 1 kg weight gain over 3 years if te metabolic rate would not increase). So, to gain weight I would have to eat so much more that the feedback mechanism that keeps by weight constant would fail, and I don't think I'm near the boundary of that region.

According to a BBC Horizon documentary that I saw a few years ago, people who have a stable weight, only gain 5 kg to 10 kg of weight if they double their energy intake. So, it could be that I would need to eat 6000 kcal per day to get to 70 kg. But I'm quite sure that if I were to stop exercising and wait until my fitness levels dropped, then I could gain weight far more easily. I would become a couch potato who only needs 2000 Kcal. And eating a bit more would already lead to weight increase, because with physical inactivity and less mucle tissue, the feedback mechanism that keep the weight constant become less effective. Count Iblis (talk) 04:09, 26 August 2011 (UTC)

Molar concentration

Hi there. I hope this will be simple for someone with a chem background.. This is NOT a homework question, it's in relation to a discussion I'm having regarding this document. It states concentrations of sodium chlorite (molar mass 90g/mol) of more than 100 .mu.mol/l can be cytotoxic. Up until now I've only come across concentrations in ppm or %. I'm trying to sub my values into the example but I'm getting screwed up with the powers.. 100 mu.mol/L is 0.0001mol/L(I think) * 1L * 90g/mol = 0.009g .. 0.009g in 1 L of water? That doesn't sound right.. Vespine (talk) 01:20, 25 August 2011 (UTC)

No, your math is fine. 100 micromolar = .000100 mol/L *90 g/mol = .00900 g/L. In terms of % by mass, you can convert the denominator to grams (at this low concentration, the density should be the density of water, so 1L = 1000 grams), this would be .009/1000 = .000009 or .0009% or 9 ppm. --Jayron32 02:32, 25 August 2011 (UTC)

That's great, thanks for that. Vespine (talk) 03:41, 25 August 2011 (UTC)

Resolved

Nuts in Chinese shops

I've noticed that peanuts, pistachios, and sunflower seeds taste differently when purchased from Chinatown shops. They're obviously not raw, but also differ vastly from anything from American retailers. What's the process they use? I don't tend to buy anything but plain nuts in shells. 66.108.223.179 (talk) 03:43, 25 August 2011 (UTC)

Probably a difference in seasoning? --Jayron32 04:01, 25 August 2011 (UTC)

Maybe monosodium glutamate. Sean.hoyland - talk 05:40, 25 August 2011 (UTC)

I buy sunflower seeds in a chinese shop which are called "stewed", these are the ones. They're still in the shell and you couldn't tell they've ever been wet, I don't even know if "stewed" is really the process used to prepare them, or if it's a "lost in translation" kind of thing, but I like them.. Vespine (talk) 06:49, 25 August 2011 (UTC)

Perhaps they are boiled. I've had boiled peanuts, and they are very different, more like beans in texture. StuRat (talk) 06:59, 25 August 2011 (UTC)

But aren't they all boiled? :/ I thought that was the only way you can cook peanuts in their shells - boil them in water and salt (or some other seasoning) and either eat them outright (which I prefer) or dry them again. And yeah, it may be a difference in the kind of seasoning used when boiling them, you can add anything from beer to sugar to chilli in the water in the process. I wonder if microwaving them works... -- Obsidi♠n Soul 10:17, 25 August 2011 (UTC)

I believe most peanuts are blanched or roasted, which leaves them crispier than prolonged boiling. StuRat (talk) 03:32, 26 August 2011 (UTC)

We used to grow peanuts, so I'm pretty familiar with boiled peanuts (and still prefer them to any dried peanuts), not so much with roasted though. Raw peanuts are anything but crispy. :P They taste vaguely vegetative and rubbery for one, and remain so even after drying (imagine raw potatoes), parents would admonish us not to eat too much raw peanuts or we'd get a stomachache. Blanching might work for unshelled peanuts but not for shelled ones. As it would not penetrate the thick peanut shells. Apparently, though, they don't boil roasted peanuts in a shell, they soak it in brine then roast it.-- Obsidi♠n Soul 04:00, 26 August 2011 (UTC)

So how do boiled peanuts taste ? StuRat (talk) 04:13, 26 August 2011 (UTC)

LOL, that's hard to describe. The texture is soft like you mentioned, like beans, and it's salty of course. The remaining water helps the flavor, like soup.-- Obsidi♠n Soul 04:26, 26 August 2011 (UTC)

OK. Mine were boiled without salt, and were definitely quite different from peanuts produced by the usual preparation methods. StuRat (talk) 04:30, 26 August 2011 (UTC)

The real answer may be quite simple. Most food crops grown today are verities that have been developed so that the whole field ripens at once and give high yields. Decades of modern plant breeding practice has resulted in the produce losing their original flavours - leaving them tasting bland. This is very evident when comparing the older non-commercial verities of vegetables grown by gardeners. Your China town probably imports direct from China like my China town in London. Look at the packaging as to their place of origin. You may well be tasting the original flavours.--Aspro (talk) 12:39, 25 August 2011 (UTC)

Facial resemblance between parents & children

I have noticed that the daughter of a mother would look almost identical to what her mother looked like during her younger days. Is this the general rule? Is there a similar rule for other family members (fathers, sons)? — Preceding unsigned comment added by 98.116.187.230 (talk) 04:28, 25 August 2011 (UTC)

Umm, heredity?? I don't think it's really a general "rule" at all about being "almost identical". You probably just notice it more when the effect is strong, and don't notice it when the effect is weak. You probably have 25% chance of looking more like your father, 25% looking more like your mother, and 50% chance looking more in between.. I look quite different to my brother, there's only 16 months age difference between us, I look quite like my father when he was younger, my brother looks like more like my mum's father when he was younger. Vespine (talk) 05:01, 25 August 2011 (UTC)

I'm not sure Vespine's numbers should be strictly understood; the complex melange of genetics that goes into a persons appearence can't be simplified that well, but the spirit is true: people may look more like either parent, may look like a mix of both, or may not resemble either that closely. It isn't necessarily that a daughter will always look more like her mother; she may look like more like her father, and likewise for sons and mothers. My brother favors my mother very strongly (same hair, facial bone structure) in some ways, and my father (slight build) in others. I am the exact opposite: I facially resemble my father, but physically more resemble my mother's family. But that doesn't mean that my family is necessarily typical; if there is a typical. People will, on average, tend to resemble one or both of their biological parents, but it isn't a 100% guarantee sort of thing. --Jayron32 05:07, 25 August 2011 (UTC)

Sorry yes, I'm not a geneticist or anything, I was just making a pretty wild generalization. I completely agree with Jayron's above assessment. Vespine (talk) 05:32, 25 August 2011 (UTC)

I'd expect this to be something that is very prone to confirmation bias as Vespine suggests above given that our brains seem to be hard wired to do facial matching. Sean.hoyland - talk 06:08, 25 August 2011 (UTC)

Yes to confirmation bias. In my own case, I'm looking more like my mother as I get older: when I was a child I looked like my paternal grandmother. However, I look almost identical to my mother's grandmother, whose image I have in a picture nearly 100 years old! I'd be interested to know if the OP, to confirm his case or otherwise, has tried to guess mothers from daughters and vice versa! --TammyMoet (talk) 12:29, 25 August 2011 (UTC)

I recall reading an article in Discover magazine some years ago that research had indicated that infants tend to look more like the father than the mother. The basic test was having people match up babies with fathers and babies with mothers. They went on to suggest that this was an evolutionary adaptation to reduce infanticide, though that always seemed like a tenuous connection to me. Surely it would be better to leave things ambiguous so that "dad" doesn't see anything in the face of the child. See, for example, our article on concealed ovulation where keeping the potential fathers guessing is explained as being adaptive. Matt Deres (talk) 10:38, 26 August 2011 (UTC)

Cockroaches!

Do cockroaches themselves create (or worsen?) unsanitary conditions, or are they simply a highly visible indicator that an environment itself is unsanitary? For example, we have two kitchens of equal dirtiness. Kitchen A is our control. We introduce a cockroach population into Kitchen B. Does the presence of the cockroaches themselves actually worsen the situation? The cockroach article's section about Roles as Pests pretty much just lists odor as a real, identifiable problem.

