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February 22

Minimum Temperature For Human Survival

What is the smallest temperature that a human can survive in indefinitely? Which is to say, suppose a human (with no clothes or shelter) is provided enough food and water to live, and that he/she is in a container of air at some constant temperature and with no wind. Further assume that the amount of air present is such that oxygen is not a concern and the temperature of the air is not influenced by the radiated heat from the person. What is the minimum temperature that would let that person survive for as long as the food and water lasts? Certainly, if the air were about 98 Farenheit, the person would be able to maintain appropriate body temperature forever. But there must exist some temperature where the loss of energy to the surrounding air exceeds the creation of energy by metabolism (or rather, the rate of conversion of food into thermal energy) such that the person is unable to sustain an internal temperature sufficient to survive. Does this temperature depend on the amount of calories provided per unit time, or is there some maximal level of calories per time that the human body can process? Assume that the food and water are provided at the outside temperature -- i.e. no heated food or water is provided. Also, would the provision of clothes and/or shelter decrease this minimum temperature, or simply prolong the period of time before hypothermia sets in? 71.70.143.134 (talk)

The article for thermoregulation states that "In experiments on cats performed by Sutherland Simpson and Percy T. Herring, the animals were unable to survive when rectal temperature fell below 16°C [~60 Farenheit]." This is not necessarily the answer to my question in that humans are exothermic, and so can maintain an internal temperature greater than the exterior given enough calories/time.

I suspect the temperature is surprisingly high. Clearly a person running in circles could maintain a sufficiently warm core temperature in very low air temperature, but the problem is sleep. Eventually that person is going to have to lay down, cease moving (save for shivering I suppose), and go to sleep - at which point their body temperature will plunge. I have no references, so I shall offer no predictions. 218.25.32.210 (talk) 01:11, 22 February 2010 (UTC)

It depends partly on whether the person has lived in the cold for a while. I've read news accounts of people in Russia taking cold showers and fishermen who use bare hands to catch fish from ice holes in -50 degree weather. Imagine Reason (talk) 03:41, 22 February 2010 (UTC)

The OP asked about the minimum environmental temperature for long term survival of a naked human with adequate food and water. This is not a situation that would frequently occur outside medical experiments or torture, since humans have been smart enough to wear clothing in cold environments for tens of thousands of years. Death would be attributed to "exposure." Wind would be a very important variable in determining the drop of core body temperature. Core body temperature likely determine survival of the individual, but temperature of fingers and toes would determine loss of digits from frostbite. A recent TV show had some "Survivor man" replicating the experience of people who nearly died when stranded during a snowstorm, In an experiment, he sat in a cold room, perhaps 23 degrees Fahrenheit (-5C), and the temperature of his core and his fingers was monitored. His awareness and manual dexterity decreased until the experiment was stopped when he seemed to be failing physiologically. Turning on fans to increase "wind" was devastating. In any realistic scenario, the person's clothing, however thin, would act as a windbreak and provide as insulation a dead air layer next to the body. Experimental data I read once (years ago, no reference citation possible) said that when an Australian aborigine and a European were asked to lie down at night on cold ground with minimal clothing, the European's body tried to maintain normal temperature in all body parts and he shivered miserable, with a severe and steady drop in core temperature, while the aborigine's body let the peripheral parts drop in temperature and defended core temperature, letting him sleep peacefully if not comfortably, implying greatly improved survival prospects under the specified conditions (which were likely too warm for frostbite). There is probably some research from military research departments on survival in cold temperatures, but it is not so likely they assumed no clothing, which would be more like some of the torture interrogation methods used by the Bush administration for suspected terrorists. In the U.S., I know of an incident wherein some young Girl Scouts survived overnight with clothing and sleeping bags under windy conditions when it got down to 13 degrees Fahrenheit (-10.5 C). Inadequate clothing is a more likely condition to be experienced. With plenty of food, shivering would exercise muscles and help maintain core temperature in the OP's scenario, but falling asleep would eventually occur and that is when the "death from exposure" would likely occur. (I recall a joke from an early TV show wherein someone tells of an unfortunate photographer who got locked in his darkroom in a building where the heat failed during a cold snap, and who ultimately died of exposure). Edison (talk) 04:57, 22 February 2010 (UTC)

It's unclear what relevance any of this has to my question. Certainly the question is hypothetical and I'm not pushing for the creation of experiments to test any offered hypotheses. Instead, I'm asking if there are any arguments from first principles which might allow one to state x temperature is such that the rate of heat loss is greater than the rate of heat creation by metabolism. Further, frostbite seems to be extraneous to the question, since it can only occur at less than freezing, and the minimal survival temperature is certainly greater than that. I understand why clothing allows us to survive extremely low temperatures, but again, I'm less interested in feats of extreme survival than in feats of prolonged survival.

This is not a direct answer but we are talking about Hypothermia, so the article Hypothermia is a good place to start. --220.101.28.25 (talk) 09:59, 22 February 2010 (UTC)

And I have just noticed that you have already looked at that article (sorry!) this is not an easy question to answer! 220.101.28.25 (talk) 11:07, 22 February 2010 (UTC)

Is wearing a layer of your food considered cheating? I suspect lard might be used for insulation. Googlemeister (talk) 16:52, 22 February 2010 (UTC)

Okay, I think I figured out an answer. This claims that the basal metabolic rate for a human is 100 watts (although it's based on a dead link). So we can lose up to 100 watts to the surrounding environment, and we can calculate the two main ways to loose heat: through radiation and conduction. Radiation is governed by the Stefan-Boltzmann law, $P=\sigma \cdot A\cdot T^{4}$, where σ is the Stefan–Boltzmann constant and A is the radiating surface area. Since the surrounding air is also radiating heat into the person, we end up with $P=\sigma \cdot A\cdot (T_{h}^{4}-T_{a}^{4})$, where T_h is the temperature of the human, and T_a is the temperature of the surrounding air. Conduction is governed by Fourier's law, $P=-kA{\frac {\Delta T}{\Delta x}}$ where A is the surface area, k is the thermal conductivity of the material (.025 for air), $\Delta T$ is the temperature difference, and $\Delta x$ is the distance. I'll pick 5 cm as about the width of the layer of warm air sitting on the skin. So the total energy loss is simply the sum of these two: $P=\sigma \cdot A\cdot (T_{h}^{4}-T_{a}^{4})+-kA{\frac {\Delta T}{\Delta x}}$. Solving this for P = 100 watts, the smallest temperature we can survive indefinitely is about 302 kelvin, or about 84 fahrenheit. This seems very high, but I suppose we did evolve on the savannah. The question is, can someone raise his or her basal metabolic rate while sleeping? Certainly someone can keep warm by aerobic exercise, but I don't know if shivering while asleep has a significant impact. 71.70.143.134 (talk)

Your $T_{h}$ isn't the standard 37 °C; in a cold environment, the skin temperature will be significantly lower even when the core temperature is maintained. Also, you can reduce the effective A by folding the body (basically, go for the fetal position). But you also lose heat through the ground (we haven't said what it's made of) and via convection (which serves to reduce the $\Delta x$; I don't know if your 5 cm is a good guess including that effect or not). Finally, that 100 W is for comfortable humans; though I don't know by how much, shivering and other mechanisms will certainly raise that power when it's needed. --Tardis (talk) 19:59, 22 February 2010 (UTC)

The convection/conduction loss is dominated by the radiative loss, so although the skin temperature might be lower than 37 C, that would not have much of an effect, and neither would decreasing the $\Delta x$ (although, decrease it far enough and we can only survive in an arbitrarily small range around 37 C). I don't know enough about how radiative heat loss works to know if the important factor there is the temperature of the skin or the peak internal temperature, but that term involves the temperature to the 4th power so small changes can have large impacts. If anyone has any idea on what the lowest possible sustainable skin temperature is, I'd be very curious -- although I suspect this might depend strongly on amounts of subcutaneous fat. At any rate, your point about the fetal position is well taken. Assuming a new surface area of 1 square meter (this is potentially low -- imagine trying to cover yourself in a square blanket one meter to a side), the smallest temperature is about 294 kelvin, or 70 fahrenheit, which is more in line with my intuition but also demonstrates the extreme dependence of my (over-simplified) model on a couple of parameters. 71.70.143.134 (talk)

Radiative loss is determined by the skin temperature just about as much as conductive loss is; skin's opacity (optics) to IR is pretty high. (Its emissivity is also pretty near 1, which is why you can just use $P=\sigma T^{4}$.) I don't know what the lower (safe) limit on skin temperature is, but the 100 W temperature is basically linear in the skin temperature (in the plausible range of skin temperatures): it drops about 1.2 times as fast (for $A=1{\text{ m}}^{2}$, neglecting conduction altogether). --Tardis (talk) 15:57, 23 February 2010 (UTC)

My own (non-expert) answer to the OP's original question is: 10 C (50 F) for a naked person outside, but clothes and/or shelter could lower the minimum survival temp to as low as -90 C. FWiW 24.23.197.43 (talk) 04:45, 23 February 2010 (UTC)

How can we conclude that some arbitrary (unpowered) shelter can't let you survive below -90 °C? What if the shelter is a space blanket inside a four-season sleeping bag inside a tent inside another tent inside an oil tanker filled with aerogel, with silver foil layers inserted at various places to reduce radiative loss? --Tardis (talk) 15:57, 23 February 2010 (UTC)

Sure you can design a shelter that will allow survival below -90 C; the reason I said -90 C is that it's the lowest temperature yet recorded in the coldest parts of the Earth, so that's the lowest temperature proven to be survivable through use of shelter. Of course shelters could be designed that would allow survival even on Pluto -- it's just that there hasn't been any need for that yet. 146.74.231.55 (talk) 23:59, 23 February 2010 (UTC)

Ah — I thought the lowest recorded temperature might have something to do with it. --Tardis (talk) 03:09, 24 February 2010 (UTC)

Speed skating

I'm watching the Winter Olympics, and the speed skaters don't run but sway from side to side. I've never skated, so I don't know the mechanics. Doesn't the side-to-side movements make the skates cut through ice that much harder? Thanks. Imagine Reason (talk) 00:13, 22 February 2010 (UTC)

To push yourself forward on ice skates you have to turn one skate sideways and push against it, you then lift that skate up, move it forwards, put it down and turn the other skate sideways and repeat. That is pretty much the only way to propel yourself (at any significant speed, anyway). A running motion wouldn't work since the skates would just slide on the ice and you would go nowhere (unless you put spikes of some kind on the toes that can dig in, which you do see on some skates, but it's not a very effective method for going quickly). --Tango (talk) 00:20, 22 February 2010 (UTC)

I believe figure skates have a pick at the front which is similar to a spike. Dismas|^(talk) 02:12, 23 February 2010 (UTC)

That is not how I would describe it. Speed skaters do not move their feet forward to backwards very much or angle the blade "side ways", except for the very first few steps off the start line. Most of the power is driven from moving the legs from the inside to the outside in a sideways motion. Admittedly the blade is angled, but I would not call it "side ways," it is still very much acute to the direction of travel. This is what creates the long and powerful "power stroke" rather then if you move your legs forward and backwards with the blades sideways. Vespine (talk) 01:03, 22 February 2010 (UTC)

The key is that skates will slide frictionlessly along the line of the blades. So a straight walking or running motion, like you would do on dry land, would only produce a cartoonish running in place effect until you eventually fell on your butt a few seconds later. Just about everyone does this their first time on ice skates. APL (talk) 04:26, 22 February 2010 (UTC)

Nuclear isomers

What exactly is a nuclear isomer? The article is way too technical for me to understand, as are most of the articles linked in the intro. I'm going to guess that it's (1) the most stable isotope of an element, or (2) the isotope of an element with the longest half-life, or (3) perhaps most stable = longest half-life, and therefore both 1 and 2. Nyttend (talk) 02:03, 22 February 2010 (UTC)

Neither of those. More like you know how you can expose glow-in-the-dark toys to light and then they give off a low glow for hours. Metastable compounds are charged with gamma rays and reradiate them slowly. By definition if a frequency of gamma radiation reradiates quickly it isn't "metastable". Absorbing or emiting a gamma ray changes the energy in an atom but doesn't change the isotope - gamma rays are pure energy unlike alpha and beta radiation. 75.41.110.200 (talk) 02:45, 22 February 2010 (UTC)

Just to be sure no-one gets the wrong idea here, let's be clear that the reference to glow-in-the-dark toys is an analogy. They actually work by luminescence or phosphorescence, which involve transitions between electron energy states, not nuclear energy states. Glow-in-the-dark toys do not involve nuclear isomers and do not absorb or emit gamma rays ! Gandalf61 (talk) 09:07, 22 February 2010 (UTC)

Here is a very vulgar attempt at popularization, which others are encouraged to improve on and/or correct. The nucleus of an atom contains a certain amount of energy in it just holding it together, like a coiled spring. In most atoms this is the minimum amount of energy required to do so. A nuclear isomer is an atom whose nucleus contains more than the minimum amount of energy. In shifting from this more energetic state to the minimum state, it can radiate a gamma ray or an electron. This does not change its overall proton or neutron count, so it remains the same element, and the same isotope, despite having undergone a form of radioactive decay.

