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January 23

Avalanche season in the Canadian Rockies

Could someone tell me what time of year are avalanches likely to happen in the Rocky Mountains in Alberta (in the vicinity of Jasper / Dawson Creek)? Also what months are the worst in terms of avalanche severity? Thanks in advance! 24.23.197.43 (talk) 03:30, 23 January 2010 (UTC)

I'm not familiar with the areas, but I'd recommend asking people who are before venturing into those areas if you have any doubts. Falconus^{p t c} 05:05, 23 January 2010 (UTC)

Well, late winter/early spring would be the worst, since avalanches are most likely when the snow and ice starts to melt and the weight goes out of balance on the slopes. At that point, there is so much snow, the slightest trigger would let the mountains come tumbling down. That being said, there is always a risk of avalanches so long as there is snow.

That said, there is no risk of avalanche in Dawson Creek (which is in BC, not Alberta) because Dawson Creek is flat and about 7 hours away from Jasper. Aaronite (talk) 06:45, 23 January 2010 (UTC)

Thanks for the info, you really helped me out on this. Now, what's the latest in the springtime that avalanches are likely to occur in the Jasper area? I'm writing a series of action-adventure novels about rescue pilots, and I need to know how late in the spring I can set the second one, or whether I should move up the first one by a few weeks. Clear skies to you! 24.23.197.43 (talk) 07:42, 23 January 2010 (UTC)

Hudson Bay ice

What months is the northern part of Hudson Bay (around Baffin and Southampton Islands) frozen over? Also, how thick does the ice get in that part of the bay? Thanks in advance! 24.23.197.43 (talk) 03:34, 23 January 2010 (UTC)

There is some general information about ice in the linked article. ←Baseball Bugs ^{What's up, Doc?} carrots→ 03:37, 23 January 2010 (UTC)

Just took a look at the article, it says that the bay can stay frozen as late as mid-June but the ice breaks up in the northern part first and then in the south. Thanks, and clear skies to you! 24.23.197.43 (talk) 06:20, 23 January 2010 (UTC)

These things usually differs from year to year. Some years, it's colder than usual and thus more ice, other years may be warmer than usual and with less ice. Depending on what month is coldest a particular winter, the answer can differ. E.G. (talk) 01:08, 24 January 2010 (UTC)

Here is a map showing current sea ice extent in the Northern Hemisphere, including Hudson Bay. ~AH1^(TCU) 19:41, 25 January 2010 (UTC)

Wow, the map shows that everything is frozen over! That's no big surprise this time of year, is it? Clear skies 146.74.230.82 (talk) 00:57, 26 January 2010 (UTC)

Help explain "bandwidth" in wired connections

I wasn't sure to post this in Science or Computing. But since I wanted more of an EE sciencey explanation, I'm posting here. I'm having a little trouble with the concept of bandwidth concerning video and/or computer cables. For example, why a Cat5 cable cannot carry 10 gigabit signals, or why an audio cable with BNC connectors can't transmit Serial Digital Interface signals. Physically, cat5 looks the same as Cat6, and a BNC audio cable looks exactly like an SDI cable. And it's just pulses of electricity right? Help me out. --68.103.143.23 (talk) 05:27, 23 January 2010 (UTC)

Um, did you read the articles you linked to? E.g. Although it is sometimes made with 23 AWG wire, the increase in performance with Cat-6 comes mainly from better insulation; 22 to 24 AWG copper is allowed so long as the ANSI/TIA-568-B.2-1 performance specifications are met" Interference including crosstalk and alien crosstalk are of course big issues with ethernet cables and the reason balanced lines are used (again as mentioned in our articles). Ethernet physical layer, Ethernet over twisted pair & 10 Gigabit Ethernet may also be of interest. Note that cat 5e (but not cat 5) can carry 10GE albeit the range being limited to 45m Nil Einne (talk) 05:31, 23 January 2010 (UTC)

As the articles at Wikipedia note, Bandwidth (computing) is more closer related to Throughput which is the term for amount of data one can cram down a wire. The concept seems quite different from Bandwidth (signal processing), which refers to the part of the radio spectrum ('band') occupied by a particular wireless signal, i.e. literally the "width" of the "band" occupied by the wireless data signal. Using the term for wired communication seems a bit "weird" until one reads the articles, and realize that the throughput of a digital system is related to the freqency of the analog signal carrying it, via Hartley's law. Thus, digital throughput is related to analog bandwidth, and they really are connected concepts. I'm by no means an expert on this stuff, but it is explained in the articles. --Jayron32 05:50, 23 January 2010 (UTC)

Bandwidth in computing is directly related to bandwidth in analog signal processing. Insofar as an analog physical layer is always present, even in digital communication, the channel capacity is limited by the frequency bandwidth that the cable connection can sustain. That band depends on, among other things, the circuit design of the amplifiers and signal conditioners at each end of the wire; and the inherent physical and electrical properties of the wire. (See distributed element model or transmission line for some elementary physics overview). A digital signal does occupy a width of a frequency band - usually in the radio frequency range of the electromagnetic spectrum - even if the signal is contained within a wire. This is because the data is digitally modulated on to a carrier (which may or may not be baseband, depending on the technology in use). Jayron's links are the best place to get started with these concepts. In actuality, there's nothing weird about transmitting radio by copper wire - it's a better medium than air, in a lot of respects for communication purposes. Nimur (talk) 07:08, 23 January 2010 (UTC)

Well, yes, its just that in computing "Bandwidth" is often used to mean "How many bits of data can I cram down this wire", which sounds more like "throughput", and at first glance sounds like it is unrelated to the radio wave frequency bands. I provided the above links to show the physical connection between the two concepts. --Jayron32 16:02, 23 January 2010 (UTC)

Best long-term energy storage?

Would someone able to read [1] and/or [2] please tell us what they say is the most economical long-term energy storage system? 99.25.112.22 (talk) 06:02, 23 January 2010 (UTC)

If you want to know for the energy storage article, Wikipedia:WikiProject Resource Exchange is the better bet if the problem is access rather then understanding. If the problem is understanding, I wonder whether trying the talk page first may be the better bet. Nil Einne (talk) 06:09, 23 January 2010 (UTC)

This sounds interesting, but unfortunately I can't access either article cause I'm not subscribed to the journal. Could you tell me in your own words what's being compared to what? Clear skies 24.23.197.43 (talk) 06:25, 23 January 2010 (UTC)

Neither paper makes a concluding remark about the most economic long-term storage solution. The first paper is a literature review on research into various materials that have been used for latent heat storage (e.g. just heating up a material). Its conclusions are that all prior research is near-impossible to compare, because of a lack of standardized measurements. They identify phase-changes of various waxes and other materials as a possible energy storage scheme, but make no clear, concise remarks on feasibility or economy of such a method. The second paper is a review of thermochemical sorption as an additional way of storing heat (sort of a chemical analog to a physical phase change, allowing some control of reaction energetics). The author summarizes the conclusions of prior studies: that chemical heat pumps are consistently the only feasible option for short term storage (because well-suited chemical storage materials don't exist).

It's my opinion, independent of my reading of these papers, that long-term thermal energy storage is uneconomical for the simple reason that heat radiates. I would suggest that alternative storage methods, like electric or chemical batteries, are the most economic storage scheme - until we find a way to economically synthesize long-chain hydrocarbons using electricity and CO2. Unfortunately, none of these solutions are actually very economic - even if ideal processes actually existed, the cost of producing new energy is presently too low to make storing "old" energy worthwhile. If you're willing to consider the reservoir behind a hydroelectric dam as a long-term energy storage mechanism, then that probably qualifies as the single best economic region-scale method of storing energy. (My back-of-envelope calculations estimate that 1 cm of rain stores 11,500 gigajoules of extractable energy in Lake Mead). Try storing that with thermal latent heat systems! Unfortunately, it's not very feasible to store this in hydrological gravitational potential energy - unless you already have a reservoir somewhere, and a source of lower water you could pump to fill it. Finally, I'd just say that energy storage is unnecessary if you switch to energy generation methods that can easily scale according to demand curves - such as nuclear-electric and hydroelectric plants. Nuclear power plants can use control rods to ramp up and down the amount of energy in the reactor. Hydro plants can control the flow of water with flow gates, ranging from zero to full-blast, to ramp production. In combination, these schemes would render energy storage moot - you could build infrastructure to meet your maximal demand, and when that is unneeded, no energy would be wasted. Coal plants, as a counter-example, cannot easily "throttle back," because they have a very narrow regime of operation (coal has to be shoveled in at roughly the same rate, while nuclear rods can be highly throttled). Solar, wind, and other energy production schemes are totally uncontrollable - you get as much power as the sun is willing to shine and the wind is willing to blow. Nimur (talk) 07:22, 23 January 2010 (UTC)

I agree 100% with Nimur, but would add that tidal hydroelectric generation could be combined with super-efficient storage by pumping water up when excess energy is available at high tide and using the extra height gain to obtain more energy back at low tide. (The process actually gives back more energy than is stored, even though the pumps and generators are less than 100% efficient, because extra energy comes from the rotation of the earth-moon system.) The varying lag in time of high tide round the coast of the UK could give continuous generation, though less energy would be available during the week of neap tides at first and third moon quarters. Dbfirs 12:40, 23 January 2010 (UTC)

Energy production is not a zero-sum game. If you build excess wind capacity, you can achieve any level of reliability you need. It increases costs, but less than flood insurance would otherwise increase them as long as you're displacing carbon. 99.38.150.198 (talk) 14:16, 23 January 2010 (UTC)

The best long term energy storage is achieved by tapping into naturally-available wells of it, like petroleum, or solar energy. If you are thinking of sitting down in a bunker waiting for the Apocalypse to come, you may be waiting a rather long time. Vranak (talk) 13:04, 23 January 2010 (UTC)

I am not waiting for the apocalypse, and I believe wind power (a form of solar) with grid load balancing such as http://ice-energy.com would negate the need for any of the traditional "reliable" baseline sources, except perhaps 20% hydroelectric, especially if it were upgraded to pumped storage hydroelectricity. 99.38.150.198 (talk) 14:16, 23 January 2010 (UTC)

Unfortunately, your belief is counter to expert opinion. For a succinct summary, take a look at Forecasts and Analysis of Energy Data from the United States Department of Energy. Even a very optimistic outlook and rapid growth of wind sector puts it at a miniscule (I would even go so far as to call it trivial and negligible) fraction of the total energy production. I think you will be hard-pressed to find any well-thought-out energy solution which uses wind energy without a baseline production scheme. Nimur (talk) 19:01, 23 January 2010 (UTC)

By "miniscule" do you mean "fastest growing?" 99.38.150.198 (talk) 03:31, 24 January 2010 (UTC)

By "miniscule" I mean that even if wind energy grows extremely fast, meeting optimistic, exponential growth curves, the Department of Energy speculates that it will be less than 5% of total electricity production capacity and supply less than 2% of total energy consumed in the United States by 2030. Data from the Energy Information Agency, supplementing the 2010 Energy Outlook report. Nimur (talk) 06:55, 24 January 2010 (UTC)

Why is there an inflection point at about year 2013 on page 21 of http://www.eia.doe.gov/neic/speeches/newell121409.pdf -- what reasons are there to believe that wind growth will suddenly slow so dramatically? 76.254.71.123 (talk) 01:10, 25 January 2010 (UTC)

That halted growth projection might be a cynical outlook on prospects for continued federal support for renewable energy. But more seriously, this 1995 report explains that most wind projects have been integrated into the grid not because they are cost-effective, but because of government programs: "In many cases, the planned projects were not selected because of their economic competitiveness, but were initiated because State governments or Public Utility Commissions provided additional incentives..." As the weak economy dries up these government incentive programs, a realistic outlook is that the more expensive alternative energy sectors will become more and more marginalized. Let me again point out the fallacy of scalability - if everybody adopted a more expensive energy solution, no macro-market would exist to subsidize it. Wind power would thus need to stand its own ground on economic merits - which it cannot do, given realistic projected energy prices over the next few decades. Here's another good resource - Wind statistics. That ever-elusive geographic intersection between land that is good for wind electric production and land that is near a place with high electric demand and finally, most importantly, land which is legally owned by somebody (state or Federal government) who can use it for power production is rapidly saturating. This overview map, map 2, and these data tables, indicate that the best sites have already been developed. What's left - we can build wind power production facilities in places where they aren't needed, but that's very uneconomic. I suspect that a combination of these factors is responsible for the 2013-ish tail-off in wind electric growth. Nimur (talk) 01:56, 25 January 2010 (UTC)

Do you really think that the Department of Energy includes political considerations in staff projections? Honestly, that could explain it, because the other explanations are all implausible. The 1995 EIA report is very much at odds with the actual experience of, e.g., Colorado, where officials call 30% renewables by 2020 possible "with or without legislation."[3] Moreover, your colleagues at Stanford and U.C. Davis have widely published a plan to reach 100% renewables world-wide by 2030 using only a subsidy scheme paid for by reduced flood costs.[4] Is there any evidence from the past five years that wind has reached anything approaching saturation? 76.254.71.123 (talk) 22:31, 25 January 2010 (UTC)

I'll tell you the same thing I tell my colleagues at Stanford and U.C. Davis. If wind energy is the wave of the future, and is so economically viable, why don't you start investing heavily in it? The usual response is a series of dumb looks - experts in wind energy don't drink their own kool-aid and don't believe blogs that claim wind will power the entire country in two decades. They also commute to work in petroleum-powered automobiles when it's inconvenient to bike. But I fear we may be far off topic by now. Maybe we can continue this discussion elsewhere. Nimur (talk) 13:51, 26 January 2010 (UTC)

After reviewing your link, which should be www.ice-energy.com, I have to do some bubble-bursting. This is not an energy-storage solution. It's not even energy-efficient! What these devices are, are commercial/industrial size air conditioners that they are selling to residential customers. The plan, if I may boil it down, is to be less energy efficient by over-cooling the AC unit during the night (when electricity is cheaper). This means that lots of refrigerant is sitting around in the unit, cold, doing nothing (and slowly warming back up). Then, although this is wasteful, they trickle the coolant into the unit for the duration of the day, when the users want to turn the AC on. They are actually using more energy for the same amount of cooling, because of inefficiency in the thermal storage (by thermal radiation, as I mentioned above). However, this scheme will ironically actually cost less, because energy is cheaper at nighttime in some markets. The plan, as it stands, is to increase demand for electricity at night - not to decrease total demand for energy.

The enthusiastic respondant will reply, "but if everyone switched to these systems, the energy demand during the daytime would be lower!" But, this is nonsense. If everybody switched to these systems, energy demand would be high at nighttime, and it would no longer be economic to charge a different rate per kilowatt hour at night. And since the inherent thermodynamics are not in favor of energy storage, more total energy would be consumed. These schemes only work as an economic way to save costs if a very few people use them. Essentially, they are playing off the market price curves of the aggregate economic system by participating as "non-ideal" consumers - they are a niche market. If that market grew to large scale, it would be subject to the same commodity pricing as we have now.

I am baffled how many of these plans I see as proposed solutions to the energy challenges our society faces. They're only one notch above the ill-conceived perpetual motion machine - and they also indicate that our schools do a bad job teaching thermodynamics. Storing energy results in losses. This is a fundamental result of thermodynamics. Therefore, any energy storage mechanism will actually increase total energy demand, compared to an equivalent system which only draws as much power as it needs currently, i.e., if the power plant can scale its production. If the plan is to transform our entire society to use an energy storage system, whether it is city-wide or locally distributed on rooftops, then we will consequently increase our total societal energy consumption, because there is waste in every energy storage scheme. Nimur (talk) 19:17, 23 January 2010 (UTC)

Tidal pumping is the one exception to any energy storage mechanism will actually increase total energy demand, but I agree that there are problems with growth of marine organisms in such systems. Perhaps the only long-term, eco-friendly, complete solution to energy needs is nuclear fusion, but this is far in the future unless a vast amount of money gets thrown at the development. Meanwhile nuclear fission will probably have to be used much more extensively to reduce global warming, with safe disposal of waste products of course. Dbfirs 20:49, 23 January 2010 (UTC)

Nimur, I'm pretty sure the anonymous poster understood all that. The idea is not to convert everybody, but to convert enough people that nighttime and daytime energy demands are roughly equal; then you can reduce your peak capacity, which might yield savings that exceed the storage losses. Or it might not; I couldn't tell you. But it's not an inherently illogical idea. -- BenRG (talk) 00:48, 27 January 2010 (UTC)

I haven't read the link, but it seems to me converting everone is not necessarily going to result in there being a lot higher night time usage then day time. It depends on various factors particularly how much of the energy usage is due to AC. From Nimur's description, you will only be moving the AC usage to be increased during the night time (and hopefully decreased during the day time), there are still clearly plenty of other things which will be used during both times and some of them may be higher at day time. For example many shops, offices and factories operate primarily during the day time and while AC will be part of what contributes to their energy usage it's not the only thing. Also given the OPs comment, perhaps one of the ideas is for a more dynamic smart usage system where the AC is turned on and off depending on the availability of energy and stores it when it's high, to be used when it's need. I'm not saying I think it's a good idea or will work. Actually from Nimur's description it sounds silly. Nil Einne (talk) 12:33, 27 January 2010 (UTC)

oxygen's diradical nature ... what about the halogens?