This series of thoughts occurred to me yesterday when my wife spotted a cockroach in our kitchen and insisted I head out to the store to buy some baited traps to kill them. I was trying to decide if removing the cockroaches actually solved (or at all helped) the real problem - the (evidently) dirty kitchen. The Masked Booby (talk) 04:44, 25 August 2011 (UTC)

Anything that crawls around in filth spreads filth. And they can carry dangerous microbes. Beeblebrox (talk) 04:58, 25 August 2011 (UTC)

(edit conflict) It's probably a dynamic situation; i.e. the filth attracts the roaches which themselves contribute to the filth. After all, roaches both shit and die; known sources of filth of their own rights. Coackroach turds and corpses sound like a clear increase of filth to me. --Jayron32 05:00, 25 August 2011 (UTC)

turds and corpses. I'm not sure why, but this made me lol.. Best science ref desk comment for a while.. Vespine (talk) 05:37, 25 August 2011 (UTC)

Cleaning the kitchen, getting rid of clutter, and making sure they can't access food sources (the food you eat and rubbish) will probably help more. And no of course they don't cause the dirt, they can actually be found even in the cleanest of homes, as long as they have ready access to food and water. Cockroaches are also not dirty per se, but they can carry dangerous bacteria to your food especially if their immediate environment is already dirty in the first place. So yeah, clean the room in addition to placing baits.-- Obsidi♠n Soul 05:41, 25 August 2011 (UTC)

Note that keeping food away from them might not be as easy as it sounds. If they can burrow into cardboard boxes, for example, that means all food in boxes must be moved somewhere inaccessible, like in the fridge, in sealed glass, metal, or plastic containers, etc.

Garbage disposals can also hold small bits of food that roaches might like, and you'll need a tightly sealed trash can or to flush anything they might find edible. However, when desperate, they might even eat things like paper and hair. StuRat (talk) 05:55, 25 August 2011 (UTC)

It is silly and specist to posit that cockroaches "love filth" and want to crawl around in "filth." The Mama roach will consume or will lay her eggs near any source of food, which might include toothpaste on a toothbrush, sugar cookies left for Santa by the Christmas tree, or any fresh food we would introduce into our mouths or serve to our families in the belief it was completely clean and wholesome. Edison (talk) 01:35, 26 August 2011 (UTC)

Where did anybody claim that 'cockroaches "love filth" and want to crawl around in "filth.' [my added emphases]? I agree that such antropomorphic motivatory terms would be inappropriate, but I don't see any suggestions of them above. "Filth" is merely a descriptive term, useful in context for its implications for us, of a subset of the substances that cockroaches regard as food or environment, but which we don't. {The poster formerly known as 87.81.2301.95} 90.197.66.127 (talk) 05:58, 26 August 2011 (UTC)

"Anything that crawls around in filth.." and "The filth attracts the roaches"implies a preference for "filth" over good wholesome food. The choice of words implies the roach would ignore Mom's fresh apple pie or the sandwich you just bought at the deli and go for the spilled milk, stale crumbs, cat throwup, and garbage. Edison (talk) 18:21, 26 August 2011 (UTC)

What is the EXACT name of the green birds on the photo?

On this photo taken in Barcelona, Spain:

• File:Doves in Barcelona.jpg

two kinds of city birds are seen:

— city doves, or Columba livia

— something like monk parakeets from True parrots

However the Myiopsitta monachus are placed into the Category:Birds of Uruguay, and the article explicitly says that Myiopsitta monachus is a group endemic to South America (while Barcelona is in Europe).

I would appreciate anybody to help to name these „parrots” correctly, which is necessary for the further renaming of the file and its correct categorization. Thanks in advance, Cherurbino (talk) 16:10, 25 August 2011 (UTC)

The article also says that they have been introduced widely in other areas, and specifically: "They are a common sight in Barcelona parks, often as numerous as pigeons." Ghmyrtle (talk) 16:21, 25 August 2011 (UTC)

I also noted an article List of non-native birds of Great Britain where the introduced birds are listed for Britain. However they list another breed, a Ring necked Parakeets — while those in Barcelona look slightly different. Cherurbino (talk) 16:23, 25 August 2011 (UTC)

The birds in Britain are a different species, Rose-ringed Parakeet (Psittacula krameri). Ghmyrtle (talk) 16:28, 25 August 2011 (UTC)

Thank you, Ghmyrtle — I think it's time to take a decision: I shall rely upon the article you've mentioned. So, let them be Monk Parakeets! Cherurbino (talk) 16:27, 25 August 2011 (UTC)

space

Would it be fair to say that space is expanding because space is what a Black hole ejects every time it consumes a bit of matter? --DeeperQA (talk) 21:16, 25 August 2011 (UTC)

No, I can't think of any way in which that sentence makes sense. Dragons flight (talk) 21:44, 25 August 2011 (UTC)

I think it's an intriguing idea. The 2D rubber sheet analogy will have more surface area when massive objects are depressing it. It's hard for me to think about this clearly now and I'll try again later. 76.254.20.205 (talk) 22:18, 25 August 2011 (UTC)

No, the OP's statement makes no physical sense. The universe expansion has nothing to do with black holes except for the fact that both are solutions of Einstein's equations, but they are completely independent solutions. Dauto (talk) 23:23, 25 August 2011 (UTC)

So then what is it that you (or Einstein) are saying that space is expanding in which does make physical sense? --DeeperQA (talk) 23:44, 25 August 2011 (UTC)

I'm not sure I understand the question. Space is not expanding in anything. It's just expanding - that is the distance between objects in space increases over time. That expansion is observed for distances in a cosmological scale such as the distance between us and far away galaxies. Dauto (talk) 23:56, 25 August 2011 (UTC)

Check out Metric expansion of space, which immediately explains that space is not expanding in anything. Staecker (talk) 00:26, 26 August 2011 (UTC)

It says "It is an intrinsic expansion—that is, it is defined by the relative separation of parts of the universe and not by motion "outward" into preexisting space. In other words, the universe is not expanding "into" anything outside of itself."

If I hear correctly what you and the article are saying then the Universe was not part of the Big Bang or effected by it but only space and time were effected by the Big Bang and the Universe existed prior to the Big Bang. --DeeperQA (talk) 05:01, 27 August 2011 (UTC)

I think I'd include matter as part of the Big Bang. If the Universe comprises more than space, time and matter, then what else is it? Dbfirs 08:06, 27 August 2011 (UTC)

August 26

Using bath to remove excess fluids

Is using a bathtub filled with water and saturated with epsom salts (or other bath salts) a recognized method of drawing out excess fluids, by changing the osmotic balance ? StuRat (talk) 03:42, 26 August 2011 (UTC)

I'm not sure such a method could do much more except dry out your skin. Excess internal fluid can't escape via your skin all that easily; a diuretic would do the job more efficiently. --Jayron32 04:01, 26 August 2011 (UTC)

Why wouldn't fluid be drawn from the circulatory system into the skin, and from the rest of the body into the circulatory system ? I would think this would take hours, but can't see what would prevent it. StuRat (talk) 04:07, 26 August 2011 (UTC)

Maybe. It could possibly take many hours (like, in the hundreds). Again, possible, but rediculously inefficient when compared to other methods of removing "excess fluids". Diuretics seem like a much more sensible solution. --Jayron32 04:13, 26 August 2011 (UTC)

Well, hemodialysis takes up to about 4 hours. There they remove fluids from the circulatory system slowly, while fluids in the tissue migrate back into the blood stream. So, do you think the migration of fluids into the skin from the blood stream would be much slower than that ? If so, why ? StuRat (talk) 04:20, 26 August 2011 (UTC)

I'd not risk my precious bodily fluids in Epsom salts. But what makes you think you have too much of them in the first place? AndyTheGrump (talk) 04:24, 26 August 2011 (UTC)

This question is not about me. StuRat (talk) 04:43, 26 August 2011 (UTC)

I'd think blood has a higher concentration of water than the outer layers of skin (I think plasma is around 90% while cells are around 70%?--so only need to be more ionic than 10% ionic vs 30%), and that skin is designed to prevent water from escaping easily whereas a dialysis tube is designed to be especially permeable for water. DMacks (talk) 04:28, 26 August 2011 (UTC)

Skin prunes up rapidly when bathing in just water, so water can move into the skin rapidly. Are you saying it's only prevented from moving out rapidly ? How so ? StuRat (talk) 04:43, 26 August 2011 (UTC)

I don't know how skin works, except that skin says it's rather waterproof. But the fact that the skin does prune to such a great degree and speed in 100% water suggests by a simple salt-concentration analysis that the outer layers of skin act as if they have a fairly high salt concentration (rapid and large amount of osmosis in). That means it would be hard to get "more ionic" enough to pull water out effectively. Also, isn't the effect fairly constrained to the skin (otherwise that absorbed water would just as rapidly diffuse into the body and dilute the rest of you), which goes against your idea of water being replaced from inside during the soak in salt-water. Is there a correlation of long baths leading to increased urinary output? DMacks (talk) 04:59, 26 August 2011 (UTC)