Now, the question of what we mean by the energy that holds a nucleus together (binding energy), and how it can be that some nuclei have different energy than others, and so forth, I think this requires a somewhat deeper quantum mechanical account to make sense of, but if you think of it as just "energy" and don't worry about where it comes from, it is much simpler for these purposes.

It probably should not be confused with different isotopes of an element (same element, different mass, often radioactive and unstable), which is what seems to have thrown you off. ^180m
₇₃Ta
and ¹⁸⁰
₇₃Ta
are the same isotopes of the same element, but they have different energies in their nuclei (the metastable, m one has more), and are thus isomers. --Mr.98 (talk) 04:24, 22 February 2010 (UTC)

One thing to add is that m represents a discrete amount of energy. If an atom absorbs x amount of energy it enters a metastable (somewhat, relatively stable) state which we designate as m. If it absorbs a different amount, say 1/2x or 2x, it decays almost instantly (not even slightly stable!) For some isotopes there will be a large amount of energy y which yield a different somewhat stable stable which we call m2 with a different half-life than m. The amount of energy represented by x and y and the ratio of x/y are all dependent on the particular isotope. Rmhermen (talk) 17:40, 22 February 2010 (UTC)

So different isomers have different amounts of binding energy, and I can always count on atoms of the same isomer to have about the same amount of binding energy? I like the "don't worry about where it comes from" idea — I already knew that there was such a thing, but I don't know anything more than it exists and basically what it does, and I really don't care about it other than that :-) Finally, do I understand you rightly to say that different isotopes would have different isomers, since you'd need different amounts of binding energy to hold together different numbers of neutrons? Nyttend (talk) 21:13, 22 February 2010 (UTC)

Let me have a go at it: consider each nucleon (proton and neutron) has a specific energy associated with it, which contributes to the total nuclear energy. Something like vibrating or rotating in place. The most stable state for a nucleus is to have each one at its lowest energy (the "ground state") possible for that nucleus (bound collection of nucleons). A nuclear isomer has a nucleon at a higher energy state than normal in that nucleus. DMacks (talk) 21:24, 22 February 2010 (UTC)

I don't know much about nuclear isomers, but I think they are the nuclear counterpart of chemical isomers—that is, different metastable spatial arrangements of the nucleons, not simply excited states. Nucleons are fermions, so they don't just stack on top of each other; the nucleus has a shell structure (about which I know nothing). (Quasi)classically, to turn one chemical or nuclear isomer into another you need to pull it apart (which costs energy) then put it back together (which gives you roughly the same amount of energy back). Quantum mechanically, higher-mass isomers can decay spontaneously to lower-mass isomers by tunneling, but the half-life is exponential in the size of the energy barrier, hence the long lifetime of some of these isomers (potentially long enough that they might as well be considered stable). Ordinary excited states, in contrast, decay quickly because there's no classical energy barrier. -- BenRG (talk) 05:16, 23 February 2010 (UTC)

We have a Nuclear shell model article:) I don't know the exact "shapes" of them (vs the standard density-plots of electron orbitals) though. I just used "Something like vibrating or rotating in place" (emphasis added) to simplify that mess, but it's definitely not true that that's what's really happening. But it's definitely not like chemical isomers either...it's the nuclear counterpart to electronic transitions and excitation rather than a change of structural organization. The article that started this discussion states "In an excited state, one or more of the protons or neutrons in a nucleus occupy a nuclear orbital of higher energy than an available nuclear orbital of lower energy." Somewhere^† there's an article talking about the actual physical (sort-of:) shape of a nucleus; this is not that. DMacks (talk) 16:52, 23 February 2010 (UTC)

^†Found it, it's in the nuclear-isomer article itself, described as distinctly a different issue from the "normal" spin/orbit energetics of nuclear energy states. DMacks (talk) 17:55, 23 February 2010 (UTC)

Birthday

Is there any statistical bias towards a particular day or month of a year when most of the people are born? —Preceding unsigned comment added by Amrahs (talk • contribs) 04:04, 22 February 2010 (UTC)

Footnotes 2 and 3 of the Birthday problem article argue that the answer in both cases are "yes" (months depend on seasons when people conceive, days depends on hospital schedules), but they are not terribly well-sourced (there is a link to this page which has some graphs of the month distribution for 1978-1987, but that's it). Perhaps if people dig up better sources on this they can fix up that citation... --Mr.98 (talk) 04:28, 22 February 2010 (UTC)

There used to be a claim that more people are born in August/September due to the holiday season. While that may have been the case 50+ years ago, it hasn't been so in recent times. The reason that I've heard is simple birth control. People can have all the holiday sex they like and not increase births 9 months later. -- kainaw™ 18:15, 22 February 2010 (UTC)

I have no empirical data to back this up (please introduce some if you have any), but I would think that contraception simply reduces births uniformly by month. That is to say, there are two classes of people: those who won't use contraception and those who will -- if the second class is having sex at the same rate per month as the first, there's no reason to suppose that the distribution of births per month changes shape. The only reason it would change is if contraception was more/less effective in certain months and/or people in one class were more/less likely to have sex in certain months than people in the other class. —Preceding unsigned comment added by 71.70.143.134 (talk) 01:16, 23 February 2010 (UTC)

(EC with above) I can believe that the variation has decreased but I'm having trouble imagining it has been eliminated. AFAIK, in most developed temperate countries, people still tend to spend more time indoors in the winter months, and more outdoors in the summer months which affect the opportunities for sex (there is of course the confounding factor that people having sex while outdoors might be more likely to fail to properly use birth control). And birth control is not 100% effective, (although the pill + proper use of condoms comes close) and plenty of pregnancies remain relatively unplanned.

And even if a pregnancy is planned, they don't generally happen overnight and so the number of times you're having sex is going to affect the chance of getting pregnant and there's likely to be some variation even when a couple is trying of the sex rates. Furthermore, it's easily possible people would be more likely to plan a pregnancy when they're stuck in doors in the winter months.

In any case, I'm sceptical there is a universal trend for August/September being the highest even if we only consider temperate Western countries, southern hemisphere countries for example would likely have different trends.

But anyway this sounds the sort of thing that should be easy to verify, in fact I'm pretty sure there's been some discussion on the RD before and in any case I don't like to make unreferenced claims. [1] [2] both include statistics from the 80-90s or so (okay the second one is Saudi Arabia so perhaps not the example we were thinking of). [3] [4] both of which require subscription includes stats for the parts of Europe, Japan and US+Canada and the second link Switzerland; for the 80-90s or so. They also provide some details of the changes (see later). [5] is from 1996 I think and says the trend exists although doesn't provide any figures for recent years. [6] [7] [8] [9] provide statistics for Italy (last one, requires subscription) and the US for the 2000s (the third one requires subscription).

All of these support the continued existance of seasonal or monthly variation. The two I mentioned that describe the changes (others may as well, I didn't always read them that carefully) are of particular interest.

The general one goes into depth about theories and also mentions how the the seasonal variation in Europe has changed to match the US variation. One proposal they mention is because there used to be a difference in how much time people spend away from home for work in US vs Europe but this isn't so much the case now which highlights another social factor. And when it comes to festivals, people who are semi-seperated may get back together for the festivals with pregnancy resulting (a rather unfortunate thing IMHO fit the couple remains unhappy or break up). It has some other interesting stuff, e.g. it isn't just social factors but temperature likely plays a role in fertility (not really that surprising) in tropical countries the cooler months and in temperate countries the warmer months because an ideal monthly average may be around 20°C. Temperate countries with particularly warm summer months have associated dips. And air conditioning may have reduced the effect of temperature.

Oh and yes, southern hemisphere countries have peaks in different months.

The Switzerland one shows yes the variation has decreased in Switzerland (although interesting enough it also increased from the 19th century until about the mid 20th century). Note that both of these make comments on the different relationships resulting in pregnancy as well.

Incidentally [10] may be interesting to those who want to learn more about the seasonal variation in fertility (this one concerns semen quality).

Nil Einne (talk) 01:30, 23 February 2010 (UTC)

Salt in the Great Lakes

If all of the Great Lakes are connected to the the ocean, then why don't they have a massive amount of salt in them? JackSlice^Talk _Adds 05:21, 22 February 2010 (UTC)

They are all fresh water lakes, significantly above sea level. All are fed by freshwater rivers/streams. They are drained via Lake Ontario by the St. Lawrence River.-- Flyguy649 ^talk 05:25, 22 February 2010 (UTC)

Thank you very much. JackSlice^Talk _Adds 05:30, 22 February 2010 (UTC)

Great Salt Lake and other terminal lakes accumulate salts because they have no outlet streams (their water leaves mainly through evaporation leaving behind their dissolved mineral load.) Rmhermen (talk) 17:23, 22 February 2010 (UTC)

The bottom of the channel between Lake Ontario, the closest to the ocean, and the St. Lawrence river is about 40 metres above sea level so the salt doesn't get across. ~AH1^(TCU) 01:07, 23 February 2010 (UTC)

When the water and other fluids in comets evaporate, do they become hollow asteroids?

Friends and I were trying to understand the implications of Comet#Debate over comet composition and the question came up about whether a comet with a near-sun orbit would eventually gas out entirely and become the rock and dust crust alone. Would it then be a hollow asteroid?

Are partially evaporated comets likely to be partially hollow?

Googling on "hollow asteroid" and "hollow comet" are almost entirely science fiction and space game hits. Thank you! 99.191.75.124 (talk) 06:27, 22 February 2010 (UTC)

Far as I've understood the literature, we think of comets as "dirty snowballs". That is, a mix of ice and rock. So from that the comets would become loose piles of rubble rather than hollow asteroids. Remember that for the rock in the comet to fuse into an compact asteroid with holes, you'd need a certain temperature. That heat would presumable cause the ice to melt away.