Oxygen's diradical nature supposedly stops its radical nature from oxidising all organic compounds at room temperature, except for the trace singlet oxygen that occasionally forms. Yet, chlorine and fluorine, etc. are not diradicals, yet they are dangerous oxidants at room temperature. Aren't a great deal of their oxidative properties non-radical in nature? Or is it because *O- (radical anion) makes a bad leaving group, as opposed to Cl-? (But F- isn't a great leaving group either...) John Riemann Soong (talk) 09:47, 23 January 2010 (UTC)

I think you are crossing wires on two sometimes slightly related concepts. Radicals can be good oxidants, but a) not all radicals are always good oxidants (consider the dozens of odd-electron metals) and b) there are lots of good oxidants which have no radical nature (say, permanganate. What makes something a good oxidant or not is much more closely related to the electron affinity of the species, rather than the odd/even nature of its electrons. Even though dioxygen has two "unpaired electrons", as predicted by molecular orbital theory, that actually gives those two electrons the opportunity to spin couple; which is actually somewhat slightly MORE stable than opposite-spin pairing. This is what gives stability to the electron configuration displayed in chromium, the s1d5 configuration rather than the s2d4 configuration. --Jayron32 15:57, 23 January 2010 (UTC)

Over-watering my Philodendron

I've got a Philodendron that much to my chagrin I seem to have over-watered: the leaves are yellowed, soft, and wilting. I understand the concept of over-watering in general - the roots begin to rot, not enough oxygen, etc. But this very plant began as a collection of cuttings sitting in a glass pitcher filled solely with water not 6 months ago. The roots developed and then I transferred it to a soil pot where it was growing fine enough until just recently. This is fascinating. Could someone please explain to me how a plant that grows perfectly well in 100% water can receive too much water when it's in soil (and quantitatively receiving less)..? 61.189.63.173 (talk) 10:06, 23 January 2010 (UTC)

When there are a few roots in water there is enough oxygen, but with many roots and organic matter and bacteria in soil there are heaps of things using oxygen, and it is all used up. Graeme Bartlett (talk) 21:49, 23 January 2010 (UTC)

I and other people find it a problem to decide when a pot plant needs watering. Purpose-made probes that suppossedly measure the soil dampness do not work. I've concluded that the way to do it is by weight - when the pot+earth feels light, water it. Pot plants seem to do better by fluctuating in the moisture of the soil rather than trying to keep them moist all the time - reflecting what happens in nature I suppose. 92.29.81.16 (talk) 11:23, 24 January 2010 (UTC)

Different plants have different preferences though. If you use the same pattern or watering with a variety of plants, you will find which ones will survive by artificial selection. Philodendron did not survive with my watering practice - once a week, but may have been to do with environment too. Light, temperature and humidity can be important too. Graeme Bartlett (talk) 00:19, 26 January 2010 (UTC)

Circulation in Whitefish

Most of my life (decades!) I have wanted to know how the flesh of whitefish remains white, even though their blood is red. How does the red blood supply the white muscle without the capillaries making that flesh look some shade of red or pink?

I have tried the following Google searches: "whitefish muscle" and "whitefish circulation".

Budgie Helen (talk) 12:14, 23 January 2010 (UTC)

Meat (of fish or fowl or other animal) is white or red based on the content of myoglobin, a muscle protein, not on the basis of the color of the animal's blood. See [5] and [6] for further detail. - Nunh-huh 12:35, 23 January 2010 (UTC)

Relative levels of myoglobin are what define "white meat" and "dark meat." As indicated to some extent in White_meat#Poultry and Muscle#Types, type I muscle is slow twitch and capable of sustained activity. It is often termed red and in chickens, for example, which do not do a lot of flying, this type exists in the legs, which perform the bulk of the bird's activities. Breast meat in chickens is white because it's primarily type II muscle, which is fast twitch and incapable of sustained activity. In ducks, which are built for a lot more upper body activity, there is really no white meat, and both uppers and lowers are red. DRosenbach ^{(Talk | Contribs)} 13:51, 26 January 2010 (UTC)

hot water storage

electric hot water tank

There is no "handyman" ref desk, so I'm going to pester the scientific folk with my inanity. I have a question regarding the pipe (and associated valve) on the bottom of my hot water tank (see visual aid). When I first moved in to the flat (at Christmas), the valve was in the "off position" and a friend (perhaps as dim as me) remarked that it may be a waste pipe and should be "open", and twisted it (seemingly forever) to the right left. I suspect that it's "cold water in", actually. All the way to the right left, it leaks water out of the top of the valve, though not very much. Too much pressure? Even about halfway to off there seems to be some slight discharge. How far away from off should the valve be? How much water is the ideal amount to let in (if it is the cold water in as I suspect) and how do I know when I've achieved this? Is there any danger or unwanted side effect to leaving it completely open with the slight leak? I find that I run out of hot water very quickly (not enough for a shower and the washing up in the same day), is there any chance it's because of this valve (or is it just because the tank is super tiny for my extortionately long showers)? Advice, guidance, knowledge, sneering, and sympathy all welcome. Thank you! Maedin\^talk 13:12, 23 January 2010 (UTC)

Have you had a look on the blue label that appears prominently on that tank? 93.132.166.231 (talk) 13:43, 23 January 2010 (UTC)

If you have a look at the diagram (as IP 93 suggests) on the heater it says that the pipe with the valve is the cold in!.:-) If there is a waste or overflow pipe I hazard a guess it may be behind the heater, possibly leading outside or connected to a drain pipe. This is installed under a kitchen counter or similar apparently? The label at the bottom says 125 L (Litres I expect). Does not seem very large, I suggest shorter(!) or cooler(!!) showers; or showering and 'washing up' (clothes?) on seperate days(!!!). I can't say too much for certain about how far the valve should be opened, if your local water pressure is 'high' then it is theoretically possible it could stress the pipes/connections. Perhaps turn it off to 3/4 and if there is no problem turn it down a bit more? Too far and your heater may shut off entirely.(or burn out if not enought water to cover the elements.) You say 'flat', if this is a rental then the landlord may be able to help? 220.101.28.25 (talk) 13:50, 23 January 2010 (UTC)

(e/c with Dbfirs below) I did say sneering is welcome, so I'll just say that yes, of course I noticed the blue label, and no, it doesn't really answer my questions, does it? You'll notice that I didn't actually ask, "is this the cold water in?" If I hadn't read the blue label, then I probably would have believed the person who claimed it was a waste pipe. I am (as you may have noticed^^) female and either don't believe labels that come on hot water tanks or assume that I am misunderstanding them, and the friend who made the initial guess was male (and I was reluctant to admit that a guy might not know what he was talking about regarding these things). "Washing up" is the British term for "doing the dishes", btw. Yes, I'm renting the flat, but landlords are notoriously tardy at responding to non-urgent queries and mine has been no different. Thanks for your help so far, :-) Maedin\^talk 14:08, 23 January 2010 (UTC)

Just open it sufficiently for your shower to operate at a reasonable flow. Closing this valve more will reduce the flow and increase your warm shower time. I was puzzled when you said turning to the right to open because most people would think you meant clockwise looking from above, and that would close the valve. Dbfirs 14:03, 23 January 2010 (UTC)

I did mean left, thanks, :-). Maedin\^talk 14:16, 23 January 2010 (UTC)

Here is the manual: http://www.ariston.co.uk/uploads/doc48ad4c024f798.pdf 93.132.166.231 (talk) 14:33, 23 January 2010 (UTC)

It's not really about "too much pressure". As you turn the spindle to open the valve, you'll notice that the amount of spindle (The spindle is the round shaft that is attached to the handle, and disappears into the body of the valve) you can see sticking out the top of the valve increases (this is because there is a screwthread cut into it further down inside the valve and, as you open the valve, this unscrews - it's what actually makes the valve work).

The next thing you need to know is that there is a seal (called the gland) around the spindle. It is just underneath that odd-looking nut (sometimes called a gland follower) that fits round the spindle where it goes into the valve body.

What is probably happening is that as you open the valve fully, the bit of the spindle in contact with the gland changes (as the spindle moves out, you try to seal on a bit that's lower down) and you've probably hit a patch that's a bit rough or dirty.

To start with, try tightening the gland follower a little bit. One or two flats is usually sufficient (a flat is one sixth of a turn - as soon as you look at it, you'll appreciate why) - but your aim is to get a decent seal without making the valve too stiff to turn. If that doesn't work, you may need to repair the gland. That needs a bit more care as, if you get it wrong, you could cause a significant flood.

In terms of how far to open the valve, standard practice is to open it fully (assuming you have eliminated your gland leak), and then close it a quarter turn (to stop the threads binding). Zeusfaber (talk) 18:18, 23 January 2010 (UTC)

As a rule of thumb - a shower uses 2 US gallons of water per minute. If you read the label right and the tank contains 125 liters then that's 33 US gallons - and should be enough for a 16 minute shower. Of course if the water is really hot - you're probably mixing it about 50/50 with cold water - so I'd guess that you could sit in the shower for half an hour without running out! You should probably be aware of the amount of hot water that other activities uses: Taking a bath can use 50 gallons - and if more than half of that is hot water from the tank - then you could easily run out. If your clothes washer uses hot water, then it'll take 10 gallons (but with modern detergents, you can save a ton of money by doing cold water washes) - and if your dishwasher is plumbed into the hot water lines then it can take 20 gallons. SteveBaker (talk) 18:51, 23 January 2010 (UTC)

Doesn't the tank begin refilling itself before it hits rock bottom empty? If it's re-filling itself with cold water you won't get the full 32 minutes of hot shower. APL (talk) 03:31, 24 January 2010 (UTC)

Yes, the tank starts filling with cold water as soon as the shower is turned on. It relies on the layering effect (hot water being less dense than cold) and lack of turbulence. By the time half the hot water has been used, a temperature drop will be noticeable, but the top half will still be much hotter than the cold water in the bottom half. Dbfirs 08:11, 24 January 2010 (UTC)

[Unindent]. Let's start by describing your tank. There are 3 copper pipes connected to it, which are all water connections. The one at the bottom is the cold water in. The next one up is the hot water out. The one slightly higher than that (with the black plastic valve on) is a pressure relief. The first 2 do what you'd expect - let cold water in and hot water out to your shower, etc. The other one takes care of the chance that your cold water pressure might just possibly be high enough to damage the tank. If it is, the black valve will release to let water out and to safeguard the tank. In all normal circumstances it will not operate ever. The pipe at the bottom has the valve that you're worrying about on it - this is a stop cock and is essentially just used to turn the cold water on and off - it's not really designed to be left partly open or closed. I would advise turning it anti-clockwise (from the top) until it won't turn any more. Taps of these sort do have a tendency to leak when not fully open or closed, so this may well help your problem with the leak.

The cyclinder has 2 electrical heater ("immersion heaters") to warm the water up - these are the white things sticking out on the right. There are 2 since this is designed to work with Economy 7 - the lower one can be used at night to heat a load of water on a cheap tariff and the upper one is used at day to top the water up on a more expensive tariff. If you don't have Economy 7, you would just connect both to the electrical supply (this would have to be done by an electrician. Both of these have thermostats to set the temperature to which they heat the water. They should both be set to 60-65°C. I would guess that if you've not got enough hot water, it may simply be that the lower one is not connected, or set at too low a temperature.

By the way - the tank doesn't heat the water as you use it (much) - it pre-heats the water, which you then draw off. It looks like it's not insulated, so (a) you could almost certainly see how much hot water is in it by feeling the tank with your hand and (b) you are wasting money by letting the tank cool too quickly. You should ask your landlord to insulate it.

HTH. --Phil Holmes (talk) 10:41, 24 January 2010 (UTC)

You guys are great, thank you so much. I just have a few more questions, mostly in response to Phil.

I am not certain if I'm on Economy 7 or not, but I'm guessing so. I've got two boxes for mains switches; one box is labelled water heater and storage heater (yes, I heat this place with bricks, if you can call that heating^^) and the other is for . . . everything else. I assume I'm right in thinking that they wouldn't be separated if they weren't on different tariffs. This would explain why a shower in the morning means I have no hot water in the evening: it's not heating up any water except at night. How does that information change your advice? It seems to me that I need something topping up the temperature on a more expensive tariff; does that mean I need an electrician to connect the top immersion heater? Is this something I should be asking my landlord to take care of, or the sort of thing I should arrange myself? (If that seems like a stupid question, I've never been a tenant before, I owned before this (with a male of the species, hence my profound ignorance of water heating).)

The other thing is that the tank isn't warm. Not even a bit. So it must be insulated inside? A friend has helpfully suggested that I could take the cover off the tank and find out, but I'm not sure I have enough testosterone for such a crazy idea.

As suggested, I've now opened the valve fully and quarter-turned it back so the threads don't bind (whatever that means). The leak is really slight and I don't have the right tool for adjusting the gland follower, so I'll leave it.

Again, thank you!! Maedin\^talk 11:51, 25 January 2010 (UTC)

Yes it does sound like Economy 7 tariff. The tank is probably a modern one that is actually much smaller inside but has insulation built in. If there are two separate immersion heaters then the second one can be wired up to a switch so that you can boost the hot water whenever you wish (at the higher rate, of course). Has this not been done already? If not then you do need an electrician. Strictly, you also need your landlord's permission (and your landlord ought to pay for the work to be done!) If you are not able to ask your landlord, then a friendly electrician might be able make a temporary connection to a 13A plug, but this would be frowned on by Health & Safety experts because the tank is not a portable appliance. If you need lots of hot water for very long showers, it is actually possible to wire both immersion heaters to switches so that you can almost heat the water as you use it (5Kw is not quite enough for an instant shower unless the water is already warmish). A good electrician could wire this so that you still retain the benefit of Economy 7 rate overnight, but it is not standard wiring, so you would need someone who really knows what they are doing. Dbfirs 16:17, 25 January 2010 (UTC)

The real test of whether you have Economy 7 is the electricity meter - if there are 2 sets of dials on it then it's highly likely - have a look at the photo in the article I linked to and you'll see what I mean - one is labelled "Normal" (daytime tariff) and the other "Low" (night-time tariff). You could also see what it says on your bill. There must be a time switch (or more likely, two time switches) somewhere that control the immersion heaters turning on and off. If you can find them and can work out how to over-ride them (i.e. nothing worse than turn them on when they're already off owing to the time) then you could consider turning the lower heater on about an hour before you need a shower. But don't blame me when your electricity bill doubles! And I think I was wrong about insulation - another look at the manual and it dos look if there is some insulation built in to the tank. More is always better, though. --Phil Holmes (talk) 17:05, 25 January 2010 (UTC)

Hi, I am pretty sure that your upper heating element has burnt out. They often do if they are set to run too hot. It is only a small task so it should be easy to (get the landlord to) replace it. It is only four screws, one on the cover and three cables - live neutral and earth. Good luck. :-) Chienlit (talk) 19:31, 25 January 2010 (UTC)

Actually, they normally use an immersion heater spanner to screw them in and out, and that can take considerable force. It would also have been sensible to suggest draining the tank before trying this, to avoid flooding the place as all the cold water rushes out of the hole previously occupied by the heater. --Phil Holmes (talk) 12:16, 27 January 2010 (UTC)

why no hair in biodegradable waste?

The Dutch version of the article Biodegradable waste says that, in general, dog or cat hair is not considered biodegradable waste ("GFT") and should be treated as "regular" waste. Why is this? Is hair not biodegradable or compostable?

And what about human hair?

Thank you in advance. 83.81.42.44 (talk) 16:22, 23 January 2010 (UTC)

It depends on what they're going to do with the waste stream. If they're going to feed it to pigs, clearly you don't want pigs eating (too much) hair. If it's going to compost, it is biodegradable, but much more slowly (and I think in wetter conditions) than other wastes - so it'd still be hair when the rest of the stuff was ready to be used. If they're going to dry it use it to power an incinerator then hair is fine. -- Finlay McWalter • Talk 16:32, 23 January 2010 (UTC)

Hair is basically 'dead', and from the fact that it can still be found (ie on Egyptian Mummys) long after soft tissues are gone, suggest that it is not biodegradeable in any meaningful way. --220.101.28.25 (talk) 17:12, 23 January 2010 (UTC)

That's totally untrue. Mummies are preserved and dried and kept underground in a sealed container in a nearly lifeless environment. In normal conditions hair is decomposed by moths, fungi, and bacteria (ref (warning: a bit grisly)). If hair wasn't biodegradable then the world would be covered in a layer of meters of compressed hair. Being "basically dead" does not grant immunity from decay. -- Finlay McWalter • Talk 18:01, 23 January 2010 (UTC)

This says that at least one species of cockroach will eat hair and even fingernail clippings...so yes - it's definitely biodegradable. However, it may well not be compostable or recyclable in any useful manner - which would explain the comment in the article. SteveBaker (talk) 18:39, 23 January 2010 (UTC)

If it's only in the Dutch version, maybe it has something to do with [nl:Coffeeshop]s and cockroaches not meant to get chilled to much? 93.132.166.231 (talk) 19:54, 23 January 2010 (UTC)

What is energy?

I am currently taking an A-Level physics course, and I am very quickly falling behind my classmates, largely because I fail to understand a fundamental part of the syllabus, which is energy. What exactly is energy? Can we see energy? Does energy have a mass? What does energy look like? Any help would be greatly appreciated. --T.M.M. Dowd (talk) 21:36, 23 January 2010 (UTC)

Energy is that physical quantity which can do work - meaning it can exert a force through some distance. It can take many forms - most of them are not directly visible. When some object with mass has velocity, the object also has kinetic energy. When an object with mass is placed high above the ground, it has gravitational potential energy. So, you don't actually see the energy, though you can observe details about the situation from which you can deduce that there is energy present. At the level of basic physics you are working at, do not worry about energy-mass equivalence. For your purposes, energy has no mass - it is a different and unrelated physical quantity. (When you progress to a more advanced and more generalized treatment of physics, especially considering very large amounts of energy, it can be shown that in fact energy and mass are related - but in classical, every-day physics, they are separate quantities). Have you read our article on energy? Nimur (talk) 22:05, 23 January 2010 (UTC)

Energy is just energy. The everyday meaning of the word is close to its meaning in physics. --99.237.234.104 (talk) 23:06, 23 January 2010 (UTC)

Understanding the concept of "energy" alone is relatively meaningless for the most part...If you could give us an example of how exactly you don't understand it, we'd be far better set to give you more useful information. If you provided us with an example question, we wouldn't answer it, but we might be able to explain the concepts you'd need to know to do it yourself. For me, light was my biggest problem in A-level Physics...well, that and practical work...) Vimescarrot (talk) 00:22, 24 January 2010 (UTC)

See Energy. rʨanaɢ ^talk/_contribs 01:24, 24 January 2010 (UTC)

Sadly, you don't get a scientific answer - because there isn't one. So you get a touchy-feely philosophical one:

Little kids like to play the insanely annoying "why?" game. "Why can't I have chocolate? Because you've had enough already. Why is that enough? Because it's not good for you to eat only chocolate. Why isn't it? Because your body needs all sorts of different foods to work properly. Why does it need that?" ...and so on. There is no answer you can give that will make them not say "Why?" in response.