That's an excellent question, I wonder if anyone ever studied this ? (It sounds like the type of research used as evidence that the government is wasting taxpayer money, though.) StuRat (talk) 05:04, 26 August 2011 (UTC)

I take long showers, and can report that I do NOT have any greater need to piss afterwards than usual. But then again, I'm just one person -- others might have a different experience (though I don't see why). 67.169.177.176 (talk) 06:29, 26 August 2011 (UTC)

Only a small portion of your body is submerged in water at any given time while in the shower, so I'd expect far less effect. Also, if you haven't meticulously documented your bathing and urinating habits, eliminated other factors (like drinking less coffee while in the shower), and plotted the results; an increase in urination following bathing may not be apparent. StuRat (talk) 06:46, 26 August 2011 (UTC)

Also, I don't know the inner workings of modern hemodialysis machines, but countercurrent exchange lets you get well beyond "equilibrium concentration" (average of inside and outside), and even a more rapid same-direction flow system could do that and use large volumes of extraction liquid (which could be themselves cleansed and recycled), whereas soaking in a bath you have limited buffer capacity for the extracted material. DMacks (talk) 04:33, 26 August 2011 (UTC)

(edit conflict) x3 @StuRat. If you see Dehydration#Prevention, you'll see that the average person loses only 350 mL of water per day through the skin, compared to 1000 mL per day through the kidneys. I can't imagine that even encasing yourself in salt would lead to significantly increased diffusion through the skin; the Epidermis is avascular meaning that dry skin doesn't have blood circulation to repleanish its water, so your scenario would require water to diffuse across several layers of skin before reaching the epidermis. Plus you haven't defined where the excess fluid is coming from. Are we talking excess blood volume, excess intracellular fluid, etc. I don't think any of those could be significantly affected by dry skin; which is all a hypertonic salt bath would do to you. --Jayron32 04:35, 26 August 2011 (UTC)

Fluid in tissue, such as intracellular fluid. I think encasing yourself in salt would dry you out rapidly. Isn't that how mummies were made ? StuRat (talk) 04:37, 26 August 2011 (UTC)

Yes, but they are dead and cannot maintain homeostasis. --Jayron32 04:46, 26 August 2011 (UTC)

Right, but what does that have to do with the rate of fluid loss through the skin ? Does being alive somehow slow that down ? StuRat (talk) 04:48, 26 August 2011 (UTC)

(undent) Look at it this way Stu: If what you are proposing were true, then the reverse would be true: soaking in a hypotonic solution (like pure water) would cause a massive influx of water into your body. You'd swell up like a balloon after a few hours of soaking in fresh water. Since that doesn't happen, then the water won't signficantly move in the reverse direction either. --Jayron32 04:52, 26 August 2011 (UTC)

Perhaps that would happen, except that your kidneys remove the water and you urinate it out (hopefully after leaving the pool). StuRat (talk) 04:58, 26 August 2011 (UTC)

(picking up on same theme from above)...I think the ball's in your court here to find some evidence of that (quick look on google scholar isn't finding me anything)--would certainly help support some of your ideas on the topic rather than speculation either way. DMacks (talk) 05:05, 26 August 2011 (UTC)

I believe that corpses floating in fresh water do become bloated with water. Isn't that evidence ? StuRat (talk) 05:08, 26 August 2011 (UTC)

If you ignore the fact that this takes several weeks, then yes. But what about corpses floating in seawater? According to your theory, they're supposed to shrivel up like raisins from dehydration, aren't they? But in fact they become just as bloated as the ones in freshwater, right? And the reason for it is, the bloating is not because of water absorption, but because of gases released into the body cavities during decomposition. In fact, even corpses on dry land that are left unburied (combat casualties, etc.) get bloated as they decompose, even though there can be no significant water absorption. 67.169.177.176 (talk) 06:26, 26 August 2011 (UTC)

Drowned corpses from Commons that are not bloated[23][24][25][[26] [27][28], one that is (warning nasty) and one that was and is relevant to the OP. Cuddlyable3 (talk) 10:34, 26 August 2011 (UTC)

The story of the USS Indianapolis (CA-35) shows that human skin is remarkably resistant to the loss of water to the sea. Wnt (talk) 13:11, 26 August 2011 (UTC)

Consider that when your body temperature increases you begin to perspire and the perspiration contains not only water but body salt. As the perspiration evaporates it leaves behind the body salt on your skin. I know this to be true from clothing put on a rack to dry between uses without washing. Salt builds up on the material until it is practically caked. Does this make me sweat more? I don't know but I do know that high body temperature is the way to go if you want to loose body water through dehydration rather than through a diuretic. --DeeperQA (talk) 05:22, 27 August 2011 (UTC)

amount of space

If all of the material in a Black hole was converted back into normal matter, ie. elements how much space would be required to contain it and what about all of the Black holes in the universe? --DeeperQA (talk) 05:09, 26 August 2011 (UTC)

Well, a supermassive black hole contains the mass of hundreds of thousands to billions of solar masses, so it would take up the space of hundreds of thousands to billions of Suns. Of course, if you wanted to prevent them from collapsing back into a black hole again, you'd need to space them out quite a bit. StuRat (talk) 05:13, 26 August 2011 (UTC)

If you multiply that by the 170 billion or so galaxies, you can account for the mass of all the supermassive black holes at galaxy centers. Whether smaller black holes would make an appreciable contribution to the total mass, I can not say. StuRat (talk) 05:18, 26 August 2011 (UTC)

I guess this is really about the maximum density of non-degenerate matter (the amount of matter you have is simply the mass of the black hole, so the volume required depends on the density). I'm not really sure what that is (it's not a desperately well defined concept anyway). It will depend on what level of degeneracy you are willing to accept (clearly you don't want neutron-degenerate matter, but is electron-degenerate matter ok?). It also depends on how many pieces you want the matter in. If you want it all in one piece, then it can't be done - it will collapse into a black hole again. If you want it in small enough pieces that it doesn't collapse under its own gravity then you need to choose where the pressure comes from. Is the pressure simply caused by gravity? In which case, the article Chandrasekhar limit will be useful. If the pressure is applied by magic, then you can do a better job (since gravity will only apply high pressure near the centre, the surface will be at fairly low pressure). --Tango (talk) 11:42, 26 August 2011 (UTC)

The matter I have in mind would be protons or possibly hydrogen atoms separated by enough space to prevent immediate collapse back into a Black hole. Lets say then minimum space to contain all of the hydrogen atoms all of the Black Holes in the Universe could make or lets jump right on up the periodic table and use the densest element separated by enough space to prevent immediate collapse at least long enough to measure how much space would be required. --DeeperQA (talk) 06:07, 27 August 2011 (UTC)

However, what I am really after is only the space that makes up an atom multiplied by the number of atoms all of the Black Holes would make rather than including the space of separation to prevent re collapse into a (many) Black Holes. --DeeperQA (talk) 06:48, 27 August 2011 (UTC)

That would depend on the configuration of the atoms. The "volume" of an atom depends on the surrounding atoms. What element or compound would you prefer? Simply divide the mass of the black hole by the density of your chosen material to obtain your answer. As pointed out above, this configuration would revert to a black hole under its own gravity. Dbfirs 07:58, 27 August 2011 (UTC)

I realize that but the point is to see if there is that much space in existance. --DeeperQA (talk) 08:23, 27 August 2011 (UTC)

If you have the necessary magic to stop it collapsing again, then you only need to make it marginally bigger than the event horizon and it won't be a black hole anymore. There is definitely enough space. The overall density of our galaxy is about one atom per cubic centimeter and the includes the black holes. If you spread that out evenly it would be a very thin gas. The density of the whole universe is even lower because of all the empty space between galaxies. --Tango (talk) 10:26, 27 August 2011 (UTC)

First human to die in space?