That said, I think that what evaporates from the "dirty snowball" is dirty water. In which case the comet gets smaller and smaller and evaporates completely, perhaps with the loose rubble disintegrating. Googling melting or disintegrating comets might turn up some good sources. EverGreg (talk) 08:53, 22 February 2010 (UTC)

Comet tail has a nice illustration of the fact that the evaporated water and the dust form separate tails (either in front or behind the comet) - so it's pretty clear that the dust is being transported from the surface as well as the ice. The answer probably comes down to whether the comet is made up of large rocks or very small pieces - but I think it's clear that the answer is always either a loose rubble pile or there is nothing whatever left at the end. SteveBaker (talk) 13:45, 22 February 2010 (UTC)

On the contrary, Deep Impact (space mission)#Results states, "The only models of cometary structure astronomers could positively rule out were the very porous models which had comets as loose aggregates of material." That probe and others have shown comets as having a rocky crust with craters (unlikely to persist in loose gravel or dusty snowballs undergoing melting and refreezing), outflowing jets of water and dust -- perhaps from heated fluid pressure internal to the rocky crust expelling the material like a geyser? -- and there is evidence that their "rock dust closely resembles material from bodies called chondritic meteorites from asteroids in the asteroid belt," which all imply the possibility of a much more solid rocky crust than small pieces of rubble. See also Extinct comet. The huge blast but lack of a substantial crater from the Tunguska event may be explained by the impact of a large but hollow object. Is there any evidence that comets and some asteroids are not composed of rocky shell crusts with hollow interiors? 99.191.75.124 (talk) 19:29, 23 February 2010 (UTC)

Hollow suggests something with large empty spaces. If you take a mixture of water and rock (such as an aquifer), and then remove the water, what you usually end up with is porous rock, i.e. rock with tons of microscopic empty spaces. I would assume that if you remove the ice from a comet, that you are more likely to see something similar, with tons of microscopic voids but very few large openings. If a comet starts with a roughly uniform mixture of ice and rock, there is no obvious reason to assume the outer layers would have greater structural integrity than the interior. Hence there is no reason to assume that the rocks in the interior are more likely to collapse together to leave a void than the outer hull would be to collapse inward and fill that void. Dragons flight (talk) 19:54, 23 February 2010 (UTC)

Why aren't we excavating more comets to find out? 99.191.75.124 (talk) 13:25, 24 February 2010 (UTC)

Insulin secretion in healthy adults per 24 hours

How much insulin, in international units (IU), is secreted during a 24 hour period in healty (non diabetic, non insulin resistant) adults?
(And how do one measure it?)
--Seren-dipper (talk) 06:58, 22 February 2010 (UTC)

Insulin dosage for a type 1 diabetic is roughly 1 IU/kilogram body weight/day. It varies between individuals and for the same individual between different days due to physical activity, infections etc. but it gives an indication of the body's need for insulin and hence insulin production.Sjö (talk) 12:30, 22 February 2010 (UTC)

That was useful, thank you! (Do you have a reference. So I can back up the allegation?)
Hmm, an indication maybe yes, but then again maybe not. I can imagine that, to some degree, a kind of insulin resistance might be present in all diabetics. Thus, the total, per 24 hour, insulin secreted could be significantly less for a healthy non-insulin-dependent, non-diabetic, compared to the 24 hour need for a diabetic.
So my question still stands.
--Seren-dipper (talk) 20:09, 22 February 2010 (UTC)

The secretion of insulin is a response mechanism, largely (though not solely) dependent on blood-glucose levels. As blood-glucose levels are largely dependent on what a person has (or hasn't) eaten, insulin production will vary fairly widely from hour to hour and day to day. See [here] for more information. A carbohydrate-rich diet will cause fairly high levels of insulin production in a non-diabetic, for example. Bielle (talk) 20:24, 22 February 2010 (UTC)

A little googling found me this link. If you look under Treatment Strategies you will find that it gives a figure of 0.5 to 1.0 unit per kg per day, so I was off a little. Since insulin production also depends on how much carbohydrates you eat, and most diabetics hold back somewhat on the carbohydrates, a healthy person might need a little more than that. As far as I know there is no insulin resistance in most type 1 diabetics because the primary cause is the lack of insulin production, not insulin resistance. Sjö (talk) 08:27, 23 February 2010 (UTC)

Than you! (Both Bielle and Sjö). The links you gave me are very helpful. :-)
I have not looked at your answers before today, but a late ‘thank you’ is much better than none at all, so again: Thank you!
--Seren-dipper (talk) 17:46, 11 April 2010 (UTC)

Uranus change in Orbit

How would the strucuture of Uranus change if it migrated into the habitable zone and stayed there for a couple hundred million years? TheFutureAwaits (talk) 09:34, 22 February 2010 (UTC)

That would depend largely on whether the inner planets are still there or not. If they are, the interactions with them would be highly significant. Ignoring that, the increased temperature and solar wind would strip the planet's atmosphere of some of its hydrogen and helium (I'm not sure how much of it) and the weather would probably get more violent (since there is more energy available). I'm not sure what else would change. --Tango (talk) 16:26, 22 February 2010 (UTC)

I guess more what I'm asking is would water form on it's surface? Does it have the necessary components for life but it's just too cold to work for the moment? You can assume the other planets don't interact with it. TheFutureAwaits (talk) 17:54, 22 February 2010 (UTC)

Did you look at Uranus? From the article: "water clouds are hypothesised to lie in the pressure range of 50 to 100 bar (5 to 10 MPa)". Also from the article: "The abundances of less volatile compounds such as ammonia, water and hydrogen sulfide in the deep atmosphere are poorly known. However they are probably also higher than solar values." Also also from the article: "The abundance ratio of water is around 7 × 10–9." -- kainaw™ 18:01, 22 February 2010 (UTC)

Only Uranus' outer atmosphere is cold, its "surface" is frozen due to pressure rather than cold. If enough of the atmosphere is stripped off the pressure might get low enough for liquid water to form, I don't really know. --Tango (talk) 18:10, 22 February 2010 (UTC)

Human Survival to Exposure

How long could a person survive (with and without injury) to a sudden exposure to each of the planets' surfaces? TheFutureAwaits (talk) 09:35, 22 February 2010 (UTC)

Some planets don't necessarily have what you'd call a "surface", just a gradient of gradually thicker and thicker gases. You'd have to define surface for those. Certainly, for the bigger gas giants, any human would be instantly crushed by the pressure if they were deep enough to be on a solid surface. I don't think Uranus or Neptune have such a surface, though I'm not certain. Vimescarrot (talk) 10:53, 22 February 2010 (UTC)

(edit conflict) Assuming you mean "exposure without any sort of environment suit or breathing apparatus", then

• Mercury - instant death due to heat (light side) or cold (dark side). Pick just the right intermediate spot near the terminator and it may be survivable for, say, 30 seconds before the near-vacuum kills you.
• Venus - instant death due to heat (hotter than Mercury) and pressure (>90 atmospheres).
• Mars - maybe survivable for a minute or two (but don't try this at home, folks !).
• Jupiter, Saturn, Uranus, Neptune - as per Vimescarrot, depends on how you define "surface" for a gas giant, but probably instant death due to pressure/heat.
• Pluto (let's call it a planet for the purposes of this question) - instant death due to cold - max surface temperature colder than liquid nitrogen. Gandalf61 (talk) 11:08, 22 February 2010 (UTC)

So if I wanted to impress my friends on Mars I could hop out of the airlock, run around for 30 seconds, come back in and have a good laugh? TheFutureAwaits (talk) 11:31, 22 February 2010 (UTC)

No, you would likely stagger out of the airlock, being careful not to hold your breath to avoid rupturing your lungs, collapse in agony due to decompression sickness, lose conciousness in 10-20 seconds, and hope that someone drags you back inside and repressurises the airlock before you finally die from hypoxia - see our article on space exposure. Gandalf61 (talk) 11:58, 22 February 2010 (UTC)

Impress them with your silliness perhaps! The pressure gradient is not all that high, but I wonder if Decompression sickness might still be possible? Pressure_suit#Exposure_to_space_without_a_spacesuit may be of interest, as it suggests that very tight fitting 'clothing' makes a big difference. See also Space_activity_suit--220.101.28.25 (talk) 12:10, 22 February 2010 (UTC)

(EC) You included pluto but forgot the third planet from the sun??? Nil Einne (talk) 12:11, 22 February 2010 (UTC)

A sudden exposure to the surface of this planet - depending on the height you'd been dropped from - would result in more or less instant death!--TammyMoet (talk) 12:42, 22 February 2010 (UTC)

Depending on where you arrived, a sudden exposure to the surface of this planet could easily result in death by drowning (in minutes or hours depending on how well you swim) or hypothermia (also in minutes or hours, but depending more on the place). In other places you might die by dehydration (in a few days) or possibly by starvation (in a few weeks) or being eaten (after a variable length of time). --Anonymous, edited 20:23 UTC, February 22, 2010.

Hmm, so are there ANY feats of daring do I could complete on Mars to impress the crowds?TheFutureAwaits (talk) 12:46, 22 February 2010 (UTC)

Just getting there would impress the heck out of me! SteveBaker (talk) 13:39, 22 February 2010 (UTC)

Obligatory xkcd link. Land on Deimos instead, then use a bike and a ramp to launch yourself to Mars. (I get the feeling this wouldn't work, but I've no idea why not...) Vimescarrot (talk) 14:26, 22 February 2010 (UTC)

You could get yourself clear of Deimos, but Deimos is pretty solidly in Mars orbit. You'd have a hard time getting enough of a velocity change to leave Mars orbit (instead, you'd just orbit roughly in parallel with Deimos). — Lomn 15:06, 22 February 2010 (UTC)

Indeed. Deimos's average orbital speed is 1.35 km/s - I can't see a bike getting up to those speeds. You would just gradually drift away from Deimos while staying in roughly the same orbit. --Tango (talk) 16:29, 22 February 2010 (UTC)

• Sorry, that's wrong. Consider that manned space missions leaving Earth orbit to return to the surface don't use retrorockets big enough to cancel 18,000 mph (um, 8 km/s) of orbital velocity -- they just use ones big enough dip the orbital perigee into the atmosphere, and aerobraking does the rest. Mars has much less atmosphere than Earth, but there is enough for aerobraking. However, I don't know how low you'd need to make the perigee for it to work with Mars, so I don't know what the true speed you'd need to launch from Deimos is. I am sure it's beyond bicycling range, though! And without that critical speed, you would indeed just end up in similar orbit to Deimos. --Anonymous, edited 22:38 UTC, February 22, 2010.

Could you survive on Mars if you had a breathing apparatus (Say like a diving mask) on a warmer Mars day? I think it does sometimes get up to 20C in places. Googlemeister (talk) 19:33, 22 February 2010 (UTC)

No. The air pressure is far too low. The air you're breathing has to be roughly the same pressure as the air pressing on the outside of your body. (Otherwise you won't be strong enough to exhale and besides you run the risk of puncturing your lungs when you inhale.) APL (talk) 19:55, 22 February 2010 (UTC)

How is it different then a diver at 10m below the surface? Googlemeister (talk) 21:16, 22 February 2010 (UTC)

Our Pressure article has the line "Scuba divers often use a manometric rule of thumb: the pressure exerted by ten meters depth of water is approximately equal to one atmosphere." So 10 metres would be presumably double the pressure, two atmospheres. The surface of Mars is a lot less than half the pressure. Plus, it's lower pressure, rather than higher pressure, which would presumably be different. That said, I don't actually know the answer. Vimescarrot (talk) 22:05, 22 February 2010 (UTC)

Good point, probably be closer to breathing air out of a car tire. Seen that done in movies, but never heard about the feasibility of doing that in reality. Googlemeister (talk) 22:18, 22 February 2010 (UTC)

Myth busted. Clarityfiend (talk) 02:05, 23 February 2010 (UTC)

The issue isn't the pressure, but the difference in pressure. Scuba divers breath air at a pressure equal to the pressure of the water (that is why deep divers need to breath different air mixtures - there are more molecules of air per breath than usual). You can't do that on Mars because even at 100% oxygen the air pressure is far too low to have enough molecules of oxygen in it. That means you would need to breath pressurised air, which is very difficult - your lungs would basically explode. You would need a full pressure suit - not necessarily inflated, the pressure could be provided by some skin tight elastic material a bit like a wet suit (although probably made out of different material). During the day on the equator the temperature would probably be such that we could survive without any kind of heating or cooling, although we might be a little uncomfortable. The lack of air means there would be very little conduction of heat, so keeping warm wouldn't be too hard. Astronauts in space suits usually have more difficulty keeping cool than warm when in Earth orbit or on the Moon, and that wouldn't be too hard on Mars (since it is further from the Sun). --Tango (talk) 22:35, 22 February 2010 (UTC)

I don't think that "Instant Death from cold" is the right answer for Pluto or the Dark Side of Mercury. It may be unbearably cold, but in total vacuum and wearing good shoes, there'd be nothing to conduct your body heat away. I think you'd get your full thirty seconds of agonizing depressurization death. APL (talk) 19:59, 22 February 2010 (UTC)

As I learned from answering my question above, the amount of thermal energy we lose via radiation vastly outstrips how much we lose via conduction -- at room temperature it's about 10 times higher (for someone who is naked and fully erect (no, the other erect)), and this would only get larger as the temperature differential increases. You'd be losing about 1Kw on Pluto, but I don't know how to convert that into how long it takes for you to die.