Well, I guess "energy" is the ultimate answer...it's end of the chain of reasoning and logic. Energy is that least, most minimal end of the line explanation for pretty much anything. You can't see it, feel it, taste it, smell it or hear it (although you can see, feel, taste, smell and hear the consequences of it). We can indirectly measure it - but not directly. We can predict how it changes from one form to another, we can even weigh it (thanks to E=mc²)...but we do not, cannot, directly deal with it.

For A-level physics, it's a letter in an equation. It's a convenient variable in the equation that explains how a pendulum swings - gravitational potential energy turns into kinetic energy which turns back into gravitational potential energy at the other end of the swing. You don't have to understand what the energy is - only how it changes form and is the intermediary between height and speed. Energy cannot be created or destroyed - it changes from one invisible, intangiable form to another. Set off a stick of dynamite and chemical energy changes to kinetic and acoustic energy and both eventually turn into heat. Turn the ignition key on your car and chemical energy in the battery becomes electrical energy in the wires, spins the starter, creating kinetic energy - the engine turns, the pressure in the cylinders produces heat with more electrical energy in the spark, you release chemical energy in the fuel and then more heat, causing expansion of the gasses, more kinetic energy, more heat - sound energy.

Everything that happens in the world is driven by energy changing from one form to another - but the energy itself is completely intangiable. It's a number in an equation...but it's the number that makes the universe tick over.

It's important at this stage to keep the curiosity about that intangiable at bay. Follow where the energy goes - do the math to follow it's passage through these various forms. Learn, do good work, pass exams, go to college, do more math, follow that energy, pass more exams. Get a job as theoretical physicist, get tenure, think about energy. Come back and tell me what the heck it is!

SteveBaker (talk) 01:30, 24 January 2010 (UTC)

That's the same conclusion that Richard Feynman came to here, and he got pretty frustrated with tautological non-descriptions of energy in schoolbooks ("energy makes it go"). -- Finlay McWalter • Talk 01:35, 24 January 2010 (UTC)

Yep. Feynman is my personal hero. His frustration was mostly with school physics textbooks though. The result of which that he produced a series of lectures that resulted in perhaps the finest set of physics textbooks in the world. After all of that - he really had no better insight into what energy actually is than use mere mortals. SteveBaker (talk) 01:52, 24 January 2010 (UTC)

Right. At this point, the important thing to do is to understand that this abstract concept has been shown, by experiment, to follow some quantitative rules that relate to kinematics and dynamics (i.e., position and velocity). The simple manifestations are easily defined with straightforward equations that relate energy to an object's velocity, its height above a surface, and so on. Nimur (talk) 01:50, 24 January 2010 (UTC)

True. Our OP also asks some very specific questions:

1. What exactly is energy? - As we've said. We don't have a deeper answer. Energy is the end of the line for explanation.
2. Can we see energy? - Not directly. We can use energy to light a light bulb and produce photons that carry the energy to cells in the back of our eyes which turn the photons into chemical, then electrical energy which flows into our brain and by a series of other electrical and chemical energy transitions causes us to "see" the energy...but can we actually see the energy? That's a philosophical question. Energy changed form...that's what it does.
3. Does energy have a mass? - Yes...yes-ish. E=mc²...or if you prefer, the far less memorable but equally true: m = E/c² to find the 'mass' of the energy, divide the amount of energy by the square of the speed of light. But gosh - isn't light kinda fast? Well, yeah - and fast-squared is a freaking huge number. So you take if you weigh your AA battery when it's new and again when it's run down - the difference in mass due to the loss of the energy is so unbelievably tiny that we have no way to measure it. On the other hand - if you set off a nuclear bomb, the tiny amount of mass that gets turned into energy gets multiplied by the speed of light squared and you get are really big kaboom!
4. What does energy look like? - Since we can't see it...(see answer 2), this is a non-question. What does something that you can't see look like? If a tree falls in the forest and there is no-one there to hear - does it make a sound? Dunno - ask one of those weird philosopher guys?

SteveBaker (talk) 02:13, 24 January 2010 (UTC)

@falling tree question: YES THEN NO. (You missed the crash because you weren't there. Just believe me about this.) Cuddlyable3 (talk) 16:33, 24 January 2010 (UTC)

I see that you're having problems with something that's very fundamental. Instead of giving you an answer that's technically correct but may or may not be helpful to you, I'll try to explain the concept using an analogy. Think of energy as currency in the world of physics. It is what enables you to do "work". Energy can exist in many interconvertible forms, just like (monetary) currencies. In the real world, if you want something "done", you need to spend money. In a similar way, if you want "work" done, say moving something a certain distance while opposing a force, you need to expend energy. If you pay someone money, you don't have the money anymore, but the recipient has it. In a similar way, when you expend energy, you don't have it anymore, it goes somewhere else, but is not destroyed. (Actually it's not strictly true, because of mass-energy equivalence, but until you're comfortable with the basics, it's better just to think of energy as something that's conserved, i.e. something that cannot be created or destroyed.) Can we see energy? Well, that depends on what exactly qualifies as "seeing" something. The fact is, some forms of energy (photons of visible light wavelengths) can stimulate our eyes and whereby be perceived. Does energy have mass? No. (Not exactly, but for your purpose right now, it's better to think of energy as something that's distinct and unrelated to mass.) --173.49.9.141 (talk) 03:30, 24 January 2010 (UTC)

@173.49.9.141 : As far as we know the conservation of energy is strictly true. Mass energy equivalece doesn't make it any less true. Dauto (talk) 06:27, 24 January 2010 (UTC)

Well, if you want the real McCoy about energy rather than the simplified lie-to-children version that is taught in pre-University physics, then here it is. Energy is conserved in classical physics because the laws of classical physics are are independent of translations in time (see Noether's theorem). More precisely, symmetries are associated with conserved or invariant quantities, and the conserved quantity associated with time translation symmetry is what we call "energy". Situations in which energy is dissipated into an irrecoverable form (which we call "heat") are always associated with an increase in entropy and hence a breaking of the time translation symmetry at a macroscopic level - the resulting asymmetry in time is called the arrow of time. Note that this is all within the context of classical physics (which includes special and general relativity). In quantum physics things are somewhat more complicated because conservation and symmetry laws are replaced by uncertainty relations between conjugate variables. For a more detailed explanation read Chapters 3 and 4 of Feynman's The Character of Physical Law. Gandalf61 (talk) 11:06, 24 January 2010 (UTC)

January 24

Maps of Australia

G'day! I'm looking forward to a drive across the Outback later this year. I will have a GPS and a road atlas, but as far as I can make out, Australia has no national grid reference system like I have in the UK. Are the reference grids on their maps just arbitrary or are they consistent from one publisher to another? Do the road atlases give any indication of latitude and longitude?--Shantavira|^{feed me} 10:49, 24 January 2010 (UTC)

Possibly. Quoting from page 3 of the 2008 "StreetSmart" Perth Street Directory (bold is added by me for emphasis) - which is Perth metro area, not the outback!

“ The black coordinates located at the corners of each map refer to the Australian Map Grid (AGD84). The pink coordinates ... refer to the Map Grid of Australia, Geocentric Datum of Australia (GDA94). The coordinates on the Regional Centres maps refer to the Map Grid of Australia (MGA94). For more information about GDA94 please refer to: http://www.landgate.wa.gov.au/corporate.nsf/web/Geodetic+Data. ”

I am not a cartographer so I don't know if this is what you are looking for, but perhaps it will help. Mitch Ames (talk) 11:41, 24 January 2010 (UTC)

Thanks, that's interesting. Looks like we need an article on that system. My GPS supports UTM, but I guess that is different. Does anyone know if I might be able to download the Aussie system to my Garmin GPS? Their website is not very informative. Maybe I should just buy a new GPS in Oz?--Shantavira|^{feed me} 12:34, 24 January 2010 (UTC)

Don't know about downloading, but a spare GPS, if you are going to rely on them a great deal, would be a very good idea. Are you for example planning to go off paved/marked roads? Our A$ is high at them moment so buying it here will be more expensive, though I have seen them for less than ≈$A150. 220.101.28.25 (talk) 13:41, 24 January 2010 (UTC)

Nah, probably only on paved roads, so the GPS is only for location rather than navigation. Your dollar is really low at the moment compared to the GBP [7]. I was amazed to discover that Google Street View now includes a lot of the Outback, including some dirt roads.--Shantavira|^{feed me} 14:43, 24 January 2010 (UTC)

You're reading the chart backwards, that graph shows GBP is low against AUD. The pound is only buying AUD $1.70, one year ago it was much stronger buying AUD$2.20. Vespine (talk) 22:14, 24 January 2010 (UTC)

Oops, thank you! Someone told me it was low. Looks like I'm not going to have quite the luxury holiday I was expecting!--Shantavira|^{feed me} 10:33, 25 January 2010 (UTC)

You have to watch those exchange rates! Petrol/fuel/gas isn't cheap here either, probably(?) cheaper then the UK. (In the Outback I imagine it will be VERY expensive, compared to city prices). Possibly add several Jerry cans to your list of necessities? --220.101.28.25 (talk) 18:33, 25 January 2010 (UTC)

Some Australian road maps (example (PDF)) include latitude and longtitude. Mitch Ames (talk) 06:51, 26 January 2010 (UTC)

Garmin GPSs are sold here, and your map provider should also have Australian maps - mine has UK/europe maps, so I don't see why the reverse wouldn't be true! Mattopaedia ^{Have a yarn} 02:18, 30 January 2010 (UTC)

Hypochondria paradox

If hypochondriacs have a tendency to self-diagnose themselves with many diseases, why do they fail to self-diagnose themselves with hypochondria, and thus realise that they actually probably don't have those diseases? Also, is this related to the Dunning-Kruger effect? --Mark PEA (talk) 14:52, 24 January 2010 (UTC)

Hypochondria is a tendency to channel anxiety into worries about one's own body health. Perceived evidence of disease is given more weight than evidence of health or reassurance from other sources of health information. I do not consider hypochondria very closely related to the Dunning-Kruger effect. alteripse (talk) 15:16, 24 January 2010 (UTC)

Hypochondria isn't deadly or debilitating. Hypochondriacs have more to worry about than hypochondria. Even if they do diagnose themselves with it, it's not important enough to bother a doctor about when they've got so many other things that could be far more harmful. Vimescarrot (talk) 15:46, 24 January 2010 (UTC)

This is the difference between psychology and physiology. Vranak (talk) 22:55, 24 January 2010 (UTC)

live jasmin

how can i block live jasmin.com from my computer —Preceding unsigned comment added by 67.246.254.35 (talk) 14:58, 24 January 2010 (UTC)

1. This question really belongs on the Computing ref desk...and they'll also want to know...
2. You need to tell us what operating system you use and what browser/email client(s) you use.
3. Do you mean to block email from that domain? Or prevent people who use your computer from browsing that web site? What precisely?

SteveBaker (talk) 16:50, 24 January 2010 (UTC)

nb: livejasmine.com is an adult webcam site that pops up (I guess from ad links or partnership links) when browsing many porn sites. I guess the original-poster wants to be able to block these popups. I don't know how to do that, but running Firefox's "flashblock" extension means that the popup window doesn't have a live webcam feed. Googling for "livejasmine popup block" finds lots of threads about how to block the popup itself. 87.114.29.120 (talk) 16:57, 24 January 2010 (UTC)

Presuming the popups need to access livejasmine.com and don't use an IP or have different domains that they continually vary, a simple (and common) solution that will work in most OSes (albeit you'll need to find out how to do it in each) would be to put livejasmine.com in the hosts file and point it to 127.0.0.1 or something similar. This will not block the popups windows from opening, it will simple mean you'll get an webserver doesn't respond message (unless you actually have a webserver locally or wherever you point it to) and as I've said will not help if the websites start using popups from an IP or they cycle between domains. And it's obviously not an effective way of stopping all software from accessing the domain, they could query a hardcoded domain name server or query the defined DNS themselves bypassing the OS DNS subsystem (if the DNS is a router you control you may be able to do something similar on the router) but it should work for browsers. Nil Einne (talk) 04:27, 25 January 2010 (UTC)

Expression of ratios

The title makes this sound like a mathematics question. I have never been able to understand an answer - or, to be fair, most of the questions- on the mathematics desk, however, so I am hoping someone with a science background will have the same information. (I sometimes understand science answers.)

I had always understood that ratios are expressed using a ":" in the form "A:B", and represent a mathematical relatipnship between A and B. In the article Vaccination controversy is the following sentence:

In the U.S. during the year 2001, routine childhood immunizations against seven diseases were estimated to save over $40 billion per birth-year cohort in overall social costs including $10 billion in direct health costs, and the societal benefit-cost ratio for these vaccinations was estimated to be 16.5.

(The emphasis is mine.) Thinking this was merely a typo for "16:5", I went to the footnoted source which contains the following sentence:

Direct and societal benefit-cost ratios for routine childhood vaccination were 5.3 and 16.5, respectively.

Thus the "ratio" presented in the WP article is correctly transcribed, but I still don't know how a ratio can be a single number. Is anyone willing to explain? Bielle (talk) 18:37, 24 January 2010 (UTC)

It's 16.5:1. The one's implied in a ratio when they only show one number like that. For every dollar spent on vaccinating kids, $16.50 is saved in health care costs down the road. You can also check out Benefit-cost ratio for information about this specific type of ratio, and cost-benefit analysis for more general information on the subject. Buddy431 (talk) 18:53, 24 January 2010 (UTC)

When the ':' and the second number is missing, it's generally accepted that ':1' is intended. So 5.3 and 16.5 really mean 5.3:1 and 16.5:1 respectively. In other words, the benefit is 5.3 times the cost or 16.5 times the cost. SteveBaker (talk) 18:54, 24 January 2010 (UTC)

Really, this is just a matter of different ways of thinking about the same thing. The ratio 14:4 is equivalent to the ratio 7:2, just as the fraction 14/4 is equivalent to the fraction 7/2. The value of the fraction as a number is 3.5 and the fraction can also be written as 3.5/1, just as the ratio can also be written as 3.5:1. But if you had the fraction 3.5/1, you would normally simplify it to just 3.5 (well, you might write 7/2 if you considered that simpler). Well, in the same way, the ratio 3.5:1 can be written as just 3.5. A ratio (of two nonzero terms) and a fraction -- or for that matter a quotient, like 7÷2 -- are really pretty much equivalent, and it's common to see a ratio expressed as a single number.

Incidentally, 7:2 is actually the way they write 7÷2 in many countries; they don't use what we call a division sign at all. --Anonymous, 19:01 UTC, January 24, 2010.

Your division sign ÷ is an Obelus. It is commonly seen today representing minus in Norway, for example in advertisements proclaiming "Opptil 30% på salgsvare" (= Up to 30% reduction on goods in sale). Pity the plight of little Norwegians who must use pocket calculators with buttons + - x ÷ while their math teacher teaches them to write + - . : for the same functions. With luck the little ones may grow up to be programmers who use + - * / respectively. Cuddlyable3 (talk) 22:20, 24 January 2010 (UTC)

Ummm... there's no obelus is that quotation... --Tango (talk) 02:42, 25 January 2010 (UTC)

Unfortunately the ratio article doesn't discuss this normalised format for expressing ratio; if this usage is as common as the above implies, then it clearly should. I did try to find a reliable source to back up this usage, but searching for "normalised ratio" and the like only finds specific ratios, rather than this general style of expressing as a ratio:1 and then omitting the :1 -- Finlay McWalter • Talk 19:10, 24 January 2010 (UTC)

Doesn't any number qualify as a ratio that can have a /1 or ÷1 or :1 or whatever done to it without it really meaning anything? --Neptunerover (talk) 19:18, 24 January 2010 (UTC)

Yes, any number can be a ratio. Ratios don't, as you say in your original question, denote any kind of relationship between the two numbers. "The ratio of X to Y is A:B" means "For every A of X you have B of Y". It's a relationship between X and Y, not between A and B. --Tango (talk) 19:37, 24 January 2010 (UTC)

You mean that's not the same difference? --Neptunerover (talk) 19:48, 24 January 2010 (UTC)

I suppose it is, but the fact that a particular (ordered) pair of numbers happens to be the ratio of something isn't very interesting. For any pair of numbers you will be able to find infinitely many things that it is the ratio of. The fact that the ratio of a particular thing is some pair of numbers is far more interesting. --Tango (talk) 20:01, 24 January 2010 (UTC)

I have a feeling you are on a topic far removed from this page and this question, and from which you already bid farewell. There's no sense confusing the OP here because of something unrelated. --Neptunerover (talk) 21:12, 24 January 2010 (UTC)

Thank you all. I understand the protocol that has emitted the ":1" when something is called a "ratio" but is expressed as a single number. I am sure, after another read or two, I will also understand the point about A of X and B of Y. Bielle (talk) 19:44, 24 January 2010 (UTC)

It would probably be clearer if I didn't state it so generally and instead gave an example. "The ratio of boys to girls in the class is 3:2" means "For every 3 boys there are 2 girls". --Tango (talk) 20:01, 24 January 2010 (UTC)

I expect to see two numbers in a ratio, even if the divisor is one. There should be an antecedent and a consequent. A number, by itself, is not a ratio. Saying "The ratio is 5.3" is unnecessarily confusing. How hard is it to say "The ratio is 5.3:1?" As a college teacher, or as a journal editor, I would have questioned such a usage. Edison (talk) 04:35, 25 January 2010 (UTC)

Well, what one expects and what actually happens are often two very different things! It is very common to drop the ":1", whether we like it or not. --Tango (talk) 06:08, 25 January 2010 (UTC)

One as a divisor is assumed, even if it isn't always written fully out. --Neptunerover (talk) 08:14, 25 January 2010 (UTC)

Incidentally, is a differential equation basically the same thing as a ratio? --Neptunerover (talk) 15:14, 25 January 2010 (UTC)

No. Not even a little bit. Algebraist 15:16, 25 January 2010 (UTC)

When ":1" is omitted, we are using a factor (as in multiple), not a ratio, but the usage seems to be widely abused. Do scientific journals really say "cost-benefit ratio" when they mean "cost-benefit factor", or is it just second-hand reporting that makes the error? Dbfirs 15:38, 25 January 2010 (UTC)

I've never heard anyone say "cost-benefit factor". I think we just have to accept that this is a meaning of the word "ratio". The English language is defined entirely by how it is used. --Tango (talk) 20:44, 25 January 2010 (UTC)

Yes, I agree I've only ever heard "ratio", but then I would expect, like Edison, to see a ratio. I suppose we have to accept that the "to one" is just understood in the context. I've made a few minor edits to our article on Ratio, but it really needs a major re-write. Dbfirs 14:17, 26 January 2010 (UTC)

Use of Enoxaparin sodium in aortic dissection.