I know some animals have died in space, like the dogs the Soviets sent up, but has any human being ever died in space? It seems both the Challenger disaster and the Columbia disaster happened within Earth's atmosphere, so I guess those deaths can't be said to have happened in space. Is the sad record "First human to die in space" still unachieved? Pais (talk) 09:41, 26 August 2011 (UTC)

The Soyuz 11 mission resulted in the deaths of Vladislav Volkov, Georgi Dobrovolski and Viktor Patsayev during preparations for re-entry to the atmosphere, in June 1971. See also List of spaceflight-related accidents and incidents. Ghmyrtle (talk) 09:49, 26 August 2011 (UTC)

Hmmmm.... the Soyuz was reentering the atmosphere, and the valve opened at 104 mi altitude, about twice the height of the Space Shuttle Columbia disaster. The boundary of outer space seems to be arbitrary but is less than 76 mi. So if the article is right about how quickly the astronauts died from the depressurization, maybe this indeed was a death in space while the other was not. But like so many such questions, the more closely examined, the less meaningful the distinction seems to become. Wnt (talk) 13:09, 26 August 2011 (UTC)

Our articles don't seem to be entirely consistent regarding where "outer space" begins. The definitions at Outer space all fall within the lower thermosphere, while Exosphere says the exosphere is the last layer of atmosphere before outer space, implying that outer space doesn't start until 100,000 to 190,000 km (approx. 60,000 to 120,000 miles) altitude. Pais (talk) 15:39, 26 August 2011 (UTC)

The traditional boundary is 100km, roughly the height of the Kármán line. This is the altitude at which it is impossible for an aircraft to fly: in order to generate enough aerodynamic lift to stay aloft, it would need to be traveling faster than orbital velocity. --Carnildo (talk) 01:59, 27 August 2011 (UTC)

For some speculation/conspiracy thoughts, see lost cosmonauts. --Mr.98 (talk) 16:16, 26 August 2011 (UTC)

Yeah, I read about them recently on the Straight Dope, that's what got me wondering about the question. Pais (talk) 19:34, 26 August 2011 (UTC)

CRUDE OIL SPILL CLEAN-UP

In my Country, Nigeria, the oil spills are very common amongst oil prospecting companies. It has got so bad that hectares of arable farm land have been polluted, water sources for drinking, fishing and irrigation have also been contaminated.

Is there any way, method and/or technology that can be deployed to clean up the polluted land and water through private/community efforts?41.78.80.68 (talk) 11:28, 26 August 2011 (UTC)

Oil degrades itself. Cleanup efforts are usually performed to protect animals, not land. Sun, wind, rain, etc... break down, disperse, and degrade oil. The University of Delaware has a nice (short) page that explains what to do here -- kainaw™ 12:54, 26 August 2011 (UTC)

It is possible that oil-eating microbes could help to reduce the problem. The effectiveness of such organisms (typically bacteria) isn't always that clear (see Deepwater Horizon oil spill#Oil eating microbes) but it's a technique. In reports they're still often viewed as experimental. [29] Nonetheless, if you live in a country where oil spills on a certain type of terrain are actually common, it raises the possibility of developing particularly effective strains for the local terrain from old spill sites. For that matter, in theory, simply collecting a truckload of soil from an old spill site and spreading it over a large area of spill at the new site should have some positive effect - I just don't know if it's enough to be worth doing. Wnt (talk) 13:00, 26 August 2011 (UTC)

There is a recently started and ongoing project on one of the Channel Islands - I believe Jersey - using precisely this method to consume a quarry pit full of oil that had been collected from the beaches and dumped there some years before after a major oil spill: it was featured in a recent BBC TV documentary. {The poster formerly known as 87.81.230.195} 90.193.78.50 (talk) 16:32, 26 August 2011 (UTC)

This is too complex an issue for any simple answer. A possible approach may be to build dikes to stop the contamination spreading. Then scrape up the worst of the surface oil into heaps for composting. Then see if the natural soil bacteria can be encourage to brake down the oil naturally by ensuring it has enough nutrients containing nitrogen etc., (dung and lime). Frequent tilling of the soil will help the bacteria and atmospheric oxygen to get to the oil. The more it is tilled the greater will be the surface area available for the bacteria to attack it. That might help to prevent more contaminates from seeping into the water supply -or it might not. It will all take a lot of time and effort and so will need to be well organized to ensure that the remedial work being done is actually yielding good results. Here are some of the techniques that are used in land reclamation. [30] . Any project would have to choose the best methods to suit their local needs and available resources. --Aspro (talk) 13:14, 26 August 2011 (UTC)

Step one in Nigeria would be to get a stable, internationally recognized, effective, non-corrupt government in place, that enforces minimum environmental standards for the oil industry. The primary problem is political, not technical. IIRC, companies in Nigeria routinely abandon marginally productive wellheads without any effective cleanup, protection or monitoring. --Stephan Schulz (talk) 15:08, 26 August 2011 (UTC)

I wonder if locals could then take it over, and produce enough oil from it to pay for clean-up efforts. StuRat (talk) 16:55, 26 August 2011 (UTC)

Not unless the locals know how to maintain oil pipeline infrastructure (assuming it was still in good condition when the oil major left). Googlemeister (talk) 18:27, 26 August 2011 (UTC)

I'm thinking of something far less ambitious, like selling unrefined crude to other locals for use as heating oil. StuRat (talk) 18:31, 26 August 2011 (UTC)

I think you vastly overestimate the value of crude oil and vastly underestimate the cost of cleanup. Also, using crude oil directly is very problematic, too. Not to mention the fact that heating is not an urgent problem in most of Nigeria, and in particularly not in those parts close to the oil fields... --Stephan Schulz (talk) 18:43, 26 August 2011 (UTC)

While I agree it's not that useful, I presume StuRat is referring to things like for cooking, boiling water etc otherwise the suggestion doesn't make much sense as you pointed out. Nil Einne (talk) 21:00, 26 August 2011 (UTC)

Right, or for starting fires for slash and burn agriculture, if they use that method there, or for making torches, etc. StuRat (talk) 05:56, 27 August 2011 (UTC)

hello.

hi. please send me the complete complete details with examples on INTERFERENCE. — Preceding unsigned comment added by Anish225 (talk • contribs) 12:47, 26 August 2011 (UTC)

See interference. -- kainaw™ 12:50, 26 August 2011 (UTC)

Hurricane Irene: hype or real concern?

So, my mother is all in a tizzy over this Hurricane (Jewish mothers tend to do that) because it is destined to hit all three of the places I live in, (DC; Greenwich, CT; New York). I have been hearing about the Metro North cancelling service and King Michael evacuating low-lying areas of Manhattan (we live on one of the hills in Manhattan so no flooding risk anyway). My mum thinks a tree might fall on our Greenwich house and I have postponed returning to DC until Monday morning as my uni is also in a tizzy (and wanted people to come in on Friday so they could get a little closer to the hurricane). Now, here is my question: Is all of this concern actually necessary or is everyone just up in arms over mostly nothing? I mean I know it's going to cause some damage, but people are acting like we'll have a Northeastern Katrina (and, let's face it, people tend to overreact a great deal). Sir William Matthew Flinders Petrie | Say Shalom! 14:10, 26 August 2011 (UTC)

Patience young grasshopper. If it hits bad and starts blowing around your ears, the answer to your question will reveal itself.--Aspro (talk) 14:51, 26 August 2011 (UTC)

Here is the current Public Advisory from the National Hurrican Center. You can also find the current predicted track on the NHC/NOAA site. Barring a severe change in the path, it is almost certain that there will be flooding in many parts of New York City. As noted in the linked advisory, Irene is a very large cyclone, with hurricane force winds extending up to 80 miles from the center, and tropical storm force winds extending nearly 300 miles. With rain saturated ground and high winds, falling trees are a definite possibility. This is a big storm, it's not "mostly nothing." Being prepared for several hours or even days without power or running water is not overkill, it's prudent. While you may not be affected where you live specifically, other areas nearby may experience effects that hinder the day-to-day operations of that region. All that said, Katrina was a different situation altogether. It was a higher category storm when it made landfall over a city that lies mostly below sea level, and New Orleans had been thought to be outside the track. -- LarryMac | Talk 14:55, 26 August 2011 (UTC)

Per Aspro, the decision whether the pre-storm coverage was hype or reasonable precaution can only be made in hindsight. If the storm fizzles or makes an unexpected turn out to sea, most people will claim the hype was unwarrented. If the storm does major damage, mostr people will claim that the coverage was warrented, and will likely go further and claim that there was not enough preparation. --Jayron32 14:59, 26 August 2011 (UTC)

Since the eyewall collapse yesterday, the storm has become less likely to strengthen over the ocean before landfall, but you can see how that widened the area of hurricane force winds here: http://www.wunderground.com/tropical/tracking/at201109_cumwind.html but NYC is likely to get about 10 inches of rain over a very short time period -- as shown at http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1902 where Masters estimates a 20% chance of NYC floodwall overtopping and inundation of the subways. If the eyewall reforms before it hits the coast, that would be bad. 76.254.20.205 (talk) 18:27, 26 August 2011 (UTC)