Yes, but the point is that the 0.3 Pa atmospheric pressure on Pluto is ~300 time less dense than here on Earth - it's a pretty good vacuum. So there is no practical difference between the heat you'd lose on Pluto versus what you'd lose in deep space...and we can be 100% sure that the vacuum will kill you long before the heat loss. But good shoes would certainly be an essential accessory for any putative unprotected sightseers who wish to avoid the misery of cold tootsies while gasping their last breath. SteveBaker (talk) 14:13, 23 February 2010 (UTC)

Atmospheric pressure on Earch is about 100 kilo-pascals, which means that Earth has about 300,000 times the atmospheric pressure as Pluto (not merely 300). Mars, on the other hand, has an atmosphere of about 1 kPa, which means we're used to "only" 100 times the pressure as we'd find on Mars. To a human, both Mars and Pluto are essentially vacuums, even though the pressures between the two differ by three orders of magnitude. Buddy431 (talk) 22:00, 23 February 2010 (UTC)

I cite the scientific source, Total Recall, in stating that survival on Mars is possible for a short period, but ultimately, jelly face syndrome sets in and kills you, unless you're fortunate enough that someone has set in process an ancient alien technology that restores atmosphere. Then, the jelly face syndrome is stopped and reversed. --Dweller (talk) 12:36, 23 February 2010 (UTC)

Pipes

What is the difference between schedule 40 and schedule80 pipes? —Preceding unsigned comment added by Rohanpradhan21 (talk • contribs) 11:40, 22 February 2010 (UTC)

Nominal Pipe Size has a table showing the differences - but essentially, the higher the schedule number, the thicker the walls of the pipe. Hence, for example, for a 2" (DN 50mm) pipe the schedule 40 has 0.154 in (3.912 mm) thick walls while the schedule 80 has 0.218 in (5.537 mm). This allows schedule 80 to support higher pressures and to generally be more robust. SteveBaker (talk) 13:36, 22 February 2010 (UTC)

Chemical differences between E150a, E150b, E150c, and E150d.

Why do they have different E numbers please? 84.13.16.216 (talk) 12:46, 22 February 2010 (UTC)

Because there are differences in the way they are prepared - and hence in chemical composition. SteveBaker (talk) 13:31, 22 February 2010 (UTC)

See Caramel color#Classification for more detail. hydnjo (talk) 15:09, 22 February 2010 (UTC)

It was that article that prompted the question! Do they have a different chemical formula? Are there different chemicals mixed in with them as a result of how they are made? 89.243.87.3 (talk) 19:00, 22 February 2010 (UTC)

Unfortunately caramelization yields a large number of different chemical compounds - here is an overview. Icek (talk) 00:06, 23 February 2010 (UTC)

L-DOPA is less water-soluble than dopamine?

OK, why does adding a charged group like a COOH group on a water-soluble compound like dopamine end up reducing the solubility? I understand the whole molecule might become zwitterionic, but they carry two formal positive charges which would seem to increase the water solubility. Is it solvent effects and things like water-cage effects? I mean surely the extra charge would make it less soluble in things like ether. John Riemann Soong (talk) 17:37, 22 February 2010 (UTC)

The solubility of L-DOPA is not in our article...got a value (with cite) for it? I can't visualize a +2 zwitterionic form for that compound...what are you actually talking about? DMacks (talk) 16:41, 23 February 2010 (UTC)

It's commonly known that L-DOPA will pass through the blood-brain barrier but dopamine will not. Hence, L-DOPA is prescribed for the treatment of Parkinson's and not dopamine. I should also have said "two formal charges", e.g. +/-. John Riemann Soong (talk) 22:23, 23 February 2010 (UTC)

So you are saying it's confusing that "because L-DOPA has more charges (even though they are balanced, for net zero charge), it appears to become less soluble (what solvent?) as seen from its inability to pass through the blood-brain barrier."? Each parenthetical is something you should consider, and also read what properties make something able to cross that barrier. There is at least one fundamental and fatal flaw in your reasoning. DMacks (talk) 22:45, 23 February 2010 (UTC)

Shouldn't the additional polar group make it even more difficult for it to pass from a water layer to a lipid layer? Or is the RCOO- group able to bind to the RNH3+ via a five-membered ring and therefore increase its overall fat solubility?

So it makes me think it's a question of structure. if the RCOO- group were somewhere else and it could not directly bind the RNH3+ group via an intramolecular ring, would it risk in fact, making it even harder to pass through the blood-brain barrier? John Riemann Soong (talk) 01:06, 24 February 2010 (UTC)

I don't know why DMacks is being a dick; L-dopa passes the BBB because it can utilise a amino acid transporter complex (4F2hc/LAT1) [11], where as dopamine doesn't have a transporter. I believe it is a similar scenario with L-tryptophan and 5-hydroxytryptophan vs. serotonin. --Mark PEA (talk) 14:51, 24 February 2010 (UTC)

Human Survival to Exposure (on Earth)

Induced by the question above I would like to ask a question that troubles my mind every now and then: how did ice age people survive? Could we nowadays average people at least survive the cold? 95.112.177.38 (talk) 18:07, 22 February 2010 (UTC)

Ice age people survived by use of clothing, Shelter and fire. Dauto (talk) 18:18, 22 February 2010 (UTC)

People didn't live on top of glaciers, and the globe was not covered by ice. You might want to start with Paleolithic#Paleogeography_and_climate. BrainyBabe (talk) 18:33, 22 February 2010 (UTC)

The ice age Earth was only 3 C (5 F) colder than today on average, and that was primarily due to changes at high latitudes. If one lived in the tropics it would be little different than today and you'd still worry about surviving the heat rather than the cold. Dragons flight (talk) 18:36, 22 February 2010 (UTC)

Right. It's worth remembering that Ardipithecus Ramidus and their descendents (who eventually became Homo sapiens, perhaps elsewhere) lived in a small region of Ethiopia near Aramis for a couple MILLION years ... I suspect there were a few ice ages in the interim. 63.17.79.127 (talk) 03:24, 23 February 2010 (UTC)

Looking at the map in the Inuit article, this culture increased their habitation of Greenland to cover most of the coast between AD 1300 and AD 1500. Presumably they had something resembling Stone Age technology, and presumably they were not "physically" different form people in sedentary cultures like modern-day Western countries. It follows that they survived in the same way as modern people do - by technology and adaption. That said, mortality in the Ice Age in the cold climates (and elsewhere) is likely to have been much, much higher than today, so for parts of the population, the answer to your question is "they didn't". Jørgen (talk) 20:07, 22 February 2010 (UTC)

That picture from the temperature record article seems to indicate a temperature difference of a about 8 C. Dauto (talk) 20:23, 22 February 2010 (UTC)

Both those records are local temperature changes at those specific high-latitude locations. Dragons flight (talk) 02:01, 23 February 2010 (UTC)

Nuh-uh. The ice cores contain information about the temperature at the place where the water evaporated which ca be thousands of miles away from those places. Dauto (talk) 04:21, 23 February 2010 (UTC)

Actually it is both, water is mass fractionated during evaporation, during transport, and again during condensation to form the snow, which is why temperature reconstructions often use both the deuterium and heavy oxygen isotopic systems to deconvolve the temperature variation at the source region from temperature variation at the precipitation region. Not to mention that the bulk isotopic composition of the ocean changes independent of temperature during the ice ages. These points aside, the temperatures reported in those records are calculated to isolate quasi-local variations, reflecting the precipitation site rather than the source region. That's part of the point. Given that both sea level and circulation pattern changes can effect the location of the source region, you want to isolate the precipitation site effects as best you can as those are more likely to be a useful history of climate change. Sometimes people also try to report the apparent temperature change at the source regions. Anyway, the details aren't relevant to the original poster, but those records are definitely quasi-local / semi-regional and not global. Dragons flight (talk) 05:49, 23 February 2010 (UTC)

Thanks for the info. I thought they did exactly the oposite and tryed to isolate the variation due to the source and that way get information from a wider area. Dauto (talk) 05:49, 24 February 2010 (UTC)

Consider that people today can live in rather frigid conditions—the Inuit, for one extreme case, and those who live in the Russian tundra for another. Humans can certainly adapt to such a temperature drop. It is not pleasant and probably supports certain social arrangements better than others, but it is possible, just as there are humans who manage to adapt to living in desert conditions as well. It does not mean that if the existing world changed to one or the other, that there wouldn't be massive problems with growing food and other such things. Rapid change is extremely dangerous for any species. --Mr.98 (talk) 04:20, 23 February 2010 (UTC)

Some of those Russian tundra dwellers you mention are Inuit. Rmhermen (talk) 14:32, 23 February 2010 (UTC)

Did they move there recently? There's no history of Inuit people living in the Russian tundra - are you thinking of the Yupik? Warofdreams talk 16:59, 23 February 2010 (UTC)

Thai (?) translation request

Hi Refdeskers, I got this t-shirt at a thrift store and am wondering what the logo says. I assume it's in Thai, but my ignorance in this area is both deep and broad. Thanks. --Sean 19:02, 22 February 2010 (UTC)

I'm afraid you forgot to post a link to the logo. I'd also recommend you post this to the Language Desk instead of the Science Desk, unless the Thai logo appears to be a chemical or nuclear decay formula. Comet Tuttle (talk) 19:23, 22 February 2010 (UTC)

There is a perfectly logical reason that I posted my request with the various characteristics you note: I am stupid. Trying again over here. --Sean 16:00, 23 February 2010 (UTC)

Egg Whites

Egg Whites

I've been trying to find out about the protein that contains egg whites in it, i did a research and came to find out that by consuming to many raw egg whites can lead to Biotin Deficiency. Egg whites from what a read here at Wikipedia contains high leves of AVIDIN, a protein that binds the vitamin biotin strongly. Now if we cook the egg whites by normal boiling in water, does the protein in the egg whites has the same effects in the human body campare as when consumed raw?71.52.59.50 (talk) 21:01, 22 February 2010 (UTC)

See Egg white, avidin, and Denaturation (biochemistry). In short, boiling the egg in water denatures the avidin protein, thus avoiding the biotin-sequestering effects of eating the raw egg white. --- Medical geneticist (talk) 00:03, 23 February 2010 (UTC)

Supervised and Unsupervised Learning

Sorry to post this here. I posted it at the computing reference desk, but it's been ignored. We should relabel the computing reference desk as the "My internet and/or home computer isn't working problem desk". I was reading the supervised learning article. At the end of the overview section it says that the Gaussian Mixture Model is one of the most commonly used classifiers. But the Gaussian Mixture Model article says that a mixture model can be regarded as a type of unsupervised learning. Can something be regarded as both supervised and unsupervised learning (as these links seem to show), or are they mutually exclusive (as I was beginning to believe)? •• Fly by Night (talk) 21:42, 22 February 2010 (UTC)

You should try being more patient and less rude. The Computing Desk is filled with some really smart dudes & dudettes. Duration before receiving an answer to your question depends largely on difficulty x GMT time it was asked. 61.189.63.173 (talk) 21:58, 22 February 2010 (UTC)

If in a hurry, ask at midnight for instant response. 71.70.143.134 (talk)

In any case, expect more than an hour for a good response if it is a specialized question. In this case, it seems to have taken a mere 2 hours for someone to give a fairly informed-looking response. Which is pretty incredible if you think about it — how many people out there can give a good response of something like this, how many of them are on the ref desk, how many of them happen to be looking at your question during the 2 hour window you have given them before getting frustrating. But if you complain about people not marching in to do work for you (for free), don't be surprised if people aren't eager to do it for you in the future. --Mr.98 (talk) 22:52, 22 February 2010 (UTC)

Easy questions can be answered by almost anyone - so you get your answer back quickly if you ask questions that boil down to "Reinstall windows and reboot - or install Linux" - but difficult questions (which this one undoubtedly is) require both the services of that rare expert who can understand your question (I know a lot about computers - and I can't answer it) and who has the time to research it - and it also takes that respondant more time to come up with an answer. So for tough questions you may well have to wait one or even several days. It says as much at the top of each of the reference desk pages:

When will I get an answer?