Is there any indication of use of Enoxaparin sodium in aortic dissection? Maybe it prevents the formation of thrombi in the false lumen (thrombi could migrate and induce arteries occlusion in brain, coronaries ...) or what else? Or Enoxaparin sodium just aggravates dissection by inhibiting coagulation? Thansk so much for replies. --62.98.29.51 (talk) 21:40, 24 January 2010 (UTC)

I've just checked the article on enoxaparin sodium -- it says that this stuff is indicated for prevention of blood clots during dialysis and abdominal and orthopedic surgery and for treatment of deep vein thrombosis and some kinds of heart attack. Nothing at all about aortic dissection or any other kind of open-heart surgical procedure. I'm not an expert on surgery, but my guess is that it would be contraindicated for open-heart surgery because it could aggravate bleeding and possibly cause a dangerous hemorrhage. Clear skies to you 24.23.197.43 (talk) 03:37, 25 January 2010 (UTC)

Aortic dissection is not a procedure. It's a real quick way to get dead. I suppose the only way to save you is with a surgical procedure, so maybe that was what you meant. --Trovatore (talk) 03:40, 25 January 2010 (UTC)

The first plausible-sounding answer is a great example of why we forbid medical advice here! DMacks (talk) 06:48, 25 January 2010 (UTC)

Speaking of which, I should retract part of my answer — according to the article, surgery is not always the treatment for aortic dissection. It depends on the details. Not that I think anyone's going to say: Doc, I have to have surgery! Some guy on the refdesk said so! But you never know. --Trovatore (talk) 08:05, 25 January 2010 (UTC)

Sorry, I really thought aortic dissection was a procedure where they open up the aorta to take out some kind of blockage and then sew it shut again. (Well, I told y'all that I'm not a medical expert!) Anyway, now that we all know what aortic dissection really is, I can say with certainty that enoxaparin sodium would ABSOLUTELY, DEFINITELY be contraindicated in that case cause all it would do is to make you bleed out faster. See, my answer was right after all, even though it was for all the wrong reasons! 146.74.230.82 (talk) 01:09, 26 January 2010 (UTC)

Quick seagull question

If there were no people to give them an incentive to venture inland to scavenge, would gulls be restricted only to coastal areas? --95.148.109.223 (talk) 22:45, 24 January 2010 (UTC)

I've seen seagulls in Colorado (far away from any coast). I'm not sure if they migrated there because of people. --Neptunerover (talk) 05:01, 25 January 2010 (UTC)

Of course, my reference to 'Colorado' seagulls may be irrelevant, as who knows when the species may have last seen an ocean. Where I saw them just happened to be at the dump as well. I suppose inland seagulls have lakes instead of oceans, where they might very well stay, if it weren't for the local dump. --Neptunerover (talk) 05:44, 25 January 2010 (UTC)

I can testify to them congregating around lakes, and not just seas. Here in Vermont we have quite a few near Lake Champlain and at least a good 10 or so miles in the parking lot at my workplace. Dismas|^(talk) 11:56, 25 January 2010 (UTC)

They're a menace, I say! (jokingly; I like live seagulls) --Neptunerover (talk) 16:38, 25 January 2010 (UTC)

But not the dead ones? Seems an interesting distinction to point out. Dismas|^(talk) 20:15, 25 January 2010 (UTC)

Interesting perhaps, but I felt it was necessary just in case someone wanted to come back with "where do you like them, on your dinner plate?" Sadly, it appears many hunters have this point of view when they speak about how much they love animals. The Native Americans were not like that at all. Hunting is a natural part of life on Earth though, so I'm not going to point fingers (hey, I used to have a BB gun, and I'm not proud of having used it to shoot things that would've kept living had I not shot them, but I was a kid seeking fun in a misguided way. When people grow up, hopefully by that time they realise that killing things isn't really any fun, assuming they ever might have at some point thought that killing is or might be fun, say from a video game.) --Neptunerover (talk) 13:11, 27 January 2010 (UTC)

Here on the Wikipedia Ref desk, we have physicists, chemists, biologists, mathematicians, computer scientists - and a seagull expert. I'm sure User:Kurt Shaped Box will be along in a moment to help. SteveBaker (talk) 05:06, 25 January 2010 (UTC)

As far as I know (and to echo Dismas), gulls will hang around/breed near lakes, inland seas and areas of marshland too, without human encouragement. If I'm remembering correctly, there are huge colonies to be found inland in Central Asia in these habitats. Gulls, being the tough, adaptable little generalists that they are, don't strictly *need* to be around accumulations of water in order to eke out a living - but they seem to be 'drawn' to it. --Kurt Shaped Box (talk) 19:57, 25 January 2010 (UTC)

I was thinking about this on my morning commute and I think that Life After People mentions what would (will?) become of gulls. Yep, just checked the article and it says that there is a large die-off but that populations come back once fish populations start to rebound. Dismas|^(talk) 20:15, 25 January 2010 (UTC)

Incidentally, the book Jonathan Livingston Seagull is very enlightening as to the life of a 'seagull', although the reliability of the book's perspective, at least on this desk, is not verifiable. (still a good book though, and short too) --Neptunerover (talk) 13:11, 27 January 2010 (UTC)

January 25

why is THF called THF?

It seems to me that you're adding TWO equivalents of hydrogen across the furan ring... not four. Shouldn't it be called dihydrofuran? Shouldn't the current (2,3) dihydrofuran be called (mono)hydrofuran? I mean, I don't think you can add more than one H2 molecule across a double bond... John Riemann Soong (talk) 06:17, 25 January 2010 (UTC)

Two equivalents of dihydrogen (H₂) are added. The "hydro" means "a hydrogen atom", not "the molecular form of that element". Like hydrohalogenation, hydroformylation, etc., each add "one hydrogen atom, one other thing". But the real why is because, just like the answer to any "why is some standard used". Something had to be agreed, and even if it is completely nonsystematic and makes no sense to anyone, it is how it is, and asking "why" doesn't lead anywhere useful (though in this case it sort-of does). [8] DMacks (talk) 06:47, 25 January 2010 (UTC)

name of those fenced-in forests of powerlines and insulators etc?

Do you know the places I mean? What are they called?

Thanks Adambrowne666 (talk) 13:04, 25 January 2010 (UTC)

Are you talking about an electrical substation? -- kainaw™ 13:10, 25 January 2010 (UTC)

it is indeed; thanks, Kainaw Adambrowne666 (talk) 20:51, 25 January 2010 (UTC)

Menstrual period pregnancy

is it possible to get pregnant during menstrual period? —Preceding unsigned comment added by 119.95.22.212 (talk) 13:20, 25 January 2010 (UTC)

Yes. The Feminist Women's Health Center has a rather nice article describing the full 28-day cycle here. -- kainaw™ 13:38, 25 January 2010 (UTC)

As an aside, there are some studies out there saying that women are not "born with all the eggs they will ever use", but continue to produce eggs after they are born. I'm not sure if that has been conclusively proved or not, though. Clear skies 146.74.230.82 (talk) 01:20, 26 January 2010 (UTC)

The FWHC site has mostly accurate information but really provides no info about incidence of fertility during menstruation other than the bald statement that "it could happen". The FWHC site is badly in need of copyediting: it's full of mistakes in spelling, capitalization, syntax, and the common but annoying failure to grasp the difference between adjectival mucous and nominal mucus. It also mixes western folk physiology and medicine in with the science-based information, though it has no trouble properly identifying as such the folk traditions of some other cultures. It also appears to promote consumer sexism by advising its readers to buy products from companies owned by women. Other than those small quibbles, a great site. A much better reference would be this one: [9]. alteripse (talk) 14:46, 26 January 2010 (UTC)

Circadian rhythm studies

Hi,

I was told that many early studies into human circadian rhythms had not been careful enough about letting outisde light in, and this screwed up their results. Does anyone know any examples and can lead me to a paper or 2?

Cheers, Aaadddaaammm (talk) 15:23, 25 January 2010 (UTC)

I'm not really familiar with that objection. In the 1930s Nathaniel Kleitman was already conducting isolation experiments in caves in Kentucky, which would seem to give pretty good control. He had also conducted other isolation experiments as far back as the 1920s that might not have been as convincing, but I don't know much about them. He published a book called Sleep and Wakefulness in 1939 that summarized his findings, but I haven't read it. Looie496 (talk) 19:15, 25 January 2010 (UTC)

wind turbine generator manufactures

I have patented a "Electric Power Train" this is for generating electricity from one of the forces (pressure)generated from automotive/railway traffic on road and rail.What I am looking for is someone who could give me the specks on the genrator/alternator being used on wind turbines at present.To name a few speck's I am looking for are how much force is needed to turn the shaft without the blades,what RPM is required to get the best results,I know you will be asking me what size generator or how much electrisity do I want to generate.I cannot say at this stage,but I do want a medium to large,For example one of wind turbine being used on the wind farm's,that will give me a good start and something to work from.If I could get contact details of a manufacture that would be good.I am based in the UK so one as neer as possible would be great. Thanks Pierre —Preceding unsigned comment added by 86.163.87.199 (talk) 15:23, 25 January 2010 (UTC)

If your plan is to mount the wind turbine on the car or train, you will be wasting more energy than you are creating by adding drag and decreasing fuel efficiency. You would do better to simply tap off the engine power directly with an alternator. This is already commonplace. If your plan is to mount the generator near the roadway or railway to collect wind from passing trains or cars, I think you will find that the amount of extractable energy is not cost effective (it will probably be darn near zero watts). In specific answer to your questions, there is no way we can answer details about force, torque, and RPM, unless you tell us your desired specifications. Perhaps you might take a look at wind power, which gives an encyclopedic overview of present technologies. If you're unfamiliar with engineering design in general, it may be worth reading up on that before you start a major venture and contracting manufacturers. Nimur (talk) 17:08, 25 January 2010 (UTC)

How did you get your patent without specifications? Perhaps I don't understand how you propose to generate your power. What pressure force are you planning to use? Here [10] is a manufacturer of small turbines who might be able to help you. Dbfirs 17:36, 25 January 2010 (UTC)

What country have you patented your invention in, and what is the patent number? Or did you mean simply "invented" or "thought up an idea?" Edison (talk) 21:26, 25 January 2010 (UTC)

Perhaps the OP's idea is to harness the recurring downward pressures of road and rail vehicles passing over a flexible roadway. Cuddlyable3 (talk) 21:44, 25 January 2010 (UTC)

That would produce even less energy! Really, though, the OP specifically said that he/she wanted to use a wind turbine, so we can safely assume that he/she is planning to harness the boundary layer created by passing cars/trains. (Oops, sorry, I just looked, the OP is definitely a he, based on his name.) Not that it would be any more cost efficient. And another objection to the OP's proposal: if he wants to use a wind turbine of a comparable size to the ones used on a wind farm, then (1) there won't be enough roadside/trackside space where to put it, (2) if the turbine is to be mounted low enough to catch the slipstream, then the blades will strike the ground, and (3) even if the turbine was somehow mounted low enough, only the very tips of the turbine blades will ever be exposed to the slipstream -- the rest of the blade will remain idle! This is clearly an impossible and even borderline ludicrous proposal, and I'm very astonished that the UK patent office has issued a patent for this contraption. Clear skies 146.74.230.82 (talk) 01:37, 26 January 2010 (UTC)

To be fair to Pierre, during the last year or so I have read in New Scientist magazine of schemes to recover energy from the pressure of foot or vehicular traffic on walkways and roadways, as Cuddlyable3 surmises, and I believe a couple of experimental setups are or have been trialled, though I can't find anything from hasty googling. One criticism of such schemes is that most of the energy they would recover would be extra energy that the person or vehicle would have to expend to negotiate such a surface, which otherwise would not be required: thus, they would in effect be using the vehicle's engine or the person's muscles as the generators and recovering the extra energy rather inefficiently.

It may be that Pierre only wants the specifications ("specs", not "specks," Pierre!) for wind turbine generators in order to crunch some comparative numbers - I can't see how such machinery could be repurposed for surface energy recovery if that's the idea, though the specification in his Patent application should make everything clear - could we have the Patent Office and Application number please, Pierre? 87.81.230.195 (talk) 03:02, 26 January 2010 (UTC)

Google energy from speed bumps will find some articles (not necessarily the New Scientist article). Mitch Ames (talk) 06:40, 26 January 2010 (UTC)

volumetric display using microscopic hemispheres? Has this been thought of yet?

Would pixel size hemispheres coated with red,green and blue phosphors with a pinhole on the flat side, inside a CRT allow holographic television. Or would the pinhole have be too small for the wavelength of light to allow standard or high definition images? Could such structures (transparent to let the phosphor colour through be constructed on such a small scale?Has anyone though of this or made a large holographic television with full vertical/horizontal parallax, (preferably with the quality of a good CRT) yet, and if so, where and when can I expect to buy one at a reasonable price? [[File:http://www.imagekind.com/services/frame_engine_https.ashx?IMID=568d016e-066a-4f08-b914-bb6e7ae59693&frameId=602&glazingId=4&topMatId=1324&topMatSpacingTop=2.5&topMatSpacingBottom=2.5&topMatSpacingLeft=2.5&topMatSpacingRight=2.5&middleMatId=-1&middleMatSpacingTop=0.25&middleMatSpacingBottom=0.25&middleMatSpacingLeft=0.25&middleMatSpacingRight=0.25&bottomMatId=-1&bottomMatSpacingTop=0.25&bottomMatSpacingBottom=0.25&bottomMatSpacingLeft=0.25&bottomMatSpacingRight=0.25&IMIDArray=&IMIDCropArray=&IMIDRotateArray=&typeId=-1&cropLeft=0&cropTop=0&cropRight=0&cropBottom=0&sizeId=1&materialId=1&maxWidth=200]] —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 15:29, 25 January 2010 (UTC)

For the second part of your question: Nobody has made any kind of holographic television yet... and even if you had one, it's not like all of your 2D television would suddenly be 3D. The signal just does not carry that information most of the time.

That being said, see 3D television. There are apparently a number of stereoscopic TVs (you wear funny glasses like in the movies) expected to hit the market this year, and ESPN is apparently starting the first full-time 3D channel, or something along those lines. These are not holographic—they are 3D in the same sense as a 3D movie. You can't look around at every angle, they just provide a little parallax.

I know SteveBaker has much to say about volumetric displays, so I'll definitely wait to see what he says about the first part. --Mr.98 (talk) 16:30, 25 January 2010 (UTC)

He probably said it last time Mr Loughlin asked about them.

I think what Loughlin is describing is a type of Lenticular display, Where each hemisphere/pixel shows a different color depending on the angle it's viewed. Certainly this idea has been thought of. (Everyone working on 3d displays thinks of this idea.) But it's just not practical. (Consider the number of pixels needed, multiplied against the number of angles each pixel could be viewed!) All that said, the technology is just now within grasp. Barely. I saw one at SIGGRAPH 09. It looked very primitive, but it was actually using a tremendous amount of computing power, and very expensive display elements to maintain the illusion. (If I recall correctly, it also had a serious overheating problem.)

I'll see if I can quickly find the reference.

APL (talk) 17:22, 25 January 2010 (UTC)

Found it. It's called the gCubik. See a (poor quality) video here. The paper on it is here, but I can't find a free copy. APL (talk) 17:27, 25 January 2010 (UTC)

Here's a better video [11]. APL (talk) 17:38, 25 January 2010 (UTC)

To get a hologram you are going to have to control the phase of waves between the pixels, and to get a wide angle view, your pixels will have to half a wavelength or less. This will be of order of a megapixel per square millimeter, or about a terapixel for a square meter display. The information required is more because you need phase as well as brightness for each pixel, to get an uncompressed TV picture you will need around a petabyte per second of data. Graeme Bartlett (talk) 00:10, 26 January 2010 (UTC)

We have to be very careful to define what we mean by a 3D display. They come in roughly four kinds:

1. Single viewer (you have to be sitting in the right place) - hence a very limited view direction - but no special glasses needed. Lenticular displays are like this.
2. Multiple viewers - but all of whom get the same view - with special glasses (that's what you get in a 3D movie or using red/cyan glasses or a head-mounted display).
3. Multiple viewers in multiple locations - all getting the correct view for where they are standing without glasses or anything. Holograms are pretty much it.
4. Multiple viewers in multiple locations - all getting the correct view for where they are standing...but with one horrible drawback (the kind of thing our OP is describing, bubble tanks, spinning grids of LED's, vibrating mirror displays, etc, ad nauseum).