Look to 1954 etc. Flooding in lower Fairfield County near the shore and along rivers. Staten Island and Long Island will likely get flooding. Lots of trees will fall. Manhattan above the old city is on a pretty good rocky spine. Jersey shore will flood (it is quite flat). Philadelphia would worry me more as the tidal surge (depending on exactly when anything hits) could cause significant flooding. DC is actually relatively inland from Hatteras (quite a bit west in fact) - I doubt it will get much more than flooding of the swampy parts (um -- which is a lot of DC). All IMHO of course. Collect (talk) 14:59, 26 August 2011 (UTC)

DC is more accurately described as NNW of Hatteras (even NNNW, if such a designation existed). --LarryMac | Talk 20:17, 26 August 2011 (UTC)

Lesser hurricanes like this typically cause less damage from wind and storm surge, but can actually produce more rain. This is because a major hurricane must move fast or exhaust it's fuel supply (warm ocean water which it rapidly cools). So, it passes quickly. A lesser hurricane, on the other hand, only slowly cools the water, so can "park" on a spot (particularly over a small island) and deliver rain for days. I don't believe this hurricane is predicted to do so, however. StuRat (talk) 18:39, 26 August 2011 (UTC)

What this hurricane is predicted to do is make landfall in a heavily-populated area that has very saturated soils due to prolonged rains. That alone increases the risk for flooding tremendously. Another risk that Irene poses is its large wind field. Large storms are able to produce stronger storm surges than their sustained winds would suggest. In fact, the latest analyses for Irene from the Atlantic Oceanographic and Meteorological Laboratory (08/27/2011 0130Z as of the time I checked) indicate that Irene has the potential to produce a "5.0 storm surge" in the Integrated Kinetic Energy scale—this is equivalent to a Category 4 hurricane. While it is impossible to know at this time whether this threat will materialize, the storm needs to be taken very seriously. Titoxd^{(?!? - cool stuff)} 03:10, 27 August 2011 (UTC)

Asian guinea pig?

According to Traditional Burmese calendar, also [31] and [32], the "planetary vehicle" or zodiac sign associated with Friday is the guinea pig. Since Cavia porcellus is native to South America, it seems unlikely to be an animal in any traditional Asian zodiac. Is there some other animal, native to Southeast Asia, that also gets called the Guinea pig? I found nothing at Guinea pig (disambiguation). 85.178.84.35 (talk) 22:53, 26 August 2011 (UTC)

According to this book (page 93), the traditional Friday animal is the ox. Perhaps the "tradition" has changed -- such things have been known to happen. Looie496 (talk) 00:30, 27 August 2011 (UTC)

August 27

Hurricane predictions - too far to the west

I've been watching NOAA hurricane predictions for 9 years. when they are threatening the east coast of the US, the early predictions invariably (or almost invariably) put the track too far to the west, and as a consequence predicting landfall too far to the south. These images show some predictions for Irene.

• 
  Advisory 7
• 
  Advisory 8
• 
  Advisory 9
• 
  Advisory 11
• 
  Advisory 13
• 
  Advisory 15

The first advisory I looked at was # 5. I didn't save it, but it had it tracking farther to the west and impacting Jacksonville. Each successive prediction had it farther to the east and north, until about #15, since when there has been little change. As far as I can remember, this always happens with their predictions for a hurricane like this over the last 9 years. Why don't they realize that there is a systematic error in their model and fix it? Bubba73 ^{You talkin' to me?} 01:35, 27 August 2011 (UTC)

Have you written to NOAA as well as us? HiLo48 (talk) 01:43, 27 August 2011 (UTC)

I don't think it would be useful to write to NOAA without some formal analysis to back up the claim. Hurricane prediction involves a lot of judgement calls, and the people who do it have to integrate large amounts of often contradictory information. NOAA maintains an archive of predictions going back for years, so it ought to be possible for an ordinary (non-academic) person to do a statistical analysis. Looie496 (talk) 01:55, 27 August 2011 (UTC)

No, I have not written to NOAA. I would think that they would compare their predictions with what actually happened and make adjustments to the models, but they don't seem to have done that. Bubba73 ^{You talkin' to me?} 02:46, 27 August 2011 (UTC)

NHC do compare what happened with a TC with what the models say and their predictions based on the Best Track analysis. See the Verification report for more details. Another thing worth pointing out is that NOAA do not own all the models that select the best track from, for example the UK Met Office and the ECMWF run models.Jason Rees (talk) 02:55, 27 August 2011 (UTC)

I just realized that there was a related question on August 24 #Hurricane Irene on Weather Underground: computer models much scarier than 5-day forecast. Bubba73 ^{You talkin' to me?} 03:02, 27 August 2011 (UTC)

Even if they knew the predictions were wrong, it could be a hard thing to fix. These predictions are based on weather models that simulate the whole atmosphere and ocean for the purposes of weather forecasting. Finding the center of the storm and tracking its motion is a highly derived quantity that depends on many other factors, such as wind fields and moisture content and surface temperatures, etc. So, even if they found that the predictions were systematically wrong, it could be very difficult to identify what part of the model needed to be fixed. Dragons flight (talk) 18:15, 27 August 2011 (UTC)

As a frequent reader of the prediction discussions, I can tell you that the forecasters rely heavily on expertise -- they don't just blindly rely on the models. It is actually rare for a forecast to represent a simple consensus of models -- sometimes one model is favored over the others; sometimes (more rarely) a forecaster will simply say that the models don't seem plausible and make a prediction that doesn't match any of them. So if a forecaster noticed that predictions were systematically wrong in some identifiable way, that knowledge would surely be taken into account. Looie496 (talk) 18:33, 27 August 2011 (UTC)

Thanks. They seem to be consistently wrong on ones like this, but I need more data. Bubba73 ^{You talkin' to me?} 21:01, 27 August 2011 (UTC)

Squirrel Behavior Question

We have both an American Red Squirrel and two Fox Squirrels sharing our lake shore property. I was told that the American Red Squirrel will tear off the testicles of the Fox Squirrel should it catch it. I have watched the American Red Squirrel "chase" the Fox squirrels, but not catch them. Is this a true "behavior" of an American Red Squirrel?

Thank You!

Lee — Preceding unsigned comment added by 75.198.53.218 (talk) 01:53, 27 August 2011 (UTC)

Sounds doubtful. Perhaps it tries to kill it by any means available, which might mean ripping off whatever it can get hold of. StuRat (talk) 06:30, 27 August 2011 (UTC)

I'm intrigued to know how the Red Squirrels gained the knowledge of orchidectomy and its effects. This story has a strong anthropomorphic odour. Richard Avery (talk) 07:23, 27 August 2011 (UTC)

American red squirrels are very territorial. Fox squirrels, on the other hand, are not and are quite gregarious. I highly doubt they'd be chasing each other for the express purpose of ripping off testicles though LOL. The American red squirrel is just doing the equivalent of "Git offa mah lawn!"-- Obsidi♠n Soul 12:01, 27 August 2011 (UTC)

I agree it's a suspicious claim, but I'll add that a territorial mammal need not have 'knowledge' of the effects of castration in order to benefit from castration of competitors. wp:or I've seen dogs target testicles in a variety of species, and it doesn't sound completely unreasonable that red squirrels may have picked up this technique over evolutionary time. Still, probably just a colorful embellishment of how they aggressively defend territory :) SemanticMantis (talk) 13:56, 27 August 2011 (UTC)

They just misinterpreted the instructions in the Squirrel Manual: "When you encounter another squirrel, try to rip-off his nuts". StuRat (talk) 16:37, 27 August 2011 (UTC)

This product may contain traces of nuts. Plasmic Physics (talk) 23:48, 27 August 2011 (UTC)

Strings and Wave Packets in Physics

Is a String in string theory the same thing as a Wave packet or something different?Pensioner.bsc (talk) 03:03, 27 August 2011 (UTC)

It's different.

The word "string" in string-theory is used to describe what most physicists would call "a degree of freedom." String theories vary widely, though, so the term is used and abused pretty wildly. Some string theorists propose that a "string" is the fundamental degree-of-freedom for the most elementary of elementary particles; and they have mathematical elaborations to help explain how a string's properties can, when observed more macroscopically, be related to physical properties like mass and charge. Personally, I don't find that any simpler than accepting the elementary properties like mass and charge; nor do I believe it provides any predictive insight; but I am not a string theorist, so I'm not privy to the details of the theories.