• It may take several days. Come back later and check this page for responses. Later posts may add more information. Please, post your question on only one section of the reference desk.

Anyway, it looks like the good people at the Computing ref desk (specifically: User:87.102.67.84) came through with a reasonable answer in pretty amazingly good time - I think you should thank them and apologize. SteveBaker (talk) 14:02, 23 February 2010 (UTC)

February 23

Material in Servo Motor Winding?

Sir/Ma'am

I am looking for the material used in servo motor coil winding. Thanks

• Copper? Noodle snacks (talk) 07:16, 23 February 2010 (UTC)

And insulator (electrical). Icek (talk) 11:01, 23 February 2010 (UTC)

All these: enameled copper wire, Solder, Insulator (electrical), see Electric motor#Servo motor Cuddlyable3 (talk) 14:54, 23 February 2010 (UTC)

Making tea with zingless water

If I boil water in order to make some tea, then get sidetracked for 30 minutes before I've poured it, I have 2 choices:

• reboil the by now tepid water and then use it
• start again with a fresh batch of cold water.

But I've always been told NOT to reboil the water, as it's lost its "zing" through the initial boiling. Always start from scratch with new water, is what I've been told to do.

For starters, how true is it about the "zing" thing? If it's true, doesn't that mean that no cup of tea ever has any "zing", because all tea uses boiled water, and boiled water is, according to this theory, zingless?

Assuming that it's true: Does it ever regain its "zing" by somehow reabsorbing oxygen from the atmosphere, and if so, how long does it take? -- Jack of Oz ... speak! ... 10:49, 23 February 2010 (UTC)

Personally I doubt all this very much. I'm in the habit of filling a kettle first thing in the morning, boiling it, and reboiling it for the subsequent cups of the day, and never notice any difference in the flavour of the tea whatever. Old wives tale if you ask me. --TammyMoet (talk) 11:36, 23 February 2010 (UTC)

Not that it's pertinent to my question, Tammy, but doesn't your practice mean that you're always boiling more water than you need (until you get down to the last cup/potful in the kettle), and thus wasting both time and electricity? and money? -- Jack of Oz ... speak! ... 20:24, 23 February 2010 (UTC)

Might be something to do with boiling away impurities? We have quite hard water here with lots of lime in it, and other things, and boiled then cooled water does taste different than water straight out of the tap. Gunrun (talk) 11:59, 23 February 2010 (UTC)

Lime and other minerals don't get boiled away. They are what's left after the water boils away. Possibly you could boil away the chlorine and byproducts if your water is treated with such. But the usually mentioned difference is oxygen (not that I know if there is any truth to oxygen changing the taste.) Rmhermen (talk) 14:29, 23 February 2010 (UTC)

Interesting. Health advice for parents of young children drinking baby formula in the UK commonly includes the advice to boil the water once only before using it to make up formula. I've often wondered what it is that they're worried about in reboiling. --Dweller (talk) 12:31, 23 February 2010 (UTC)

I was told that the more the water boils, the more oxygen it loses, and the flavour of the tea depends on interaction with that oxygen. However, I haven't been able to find a reliable source for that.--Shantavira|^{feed me} 13:47, 23 February 2010 (UTC)

@Dweller - I think there's either some miscommunication or a bit of social engineering going on. The worry with formula is that parents will boil the formula, which breaks down some of the nutrients. Liquid formula should be heated by placing it in an indirect heat source like a pot of heated water rather than in a microwave or on a stove top. With dried formula, I think the concern is that parents will do up a large batch (properly) and then directly reheat the formula as needed through the day, causing the same problem. If you were to essentially do the operation "in parallel" (mix formula and multiple-times re-heated water in a cup as needed, rather than re-using a pot of re-hydrated formula "in series") there would be no problem. Matt Deres (talk) 15:30, 23 February 2010 (UTC)

We had these permanent, continuous boiling water urns at our office which just automatically topped the water up as you used it and kept it relatively close to boiling all the time. Never heard anyone complain about lack of zing. They were never turned off, so in the morning you'd be drinking water that has been boiled several times over night. As far as I have seen those kind of urns are not uncommon. If that means anything.. Vespine (talk) 01:11, 24 February 2010 (UTC)

As far as I know, there are two things one might worry about regarding reboiling of water for drinking. Both has to do with potentially harmful trace amounts of pollutants:

1. Plain tap water is far from chemically pure. Many of the pollutants in it, have a boiling point higher than the H₂O (pure water). Therefore: The longer total time you boil polluted tap water, and the longer total time you keep it steaming hot, then the higher concentration of pollutants you get. (Because some of the water evaporates while pollutants remains in your boiling pot).
2. Hot water dissolves pollutants far more easily than cold water does, and the longer time hot or boiling water stays in direct contact with a material the more of the material will be dissolved. Something from the plastic or metal (alloy) in your boiling pot is quite likely to give off trace amounts to your water. And that may bee something that you would be better off not swallowing to much of in the long run.

One such cup of tea will not kill you, but some people find it to be worth the effort, in the long run, to make it a habbit not to reboil water for consumption.
For many people, this above explanation is far to tiring. The "Zing"-explanation is much quicker and since many people actually do keep on doing what their knowledgeable (great great) grandmother once stated was the right thing to do, then the zing explanation may be the best one after all.
--Seren-dipper (talk) 04:43, 24 February 2010 (UTC)

That makes a fair amount of sense, Seren-dipper. -- Jack of Oz ... speak! ... 12:52, 24 February 2010 (UTC)

I don't have specific scientific evidence but I buy into the theory that brewing good tasting tea requires oxidation, and if the water sits stagnant for too long (such as during successive boilings) it will lose it's oxygen content and the resulting tea will not have as much flavor. Other brewed beverages such as coffee rely on similar processes, however it is up to the raw material (The tea or coffee used) to be susceptible to oxidation during brewing in the first place, so not all teas/coffees will show a change in flavor by changing the oxygen content of the water. --144.191.148.3 (talk) 14:38, 24 February 2010 (UTC)

I've been unable to find the solubility of oxygen in water at temperatures above 50 degrees C. But I feel that since oxygen redissolves quite quickly in water; and convection currents mixing the surface layes would make equilibrium happen even faster. If someone thinks there is a difference in tea flavour due to oxygen concentration they can put a lid on the cup or put immediately after pouring and see what changes. Polypipe Wrangler (talk) 12:51, 28 February 2010 (UTC)

Ice on car Windscreens.

Its cold in the UK and I find ice forming on my car windscreen but not on any other windows of my car. I looked at other cars as I was driving to work and this seems to be the case on most of them. Why is the ice only forming on the windscreen and not on the other windows? --Cipher-xs (talk) 11:33, 23 February 2010 (UTC)

The windscreen usually is the window facing more empty sky than the other windows. The sky serves as an infrared radiation sink. The other windows's loss of heat by radiation is compensated by reception of infrared from the surroundings. Note that this only happens on cloudless, still nights, as clouds radiate back, and wind tends to enhance the heat loss compensation by convection. DVdm (talk) 11:39, 23 February 2010 (UTC)

Is there not also a precipitation of water from the air, which tends to fall and thus coats glass in proportion to the surface it presents when seen in plan view? --Tagishsimon (talk) 12:26, 23 February 2010 (UTC)

Probably, yes. Hadn't thought of that one. DVdm (talk) 12:59, 23 February 2010 (UTC)

There are at least two types of ice commonly called frost. The first is the kind described in the frost article (which itself is two types - convective and radiative), the second is (sadly a redlink) what I have heard called frozen dew. The first is where a surface gets cold enough to freeze water out of the air, the second is where a dew forms and then the temperature drops enough to freeze it. In the first case your windscreen cops the worst of it because it faces the cold sky (as DVdm said). In the second your windscreen cops the worst of it, but rooves, boots (trunks) and bonnets (hoods) also get a pretty white coat --Polysylabic Pseudonym (talk) 08:07, 26 February 2010 (UTC).

Orbits

I know that most of(Pluto isn't a planet anymore I forgot) the planets in our solar system orbit on the same plain, and orbit in the same direction, because of how our solarsystem was formed or something? Anyway not my question. My question is would this happen naturally anyway? My friend says that if we were to introduce a new planet to the system it would eventually level into the same plane as the other planets, regardless of where you placed it (Obviously giving it enough velocity to orbit the sun), whereas I can't see why it would. Why couldn't a planet orbit the sun at a 90 degree angle to everything else. Also is there any reason why a planet couldn't orbit in the opposite direction of the other planets? Gunrun (talk) 11:57, 23 February 2010 (UTC)

He might be thinking of Accretion disc where a circular cloud form into a pancake-flat disk by conservation of angular momentum when some material fall into the center and become the star. This explains why all "original" planets orbit in the same direction, they were formed from the same pancake.

I can't see how what your friend proposes could happen for a new planet at a steep angle to the rest. But the conservation of angular momentum means that if the new planet gradually "falls into place", it aquires angular momentum in the solar system and therefore other planets must loose it. At the same time, the total kinetic energy must be conserved too. I can't see how this should happen, so I'm guessing your friend is wrong. :-/ —Preceding unsigned comment added by EverGreg (talk • contribs) 12:50, 23 February 2010 (UTC)

Yeah - I think it would happen, although it would take a very long time - and Pluto has not yet done that...further evidence that it was not formed like the other large bodies in the solar system. Let's imagine an object orbiting in a plane that's (say) 30 degrees from the ecliptic - for half of each orbit it's on one side of the ecliptic, for the other half, it's on the other side. The gravitational fields of every single other body in the solar system are exerting a force on that object. The vector sum of all of those forces is overwhelmingly towards the sun (which is why the object is orbitting) - but the other planets are each creating an additional very tiny pull - which can be resolved into a net force parallel to the ecliptic and another at right angles to the ecliptic. The 'parallel' force will vary as the various planets, moons and other debris go around their orbits and seem more or less random (although dominated by wherever Jupiter happens to be). But the force at right angles to the ecliptic is ALWAYS in the direction of the ecliptic. When the object is below the ecliptic, this net force is always in the upwards direction, when it's above the ecliptic, the force is down. This means that the orbit is going to gradually be pulled around until it's in the same plane as everything else. You can see this kind of effect happening in (for example) Saturns rings. When two house-sized chunks of ice smack into each other, the fragments will scatter off in all directions - if it were not for this kind of effect, the rings would quickly break up and turn into a random spherical shell of chaotic colliding debris - but their relative gravitation forces them all into an almost perfectly flat, insanely thin disk. That's likely why galaxies are pretty flat too. SteveBaker (talk) 13:50, 23 February 2010 (UTC)

When the planet is attracted to the ecliptic, it seems that the planet would oscillate around the ecliptic, not settling into it. The sum of kinetic and potential energy for the new planet would have to be conserved after all. EverGreg (talk) 14:08, 23 February 2010 (UTC)