The problem with the OP's idea is that you can't control transparency. You can't stop light from the back of the object from shining through to the front - or from the left through to the right - and vice-versa. So everything looks ghostly. You can't ever display a realistic picture - period.

So - we're back with holograms - which are still ruinously expensive to generate in realtime. But we're getting there. Graeme is technically correct about needing a petabyte per second to broadcast raw volumetric data at hologram densities - but that's not the plan. You can send (for example) octree-encoded data about the shape of the objects and use on-the-fly wavefront reconstruction to generate the hologram. That blows away the bandwidth issues (well, relative to a petabyte per second at least!) - and shifts it into doing crazy high numbers of calculations. But that's actually more do-able. So I think it's possible that we'll see animated, interactive true holographic 3D displays in our lifetimes - but it's not certain.

Bottom line then: We're stuck with glasses until we get crazy amounts of CPU time...and sadly, the OP's idea isn't gonna cut it. Vibrating or spinning mirror displays can do the same job better, cheaper and much more easily. SteveBaker (talk) 01:50, 26 January 2010 (UTC)

I would dispute the transparency claim, the hemisphere has an opaque flat side with a pinhole, it would be like looking through a tiny hole in a fence from all angles, except there could be a lot of them, too small to see. I think opacity would occur, but the other practical problems including data rates are grim. —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 03:50, 26 January 2010 (UTC)

So you're saying that you build a cube packed with these hemispheres - each of which can produce light in any color and has a hole in it to allow light from behind to come through it? Your explanation is less than clear and the image you linked to doesn't help! SteveBaker (talk) 14:54, 26 January 2010 (UTC)

I really think you're describing something similar to the gCubik device I mentioned above. It worked on little hemispheres. It looked like a toy, and had serious problems, but it pushed the limit of modern technology.

Incidentally, I think you would have really enjoyed the "Emerging technologies" section of the SIGGRAPH 09 show. Besides the gCubic, there was this, which is very similar to what you described last time you asked. However, there's still nothing even close to the quality that you described the first time you asked.

Of course, you're the one with a direct communication line to the future, why don't you tell us what the future holds for 3d displays? I'd very much like to know. :-) APL (talk) 05:37, 26 January 2010 (UTC)

The gCubik is just a standard 'lenticular' display (a small improvement on the prismatic 3D display that's been used in things like 3D postcards for 50 years or more). Each display produces a 3D image - but only over a relatively small field of view. By gluing them onto the six faces of a cube, you hope that people concentrate only on the side that's facing towards them - ignoring the other sides that aren't making much sense from this angle. So the limited lenticular display only has to produce a fairly small field of view (out to maybe 90 degrees) through each side of the cube to make something that's kinda-sorta useful. SteveBaker (talk) 14:54, 26 January 2010 (UTC)

gCubic is lenticular, but it's lenticular in two directions, it's the only display I've ever seen that's like that. The lenses are not linear prisims, they're (roughly) hemispherical dots. Loughlin's post is not entirely clear to me, but this device uses clear "pixel size hemispheres", to create a coherent 3d image that is roughly correct (Within 5 degrees or something. So, let's say 'very roughly'.) when viewed from any angle. Then they built it into a cube, creating a heat management disaster. APL (talk) 16:17, 26 January 2010 (UTC)

Anyway, my real point in bringing it up, and I think I didn't make that clear enough, was that this obvious idea ("What if we made pixels that looked different from every angle!") isn't really practical. The absolute cutting edge, state of the art is nothing more than a fun tech demo, and the technology requirements go up asymptotically with your resolution. So it will probably never be practical for high-def, almost certainly not in our lifespans. APL (talk) 16:24, 26 January 2010 (UTC)

I was about to ask a question about the '3D' glasses as used to see the movie Avatar in 3D. But I looked up the relevant article and here's the link for anyone interested. RealD Cinema 220.101.28.25 (talk) 09:54, 26 January 2010 (UTC)

(NOTE TO RESPONDENTS: In case you missed APL's reference to our OP having a 'direct communication line to the future', Trevor has asked about 3D displays here on WP:RD/S a couple of times in the past (see APL's links above) - but he also claims to have built a practical device that can predict the future using "retrocausal data transfer".) SteveBaker (talk) 14:54, 26 January 2010 (UTC)

Voltage divider

I had a question about the voltage divider article, specifically the derivation of the formula V_out=V_in*R_2/(R_1+R_2). I see that V_in should be I(R_1+R_2), and that therefore the potential after the first resistor is IR_2. But when a path for the output voltage is provided, why should the current running through the first and second resistors be the same? —Preceding unsigned comment added by 173.179.59.66 (talk) 19:18, 25 January 2010 (UTC)

By definition if R1 and R2 are in series, the same current flows through them. The formula is for ideal conditions, and does not assume any of the current through R1 flows through a physical voltmeter instead of R2. In practice a modern digital voltmeter has an input resistance of perhaps 6 megohms. Older cheap analog voltmeters could load down very high resistance circuits and affect the measured voltage appreciably. Whatever the input resistance of the voltmeter, it could be modelled as a parallel resistor across R2. If R2 has less than 1/100 of the resistance of the voltmeter, then the voltage would be off by less than 1%. A Potentiometer (measuring instrument) (in the older sense, rather than a variable resistor in the modern usage of the term) can be used to measure voltage without extracting any current once the adjustment is complete, by having a very sensitive galvanometer between the measures point and a known voltage, with the known voltage adjusted until no current flows through the galvanometer. Edison (talk) 20:46, 25 January 2010 (UTC)

extrasolar planets

I did not note any mention in the article, but have there been any extrasolar planets discovered in binary star systems? Googlemeister (talk) 19:57, 25 January 2010 (UTC)

Yes. There are at least three planets in the Upsilon Andromedae system, for example. Algebraist 20:01, 25 January 2010 (UTC)

Alpha Centurai#Possibility of planets mentions Gamma Cephei also. —Akrabbim^talk 20:03, 25 January 2010 (UTC)

With the Upsilon Andromedae system, how can they tell the difference between a planet proper, and a red or brown dwarf star? Googlemeister (talk) 20:08, 25 January 2010 (UTC)

Our theories tell us the minimum mass of a brown dwarf and the observations of Upsilon Andromedae give estimates of the masses of the planets, and they are well below the brown dwarf threshold. Our article only gives lower bounds for the masses of the planets for some reason, but upper bounds will also be known. --Tango (talk) 22:11, 25 January 2010 (UTC)

Not necessarily, observations of gravitationally induced wiggling generally constrain the product M*sin i, where M is the mass and i is the inclination of the orbit. So you get a lower bound if the orbit is perfectly aligned for our viewing and sin i = 1, but it is unbounded in the upper limit since the planetary orbit might be directly skew to what we hope to observe. And there is no direct way to constrain i from wiggling alone (usually). You'd need to follow up gravitational detection with some other method to find an upper bound and that hasn't yet been done in many cases. Dragons flight (talk) 22:50, 25 January 2010 (UTC)

If there is just the one planet, then that's true. In this case, it's a whole system of planets and the interactions between them put constraints on the inclinations. The article mentions this. --Tango (talk) 23:40, 25 January 2010 (UTC)

Laws of Thermodynamics

What are some everyday examples for all the Laws of Thermodynamics or how can I explain these laws to a kindergartener? --Reticuli88 (talk) 20:35, 25 January 2010 (UTC)

On At the Drop of Another Hat, is the song "First and Second Law" by Flanders and Swann. Its annoyingly catchy and a fun way of teaching kids that basic concept. a brief search of the web will let you hear it for yourself. Rockpocket 21:02, 25 January 2010 (UTC)

Try it with something like lego blocks. The first law says that nothing is created or destroyed, it only changes form. Any legos you use can't be used to build something else. If all of your legos are part of a house, and you want to build a car, you need to take some legos from the house. Legos are thus, conserved. The second law says that things just become messier unless you do something to clean it up. Hence, the legos don't pick themselves up! The room would just get messier and messier unless you spend some time to pick up the legos and put them away. However, time spent putting legos away means you can't do something else during that time. So you can't get something for nothing. Either the room gets to messy to play in, so you can't play with anything because its a complete mess, OR you spend time cleaning it up, and then you don't have any more time to play. Either way you can't play all that you want. Entropy is a mean bitch that way. The third law is a bit tougher, but basically it's the cabinet where you put your toys away. The third law simply tells you where all the toys go when you pick up the room. Or, as someone eloquently put it to me:

• The first law says you can't win or lose, you can only tie.
• The second law says that you can't even tie, you can only lose.
• The third law is the rules of the game.

Just some ideas bouncing around my head.--Jayron32 21:18, 25 January 2010 (UTC)

The third law is that you can't quit the game. --Anon, 22:42 UTC, January 25, 2010.

You might like to try the 'simple English' Wikipedia article.

I like the idea of a Lego analogy - but I think we could do better (and list all four laws):

0) If I have six lego bricks and you have six lego bricks and your best friend has the same number of bricks as you - then she also has the same number of bricks as me.

1) You only have just so many bricks. No matter what you build or how you put them together, there are always exactly the same number of bricks. Even if you lose bricks down the back of the sofa or your dog eats some - the bricks still exist...somewhere!

2) If you make a nice tidy pile of lego bricks - carefully arranged by size and color - then if someone shakes them up - they never get any tidier. It takes a lot of work to make a tidy pile of lego bricks - but hardly any effort for your little sister to mess them up again.

4) 3) If you had a small box that was only just big enough to fit all of the lego bricks inside - they'd have to be really, really tidy to fit inside! If you jumble them all up - they wouldn't fit properly.

Physicists call untidyness "entropy".

SteveBaker (talk) 00:31, 26 January 2010 (UTC)

0, 1, 2, 4? Thermodynamics is weird! ;) --Tango (talk) 03:21, 26 January 2010 (UTC)

Binary counting perhaps? 2, 4, 8, 16, 32, 64 etc. :-) 220.101.28.25 (talk) 05:36, 26 January 2010 (UTC)

I never liked rule 3 and it's too hard to do with Lego - so I invented my own rule #4....or it was a typo...you choose! SteveBaker (talk) 13:58, 26 January 2010 (UTC)

I don't see the point in teaching such abstract concepts. Small children should be encouraged to be inquisitive of knowledge, appreciative of nature, and skeptical of any claims. 66.65.139.33 (talk) 02:24, 26 January 2010 (UTC)

Yeaaah. Who says we can't build a perpetual motion machine ? Scientists ? What do they know ? I bet they just haven't been inquisitive enough. Let's try flying a kite in a thunder storm ... Gandalf61 (talk) 11:00, 26 January 2010 (UTC)

Certainly, if anyone ever does build a perpetual motion machine, it'll be with Lego. :-) SteveBaker (talk) 13:59, 26 January 2010 (UTC)

I hope you don't mind my being forward, but I must wonder what the purpose of explaining thermodynamics to a five year old would be. Even if they are prodigal and could understand it, I shouldn't think they would have the intellectual curiosity to understand it. Vranak (talk) 14:52, 26 January 2010 (UTC)

You said it better than I did. 66.65.139.33 (talk) 15:15, 26 January 2010 (UTC)

While it's probably unlikely that they'd really grasp the concepts enough to appreciate your answer, they would learn something much more important - that such things can be questioned. My daughter was 6 when I started showing her Eureka! episodes. While she obviously can't get out of it what a high school student would, she's at least familiar now with concepts such as "entropy" and "atoms". Young kids are smart - never doubt it for a moment; a five year old has a better grasp of using English than any programmed AI system and can run and climb better than any robot - and they do it almost entirely without instructions of any kind. Matt Deres (talk) 17:14, 26 January 2010 (UTC)

do E. coli process cellulose?

If so, if you eat lots of pure fiber, can you get drunk off the EtOH they produce? John Riemann Soong (talk) 21:16, 25 January 2010 (UTC)

Probably not. Remember that if it worked that way, someone before you would have thought of it. Plus, intestinal flora (of which E. Coli is but one part) produce prodigious amounts of CO2 during the ethanol producing process. So, anything which could produce enough ethanol in your gut to make you drunk would probably also produce enough gas to make you painfully crampy and bloated to the point that being drunk wouldn't be worth it. If you REALLY want to make booze and don't care much about the enjoyment of drinking itself, then it's just best to let the fermentation go on outside of your body. See pruno for a simple recipe. --Jayron32 21:23, 25 January 2010 (UTC)

Wouldn't that just mean I would fart a lot? For why it's not been thought of yet (or why it's not popular), people usually don't eat pure fiber. And other sugars would be digested before it could get processed into ethanol.

And the main idea is to get drunk without tasting a single drop of alcohol. John Riemann Soong (talk) 21:33, 25 January 2010 (UTC)

In theory, I suppose an alcohol enema would work. But the alcohol would hit the bloodstream fairly directly, I reckon, and you wouldn't have the safety of gradual absorption or vomiting to prevent acute alcohol poisoning. Much safer and more pleasant to just drink it. Brammers (talk) 21:40, 25 January 2010 (UTC)

Naturally, Wikipedia has an article (section) on this: Enema#Rectal drug administration. Comet Tuttle (talk) 22:07, 25 January 2010 (UTC)

Very few organisms can digest cellulose -- our termite article discusses this a bit. Looie496 (talk) 21:42, 25 January 2010 (UTC)

"Designated drunk: Can you get intoxicated without actually drinking alcohol?" APL (talk) 22:53, 25 January 2010 (UTC)

The kind of E.coli that you got inside your azz do not digest cellulose, as far as I know. That said, there are some mutant / genetically engineered strains of E.coli that do convert cellulose to ethanol -- I've studied those firsthand for the oil company's cellulosic ethanol project that never got past the lab studies stage. You really wouldn't want to drink the product, though, because of the high concentration of fusel oil -- not unless you wanna get really drunk really quick and don't give a dam about the horrible taste or any tummyaches you might get later. You can burn the stuff in a car engine, though, but it won't be cost-effective in the current energy market. Clear skies 146.74.230.82 (talk) 01:49, 26 January 2010 (UTC)

If there were bacteria capable of efficiently digesting cellulose, why wouldn't they very quickly reduce all trees, woods, grasses into a bubbly slime? 95.115.188.228 (talk) 07:59, 26 January 2010 (UTC)

Plants have their own defences. John Riemann Soong (talk) 11:30, 26 January 2010 (UTC)

Even inside the lifeless wood of the trunk? 95.115.188.228 (talk) 17:13, 26 January 2010 (UTC)

Well there you start to get lignin, and plus all those tannins are kind of acidic. John Riemann Soong (talk) 18:55, 26 January 2010 (UTC)

indonesia plate

Is Indonesia part of Eurasian plate or Australian plate. Since Scotese map concludes indonesia will collide with Australia, but the map we have Eurasia in green shows indonesia is not in that county but in orange this shows Indonesia is part of Australian plate. how can Indonesia collide with Australia when the sense is like "taking a train to school" and "what you ate for lunch". This is strange when something inside a plate collides with something inside a plate. --209.129.85.4 (talk) 20:54, 25 January 2010 (UTC)

In fact there are some smaller plates involved (at least in some versions), most of Indonesia lies on the Sunda Plate, a tiny part near Aceh is on the Burma Plate while the eastern part is part of a complex mess of microplates. None of Indonesia is on the Australian Plate. However, the Sunda Plate is actively colliding with the Australian Plate at its eastern end. Mikenorton (talk) 21:48, 25 January 2010 (UTC)

how do I get rid of awful vibration artifact in my speaker setup?