A "wave packet" refers to the conceptual idea of a propagating disturbance that has a meaningful degree of spatial locality as it travels. In other words, the simplest idealization of a wave is an infinite plane wave that is totally uniform everywhere. A "wave packet" is a more practical realization that describes a wave disturbance with finite dimensions. You can use a variety of mathematical tools to help understand wave packets and localization - particularly, fourier decomposition.

But, to summarize, "string" and "wave packet" refer to totally different conceptual ideas. Nimur (talk) 03:52, 27 August 2011 (UTC)

Thanks. I've been reading some pop science, Michio Kaku & Jennifer Thompson "Beyond Einstein" OUP 1999.Pensioner.bsc (talk) 20:19, 27 August 2011 (UTC)

Where do the baloons go

When helium baloons rise in the atmosphere and complete their pupose do they continue rising and expand in the diminishing atmospheric pressure untill they burst and fall back to earth? Do they continue on into space and drift around like a bubble? Or do they acheive some sort of equalibrium and drift around in our upper atmosphere? I did search but could find no answer.190.56.16.48 (talk) 05:57, 27 August 2011 (UTC)

When they rise to the point of the pressure of the air outside the balloon being lesser than the pressure of the air inside the balloon, then the balloon pops and falls to the ground. I believe this was illustrated in a Calvin and Hobbes strip. --Σ _{^talkcontribs} 05:58, 27 August 2011 (UTC)

What is just as interesting to me is where does the helium go? I believe from things I heard long ago that free helium in the atmosphere does continue to float up and disappear into space. This means that every helium balloon is a loss of helium from the earth. HiLo48 (talk) 06:07, 27 August 2011 (UTC)

The question is "Does the earth's gravity have enough power to indefinitely maintain the atmosphere"? If the answer is no, we've been wasting helium for many, many years. --Σ _{^talkcontribs} 06:18, 27 August 2011 (UTC)

Yes, we have been wasting helium for many, many years. I've done my research now. The Helium article tells us that the helium we use commercially (including in balloons) comes from natural gas, a non-renewable resource, and also that "most helium in the Earth's atmosphere escapes into space by several processes". HiLo48 (talk) 07:19, 27 August 2011 (UTC)

Couldn't help noticing that helium baloons all seem to be much larger than the volume of helium in them. Therefor if the baloon expanded to it's full extent then the pressure inside would be minute and it's concievable that the strength of the material could contain that tiny pressure differential and allow the baloon into space.190.56.16.48 (talk) 06:30, 27 August 2011 (UTC)

There are concerns about a shortage of helium. And this video shows what happens when you send an iPhone up to space with a weather balloon. Dismas|^(talk) 06:48, 27 August 2011 (UTC)

Wow, that is one excellent video! Richard Avery (talk) 07:17, 27 August 2011 (UTC)

Having been party to high altitude baloon experiments I happen to have some first-hand knowlege. The natural latex baloons normally used are manufactured to have a specific strength, so they burst when they reach a specific size (~11m in the case of the experiments I was party to). The amount of helium in the baloon and the weight of the baloon and it's payload would determine at what altitude that happens. I know of one baloon that carried a payload of a little under 1kg to an altitude of over 115 000 feet when it burst. If the baloon were to reach an equilibrium altitude before it reaches its burst point it would drift at that altitude until the latex is degraded by UV radiation, then it bursts (usually a matter of a few hours - provided it's in daylight of course). As the baloons are natural latex they are completely biodegradable and in fact if left outdoors in the sun and weather will completely decompose in a few weeks or months. Roger (talk) 08:32, 27 August 2011 (UTC)

Party balloons are usually made from metallised PET. Although more gas tight than latex they never the less are permeable to helium. Helium gas are very small atoms and escapes by atomic diffusion. Temperature and gas gradient affects the speed that this happens. A party balloon also has a large surface to volume ratio so it will lose positive buoyancy faster than a airship (which may also have a secondary barrier) and its lift will not be as great. Indeed the helium mix (its not pure helium) and the weight of the envelope (balloon) will only give sufficient positive lift for a few hundred feet for an ordinary balloon. So a party balloon will just go up to its equilibrium hight then slowly descend again.--Aspro (talk) 10:40, 27 August 2011 (UTC)

Discoloured teeth from drugs/meds

I'm pretty sure that there was a medication that resulted in a lot of people (maybe just in the UK) having discoloured teeth because of either some medication they took or their mother took. It's not fluorosis but something similar. Does this ring a bell with anyone? Thanks. --87.112.226.247 (talk) 09:30, 27 August 2011 (UTC)

Tetracycline#Cautions.2C_contraindications.2C_side_effects. --Aspro (talk) 09:37, 27 August 2011 (UTC)

Shoddy reporting story???

http://www.huffingtonpost.com/2011/06/29/diet-soda-weight-gain_n_886409.html

How can diet soda (by its own) increase the weight of people if it has no calories? Is it some case of correlation does not imply causation? Seems to me as if this was written with the "I didn't make myself fat, it's the fault of external factors beyond my control" perspective. Raskolkhan (talk) 13:43, 27 August 2011 (UTC)

Something with no calories might still affect your metabolism changing how many calories you retain from other stuff you eat. I am personally very suspicious of artificial sweeteners for that very reason. Dauto (talk) 13:52, 27 August 2011 (UTC)

Its explained here, but there doesn't appear to be a free copy of their actual paper available.[33]--Aspro (talk) 14:00, 27 August 2011 (UTC)

And there are many other ways where consuming things without calories may cause you to gain weight. Here are a few:

1) Consuming salt may cause you to retain water.

2) Consuming things which accumulate in the body will increase your weight, like arsenic or lead. Of course, they will also kill you, at which point you're likely to lose weight.

3) Consuming something which causes you to grow tumors may make you gain weight. StuRat (talk) 16:31, 27 August 2011 (UTC)

I'd like to know how the study was controlled before putting too much weight on it. For example, was the control group drinkers of regular cola? or people who don't like cola? Or people who wanted to drink cola, but were forbidden for the purposes of the study? Besides the cola did they make sure that both groups were eating and drinking the exact same things?

It occurs to me that people who drink a lot of cola might be big fans for sweet foods in general, while people who don't like cola might prefer healthier foods in general. This is certainly true of people I know in my life.

(In short, People who drink a lot of cola might also eat a lot of junk food.)

These sorts of seemingly minor differences in how the study is run can drastically change the meaning of a scientific study, but the news never reports these details. Without reading the study itself you can't draw any conclusions. APL (talk) 21:20, 27 August 2011 (UTC)

In fact, check this out, from the press release :

"The results were adjusted for waist circumference, diabetes status, leisure-time physical activity level, neighborhood of residence, age and smoking status at the beginning of each interval, as well as sex, ethnicity and years of education."

Notice that "Diet" is conspicuously missing from that list. Why is that? That's the obvious thing to adjust for!

Makes you wonder if the creators of the study didn't have an axe to grind. (Or it makes you wonder if they ran the numbers once taking diet into account and got a boring non-publishable result, and wondered "what can we forget to calibrate for that will get us into the news so we'll all have jobs next year?")

Until I know otherwise I'm going to assume that this study just proved that "eaters of Junk Food will get fat even if they drink diet soda". APL (talk) 21:31, 27 August 2011 (UTC)

You're missing the entire point of the study. The idea is that your body expects that something sweet is coming, prepares for it (presumably by releasing insulin), and when it doesn't get it, makes you crave sweets. Thus, you gain weight by giving in to the enhanced cravings. Obviously you can't gain weight if you are denied the additional food you crave as a result of drinking the diet soda. Unless you intend to put diet soda drinkers across the nation in shackles to prevent them from eating more sweets, such a study as you propose would be useless. StuRat (talk) 22:22, 27 August 2011 (UTC)

StuRat, I understand that was the point of the article, but that's not what the press release says that the scientists studied.

The study shows that there is a statistical "link" between drinking diet soda and gaining weight! Well, no kidding! I could have told you that! Do you know any health food nuts that drink soda of any kind? I sure don't. Since the study (apparently) didn't control for type of diet, The "Health Food Nut" demographic would be enough to cause a statistical "link", while telling us absolutely nothing about artificial sweeteners. In addition, the lack of healthy drink alternatives at Fast Food joints would also be enough to cause a statistical "link" between diet cola and weight gain, also without telling us anything useful about artificial sweeteners.

Imagine that you go to McDonalds six times a week and order a Diet Coke with your super value meal. That will make you a "Diet Cola drinker" for the purposes of this study, but is it the cola that's making you fat?

(If Bob only drinks fruit juice he buys with his groceries at "Whole Foods", and Alice only drinks Diet Soda she purchases with her meals at McDonalds, it's safe to say that Alice is more likely to gain weight for reasons that have absolutely nothing to do with the diet soda.)