Well, conservation is managed because the other planets (etc) get pulled slightly towards the plane of this rogue body - so the entire plane of the ecliptic tilts slightly in reaction to this new body. However, unless the new body is utterly gigantic, that effect would probably be too small to measure. SteveBaker (talk) 21:21, 23 February 2010 (UTC)

Thanks steve,think that answers my first question pretty well. Does this mean if you had a planet orbiting in the other direction to the others (say they go clockwise this one goes counterclockwise) it would eventually get slowed down and thus move closer to the sun (Like how a space station de-orbits) presumably bringing it onto a collision course with a planet coming the other direction, or would such a planet be impossible?) Gunrun (talk) 13:57, 23 February 2010 (UTC)

Yes to this new hypothetical question that doesn't explain where the rogue planet came from. Eventually all the established planets would orbit very slightly slower but we can't predict whether the rogue planet collides with a planet before it crashes and burns in the Sun. Cuddlyable3 (talk) 14:40, 23 February 2010 (UTC)

Didn't you mean "would orbit very slightly more slowly", Cuddly? (Sorry, couldn't resist).  :) -- Jack of Oz ... speak! ... 20:35, 23 February 2010 (UTC)

So in an act of pure malice after being downgraded to a mere dwarf planet, Pluto wreaks revenge by smacking into the Earth in a few billion years? SteveBaker (talk) 21:24, 23 February 2010 (UTC)

hey, wouldn't you? heaven hath no fury like a planet scorned...--Ludwigs2 21:29, 23 February 2010 (UTC)

...a dwarf planet scorned... :-) SteveBaker (talk) 04:05, 25 February 2010 (UTC)

If it would just ditch Charon, It would be back to planet status. Googlemeister (talk) 21:42, 23 February 2010 (UTC)

freezing point

What is the freezing point of 80 proof alcoholic beverages?

Thank you.

Ken Carter

—Preceding unsigned comment added by 97.91.189.14 (talk) 15:28, 23 February 2010 (UTC) 

Sorry I can't help but I removed your email, in accordance with our guidelines and to avoid you getting spam. --TammyMoet (talk) 15:39, 23 February 2010 (UTC)

This site suggests -23 °C (-10 °F) for a 40% ethanol solution (which equals 80 proof); however this site suggests -33C for 84 proof. Vodka is essentially diluted ethanol, so it should freeze at that temperature, as will most other spirits. Other alcoholic beverages (like Southern Comfort) may contain significant amount of sugars that may affect the freezing temperature. Regardless, it won't freeze in a household freezer. -- Flyguy649 ^talk 16:53, 23 February 2010 (UTC)

One thing I have heard (and this is unsourced), is that if you start to freeze vodka, small ice crystals will begin to form. These crystals are mostly water, so if you remove them, you increase the proof. Googlemeister (talk) 17:43, 23 February 2010 (UTC)

See Fractional freezing. -- Flyguy649 ^talk 18:04, 23 February 2010 (UTC)

liver

pls can you help me to answer this question how can diesel affect the liver of a male wistar pls this is a project work —Preceding unsigned comment added by 41.204.224.39 (talk) 15:48, 23 February 2010 (UTC)

First have a look at the effects of diesel on wistar rats in general. Then as a followup, take a look at this research report, for example, which discusses other systemic effects, including the liver. You might be interested to know that Google Scholar is available to help you find specific scientific publications. I just searched for "wistar diesel liver" and found a huge quantity of interesting results. If you know what you're looking for specifically, you can narrow down the search. Nimur (talk) 16:43, 23 February 2010 (UTC)

Octanediol

What is it and what are its uses? --Reticuli88 (talk) 16:04, 23 February 2010 (UTC)

oh, is the same thing as Octane-1,8-diol? --Reticuli88 (talk) 16:05, 23 February 2010 (UTC)

"Octanediol" is a somewhat generic name. It probably has an implied meaning of one specific chemical (or group of them) in some contexts. The "1,8" is one specific chemical of this type ("diol" is "two OH groups", the "1,8" says there is one of them on each end of the chain rather than scattered along the middle). DMacks (talk) 16:34, 23 February 2010 (UTC)

Do you know which brands contain Octane-1,8-diol as descibed in the article? --Reticuli88 (talk) 16:38, 23 February 2010 (UTC)

Fisher Scientific sells many types, each specified with a full IUPAC name. They do carry 1,8-octanediol. Nimur (talk) 16:47, 23 February 2010 (UTC)

LOGIC GATES

Q1 Explain factors to be considered when constructing logic gates? Q2 Explain the positive as well as negative logic? Q3 Explain Digital Families and their characteristics? —Preceding unsigned comment added by Jyoti.prakash1507 (talk • contribs) 17:46, 23 February 2010 (UTC)

Read the article Logic gate. I have a feeling that you will also find Binary numeral system interesting. However we shall not do your homework for you. Cuddlyable3 (talk) 18:19, 23 February 2010 (UTC)

Agni III

Why does not the Agni III burn when it reenter in the atmoshphere. —Preceding unsigned comment added by 58.68.8.189 (talk) 17:49, 23 February 2010 (UTC)

I'm not sure about the Agni III in particular, but our atmospheric reentry article discusses a variety of techniques for engineering vehicles to survive reentry. -- Coneslayer (talk) 17:54, 23 February 2010 (UTC)

time dilation?

Does time really move fast near to gravitational field and slow when at far from gravitational field? I feel that though time is considered as the fourth dimension but still it is virtual in concept. So when we say that time moves fast or slow i think we take into account relative time (with respect to something) and not the absolute time. Though near Black hole time change is certain but still the absolute time(Universal Clock) has the same time. —Preceding unsigned comment added by Itsrohit (talk • contribs) 18:12, 23 February 2010 (UTC)

Yes. Time dilation is a real effect.

It has been verified with atomic clocks. See Time_dilation#Experimental_confirmation.

See also Effects_of_relativity_on_GPS

APL (talk) 18:58, 23 February 2010 (UTC)

Oh. To answer your second question : No, as far as we know there is no "universal time". Time itself runs differently for observers in different reference frames. There can be no "universal time" without an absolute reference frame, but there isn't one. See Special_relativity#Lack_of_an_absolute_reference_frame.

APL (talk) 19:02, 23 February 2010 (UTC)

(ec)Yes, the effect can be measured with real clocks, which of course don't care about theories or dimensions. Also note that there nothing virtual about time. Time is just what we read on clocks, which is the reason why a concept like absolute time is as meaningless as a concept like, say, blue time. DVdm (talk) 19:06, 23 February 2010 (UTC)

Time is a completely variable thing. Because it's affected by both the speed you're moving and the force of gravity, as I type this email, the tips of my fingers are experiencing a very slightly different rate of time flow than the rest of my body because they are moving relative to it. Time can be running at different rates at every point in the universe. It's even more weird than that. The entire concept of two events "happening at the same time" is utterly meaningless unless they are at the exact same point in space - and so is the concept of "Event A happened before Event B". We can only use those relationships because we are all moving at very close to the same speed and in roughly the same gravitational field - and the differences in the rate of flow of time on "human scales" is so microscopically small that we can't tell that we have this rather deep misunderstanding of the way that the universe operates. Even when we understand this intellectually - the "gut feel" that time stays very firmly nailed down is hard to shake. SteveBaker (talk) 20:51, 23 February 2010 (UTC)

"The future is already here - it is just unevenly distributed" - William Gibson -- Finlay McWalter • Talk 21:00, 23 February 2010 (UTC)

Don't go too far with the weirdness! "A before B" (or the reverse, as appropriate) is a perfectly valid, invariant relation for all events with timelike separation, which is quite the superset of "at the exact same point in space". You get that some observers will say (in their coordinates) "A was before B" and others "B was before A" when the separation is spacelike. --Tardis (talk) 21:21, 23 February 2010 (UTC)

Yeah - you're right that in a lot of cases it's OK to say that two events happened in a particular order - but not in all cases. Basically if the two events happen so close together time - but so far in space that light from one event has not yet had time to reach the place where the other event happens before it happens - then some observers may disagree about the order they happened in. If there is time for light to travel between them then their order is well-determined for all observers. SteveBaker (talk) 21:39, 23 February 2010 (UTC)

One of Einstein's great observations—and most controversial statements, even in his own time—was that there is no way to possibly measure absolute time and thus it doesn't actually exist. (Or, put another way, it must thus be an inherently metaphysical concept, and not part of science.) He believed in local time—as did many other people at the time—but he was really the only one who threw out the concept of absolute or universal time as being superfluous and unwarranted. Over time scientists have come to go with Einstein's approach—simply because his definition of time does seem to work out, does produce the weird experimental effects he predicted it would, and does not seem to require an idea of absolute time to work. --Mr.98 (talk) 22:11, 23 February 2010 (UTC)

Do most people get enough vitamins and nutrients from their regular diet?

I've always been slightly suspicious of dietary supplements like multivitamins (I believe Sheldon from The Big Bang Theory once described them as things that "make your urine very expensive", which I thought was apt), so I figured that once and for all I'd read the damn wikipedia article and the arguments for and against it. The arguments against them in the article are a lot stronger than the arguments for them unless you're a post-menopausal woman or suffering from malnutrition (in which case you have bigger problems, I suppose). The pro-side is basically one paper, one editorial and one doctor, while the con-side is the NHS, HHS and the UK Food Standards Agency.

However, there was one argument that wasn't addressed that I'm very interested in: doesn't most people living in affluent countries pretty much get everything they need (in terms of vitamins and minerals and such) just from a regular diet, even a pretty unhealthy one? I mean, comparatively speaking, isn't a western diet is hugely diverse by historical standards? Look at a Big Mac: not the healthiest of meals, but it has salad, tomatoes, beef, bread, cheese and pickles in it. I mean, that's like an explosion in different varieties of nutrients! Compare that to a stone-age meal consisting of badly cooked mammoth and a few berries, and it's hard to see the case for modern people needing additional nutritional supplements.

Is my intuition correct? Surely there has to have been studies that look at the average persons diet and checked whether it matches up with the Recommended Daily Intake? Belisarius (talk) 18:28, 23 February 2010 (UTC)

I've heard the same thing, and I'd love to have a definitive understanding of how often people do or don't have aspects of malnutrition while on a typically Western diet. I certainly know of anecdotal cases of people in the modern world where supplements were important, but those generally involve restricted diets that wouldn't necessarily be called typical. For examples, vegans often take supplements to deal with nutrient that can be hard to obtain from an all plant diet. My mother does similar things to deal with restrictions caused by her food allergies. And I once knew a grad student that was diagnosed with scurvy (lack of vitamin C). It is very rare to see that kind of basic malnutrition in the USA, but it is still evidently possible to make such poor diet choices that one unwittingly misses out on basic nutrients. So, I guess my point is that supplements do have uses, but I don't know how useful or not they are for the typical Westerner. Dragons flight (talk) 19:00, 23 February 2010 (UTC)

Short answer: yes they do get enough vitamins. If they didn't they would be dead. But since 100% of people are alive, then by logical analysis, everyone gets enough vitamins. Maybe not -ideal-, but they seem to get by alright. Besides, a severe deficiency in any important materiel will result in particular cravings. Vranak (talk) 19:04, 23 February 2010 (UTC)

A lot of things have their effects over long periods of time and shorten your life. By your logic, smoking is perfectly safe. 92.29.57.43 (talk) 23:52, 23 February 2010 (UTC)

What a ridiculous answer. They aren't dead yet, so obviously everyone is in good health. That's just stupid. Also, the body may be smart about some things, but it isn't magic. It can only give you cravings for things it is internally set up to measure and understand, which isn't everything. Most Westerners do fine, but don't mistake that for saying proper nutrition isn't relevant to good quality of life. Worldwide, malnutrition still contributes to ~60% all deaths every year, mostly in the impoverished third world countries. Dragons flight (talk) 20:13, 23 February 2010 (UTC)

It's not the least bit stupid. Dead is dead is dead. But yes, your point is well-taken. I generally reserve my consideration for countries that don't suffer widespread famine. In fact I would submit that any nation where people starve to death is no nation at all. Vranak (talk) 20:40, 23 February 2010 (UTC)

Sure! Like Ireland in the mid-19th Century, or China during the Great Leap Forward. Ireland and China weren't nations! They were, um, these things ... where people of similar ethnic groups governed by the same people, um ... just happened to live ... But definitely not "nations."63.17.65.39 (talk) 02:20, 24 February 2010 (UTC)

It is kind of stupid. Malnutrition is not the same thing as starvation. Plenty of people are malnourished in all nations. It is not an issue of "widespread famine"—there are plenty of places where a poor diet is common amongst huge sectors of the population, and the results of that are medically palpable (lowered IQs, shorter statures, etc.). Heck, even if you are extremely well-fed you can easily run afoul of malnutrition if you don't eat the right thing. I know of a guy who ate nothing but hot dogs and soda for an entire summer and got scurvy as a result. (Which was itself pretty stupid, but it illustrates the point well!) --Mr.98 (talk) 22:14, 23 February 2010 (UTC)

I know some purists will object, but you can prevent scurvy while on the hot dog diet simply by adding ketchup. Googlemeister (talk) 14:06, 24 February 2010 (UTC)

Alright, I see we are not on the same wavelength here. Vranak (talk) 01:03, 24 February 2010 (UTC)

Bluntly, Mr.98 is on the right one, and you're on the wrong one. "Not getting enough nutrients" is not remotely close to the same thing as "dead".