Just to be clear that this isn't some "audiophile" mumbo-jumbo, I'm not speaking of some subtle effect that's bothering me on a subconscious level, I'm talking about a really clear, awful sound that's really as clear as day. The sound I'm talking about is this awful vibration sound that you usually get when you record something and for example yell into the microphone much louder than it can support. Problem is, I'm not playing anything that has that sound in it, and further, I am NOWHERE NEAR the limit of the speaker set up -- it could be way, way louder (WAY louder). So my question is: how do I get rid of that awful noise? Like, am I supposed to turn the line out (playing from a music device/my computer) down, or up, or almost completely up, etc. The setup is: computer -> remote (with volume control) -> speaker system (with separate sound volume on the back, independent of the volume knob). Is there some way to set these to get the desired effect? THanks! —Preceding unsigned comment added by 84.153.202.229 (talk) 23:31, 25 January 2010 (UTC)

Your speakers are farting. Possible cause 1: you are over-driving them. From your description, this seems unlikely. Possible cause 2: one or more cones is physically damaged. The general cure for that is reconing them or replacing them entirely. To assist in the diagnosis, are you able to detach the speakers from the current setup & drive them from some other set-up (to see whether the problem stays with the speakers, or is associated with the PC/Remote setup?. And in any event, think yourself lucky. I've spent half an evening under my desk trying to get my PCs headphone socket working, with no joy :( --Tagishsimon (talk) 23:38, 25 January 2010 (UTC)

The artifact you report might be clipping due to overdriving the system with too high an input. If you have a friend with an audio oscillator(signal generator) and an oscilloscope, it might be possible to input sine waves (pure tones) at varying frequencies and amplitudes and determine when the objectionable sound comes out of the speaker. If the recorded and played back sounds are free of clipping, then maybe the fault is somewhere between sound source, amp, and speaker. Perhaps the speakers are damaged, as mentioned above. Try borrowing and listening to good speakers, while keeping the volume below a level which would damage them. The square waves resulting from clipping can damage speakers. Edison (talk) 02:29, 26 January 2010 (UTC)

I've noticed I can get clipping (audio) on my headphones, plugged directly into the computer, if I have the computer's volume turned way down low and the volume on the media player turned up high... or was it the other way round? Anyway, worth considering that sort of internal clipping, whatever it is. 81.131.17.2 (talk) 11:16, 26 January 2010 (UTC)

January 26

Cloning question

Have we yet devised a theoretical method by which the memories and personality from the original might be restored/awakened in a clone? I know that there was some idea a while back of actual memories being encoded in genetic material but I don't know if that's been discredited now. —Preceding unsigned comment added by 95.148.105.150 (talk) 00:20, 26 January 2010 (UTC)

It sounds pretty fishy to me. Considering we don't really have a great understanding of the neurological basis of memory anyway, but the formation of memories is clearly somatic and not genetic, the idea that you could code memories in genes seems rather... unlikely. We'd need a far better understanding of how memory itself worked in the brain to begin with, much less a light-years superior understanding of the human genome. --Mr.98 (talk) 00:37, 26 January 2010 (UTC)

Aside from any other consideration - there is nowhere near enough 'space' in a DNA molecule to store that much memory. At best - each 'letter' of the DNA is one of C,T,G,A - two bits of information per base-pair. Human DNA has about 3x10⁹ 'letters' so it can store at best 6,000,000,000 bits - less than 1Gbyte. That's just pathetic! You can easily store more than that on a regular CD-ROM. My PC has five times that much main memory! And bear in mind that this DNA also has to contain enough information to construct our clone's entire body, to run it's biochemistry, to repair and regrow bits of the body that fail, etc. There is simply not enough space to store the memories of even a few days let alone a lifetime. So - a clone is no different than an identical twin - it would be born just like any other baby - grow, learn, experience the world and end up a very different person. Memories in the brain are retained over the long term as physical connections between neurons which change over time. The clone would have to have an exact duplicate of all of those neural connections - but that can't be because a clone has to be grown from a baby - and the baby clone's brain doesn't have enough space - enough cells to store an adult brains' worth of memories. So this is a complete and utter bust. There is no way to do this. SteveBaker (talk) 02:14, 26 January 2010 (UTC)

Though when you consider that ~30 billion memory-associated neurons in the cortices and hippocampus have 6,000,000,000 bits each, the capacity is not quite so pathetic. Each cell is terminally differentiated, so it doesn't actually need to contain enough information to construct our clone's entire body, just enough to code for the transcriptome of that particular neuron. How much genome variation (coding capacity) there is between neurons is currently unknown, but there are some suggestions that they could be quite significant and play a role in brain development and maintenance. The idea of genetic memory is a bust, of course, but not necessarily because of limited coding space. Rockpocket 06:32, 26 January 2010 (UTC)

Oh, sure, memory could be stored using DNA (although there is no evidence to suggest it is and plenty to suggest otherwise), but that wouldn't help a clone. When you clone someone you only get to use one set of DNA, not one for each cell. --Tango (talk) 10:30, 26 January 2010 (UTC)

Yep - and that's why Rockpocket's answer is not relevant to this question. If our memories were routinely stored in DNA, consider how long it would take to retrieve one. Somehow, the brain would have to locate the right cell that contained the DNA where the answer was stored - then somehow duplicate the right section of that DNA and use that to provide the answer. How would the indexing mechanism work? How would we find the right molecule? No - the brain is a computing machine and the connectivity of the neural net is what stores information AND allows it to be retrieved so quickly. SteveBaker (talk) 13:54, 26 January 2010 (UTC)

You would need to use some kind of nano-tech duplication technology (which no-one has invented yet) and actually copy the body, including the brain. If you use a normal cloning technique it is, as Steve says, just like having an identical twin. --Tango (talk) 02:19, 26 January 2010 (UTC)

This is another form of Lamarckism, and has long been discredited save for some fringe scientists who keep trying to bring it back. It is futile. 66.65.139.33 (talk) 02:20, 26 January 2010 (UTC)

Such memory transfer is of course a popular device in Science Fiction, where it may be used to raise philosophical questions about the nature and continuity of identity and selfhood in addition to being a useful plot device. A recent example of the many novels, etc, exploiting the idea is John Scalzi's Old Man's War. 87.81.230.195 (talk) 02:31, 26 January 2010 (UTC)

If by 'restored' you mean, copy the mind of the original into the clone? As Mr.98 says, our understanding of the brains memory (or even its 'programming') is not good enough. It seems an unlikely possibility. But, then so was flying etc. I would think ESP is more likely than Genetic memory. Not deriding your question, but the general concept (with a different mechanism) is also nicely addressed in the novel "To Your Scattered Bodies Go" by Philip Jose Farmer. Note I wrote this(slowly) while others were posting so it doesn't take into account all the erudite responses before me. --220.101.28.25 (talk) 02:44, 26 January 2010 (UTC)

Lamarckism as referred to by IP 66.65.139.33 above, DNA & Genetics--220.101.28.25 (talk) 05:43, 26 January 2010 (UTC)

Pretty much nobody nowadays believes that memories are stored using DNA -- the almost universal belief is that they are stored by modifying the synaptic matrix, that is, the connections between brain cells. So, replicating the full set of memories would mean replicating the synaptic matrix, which would involve nanoengineering far beyond our current capabilities. It isn't even just a matter of making the synapses match: the numbers and positions of brain cells are themselves dependent on experience, so a clone and an original won't even have matching sets of brain cells. Looie496 (talk) 16:39, 26 January 2010 (UTC)

What our question-asker is probably thinking of is the theory of Memory RNA. The Wikipedia article isn't very good, but it hits the important fact that the theory is "now discredited". APL (talk) 16:46, 26 January 2010 (UTC)

Appreciate the answers. Thanks. So it's completely beyond the realms of possibility that if/when humans are cloned, that the clones might grow up and experience unexpected 'echoes' of the memories or character traits of the original? --95.148.104.185 (talk) 00:42, 27 January 2010 (UTC)

moonrise

Is there a pattern/schedule of the moon setting and rising like the sun? One night at around 7:00 PM, I happened to see the moon in a short distance from the horizon. On another night at around 7:00 pm, it was already at the "noon" position. --121.54.2.188 (talk) 00:55, 26 January 2010 (UTC)

Basically, it rises ~49 minutes 50m28s later each time, because it is in orbit around the earth and the earth has to turn a bit farther than one day's worth to catch up. --Tardis (talk) 01:09, 26 January 2010 (UTC)

Cool, so the moon doesn't only change faces but schedules as well. --121.54.2.188 (talk) 01:19, 26 January 2010 (UTC)

Not sure what you mean by "change faces". It only ever shows the same face to Earth, but not all parts of it are illuminated all the time. Re the "schedule", did you ever notice that a full moon always rises shortly after sunset? That's when its Earth face is getting maximum illumination from the Sun; but non-full moons rise at other times, when the Earth face is at some angle to the Sun. -- Jack of Oz ... speak! ... 02:54, 26 January 2010 (UTC)

My bad, I meant phases, not faces.--121.54.2.188 (talk) 05:51, 26 January 2010 (UTC)

If you are trying to understand what Jack is saying and struggling to work out why it works, try drawing a diagram, it can be very helpful. --Tango (talk) 03:18, 26 January 2010 (UTC)

The article Lunar phase contains several (potentially) helpful diagrams. -- 174.21.135.237 (talk) 03:59, 26 January 2010 (UTC)

(I improved my approximation; I had been in a hurry.) --Tardis (talk) 19:58, 26 January 2010 (UTC)

A short answer is, when the moon is full it rises when the sun sets. Each day after that the moon rises later and later, and wanes, until it rises when the sun rises--the new moon. After that it appears as a crescent in the morning, setting soon after sunrise. Every day it rises later and later, and the waxes larger, until when full it once again rises when the sun sets. The article linked above will explain all this in more detail. Pfly (talk) 09:43, 26 January 2010 (UTC)

Small correction. A waxing crescent moon rises soon after the sun rises and sets soon after the sun sets. It is in the sky for most of the day, but not easily visible in daylight; it is most visible around dusk. A waning crescent moon rises shortly before sunrise and sets shortly before sunset. It is also in the sky for most of the day, but most easily visible around dawn. Gandalf61 (talk) 13:43, 26 January 2010 (UTC)

Red bull exhaust pipe and rust

http://thereifixedit.com/2009/11/26/red-bull-gives-you-ignition/

One of the commentators said that at least the pipe won't rust since the red bull can is made of aluminum. But would it only hasten the deterioration of the exhaust pipe by acting like a Sacrificial anode or something.

By the way I think Steve would enjoy (or get horrified by) the "fixes" given in the site.--121.54.2.188 (talk) 06:01, 26 January 2010 (UTC)

Looks like it's well away from the outlet manifold so heat (melting/softening) shouldn't be an issue. Looks like a good job actually, for temporary use. If the 'aluminum' acts as the anode it will corrode, not the steel pipe. If the pipe is mild steel the Sacrificial anode article under examples says "protection of voids in the glass lining of mild steel water heater tanks via use of magnesium or aluminum alloy anodes". Not 100% sure of this. Depends on exactly which dissimilar metals are involved 220.101.28.25 (talk) 11:08, 26 January 2010 (UTC)

Yeah, that's right. Aluminum has a much higher reduction potential than steel. So what will happen is the Aluminum will corode, and the iron will stop rusting. I have lost several good aluminum pots and pans when I made the mistake of keeping them in the same drawer as steel ones; when the steel ones started to rust, even a little bit, it caused the Aluminum pans to develop a nasty black film (aluminum oxide) which rubbed off on everything, and resisted washing off. I eventually ditched the pots, and learned to keep those materials in seperate locations. --Jayron32 13:32, 26 January 2010 (UTC)

I've seen worse "fixes". My concern with this "fix" is that the connection between the can and the pipe doesn't look gas-tight - so in all likelyhood it's leaking nasty carbon monoxide into places where it can get sucked into the cabin. The vibration that's transmitted between the bucking/shaking engine and the fixed-to-the-frame tailpipe will find the weakest point. In a very short amount of time, the can will be bent enough it won't be a tight fit and then the occupants of the car will start losing brain cells to CO poisoning (although evidence suggests that this had already happened when they were considering the fix!) Also, there is scope for the can to melt - although it's hard to predict that without knowing a lot more about the vehicle. Exhaust pipes are made from heavy gauge steel - not thin aluminium. Car manufacturers would certainly use thin aluminium if they possibly could. The fact that they don't speaks volumes about the suitability for the job! This is the kind of botch that I'd certainly consider as a "get me to the nearest garage on a dark and stormy night" fix...but no more than that.

It's the 'invisible' fixes that are most worrying. When I bought my 1963 Mini, the previous owner had started to restore it - and had not understood that the pitch of the threads on the 'whitworth' bolts that British cars used back then is not the same as the thread pitch on US cars. Hence, when he replaced a nut or a bolt, he would - with 100% reliability - strip the threads. Of the 16 lug nuts holding the wheels onto the car, 8 were stripped in this way. One wheel had three out of four stripped - not one wheel had four good lug nuts! All of the bolts on all of the shock absorbers were stripped. His efforts to add seatbelts to a car that was manufactured without them (and without hard attachment points to which to add them) were...um...creative and exciting. SteveBaker (talk) 13:48, 26 January 2010 (UTC)

Does this mean I can stop any iron thing from rusting - handtools for example - by attaching some aluminium cooking foil to them? Or wrapping them in aluminium foil? 92.24.54.79 (talk) 22:13, 26 January 2010 (UTC)

is this a valid question here?

Is this desk the proper place to ask a physics question? Is there perhaps a better place where physics discussions take place, such as the argument pages there are concerning mathematics? --Neptunerover (talk) 08:46, 26 January 2010 (UTC)

General Physics goes here, but Mathematical Physics (which looks just like Maths) goes on the Maths Desk, I would say. Dbfirs 09:58, 26 January 2010 (UTC)

Okay then, my next question concerns the form of the question I want to ask, since I want to make sure I am not asking what would be an inappropriate question, no matter on which desk I ask it. I'm wishing to make a short statement that I consider valid, after which I'm hoping to be offered suggestions concerning my perceived validity of the statement, since I'm wondering if perhaps there might be things I am not taking into consideration. --Neptunerover (talk) 10:31, 26 January 2010 (UTC)

The intention of the Wikipedia Reference Desks is to respond to factual questions that can be answered by reference to Wikipedia articles, reliable sources outside of Wikipedia, or, occassionally, through the previous experience of individual editors. The reference desks are not intended to be a chatroom, a soapbox for promoting individual opinions, or a forum for debating controversial topics - see Wikipedia:Reference desk/Guidelines. Whether your question will meet these criteria or not depends upon the contents and context of your "short statement". Gandalf61 (talk) 11:16, 26 January 2010 (UTC)

Please don't keep us in suspense Neptunerover. Ask if it's suitable 220.101.28.25 (talk) 11:24, 26 January 2010 (UTC)

If you want to know if your understanding of existing physics is correct, then ask away. If you want to ask if your own theory that you have come up with might be correct, then you'll need to go somewhere else. --Tango (talk) 12:57, 26 January 2010 (UTC)

Is this desk the proper place to ask a physics question? - Yes. Physics is science and this is the science reference desk and our job here is to answer questions.

Is there perhaps a better place where physics discussions take place, - Yes there are better places to hold discussions. Discussions (as in: general chit-chat) are not encouraged here - we're here to provide answers to specific questions. Sometimes we do get derailed into discussions but that's not really supposed to happen. So there is undoubtedly a better place (outside of Wikipedia) to hold discussions (as opposed to questions).

SteveBaker (talk) 13:27, 26 January 2010 (UTC)

I wouldn't say that I'm looking for a discussion, but rather just input. It's not like I generally have very many people of intellect around me who I can bounce things off of, not that anyone here would know that. So I'll make my statement and answer anything if I am asked anything, but I'll do what I can to avoid expressing anything else. --Neptunerover (talk) 16:17, 26 January 2010 (UTC)

The direction of the force of gravity is reversible depending upon how one looks at it. While this may seem to go against everything we've ever been taught, the direction of the force of gravity is not necessarily 'down', but just as well it can be considered as a force going 'up'. Not to say that gravity would make things go up, but what is meant is that because of gravity's upward force, things go down. No matter how counter intuitive the idea may seem, this idea of gravity being based upon a constant upward acceleration is well supported by General Relativity. Is the Earth pulling us against it, or is it pushing up against us? In either case, the math is exactly the same. I think pushing upward explains the force better than a weird suction downward, considering that if the Earth is pushing against me, it makes sense that I should be held firmly against it. However, if the earth is pulling me toward it, how is that accomplished without a rope or tether of some type? Occam's Razor says that if you can explain something simply, stick with that. (Important note: How 'pushing outward' might be accomplished in 3 dimensions is not part of the subject of the preceding statement, and should not be considered when judging its validity, please.) --Neptunerover (talk) 16:17, 26 January 2010 (UTC)

For Earth to be pushing against everyone on its surface at once, it would have to been expanding outwards at a rate of 9.8 m/s, wouldn't it? Which it demonstrably isn't. And I seem to recall this conclusion being reached last time you tried to discuss this. Vimescarrot (talk) 17:33, 26 January 2010 (UTC)

In addition to the above, "pushing" fails to explain orbits. Also, let's be clear about what Occam's razor really is. It's a recommendation (and nothing more) to prefer (not "always select") the explanation with the fewest unsupportable assumptions. Leaving aside the initial caveats, "ignore the problems of three dimensions" is a pretty major unsupportable assumption. — Lomn 19:10, 26 January 2010 (UTC)

Gravity is a natural phenomenon by which objects with mass attract one another. The OP talks about Earth's gravity but it can be demonstrated that all objects have gravitational attractions to each other. Classical mechanics gives Newton's law of universal gravitation. The invisible force of attraction between two objects is a pull in the direction of the other object and therefore when one changes one's reference frame from one object to the other, the pull direction reverses. It is however the same attraction. If the OP is making the point that gravity both pulls the Earth towards Neptunerover and pulls Neptunerover towards Earth then that is correct. It is consistent with what is taught and there is no good reason to invoke General relativity, a need for a rope or to suppose another explanation would better suit Occam's Razor. Kepler's laws of planetary motion require Newton's laws to work in 3 dimensions, which they evidently do. Cuddlyable3 (talk) 19:13, 26 January 2010 (UTC)

Hmm... reconsidering this, it looks more like you're just redefining all forces to "go" in the opposite direction. I think you'll find this a far less intuitive approach when carried to its logical extremes, even if you find it sensible in the case of gravity. Pushing boxes south to make them move north? Friction in the direction of motion as a braking effect? Nope, I don't think it'll fly. — Lomn 19:16, 26 January 2010 (UTC)

GR tells us that gravity and acceleration are equivalent locally. That means a small object can't tell the difference between the two situations without observing distant objects. If you do observe distant objects, the difference becomes immediately apparently - acceleration is only equivalent to a uniform gravitational field, and the Earth's isn't. Objects on different parts of the Earth are accelerated in different directions (all toward the centre of the planet), that means the Earth would have to be accelerating in different directions, which isn't possible without it being ripped apart. --Tango (talk) 19:38, 26 January 2010 (UTC)

Consider a sphere with a painted stripe around the middle (like one of the striped balls here). The width of the stripe is constant, but the boundaries of the stripe curve outward, locally, at every point. If that's hard to visualize, note that the standard of straightness is a great circle and the boundaries of the stripe are not great circles. A great circle tangent to the boundary at one point would pass through the colored region and be tangent to the other boundary at the antipodal point. If you think of different cross-sections of the stripe as different times, the great circle (a geodesic) oscillates back and forth from one side of the stripe to the other, like a ball dropped through a hole in the Earth in that old thought-experiment. This is very closely analogous to what happens in general relativity. Every point on the surface of the Earth is accelerating outward, but the overall size doesn't change because of the spacetime geometry. If Earth was uniformly dense and spacetime was Euclidean then Earth's internal geometry would be exactly the geometry of the painted stripe (with two more dimensions added). It's different only because the density isn't uniform and spacetime geometry isn't quite the same as Euclidean geometry. -- BenRG (talk) 23:27, 26 January 2010 (UTC)

Well, yes, you could say the Earth is expanding in some really weird coordinate system and, technically speaking, the weird coordinate system is just as valid as the more familiar ones, but I don't think that really helps the OP. When we say "expand", without qualification, we mean expanding with respect to conventional coordinates. --Tango (talk) 23:35, 26 January 2010 (UTC)

Refrigeration not supported at low ambient temperature

I've read the article on refrigerators which seems to confirm my understanding of how household fridges work. I've also searched the archive but couldn't find an answer to my query. I have a Smeg fridge (http://www.smegtech.com/site/smeg/pdf_libretti/914773907-GB.pdf) which is currently in an unheated garage. I wanted to use it for extra capacity around Xmas but, although it clearly had power (the interior light worked) there was no sign of the compressor(?) starting up. On checking the manual, I found that it is only designed to work if the ambient temperature is at least 16c. At the time it was probably about 2c. Firstly, why is that? I'd have thought that it would assist the fridge in dissipating heat if the ambient temperature is cold. Would the refrigeration cycle not work properly or could some harm come to the device? Is it likely that the device has a cut-off so that it won't 'start-up' if the temperature is too cold? --Frumpo (talk) 11:02, 26 January 2010 (UTC)

That's a normal problem. The refrigerator requires outside warm air to evaporate the liquid that's flowing through it (when it evaporates, it cools), which will return to the refrigerator, be compressed by the pump, and absorb more heat (it's a cyclical thing). If the outside air temperature gets too low, it won't efficiently evaporate the gas, which effectively halts the cycle. See Vapor-compression refrigeration. If your refrigerator cuts out at 16c outside air temperature (which will quickly become inside air temperature), you will want to be very careful about what you eat from it - there are many foods that should not be stored at such a high temperature. Falconus^{p t c} 12:44, 26 January 2010 (UTC)

If you garage is consistently around 2C over the xmas period, then you don't need a fridge - just put stuff in the garage as it is. If the garage spends a significant amount of time at temperatures between about 5C and 16C, then you have a problem - it's too warm to do without a fridge and too cold for the fridge to work. A lot of people keep extra fridges or chest freezers in their garages without problems, though, so I guess there are ones out there that can handle the low temperatures. Maybe you just need to get a different fridge. --Tango (talk) 12:55, 26 January 2010 (UTC)

Hall effect EEG?