Until there's some indication that they controlled for this variable (And, as I said, It's conspicuously missing from the list of variables they controlled), then I don't see that this study tells us anything that isn't already obvious.

76.28.67.181 (talk) 00:27, 28 August 2011 (UTC)

To respond more directly to sturat's point, all the scientists' theories about how artificial sweeteners cause weight gain are BS until they demonstrate that artificial sweeteners do cause weight gain, and judging from their own press release (since I can't find a free version of the paper) I'm not convinced that they've proved that at all. They may have simply demonstrated that Cola's are primary drunk by people with poor diets. Which seems likely to me.

(If your concern is that drinking diet cola will actually cause someone to switch from salads to cheeseburgers, then the correct course is obviously not to just ignore that variable completely! but to create an experiment that tests that concern. Possibly by restricting the study to people who have recently switched from regular cola to diet.)

76.28.67.181 (talk) 00:41, 28 August 2011 (UTC)

Are you APL ? StuRat (talk) 00:39, 28 August 2011 (UTC)

Oh. Yes. Sorry. APL (talk) 01:19, 28 August 2011 (UTC)

What you could do is ensure that everyone had identical dietary habits before you started the study, then give half of them diet soda and the other half diet soda with the artificial sweeteners removed. However, you obviously would then have to let them eat what they want during the study, as that's the only way to determine if drinking diet soda makes you eat more calories. StuRat (talk) 00:49, 28 August 2011 (UTC)

You seem to be trying to compare regular soda with diet soda. That might be a valid study, but I'd expect that both are far worse than drinking something healthy (like water or unsweetened tea). Since they advertise diet soda as allowing you to lose weight after the switch from regular soda, such a study might dispel that myth. StuRat (talk) 00:57, 28 August 2011 (UTC)

Oh, I agree with that. My point was just that you can't look at "Diet Soda Drinker" as though it was a completely independent variable. In society at large, it's clearly not. It tends to be closely associated with things like "Hamburger Eater" and "Processed food buyer" which will obviously impact a study of waist measurements.

Of course, The scientists involved may well have grouped the people in their study by diet habits, perhaps the press-release writer simply didn't mention it. I should have emphasized that, because I really do hate to criticize scientists based entirely on how their work is reported in the press. I guess that brings us back to the original question of "Shoddy reporting??" APL (talk) 01:19, 28 August 2011 (UTC)

space moving

If space can expand then space can move. If space can move then can space move at different speeds and if so do the different speeds result in compression and decompression like sound waves in air and if so could space expansion just be the part of the wave (front) we are in at this moment? --DeeperQA (talk) 14:20, 27 August 2011 (UTC)

YES! space compressional waves can propagate through space itself. See gravitational waves. Dauto (talk) 14:24, 27 August 2011 (UTC)

Is space expansion related to gravity? --DeeperQA (talk) 14:47, 27 August 2011 (UTC)

Yes, absolutely. Space expansion is a particular solution to Einstein's gravity equations. See Einstein field equations. A gravitational wave is a different solution for the same field equations Dauto (talk) 15:01, 27 August 2011 (UTC)

Nevertheless, they are not a good explanation for the observed expansion of space because they don't lead to a uniform expansion in all directions at the same time. Dauto (talk) 14:26, 27 August 2011 (UTC)

Please consider the effect of blowing up a balloon and then not blowing it ups as fast - the traditional way of demonstrating what happens to galaxies if they were dots on the surface of a balloon. --DeeperQA (talk) 14:45, 27 August 2011 (UTC)

The rate of blowing up cannot be arbitrarily increased and decreased at will. The rate changes according to Einstein's field equations. The presence of matter has the effect to decrease the rate of expansion - that's the usual behavior of gravity. The presence of dark energy may have the unusual effect of increasing the rate of expansion - that's unusual but it is still a gravitational effect. Dauto (talk) 15:01, 27 August 2011 (UTC)

It would be a good idea to not start a new section for each question if their all about the same topic. I've noticed that you have created three sections, all questions about space-time. Plasmic Physics (talk) 14:51, 27 August 2011 (UTC)

Our minds work differently. --DeeperQA (talk) 15:15, 27 August 2011 (UTC)

shrinking galaxies

Are there any galaxies that are growing smaller? --DeeperQA (talk) 14:49, 27 August 2011 (UTC)

Galaxies usually don't shrink or expand. They orbit their centers spinning around themselves. Dauto (talk) 15:08, 27 August 2011 (UTC)

But on the other hand if it's true that all/most galaxies contain a supermassive black hole at their centre, then whether by accretion or act of super nova, collapse of massive material toward the centre seems intuitively to indicate shrinkage of the entire galactic body.Phalcor (talk) 16:04, 27 August 2011 (UTC)

Not really. Only stars close to the black hole are pulled in. Most stars in the galaxy are in a stable orbit about the galactic core. StuRat (talk) 16:23, 27 August 2011 (UTC)

Which for me begs the question:- Does the collective gravity of the stars near the centre remain the same pre-black hole formation and post black hole formation?Phalcor (talk) 16:44, 27 August 2011 (UTC)

(Pedantic linguistic aside for the interested: Phalcor probably means 'raises the question'; 'begs the question' means something else entirely :) — Preceding unsigned comment added by SemanticMantis (talk • contribs) 17:15, 27 August 2011 (UTC)

Yes, the mass remains the same. When a black hole swallows a star, it's mass increases by that amount (minus whatever streams out as jets). StuRat (talk) 17:29, 27 August 2011 (UTC)

..and thereby more space is made available or created? --DeeperQA (talk) 17:53, 27 August 2011 (UTC)

If by "made available" you mean that space once occupied by a star is now empty, that's true. The diameter of the black hole's event horizon will also have grown, but I don't think it's increase in volume is as much as the decrease in the star's volume (hopefully somebody else can verify this). StuRat (talk) 18:12, 27 August 2011 (UTC)

DeeperQA, based on this and your previous questions, you seem to want to explain the cosmological expansion as having something to do with individual bodies collapsing into black holes. It doesn't work that way. There was an explosion at the scale of the whole cosmos and matter is still flying apart from that explosion. The expansion is not affected by anything that clumps of matter do locally, such as collapsing into black holes. There is no need for any process to "make space available" for the expansion. All space at a given time is "new" since it is a different set of spacetime points than the space at any previous time. -- BenRG (talk) 19:59, 27 August 2011 (UTC)

So you are saying that prior to the Big Bang space was compressed like air in a tank and that the Big Bang is when the tank burst and the air began filling the vacuum surrounding the tank, ie. space filling the Universe? --DeeperQA (talk) 20:10, 27 August 2011 (UTC)

No, not at all. "Space" and "vacuum" are the same thing, and, as I said above, space at different times is different space. If you were standing in a trapezoidal room, you wouldn't ask how the space from the wide end of the room was compressed to fit in the narrow end, or what the room was expanding into. There's no law of width conservation that says that rooms have to be rectangular. -- BenRG (talk) 20:42, 27 August 2011 (UTC)

So you are saying that time changes space or vacuum and that vacuum is expanding but not due to Black Holes releasing the vacuum which makes up atoms? --DeeperQA (talk) 22:13, 27 August 2011 (UTC)

"Releasing the vacuum", there isn't a bit of sense in that! A vacuum isn't released, for something to be released it must first be contained. Plasmic Physics (talk) 23:43, 27 August 2011 (UTC)

You cannot start at the end of a thread and understand it. Please try again. --DeeperQA (talk) 00:15, 28 August 2011 (UTC)

Largest LED

What is the world's largest light emitting diode and what kind of equipment, material, and skill would it take to make a larger one? 208.54.5.228 (talk) 18:23, 27 August 2011 (UTC)

Are you asking about 1 individual LED cell, or a large screen composed of many LED cells ? StuRat (talk) 22:35, 27 August 2011 (UTC)

I read the question as asking about one single LED. 82.43.90.90 (talk) 23:14, 27 August 2011 (UTC)

If so, the question is why you would want to build a large single LED when a bank of smaller LEDs would be far more efficient. One large LED makes about as much sense as sandpaper with one large grain on it. StuRat (talk) 23:17, 27 August 2011 (UTC)

The question is not about efficiency, it's about a world record in the electronic industry. Plasmic Physics (talk) 23:34, 27 August 2011 (UTC)

Well then, I suppose they could do like the do with pumpkins, and make a huge one, even though it's of no use other than for winning contests. StuRat (talk) 00:35, 28 August 2011 (UTC)

Why do most Jews not look, well, semitic?