Just as an example, if I recall correctly, having inadequate serum levels of vitamin D means you're more likely to get cancer, or at least some kinds of cancer. Does everyone who doesn't get enough D, get cancer? Certainly not. But that doesn't mean you can be sanguine about D deficiency, even if you haven't yet gotten cancer.

Of course you don't want too much D either; it's a complicated question. --Trovatore (talk) 01:09, 24 February 2010 (UTC)

The only proof that someone did not definitively get enough nutrition is if they die. Otherwise they can make a recovery. So there is no absolute way of calling someone 'malnourished' because they may just pull through, and their deficiency was never really that critical, if it did not quite finish them off. Still, your objection is noted and respected. Vranak (talk) 02:01, 25 February 2010 (UTC)

So you're saying you don't mind getting cancer, heart disease, or high blood pressure from incorrect nutrition, provided there's no actual proof that that was the cause? --Trovatore (talk) 02:07, 25 February 2010 (UTC)

It has become abundantly clear to me that you lads are not interested in the truth, so I take my leave from this debate. Vranak (talk) 03:58, 25 February 2010 (UTC)

It's become abundantly clear that you're ignoring good answers. If someone has a deficiency of a certain vitamin, they become diseased. Disease does not equal death, it means that you're not at optimum efficiency and if you continue to degrade in health, you could die. Furthermore, there are not just two levels of well-being when it comes to vitamins. For example, someone who has a lack of vitamin C will get scurvy, but it doesn't mean they'll die from it. It means they'll become ill, and if they continually lack the vitamin in sufficient quantities over time, they'll die. However, if they get treatment, they'll live. If they get just under the bare minimum quantity of vitamin C, they can present with some symptoms of scurvy but not die. There's the proof that your theory is flawed. I can prove that the last person mentioned didn't get enough vitamin C because they presented with the symptoms, but they didn't die. Therefore, you can prove someone has a lack of nutrients even if they're not dead. Regards, --—Cyclonenim | Chat  18:14, 25 February 2010 (UTC)

You can see what percentage of the most commonly needed stuff is in your food because it's right there on the mandatory labelling - so you don't have to take our word for it...you can figure it out for yourself. But even the most dull and non-nutritious seeming breakfast cereal has something close to the recommended amount of just about everything (and that's not counting the milk you pour onto it - which, remember is sufficiently "well rounded" in nutrients to grow a tiny calf into a modest sized cow with no supplementation). Since that's only the first meal of the day - it's pretty clear that you'd have to go out of your way to pick a sufficiently poor diet. The exceptions (and they are important ones) are pregnant women (who will reduce the risk to the baby by taking some specialised supplements), nursing mothers, older people, people with dark skins who live in the extreme north or south of the planet, sick people, malnourished people and so forth. But if you are in your prime and eating "normally" - you should be just fine without any kinds of special supplements whatever. Like I said...check the product labelling and then you'll know for sure. SteveBaker (talk) 20:26, 23 February 2010 (UTC)

Well, the labeling is only for a fairly restricted group of nutrients — by no means everything that you might want more of (or, sometimes, less of). Most phytochemicals that aren't actual recognized vitamins, for example, don't get called out on the label, but your health is at more risk if you don't get enough of them. I'm talking about things like soluble fiber, polyphenols, many many more. Omega-3 fatty acids are another group of nutrients that many Westerners don't get enough of. You don't have to be poor to be in this boat; it might be that you just don't particularly enjoy the foods that provide these nutrients. The best solution to that is to recalibrate your food preferences, which is possible to some extent. But if you absolutely can't, or refuse to, then supplementation may be an option. --Trovatore (talk) 22:34, 23 February 2010 (UTC)

"Westerners"? If that means you consider Europe, Aus, NZ, etc to be homogenous with the USA then that is a mistake - we tend to eat different foods and have a different culture and conventions. 92.29.57.43 (talk) 23:47, 23 February 2010 (UTC)

You're right, it was a careless choice of words. I meant people in affluent countries, in countries where access to food isn't really a problem. Belisarius (talk) 00:42, 24 February 2010 (UTC)

I read a detailed academic study online a while ago that said that taking a multivitamin everyday was worse for you than not taking one. Because of that, I stopped taking them and concentrated on eating more vegetables, fruit, and oily fish. Have not been able to find a link to that article unfortunately. 92.29.57.43 (talk) 23:51, 23 February 2010 (UTC)

Vitamin B12 deficiency can be a real problem for vegans.--Shantavira|^{feed me} 06:53, 24 February 2010 (UTC)

Despite deciding to stop taking a daily multivitamin after reading a scientific paper about this, I do take Vitamin D during the winter, after reading a Scientific American article about this that I think was published in November 2008. The modern diet has a lot of saturated fat and salt, both of which I am trying to avoid by avoiding processed food, and also red meat and dairy products. 92.29.32.229 (talk) 20:57, 26 February 2010 (UTC)

Linus Pauling

In the reference to Linus Pauling it states that he died in 1994 and that he taught at Oregon State University in 1996. Must have been interesting classes. I don't know if he actually taught at OSU but I think he didn't do it in 1996.

Regards all,

Stephen Wilson —Preceding unsigned comment added by Zashiban (talk • contribs) 19:01, 23 February 2010 (UTC)

I don't see where it says that he taught at OSU. It says that the Linus Pauling Institute moved there in 1996, but that's a different thing. Looie496 (talk) 20:16, 23 February 2010 (UTC)

Err, yeah, read a little closer. It does not say what you think it does. --Mr.98 (talk) 21:33, 23 February 2010 (UTC)

Mr 98 it really would be way more helpful if you could say exactly where the problem is. If you have spotted the discrepancy, (and well done for that) let's get it sorted and move on. Caesar's Daddy (talk) 08:43, 24 February 2010 (UTC)

This is best handled on the belonging talk page. However, my curiousity was spiked, and I felt the need to quote what has been written (and not edited, by the look of the history): In 1996, the Linus Pauling Institute moved from Palo Alto, California, to Corvallis, Oregon, to become part of Oregon State University, where it continues... Bolding is mine. All other searches for "1996" yield results outside this context. However, he studied at OSU (first line in #Career). I can conclusively say that Mr 98 is wrong. 77.18.74.19 (talk) 10:06, 24 February 2010 (UTC)

Ummm...I don't think Mr98 said anything wrong...perhaps you were confusing him with the OP? It looks like Mr98 made basically the same response as the rest of you.PhySusie (talk) 17:28, 24 February 2010 (UTC)

Ah, I thought Mr98 was replying to Looie496. :) My bad. 77.18.12.14 (talk) 16:55, 25 February 2010 (UTC)

In theory, posts that are indented are responding to the post which is of lesser indent to the one above it. If I were responding to Looie496, I would have indented it one more time. (I'm seriously surprised that this is any real confusion.) --Mr.98 (talk) 14:19, 26 February 2010 (UTC)

Sodium

How can I extract pure sodium from baking soda (sodium bicarbonate)? --J4\/4 <talk> 20:11, 23 February 2010 (UTC)

Basically you can't. See Downs cell for the simplest method of producing pure sodium. Looie496 (talk) 20:21, 23 February 2010 (UTC)

Why not? Baking soda has sodium in it, after all. --J4\/4 <talk> 20:27, 23 February 2010 (UTC)

I didn't mean that it's impossible in principle, just that it's impossible without very serious equipment. The article I pointed to should give you an idea of why. I don't actually know how to do it with sodium bicarbonate, but it must be harder than the Downs cell process. Looie496 (talk) 20:31, 23 February 2010 (UTC)

In layman's terms: Sodium (as I'm sure you know) is highly reactive. When it reacts with things it puts out a LOT of energy. Hence, to get it separated back out again, you have to somehow replace all of that energy and fight Sodium's tendency to react with whatever happens to be nearby. It follows that getting pure sodium out of its compounds is difficult. (You can't get it out of common table salt either!) SteveBaker (talk) 21:31, 23 February 2010 (UTC)

(e/c) put simply, sodium is very reactive, you can ionize it in solution fairly easily (plop plop fizz fizz) but getting it out of solution without it recombining with the other solutes (or other materials) is a bear and a half. --Ludwigs2 21:34, 23 February 2010 (UTC)

IMHO, if you want detailed advice on how to make sodium, you'll be better off using table salt as your starting material. The best method is to melt it (it melts at ~800 C) and then electrolyse it using a graphite anode and a steel cathode with some kind of hood over it to catch the molten sodium as it rises and thus prevent it from reacting with air. Warning: chlorine gas given off at the anode is highly toxic, avoid inhalation. Also, all solid/liquid materials will be red hot, don't burn yourself. As for the other, common-sense advice: Don't try this at home, at least unless you really know what you're doing. Clear skies to you 24.23.197.43 (talk) 01:27, 24 February 2010 (UTC)

Let's try also to explain this in a different manner. Sodium comes in two forms: Sodium metal, where each atom has 11 electrons, and ionic sodium, where each atom has 10 electrons. The nucleus of sodium contains 11 protons, so that makes sodium metal neutral, and sodium ions have a charge of +1. Energetically, it turns out that sodium ions are MUCH MUCH MUCH more stable than neutral sodium. That's why when you add sodium to water, it releases so much energy; in giving an electron to the water, the sodium becomes more stable, and in the process releases the pent-up energy that was making it unstable (which explains the big boom). You can look at it this way:

• Na⁰ --> Na⁺¹ + 1 electron + a shitload of energy

Well, what the OP is proposing is to reverse the reaction; take the IONIC form of sodium (which is the form in sodium bicarbonate) and turn it into the METALIC form of sodium (the neutral one). So if you run the reaction backwards; you would get

• Na⁺¹ + 1 electron + a shitload of energy --> Na⁰

So the first thing you need is a shitload of energy; basically you need exactly as much (or more) as you release if you were to add the pure sodium metal to water. As the OP is aware, that's quite a bit. The second problem is that you need to do it in such a way as to keep the sodium metal away from anything that would give it a pathway to give away that electron again. Any environment that contains any water, for example, will just lead to your newly-made sodium metal instantly reverting back to its ionic form, and you'll never get a measureable amount of the pure metal. The Downs cell noted above is the only really practical method of creating metallic sodium, and it is a complex process that requires some exotic equipment and a lot of energy to work. --Jayron32 16:40, 24 February 2010 (UTC)