Supposing a conventional EEG was taken using head electrodes. Would a powerful magnetic field around the subjects head, oscillating in a three dimensional raster pattern, alter the "focus" of all the electrodes in such a way as to vastly increase the spacial resolution down to the level of individual brain cells?Trevor Loughlin (talk) 13:58, 26 January 2010 (UTC)

No. --BozMo talk 14:13, 26 January 2010 (UTC)

From the title I guess the OP is thinking of using Hall effect sensors as the head electrodes. Hall effect sensors cannot generate magnetic fields so the 3-D magnetic raster scan (interesting notion) would be generated by an array of electromagnets. Focussing the magnetic field would be a difficult design problem and the only use for the Hall sensors would be to measure how well it was achieved. Cuddlyable3 (talk) 14:58, 26 January 2010 (UTC)

The article on Transcranial magnetic stimulation might be helpful here. It can't be used for the proposed purpose, but it might give you an idea of what would happen if you created such strong magnetic fields. Looie496 (talk) 16:52, 26 January 2010 (UTC)

Psychological reason for former students talking about how strict/tough teachers were

I was under the impression, and the article on memory seems to agree, that we remember mostly the good things. Obviously, people remember some negatives. Still, on a few alumni Facebook pages for American Junior High Schools, I notice former students, now in their 30s and 40s, talking more than usual (maybe 30-35% of posts) about teachers' discipline and how strict they were in 6-9th grade. My question is, why? Why are they choosing to discuss this when reminiscing?

I'm theorizing maybe it's how bad the students were; maybe not all the posters, but perhaps they're remembering some really rough kids but can't recall specifics on that - but they can recall teachers and how they handled it. While the ones I'm reading are from a city of 100,000 - not exactly a crime-riddled urban area - I'm sure the neighborhood plays a part.

It just seems strange that so much time is focused on negative thing, instead of different assignments, social activities, and so on; which are mentioned, but not as much. It especially seems strange because of the notion that "what's too painful to remember, we simpy choose to forget." (Okay, the line is fromt he song "The Way We Were," but you know what I mean.)209.244.187.155 (talk) 14:40, 26 January 2010 (UTC)

I don't know that there's a psychological reason for it, but I can give you a social one - happy stories are boring. Nobody wants to hear "Oh man my teacher was soo much better than yours" for very long, but everybody wants to swap/compare horror stories. Every tell a story about getting injured? A group of friends can go back and forth telling different, painful stories for an hour. Same thing - it's rude and annoying to try and compete for "best" but if you're competing for "worst" the only person who loses is you. School-age people also do it with sleep - "I only slept five hours last night." "Yeah well I got 3.5!" "Lame, I pulled an all-nighter." Someone saying "Damn, I slept 9 hours last night I feel great" is no fun. ~ Amory (u • t • c) 14:47, 26 January 2010 (UTC)

Presumably because their teachers were strict. And at that critical age, the conduct of adult figures in your life can have a profound influence on your psyche for a very long time. So I guess it's just 'digging in the dirt' as Peter Gabriel puts it. Vranak (talk)

Perhaps they have children in school now and they are witnessing the dumbing-down of the school system. I see it at a college level. I have students who invariably made straight A's. They almost all took advanced courses. They scored very high on the SAT. Then, when I show them long division (to explain what modulo means), they say that they've never seen it. That is just one example. It also shows in the fact that the exams for the class have not changed in the last 10 years, but the scores on the exam go down every year. They used to be above 90% for most students. Last semester, the average was around 65%. It is clear from my perspective that there is a dumbing-down in the school system. I don't blame the students. They are not genetically dumber. I could blame less-than-strict teachers, but I don't. I blame the parents who feel it necessary to give A's to students without requiring them to earn the grade. -- kainaw™ 14:57, 26 January 2010 (UTC)

To be fair, long division is a skill that's fading fast. I'm trying to recall the last time I had to do it - and I'm pretty sure it was over a decade ago - and I'm someone who does a LOT of math and arithmetic. It's worth teaching it for lots of reasons - but expecting everyone to know it well is asking a lot for what is essentially an unneeded skill. We don't teach kids to use slide-rules either. SteveBaker (talk) 15:11, 26 January 2010 (UTC)

It's very hard to compare student ability in 2010 to student ability in 1965. A child nowadays is a computer expert - in 1965, if they'd heard of computers, you'd be lucky! Sure, they waste some of that technical expertise on video games (Sorry Steve), various online garbage, but they also know how to type, how to use a word processor, how to query the internet for information. Their skills toward those goals are greatly enriched over those of a student in 1965, who consequently had more mental acuity to focus on "pure" subjects. So, while there aren't all that many 9th grade hackers (despite what you see in the mass media), there is an enormous repository of cultural and institutional knowledge about computers which doesn't get graded. Technological expertise is only one example of a huge class of useful skills which are never graded. When you cite lower total scores on tests, without accounting for the redirection of intellectual activity to other, un-tested subjects, you're failing to account for this sort of skill-set displacement. In other words, our kids aren't stupider, they're just focused elsewhere.

I sincerely hope that this does not mean focus is lost on core subjects I consider critical - basic math and literacy, for example. But to some extent, this defocusing is not a total loss. I grew up wasting a ton of my time on video games - and I learned a ton about graphics acceleration, programming design, and computer architecture by proxy. I was never tested on those concepts in a math class, or even in a programming class. Yet, now, when I encounter older programmers, traditionally trained in more conventional ways, who could probably best me in a long-division competition, they're often unable to discuss the merits of PCI-X vs. PCIe - or even comprehend this entire way of thinking about program design. But, that skill is very relevant in today's computer engineering job market - a lot more so than many concepts that I was formally tested on during schooling. I imagine the same argument can be made for a variety of other extra-educational knowledge that is acquired.

So, while it may be accurate to say that the scores lower on the same tests as they are given year by year, this line of reasoning suffers from a fundamental flaw. If the test does not change from year to year, it implicitly assumes that the same material is relevant from year to year - that performance of the same skills of the previous generation is a merit. In some sense, that encourages stagnation and repetition - if our kids do the same thing we do, but only incrementally better, then what progress has been made? As much as it's a tear against a dumber or less-motivated populace, it's equally an indictment of an education system that does not know how to adaptively adjust its testing to normalize for relevance and currency.

This is a very hard problem - we aren't going to just throw formal education out the window (well, we could, and many prominent philosophers such as Ivan Illich suggested that we should). But there has got to be a happy medium - an education system which adjusts to current needs, accepts that society isn't going to collapse just because long division, aether theory, and FORTRAN 77 are dying arts, and trains kids for what they need to know today. Nimur (talk) 15:33, 26 January 2010 (UTC)

Tossing out long division is acceptable, but having students perform worse every year at college level is not acceptable. Instead of improving education, we do things like "recenter" the SAT to make the less-educated students feel better. There is no genetic reason for modern students to perform worse on the SAT. They should perform better than those students in the 50's and 60's who didn't have computers and the Internet to fill them with valuable information. The fact that they don't implies that something is broken. Some blame the less strict teachers who just shove the students from one class to the next. I already stated that I blame the parents. -- kainaw™ 15:55, 26 January 2010 (UTC)

I also want to point out that this question is about why 30-40 year olds state that their teachers were stricter. It is not about how smart students are. My answer to the question leads to the debate about how smart current students are, but that is not the topic here. Further, this is not a forum for debate. So, please feel free to disagree with me and tell the person next to you what an idiot I am, but don't make my answer a means of hijacking the thread to debate modern vs past students. -- kainaw™ 16:04, 26 January 2010 (UTC)

The point I think some people are trying to make is that "recentering" the SAT is not, in itself, a bad thing at all. A hypothetical SAT from a century ago would have little meaning to us now (Latin conjugation, what the hell?), so it shouldn't be surprising at all that it would constantly be in need of shifting. Modern primary school math places a heavy emphasis on learning how to approximate answers and very little on obtaining the results. To people of my age that seems like a dumb thing to do, but it's simply an acknowledgement that precise mathematics is not used by most people and that calculators can perform any function flawlessly. Approximating that 21/5 is "about 4" is much more useful to most people than doing the long division. If SATs don't keep step with what's being taught, the grades will shift downward. Matt Deres (talk) 17:44, 26 January 2010 (UTC)

The most basic principle of storytelling is that every good story involves a conflict and a resolution. Without a conflict there is no story. Nice teachers don't tend to generate strong conflicts, so they don't tend to generate good stories. Looie496 (talk) 16:47, 26 January 2010 (UTC)

Thakns for the answers; I hadn't looked at it from the storytelling/one-upping angle, but yes, that's very likely. Also, considering that a couple of them talked about sneaking out to smoke then, while I don't like to pass judgment on how they acted, maybe some of it is reliving the thrill of trying to away with stuff, too; even if they did get caught at times. I imagine that for some, there is a point to reminiscing about the thrill of trying to get away with stuff, whereas that thrill isn't there anymore now; as adults, they have the freedom, and any stuff they would have to "get away with" would lead ti the threat of jail or large fines if caught; they've matured enough to realize that's not worth the risk.209.244.187.155 (talk) 19:05, 26 January 2010 (UTC)

Improving Loudspeakers

                            LS1              LS2
             |¯¯¯|  |\        /|            |\
frequency____| ? |__| \___|¯|/ |   Room     | \|¯|__
   sweep   | |   |  | /   |_|\ |            | /|_| |  |\
           | |___|  |/        \|            |/     |__|-\
           |                                          |  \___test
           |__________________________________________|+ /   output
                                                      | /
                                                      |/

I have a stereo audio system and want to improve the sound in my listening room. I think it is possible to compensate for the non-linear frequency responses of my loudspeakers and room acoustics by adding a filter at the preamplifier stages of both channels. I have a graphic equalizer but I hope to get a better result than from adjusting it by ear. If I could measure the exact correction needed then I could optimise the equalizer settings or possibly build a better filter. I propose to measure the audio performance as shown in the diagram where:

"?" is the equalizer or filter to be designed

LS1 is one loudspeaker that is driven with a swept frequency test signal

LS2 is an identical loudspeaker operating as a microphone.

I assume that the loudspeakers' frequency responses are the same whether they are driven at low level or used as a microphone. I intend to adjust the stage "?" to minimise the test output at all frequencies. That should compensate for the room acoustics. But can you suggest how to handle the following snag with my plan: the optimised stage "?" will introduce twice as much compensation as is needed for the non-linearity of a loudspeaker. How do I design a compensator for one loudspeaker? Cuddlyable3 (talk) 14:46, 26 January 2010 (UTC)

Back in the early 1980's Philips used to make "Motional feedback speakers" that did more or less exactly this - so what you're trying to do is certainly possible...and with 1980's technology too! However, you'll need to allow for the time delay in the audio getting from LS1 to LS2 - sound travels V-E-R-Y--S-L-O-W-L-Y compared to electricity! You're definitely going to need either some phase compensation or a programmable delay between the input on the left and the comparator on the right. You might also look at Powered_speakers#Servo-driven_speakers - where you use an accelerometer to directly measure the motion of the speaker cone in order that you may compensate for it's frequency response - although (obviously) that doesn't take account of the room acoustics. SteveBaker (talk) 15:06, 26 January 2010 (UTC)

Nitpick, Steve - sound travels slowly compared to the electromagnetic signal in the other wire. Nimur (talk) 15:10, 26 January 2010 (UTC)

What does it mean when SteveBaker writes "for it is frequency response" ?

We do (of course!) have an article about Motional Feedback speakers - but it's not exactly helpful! SteveBaker (talk) 15:45, 26 January 2010 (UTC)

Motional feedback is interesting, expensive, has only been applied to low-frequency (woofer) speakers and it is not what I propose. The block "?" will provide forward correction and not introduce feedback. I shall disregard phase, sound delay LS1 to LS2 and longer delays in the room acoustics by making the test comparator compare powers of the two signals and the frequency sweep will be slow. The ear is relatively insensitive to constant phase error so phase changes that "?" introduce will probably not be noticed. In any case a phase linearising stage can be added to "?" if that is found necessary.
Where is the snag is with the following procedure? 1) Adjust "?" until test output is constant (or zero with gain adjustment) for all frequencies. 2) Build two compensator circuits that each implement half the distortion of "?" and attach them to the two channels. 3) Now I have a system where speaker non-linear frequency responses are fully compensated but room acoustics are half compensated. 4) Run the measurement again (one of the compensators is in the "microphone" channel). Only the remaining uncompensated room acoustics need to be corrected and that can be done by adding the second "?" in full to both channels.That sounds unclear but at least Nimur I understand what SteveBaker means by electricity.Cuddlyable3 (talk) 17:02, 26 January 2010 (UTC)

Tyre pressure

If you inflate a car's tyres to a certain pressure and then add weight to the car, does the pressure in the tyres increase, or does the pressure remain the same because the tyre has retained the same volume, albeit that it has deformed slightly? I imagine that if the tyre were to be equally compressed on all surfaces (say by taking it underwater) then the internal pressure would increase, but I am not clear if compression on one part of the surface would be compensated by the expansion on other parts of the surface leading to static volume and pressure. Any help appreciated. AChangeOfPressure (talk) 15:02, 26 January 2010 (UTC)

Pressure depends on the force and area ,force is mass * acceleration so if the Mass is increased the pressure increases .If by compression you mean applying force then the pressure increases--NotedGrant Talk 16:08, 26 January 2010 (UTC)

Not sure if I was sufficiently clear in my original question, so let me clarify. Imagine an example where I inflate the four tyres of a car to a pressure of 30 PSI, then I add a significant amount of weight to the car (in terms of passengers, luggage etc) equally distributed across the four tyes and then take a new reading of the internal pressure of the tyres with a pressure gauge. Will they have increased above 30 PSI? Thanks AChangeOfPressure (talk) —Preceding undated comment added 16:19, 26 January 2010 (UTC).