Why is it that most Jews, for example this chap on the right have lighter coloured skin than most Arabs from Israel and the surrounding area? I am of course aware that Jews come in all colours (shapes, sizes, etc) but one would have thought that with a religion/culture where, for want of a better way of putting it, breeding within the group had such importance it's curious that your average Jew is relatively light skinned. What's up? Egg Centric 18:48, 27 August 2011 (UTC)

Because Rabinovich is basically Ukrainian. Compare with Jews who were not in the diaspora: Mizrahi Jews and Arab Jews.-- Obsidi♠n Soul 19:02, 27 August 2011 (UTC)

But until recently Jews were supposed to have been descendants from the twelve tribes of Israel, right? It shouldn't matter how long his ancestors lived in the Ukraine (within reason, pedant in me has to point out presumably eventually evolution would act to select a skin colour roughly the same as the rest of the population if it was an adaptive advantage, but certainly not in such a short time period). Even now conversion from outside tribal descent is a really sticky issue AIUI. Or am I horribly misinformed? Egg Centric 19:04, 27 August 2011 (UTC)

I think our article on Ashkenazi Jews will probably answer the question, particularly the section on genetics near the bottom. Looie496 (talk) 19:09, 27 August 2011 (UTC)

I think it's also probably a misconception on your part that all Middle Eastern peoples are dark-skinned. Persian, Levantine, and Central Asian peoples (like the Turks and the Pashtun for example) are usually quite light-skinned. Arabs have a slightly darker skin tone, but that's probably just the desert sun.-- Obsidi♠n Soul 19:22, 27 August 2011 (UTC)

The genetics certainly support the common group of ancestors theory, ruling out intermarriage as a cause - and yes I know that Turks, Lebanese etc are pretty light skinned - but I really don't think they're as light skinned as the Jews I have in mind. A theory just entered my own head - perhaps the lighter skinned ones were more likely to emigrate north while the darker skinned ones were more likely to head south. Any research on this? Ethiopian and (the remaining) Sudanese Jews are pretty dark, I know this. Egg Centric 19:39, 27 August 2011 (UTC)

IMO, highly unlikely that migration patterns would follow very minor variations in skin color. :/ More likely that those who went south are darker skinned due to either the climate or intermarriage with local populations and that the original groups were light-skinned (compare peninsular Arabs with sub-Saharan Arabs). The taboo against intermarriage or conversion might not be present or more relaxed in non-European Jewish populations. The article on Arab jews specifically points out that they probably were of Arab ethnicity for example.-- Obsidi♠n Soul 20:00, 27 August 2011 (UTC)

Before we resort to some very crude ad hoc speculations, let's note Jewish ethnic divisions and Genetic studies on Jews. To summarize the results, while Jews indeed have tended to remain apart as an ethnic group, matters of the heart are not so readily predicted; though there is a remarkable degree of preservation of the male lineages, there are signs of gene flow in every population. Note that conversion to Judaism is possible, for example. I don't think people would be people if they could live side by side on a continent for a thousand years without visible evidence of union. Wnt (talk) 20:21, 27 August 2011 (UTC)

Exactly.-- Obsidi♠n Soul 20:48, 27 August 2011 (UTC)

Weird maple disease

The Norway maples in our yard seem to be afflicted with some weird disease. The leaves have multiple large black spots about the size of my thumbnail, that have some tiny yellow specks inside them and a yellow rim. They are distributed more or less randomly over the leaves. Do you have any clue what this could be? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 19:39, 27 August 2011 (UTC)

Tar spots on sycamore

Hmmm... might be tar spots caused by Rhytisma acerinum.-- Obsidi♠n Soul 19:54, 27 August 2011 (UTC)

That looks exactly like what they have. Thanks! Whoop whoop pull up ^{Bitching Betty | Averted crashes} 20:14, 27 August 2011 (UTC)

Light reflecting off light

Can a light beam reflect off the photons in another light beam? Whoop whoop pull up ^{Bitching Betty | Averted crashes} 20:21, 27 August 2011 (UTC)

Yes, photon-photon scattering is possible, but it is highly inefficient at typical energies so you need a very, very large number of photons in order to have an observable number of scattering events. At the human scale, two beams of light are always going to appear as if they pass right through each other. Dragons flight (talk) 21:02, 27 August 2011 (UTC)

Think of it like firing two guns across the path of one another. It's possible the bullets will strike each other, but highly unlikely. StuRat (talk) 22:28, 27 August 2011 (UTC)

What about the Double-slit experiment?-- Obsidi♠n Soul 22:44, 27 August 2011 (UTC)

That's completely different; that's wave interference. It has nothing to do with photons scattering off one another. --Trovatore (talk) 22:48, 27 August 2011 (UTC)

But wouldn't it mean that there is a possibility that photons are pure waves and thus collision would behave differently than if they were particles? I mean, it's unknown of course and I only have a very basic understanding of physics, but... -- Obsidi♠n Soul 23:04, 27 August 2011 (UTC)

Just because they vibrate does not make them waves. Electrons vibrate and thus can appear like waves, but are they waves? No! Whoop whoop pull up ^{Bitching Betty | Averted crashes} 23:11, 27 August 2011 (UTC)

Note that the smallest thing anyone has ever actually seen is an atom. We can only posit whether anything smaller than that is a wave or a particle by their behavior. And as discovered from the aforementioned experiment, photons (and electrons and apparently all matter) behave both as a particle and a wave, either like a single bullet or like ripples in a pond (not sinusoidal wiggling vibrations like I think you just described electrons as). Though not being a physicist, I don't know if that's accurate as well. That has been a point of debate for the some time and the current scientific consensus is that they can be one or the other, some physicists call them wavicles, some like I mentioned earlier stick by a wave-only hypothesis for everything (it's actually the older theory, until Einstein demonstrated that light behaved as individual particles as well).

Anyway *shrugs* :S I'm actually also asking a question, heh, not giving an answer (as I've confessed I'm completely ignorant in this field). If they can behave both as a particle and a wave, when photons do collide, would it be as particles or as waves?-- Obsidi♠n Soul 23:59, 27 August 2011 (UTC)

Unfortunately normal language and intuition does not cover the situation well. QM is just weird at a very fundamental level, and you can't get around the basic weirdness by choice of words.

QM and relativity showed up at about the same time, and both broke people's intuitions. Even today, students may study them at about the same time, and experience the intuition-breaking at around the same time. So it takes a while to realize that relativity's weirdness is something you can come to terms with just by adjusting some of your expectations, but QM is weird at a much deeper level. QM challenges metaphysical realism itself. There are interpretations of it that save some form of realism, but always at a cost.

A lot of treatments of how surprising QM is focus on indeterminism, which I think is a mistake. Indeterminism is not counterintuitive. Most people believe in a form of free will that requires indeterminism. If you break realism, though, that's much harder to come to terms with. --Trovatore (talk) 23:28, 27 August 2011 (UTC)

If you have light reflection off light, that is nonlinear behaviour. It may be possible for two high energy gamma ray photons to collide and make an electron positron pair. Also if you shine light through a non linear optic material you can get many interesting interactions. Graeme Bartlett (talk) 23:38, 27 August 2011 (UTC)

August 28

Plants in anoxic environments

Plants "breathe" CO₂ in a manner analogous to animals breathing in O₂. But, as I recall, a 100% oxygen environment would kill us all in only a few days (or less, depending on pressure). Would a 100% CO₂ environment be similarly toxic to plants? How about a nitrogen/carbon dioxide mix similar to air but without the oxygen? GeeJo ^(t)⁄_(c) • 01:01, 28 August 2011 (UTC)

Plants also need to be able to breathe oxygen as well. While oxygen is produced as a byproduct of photosynthesis, plants still need to take in oxygen for cellular respiration. The whole point of photosynthesis is to store carbon for later use; plants then use the products of photosynthesis to generate energy for various cellular processes; just as in animals these processes require an external source of oxygen. Think of it this way: you produce water as a waste product, but you still need to drink water to survive; the processes that make waste water are not the same processes that use water. Likewise in plants, some processes make "waste" oxygen, but other metabolic processes require oxygen to work. --Jayron32 01:36, 28 August 2011 (UTC)

Bug Help

Hello WikiReffers,

Please help, I keep finding these bugs in my appartment. Theyre about 0.5cm long, and I want to know what they are, and what I can do about it, if anything. I live in a large canadian city in Southern Ontario.Flickr Picture As always, much appreciated!

--Cacofonie (talk) 01:36, 28 August 2011 (UTC)