There are two effects happening at the same time. Increased load will deform the tyres; if this reduces their volume then pressure in the tires will increase. But at the same time the size of the contact patch is increased, so the load is supported over a greater area. So if you add a load that is 10% of the weight of the car, the tire pressure will not necessarily increase by 10% - it may only increase by 5%, while the area of each contact patch also increases by 5% (yes, I know there is a simplification there). I don't know the relative sizes of the two effects in practice - it probably depends on all sorts of factors such as the size and design of the tyres. Gandalf61 (talk) 17:07, 26 January 2010 (UTC)

Human Underwater Speed Record

What is the world record for speed acheived by a human underwater? I mean unassisted though I suppose they could be in some sort of human powered sumarine, wetsuit with fins, etc. TheFutureAwaits (talk) 16:44, 26 January 2010 (UTC)

Evolution

What proof is there for evolution? How do I know it isn't just an atheist hoax? --J4\/4 <talk> 16:54, 26 January 2010 (UTC)

First, read the article on evolution. It will detail some of the arguments that have been made. This is the subject of a huge amount of scientific and popular literature and it would be impossible for us to provide all the information here. If you have a specific question regarding evolution, please re-phrase your question. --- Medical geneticist (talk) 16:59, 26 January 2010 (UTC)

Do I look like I would hoax you? File:Ape shaking head.gif

Cuddlyable3 (talk) 17:27, 26 January 2010 (UTC)

Also, I think it's been done. Vimescarrot (talk) 18:01, 26 January 2010 (UTC)

The largest organized Christian denomination in the world has stated there is no conflict between any part of the scientific theory of evolution and christian faith. Many Christians of many other demoninations also see no conflict, nor do many members of other faiths. Many scientists are also devoutly religious, and have no problem with the fact that evolution is happening, and also having a devout faith. The conflict is a false one, perpetuated by people who need there to be a conflict for their own selfish reasons. --Jayron32 21:33, 26 January 2010 (UTC)

One thing I would like to add is that your primary premise is very flawed. Not all people who believe in evolution are atheists, not by a long shot, even Darwin wasn't strictly an "atheist", he didn't believe in a personal God. In fact, Catholics who don't believe in evolution are a minority, even in the US 58% of Catholics answered a poll that they believe evolution to be the best explanation of the origin of human life on earth. An even larger percentage of Jews, Hindus and Buddhists believe in evolution and even as much as 45% of Muslims in the US. We even have an article about it: Theistic evolution. Vespine (talk) 22:14, 26 January 2010 (UTC)

I assume you must be talking about the OP. I have never, here or anywhere, made the claim that there is any connection between the theory of evolution and athiesm. Quite the contrary, if you read my comments, I make the exact opposite arguement. Could you clarify the antecedant of your pronoun, por favor? --Jayron32 22:28, 26 January 2010 (UTC)

There is no strict "proof" in science, only theories and evidence. The evidence for evolution, however, is overwhelming. The Origin of Species lays down the basic case so convincingly that it has nearly immediately been widely accepted - despite the fact that at the time no hereditary mechanism supporting evolution was known, we had few fossils, and no genetic evidence. Indeed, Darwin comes as close to a proof as science can come - geometric increase of populations, finite carrying capacity of habitats, and variability of heritable traits more or less implies evolution mathematically. The suggestion that it is a atheist hoax is entirely unsupported. Many of the past and current researchers supporting evolution are religious people. Many large Churches have accepted evolution. And any conspiracy would need to be so gigantic as to be impossible to keep secret. --Stephan Schulz (talk) 22:23, 26 January 2010 (UTC)

Proof is everywhere. The evolution of bacteria in hospitals in response to our best efforts to nuke them with antibiotics. Rats that are resistant to rat poison. Rabbits that survive mixamatosis. Lactose (in)tolerance in humans. My current favorite is the Recurrent laryngeal nerve in giraffes. Rows and rows of fossils in just about any decent natural history museum. However, here is a good one:

There is a species of moth in the UK that are normally white - this is because they live on trees with very light colored trunks and it helps them be camoflaged from hungry birds, very rarely, a mutant dark colored moth (of the same species) would show up. When the industrial revolution hit the UK, and everything was run from coal, there was a vast amount of dirty soot in the air and the places where these moths came to rest became blackened. Within a very small number of years, butterfly collectors noticed that the rare dark variety were becoming much more common and the 'normal' light colored ones were becoming harder and harder to find. The moths had evolved an adaptation to all of that sooty pollution. Moreover - when the "Clean Air Act" was passed in the UK and the clouds of filthy carbon-laden emissions more or less ceased, the process reversed itself and the dark colored moths started to vanish with the light colored ones again becoming the most common. Again, the moths had evolved.

I could sit here and type in convincing examples all day - but I'll restrict myself to just one - and recommend that you read almost anything by Richard Dawkins who is truly excellent at providing convincing examples that the "intelligent design" loonies can't possibly counter (which is why they hate him with such a passion - and why our OP will probably never read a book by him).

SteveBaker (talk) 22:40, 26 January 2010 (UTC)

SteveBaker is referring to Peppered moth evolution, which is a long article that goes into a great deal of detail to creationist alternative explanations, and the political controversy. Comet Tuttle (talk) 23:45, 26 January 2010 (UTC)

If you look at the sort of people who have done work on how evolution actually works—e.g. Ernst Mayr, E.O. Wilson, Stephen J. Gould, Charles Darwin, and so on—rather than the real evolution evangelicals (e.g. Richard Dawkins), what you see is a body of people who have spent an immense amount of time looking at very small pieces of the world (birds, ants, snails, barnacles), compiling lots and lots and lots of mind-numbing data that seems to indicate, in quite a detailed way, exactly how evolution appears to have worked. They disagree with one another on many points—they are not in strict collusion. But it seems like an awful lot of effort to go through for just a hoax. These are people who have devoted their lives to very tedious and basically obscure details that shed light on a bigger whole. This is not, generally speaking, how hoaxsters operate. Whatever they are doing, it is not a hoax. They could certainly be wrong, or could interpret evidence incorrectly, and so on. But their sincerity in the effort is fairly evident in the work itself. They are not trying to pull a fast one—they are pulling a rather slow one, if anything.

If you'd like to know about evolution, read one of the books by any of the aforementioned scientists. Go ahead, it won't hurt. Make up your own mind as to whether they are serious about it. They are subtle thinkers and not one of them is trying to proclaim atheism upon the world.

Dawkins is not so subtle, though he is clever. But he definitely does believe that evolution leads to atheism. Plenty of scientists disagree with him on this point, though. In the end, whether evolution and religion are ultimately compatible is a philosophical/metaphysical question, not a scientific one. Evolution is not compatible with a very literal and narrow reading of the Bible—neither is modern medicine, or really any basic scientific outlook. Whether you see that as a reason to reject science—despite all of its apparent mastery over nature (your computer that you are reading this on right now would not work if quantum mechanics wasn't basically correct)—or whether you see that as an imperative to read the Bible in a more interpretive way, is obviously a personal decision. --Mr.98 (talk) 23:37, 26 January 2010 (UTC)

Happy Brains à gogo, TMS Experiment

A Boscovich/Nikola_Tesla type Electromagnetic Household Theory. I'd like to prove similarties to the Apple IPOD users with an unawared type of Transcranial_magnetic_stimulation. Lets say some magnetic chemically bonded minerals of sorts is in the American foodstuffs and/or water supply. And the magnetic field of the two Ipod Headphones (if you just hold the two white factory Apple Ipod earpieces together, they stick magnetically) creates similar effects to TMS. As well as Cellphones and Bluetooth tech users. My experiment in this would be, and here's the question in regards, to buy a used Etch-a-Sketch, break open, and put in a Fishbowl full of water. With this magnetic dust, if my Theory is correct, would the Etch-a-Sketch dust form a visible magnetic field in the bowl if I held the two Ipod earpieces at opposite ends? --i am the kwisatz haderach (talk) 17:18, 26 January 2010 (UTC)

What makes you think that an Etch A Sketch is filled with "magnetic dust"? --LarryMac | Talk 17:22, 26 January 2010 (UTC)

Pretend he said Magna Doodle instead of Etch A Sketch. (And that just about exhausts my ability to make sense of the question.) -- Coneslayer (talk) 17:24, 26 January 2010 (UTC)

I don't know, I discriminated it by its gray color. Maybe one of those Magnetic Moustach Pen/Dust toys. So usage of Finely grounded visible Magnetic Particles. --i am the kwisatz haderach (talk) 17:27, 26 January 2010 (UTC)

TMS requires an incredibly powerful magnet. The magnetic fields created by an IPOD or any other household device are orders of magnitude too small to matter. Looie496 (talk) 17:44, 26 January 2010 (UTC)

I should add, the reason I brought this up is when I drink Coffee from the Starbucks, at my workstation, I have really good Radio reception. But if I don't drink of the corporate cup, my desk radio has a lot of static. I then concluded that I'm a radiowave receptor, and when I'm full of the metalic minerals, I get good music. --i am the kwisatz haderach (talk) 17:46, 26 January 2010 (UTC)

We are all radiowave receptors. Some people can hear long-wave amplitude modulated radio transmissions in their fillings! Are you writing a Science Fiction (or fantasy) story? Dbfirs 18:43, 26 January 2010 (UTC)

Is it possible that you only go to Starbucks on days when it is not raining? APL (talk) 20:20, 26 January 2010 (UTC)

I am reading a bunch of sci-fi actually. And I watch Noir-films. I also want to add, that I'm not trying to equal the effects of TMS, so the exact radiofrequencies of those magno tests--i'm not trying to match. I'm just questioning the possiblities of a weak electro spectrum. Something that ties in with microwaves from electric power lines over the streets, or plasma/lcd screens in homes. And I wanted to test this theory, with a fine Ferrofluid powder--these things don't need extremely powerful magnets. I want to create a new term calling these things in our drink MAGNO-MINERALS. --i am the kwisatz haderach (talk) 18:57, 26 January 2010 (UTC)

I would encourage you to pause, and first execute a controlled, double-blind experiment on your fundamental premise that drinking from the corporate cup is the exact factor that is altering your radio reception. The assertion seems silly on its face. Comet Tuttle (talk) 19:42, 26 January 2010 (UTC)

Can anyone answer his original question? Would the small magnets in a set of earbuds create enough of a field to be seen with iron filings? I suspect that they would, at least for filings near the earbud, but the best way to find out's just to try it. And I think the whole fishbowl/Magnadoodle thing is a bit more complicated than you need. Just buy some iron filings, sprinkle them on paper, and stick the earbuds underneath the paper, about 8 inches apart from each other. Buddy431 (talk) 21:09, 26 January 2010 (UTC)

This Youtube video is a good tutorial on making a magnetic field viewer that is probably more sensative than just sprinkling iron on a piece of paper. I doubt that actual ferrofluid would react at all to ear buds, and besides it is expensive and messy. APL (talk) 22:40, 26 January 2010 (UTC)

TMS is not a subtle thing. It feels like someone knocking on your head. (At least, it was when I had it done to me, about five years ago.) Just pointing that out. I find it very unlikely that your choice of coffee has anything to do with your radio reception. That sounds a wee bit crazy to me. --Mr.98 (talk) 23:19, 26 January 2010 (UTC)

why has no one investigated the acid-base properties of chloramines?

I just want to find out how much having the chloro groups on there influences the acidity of the amino proton as well as the pka of its conjugate acid. However, google gives a grand total of zero results for such queries as "pka of chloramines" and "basicity of chloramines". HELP?!!! John Riemann Soong (talk) 18:32, 26 January 2010 (UTC)

Surely this must be a simple undergrad experiment, right? It can't be that troublesome to measure the pka of a chloramine. I just don't have the clearance for that kind of thing right now. John Riemann Soong (talk) 20:14, 26 January 2010 (UTC)

um, yeah, I googled "pka of chloramines" and got a shitload of sites which have information on that. I don't get one site that lists a bunch of pKa in like a table format, but I get LOTs of good stuff. Are you sure you typed the right thing in? This site gives the pKa of chloramine itself. This pdf seems to have a bunch of general properties of chloramine. here is a scholarly paper on the a specific experiment to determine the pKa of a specific chloramine derivative. I'm not sure how you could NOT find stuff. Both a straight google search and a google scholar search turn up tons of links. Also, have you tried both the CRC handbook and the Merck Index? They both tend to have lots of physical data on various compounds. --Jayron32 21:27, 26 January 2010 (UTC)

I don't get why there isn't an easily-available pKa index stored on a central federal science database or something? I don't have access to print materials. John Riemann Soong (talk) 00:08, 27 January 2010 (UTC)

Also that site doesn't give the pka of chloramine. It's a mirror site of Wikipedia. Also some other sites give irrelevant pkas of the wrong functional group -- like they give the pka of some alpha-proton or carboxylic acid that happens to have a chloramine group on it.

The guide you cited also doesn't say anything about the acid-base properties of chloramine. It gives a bunch of irrelevant stuff about water treatment and all that. I'm simply trying to oxidise an amine-alcohol compound with bleach to get a carbonyl group while minimising the amount of chloramine side product. I don't know why everyone seems to be focusing on the annoying water treatment aspect (no one should use chloramine for water treatment) and not on the organic synthesis perspective, which seems more important. John Riemann Soong (talk) 00:24, 27 January 2010 (UTC)

Finally, that last paper talks about a molecule with a sulfonyl group on it ... uhhhhh that's like talking about trichloroacetic acid when the pKa of acetic acid is desired. And I can't even access the paper because it's only an abstract. =( John Riemann Soong (talk) 00:28, 27 January 2010 (UTC)

You ask far too many inane and absolutely ridiculous questions. Open up a bloody book, or in this case, spend more than 30 seconds quickly perusing google before harassing these lovely Wiki reference desk folks. And stop asking questions like you've got an epic hardon for the answer and need "it" immediately. Try to be a bit less neurotic and nicer. MrFudgey (talk) 23:36, 26 January 2010 (UTC)

I do try to be nice but I don't know why my question goes unanswered for days. I mean, people ask simple questions all the time. I don't have access to anything besides my textbook, which btw, doesn't cover chloramines as functional groups. Also, when I google "pka of chloramines" (with quotes) I get no results, whereas without quotes returns me irrelevant results.

I spent around 5 minutes before giving up. Researchers often know pKas from experience so I thought it was something someone could tell me right off the top of the bat (along with the pka of phenol being around 9-10, mercaptans 10-11, amines 35 for the conjugate base and 10 for the conjugate acid, etc. John Riemann Soong (talk) 00:07, 27 January 2010 (UTC)

planetary nebula

Do planet survive inside panetary nebula or they will get destroy in planetary nebula. Planetary nebula is between RGB and white dwarf, if Mars go in shell of planetary nebula will it be vanish? --209.129.85.4 (talk) 20:46, 26 January 2010 (UTC)

Planet to keep a descent atmosphere

What do planet need to have a descent atmoshpere. Since Tango always say Titan will bleed away it's atmoshpere it is always unsource statement. This said Titan might keep it's atmosphere in 6 billion year sun, just the orange haze at the upper part will deplete, but it will keep some, just not that thick. Do planet diameter matter? Could planet be 1/10th the size of earth and still have an atmosphere. Pluto is also made of ice, I never hear anybody else say Pluto will just outgass. Could surface gravity also be weak and have the planet hold it's atmosphere.--209.129.85.4 (talk) 20:53, 26 January 2010 (UTC)

It's basically all about gravity. So the size and density of the planet/moon/whatever is what matters. Also, if the body is too cold then there may be no materials in it's makeup that are gaseous at those temperatures. Whether a planet like Pluto would outgass from icy stuff on the surface also depends on temperature. SteveBaker (talk) 21:50, 26 January 2010 (UTC)

Temperature is more important than that. The particles in the atmosphere will have velocities based on the Maxwell-Boltzmann distribution. That is a function of temperature. That means that, at higher temperatures, a greater proportion of the particles will have escape velocity and will escape. The remaining particles then exchange momentum through collisions and get back to the same distribution, meaning some more particles have escape velocity and escape. This process means that any atmosphere constantly loses particles to space, the atmosphere can only survive over long time scales if enough new gas is added to compensate for the losses. Those losses depend on temperature, so at higher temperatures you need more replacement gas to maintain the atmosphere. That is one of the main reasons that Titan has a thick atmosphere while the Moon, which is a very similar size and mass, and essentially no atmosphere at all. If Titan warmed up to similar average temperatures as the Moon, it would lose its atmosphere. I will try and find some references for that. --Tango (talk) 22:42, 26 January 2010 (UTC)

First of all, the source cited by the article the OP links to is talking about Titan getting warm enough for a water-ammonia ocean to form, not a water ocean. They are talking about maximum surface temperatures of about -70°C - a long way below Earth-like temperatures, but perhaps warm enough for life based on a slightly different biochemistry to us to arise. Those lower temperatures mean the atmosphere would escape far slower than it would at Earth-like temperatures, so could well survive for millions of years. --Tango (talk) 22:56, 26 January 2010 (UTC)

I have failed to find any reliable sources talking about Titan at Earth-like temperatures since a red giant sun isn't expected to heat it that much and people discussing terraforming dismiss it as essentially impossible, so no-one gets as far as thinking about what would happen to the atmosphere at those temperatures. --Tango (talk) 23:29, 26 January 2010 (UTC)

. Tango, I've heard the same argument about the Maxwell tail that you give on many occasions. It is certainly true that an object with a hot enough surface or a low enough escape velocity will bleed atmosphere into space. But I'm not sure how relevant that is to an object the size of the moon. Lunar escape velocity is ~2.4 km/s. At 300 K, an oxygen molecule has only a 1×10⁻¹⁵ probability of having enough velocity to escape (i.e. from Maxwell-Boltzmann). And in order to escape it needs to be moving in the right direction and living in a part of the atmosphere that is already of such low density that its mean free path is nearly infinite, or else it will collide with other molecules and lose energy before escaping. Once you combine low probability with low density, it seems like the rate of mass loss to the Maxwell tail for any gas much heavier than helium should be nearly nil under lunar gravity. By comparison it seems like collisions with solar wind particles, with typical velocities of 400-750 km/s, would be a much more effective means of providing gas molecules with enough velocity to escape out into space. So I'm not sure drawing your comparison to the Moon makes sense because I'm not sure if losses on the Maxwell tail are really a determinative factor for the Moon's lack of atmosphere. Dragons flight (talk) 00:40, 27 January 2010 (UTC)

Number of seeds contained in a grape

How many seeds are on average contained in a grape?--87.11.120.169 (talk) 21:10, 26 January 2010 (UTC)

Seedless varieties have zero, Grignolino grapes can have as many as 10. Most normal varieties have between 2 and 4. SteveBaker (talk) 21:47, 26 January 2010 (UTC)

• Thanks for the aid!--87.11.120.169 (talk) 23:00, 26 January 2010 (UTC)

January 27

What is the meaning, and/or purpose of human life?

No, I'm not asking for a definitive answer to this question. :) Rather, I'm curious as to *how close* the 'hard' sciences are to providing an definitive answer to the question. Can this question be answered by 'hard' science? Is anyone working on it? Or has the answer already been provided a long time ago, in that the meaning and/or purpose of human life is, simply 'to survive and to reproduce'? --95.148.104.185 (talk) 00:34, 27 January 2010 (UTC)

[[12]] --i am the kwisatz haderach (talk) 00:37, 27 January 2010 (UTC)

I'm not aware of any reason for "hard" sciences to be pursuing an inherently subjective philosophical problem. Philosophers, on the other hand, have produced loads of answers. See meaning of life. — Lomn 00:39, 27 January 2010 (UTC)