Water is partly ionic, so it has free H⁺, and OH^- ions. Table salt is Na⁺ Cl^-. When you electrolyse a solution, the ions with with least electrode potential with be released. H⁺ is less than Na⁺. This is why electrolysis of sodium salts is normally done with molten salt, as is stated above. CS Miller (talk) 18:57, 25 February 2010 (UTC)

acid

once spilled strong acid has dried is it inert or is it still caustic —Preceding unsigned comment added by 67.246.254.35 (talk) 22:15, 23 February 2010 (UTC)

AFAIK it depends on the volatility of the respective acid anhydride. Hydrochloric or nitric acid may volatilize completely, leaving no caustic residue (unless it had soaked into the surface instead of evaporating); sulfuric or hydrofluoric acid, on the other hand, will remain caustic after having dried up. However, even with fairly volatile acids, there's no way to really be sure that it has really dried up and not just soaked into the surface. Always clean up acid spills promptly and follow safety guidelines. 24.23.197.43 (talk) 01:35, 24 February 2010 (UTC)

"Acids" are usually solutions of acidic chemical dissolved in a solvent. So you have to figure out what you mean...is the solvent evaporating, leaving an extremely concentrated acidic residue, or is the acid chemical itself evaporating. Most of the common strong acids, and many of the common weaker ones (that still might be very corrosive) are volatile enough to evaporate completely with their solvent: if you are in a situation where the water is evaporating, the acid will also. To put another way, acids are acidic--evaporating them merely changes the physical state of them, so whereever that physical acid chemical goes, in whatever form it is, that's where the acidic properties exist. DMacks (talk) 02:52, 24 February 2010 (UTC)

im talking about car battery acid ( i think sulfuric ) —Preceding unsigned comment added by 67.246.254.35 (talk) 03:21, 24 February 2010 (UTC)

Yes, car battery acid is sulfuric acid. Also, what kind of surface did you spill it on? If you spilled it on dirt, grass, or sand, it probably would have soaked in and would not leave any caustic residue. If you spill it on concrete, tile, or wood, I think the acid would evaporate with the water. So in any case, I think it would be safe, depending on how long ago you spilled it. --The High Fin Sperm Whale 04:12, 24 February 2010 (UTC)

You can neutralise it with sodium bicarbonate which will fizz as it reacts. There may be some bisulfates left after sulfuric acid reacts with concrete, and these can be neutralised. Graeme Bartlett (talk) 11:25, 24 February 2010 (UTC)

the battery exploded in my car hood the acid is all over the engine parts ect under the hood —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 15:25, 24 February 2010 (UTC)

In that case, you should take your car to a mechanic to check for acid corrosion to engine parts and bodywork -- most car parts are made of carbon steel, and sulfuric acid will corrode it readily and could cause serious damage. (BTW, why don't you sign your posts?) 24.23.197.43 (talk) 05:50, 28 February 2010 (UTC)

"local hour angle" in astronomy

I'm trying to do some astronomical calculations based on the "Astronomical Formulae..." book by Jean Meeus. I almost have it, but I have a question about "local hour angle". On page 44 (chapter 8) he defines (along with the observer's latitude) "H = the local hour angle, measured westward from the South". Is the local hour angle simply the observer's degrees of longtitude? Bubba73 ^{(You talkin' to me?)}, 22:42, 23 February 2010 (UTC)

I'm not certain of this, but I think it refers (in the context of your probable interest) to the angle in right ascension between the meridian and the horizon, measured from south to west. If RA is in degrees, divide by 15 to put it into hour:minute format. This is also called the western diurnal semi-arc. More broadly (outside your context), it is "the angle between the great circle that passes through the poles, and that which bisects a specific point in the heavens" ("Encyclopedia of Astrology" by Nicholas Devore). 63.17.65.39 (talk) 02:35, 24 February 2010 (UTC)

The local hour angle is the angle measured westward from the meridian (that is, the projection of the line of longitude the observer is standing on onto the celestial sphere) to the hour circle of the celestial object, measured westward along the celestial equator. See "hour angle" in the Glossary of the Astronomical Almanac. I don't really see how thinking about "south" helps understand this. Jc3s5h (talk) 02:53, 24 February 2010 (UTC)

Yes, the mention of "south" confuses me. I think it may be an error in the book, since the same phrase is used for azimuth (where it does make sense). Bubba73 ^{(You talkin' to me?)}, 03:45, 24 February 2010 (UTC)

Perhaps I need to back up some. I am writing a program to calculate the altitude and azimuth of the Moon, given (my) latitude, longitude, and the time. Chapter 30 of the book by Meeus give how to calculate the geocentric latitude and longitude (lambda and beta). The program is doing that - it agrees with the example in the book. (The Moon's motion is complex.) But I'm stuck on getting from there to altitude/azimuth.

Chapter 8 of the book shows how to calculate alt/az from my latitude, the declination, and the local hour angle. The description of the local hour angle isn't clear to me. It shows two ways to calculate the hour angle, based on the local sidereal time and the right ascension (alpha). But I don't know if these r.a. and dec correspond to the geocentric lat and long.

Just before that it shows how to calculate right ascension and declination from lambda, beta, and the tilt of the Earth's axis. I suppose I need to do that to get the declination to use in the alt/azimuth calculation, but I'm not sure.

So my problem is how to get from geocentric lat/long to alt/azimuth, given my latitude, longitude, and the time. How is that done? (I'm confused.) Bubba73 ^{(You talkin' to me?)}, 05:01, 24 February 2010 (UTC)

Forget that "south" business. It is conflating hour angle with something else . If someone was considering a point on the celestial sphere, say the position of a star, and you wished to instruct him how to find another point, you would have to tell him in what direction to look from there. Due South is 0°, Southwest is 45°, East is 270°, and so forth. Also supply the distance, and you've done it. B00P (talk) 06:39, 24 February 2010 (UTC)

Don't forget the south, it's correct and belongs in the explanation (assuming you're in the northern hemisphere). If you stand facing south, an object on the meridian, in front of you, has an hour angle of 0^h. Now turn around and face north. An object directly in front of you has an hour angle of 0^h if it's above the north star, but an hour angle of 12^h if it's below the north star. To put it another way, each day and night a circumpolar star will cross the meridian twice, but it's the meridian to the south that it crosses at 0^h hour angle. -- Coneslayer (talk) 12:28, 24 February 2010 (UTC)

That said, the formulas should "just work" for your calculation, and you don't need to worry that HA is measured from the south. You do, of course, need to worry about whether azimuth is measured from the north or south. -- Coneslayer (talk) 13:10, 24 February 2010 (UTC)

OK, I have Astronomical Algorithms, which I think is an older edition of the book, but unfortunately the chapter/equation numbers don't match up. I think you've basically got it figured out. You have geocentric latitude and longitude (lambda and beta). Convert those to RA & dec (alpha and delta) using the relations you've found. Then get the hour angle based on RA and local sidereal time (or RA, observer's longitude, and Greenwich sidereal time), and use the relations you've found to convert HA & dec to altitude and azimuth. All good? -- Coneslayer (talk) 13:03, 24 February 2010 (UTC)

Astronomical Algorithms is actually a newer book (also by Jean Meeus) than the one I have. I'll try to finish it up, based on what seems right. Unfortunately, there is no complete example of getting the Moon's position in alt/azimuth in the book, so I'll have to check it some other way. Bubba73 ^{(You talkin' to me?)}, 01:40, 25 February 2010 (UTC)

Bubba, I have the correct answer (and my answer above from "63.17.65.39" was correct, but I thought you wanted it relative to the horizon -- but I see you're referring to the moon). It's very simple: subtract the right ascension of the moon from the right ascension of the meridian (RAMC). RAMC is the same as local sidereal time. If the RAMC is less than the RA of the moon, add 360 degrees (or 24 hours) to the RAMC. So it's just subtraction! 63.17.57.56 (talk) 02:21, 25 February 2010 (UTC)

Another way to think of "local hour angle" -- in this case, the LHA of the sun -- is "At my latitude on earth, how many 'time zones' away is the sun at 'high noon'?" So if you're in New York and it's 3 PM, it's noon on the west coast -- so the "hour angle" of the sun in NY is approximately 3:00, because LA is 3 time zones from NY. (A better example would be two cities at the same latitude, but you get the point.) The same goes for the moon or anything else, except it's "the moon's noon," i.e. high point. Along the same line of geographical latitude, the hour angle is simply how far away in geographical longitude (equivalent to right ascension) a point in the sky has reached its maximum height ("due south"). If the moon is due south (at its high point) in LA (longitude 120ish), the moon's hour angle in NY (longitude 75ish) will be appproximately 45 degress, or 3 hours. (Again, literally speaking, it has to be along the same line of latitude on earth, and time would be measured as on a sundial, not a regularized clock. I just say this to avoid the usual pedantic corrections.) 63.17.57.56 (talk) 04:09, 25 February 2010 (UTC)

It is my bedtime - I'll read that tomorrow. But in the meantime there are two things I don't understand. The final step is calculating the altitude and azimuth. Meeus shows how to do that in equations 8.5 and 8.6. But these equations depend only on the observer's latitude, hour angle, and delta (the declination). Why doesn't the R.A. enter into it? Secondly, is that declination the parameter calculated for the Moon in geocentric coordinates? Bubba73 ^{(You talkin' to me?)}, 06:16, 25 February 2010 (UTC)

You needed the RA to get the hour angle, so that's how RA enters into it. The declination (along with the RA) is calculated from the geocentric coordinates (you originally wrote: Just before that it shows how to calculate right ascension and declination from lambda, beta, and the tilt of the Earth's axis. That's where the declination comes from.) -- Coneslayer (talk) 12:20, 25 February 2010 (UTC)

February 24

Traffic fumes versus tobacco smoke

How does the deadliness of traffic fumes compare with those of tobacco smoke? Would living a few feet away from very busy roads - unfortunately not uncommon in the UK - be equivalent in its health risks to smoking X number of cigarettes a day? The (very) microscopic particles from diesels are one serious risk for example. 92.29.57.43 (talk) 00:51, 24 February 2010 (UTC)

Prob'ly not -- when you smoke cigarettes, you deliberately inhale the smoke, maximizing your exposure to all the nasty stuff in it. As opposed to just breathing air that happens to contain a certain amount of smoke, which is what you do when you live next to a busy road. Plus, the natural air currents tend to dilute the traffic fumes to a very low concentration, unlike when you smoke tobacco. So no, living next to a busy road is nowhere near equivalent to smoking X cigarettes a day -- more like sitting in a bar where other people smoke. But if you want a gram-for-gram comparison of engine exhaust vs. tobacco smoke, diesel exhaust contains more aromatics and heavy metals, while cigarette smoke contains more of the nasty carbonyl compounds (aldehydes/ketones) and amines/nitro compounds (but some aromatics and heavy metals as well). So gram-for-gram, I'd say it's too close to call. FWiW 24.23.197.43 (talk) 02:00, 24 February 2010 (UTC)

You forget an important difference. A smoker breathes in cigarette smoke about 10-20 times per cigarette (10-20 puffs). With about 10-20 cigarettes per day, that's about 300 breaths. The surrounding air, with all its exhaust fumes, you breath in constantly, every breath you take, day and night. With 20 breaths per minute that would be about 30.000 breaths per day. That's 100 times more! And quite often, constant exposure to something unhealthy is in the long run more damaging than more severe, but interrupted exposure. Of course, smokers often breathe in their own 'second hand smoke' as well, but that's a bit harder to assess (and becoming less common with smokers stepping outside for a smoke). DirkvdM (talk) 16:31, 24 February 2010 (UTC)

A few years ago this was a newsitem in the Netherlands. A research had shown that children who grew up (or went to school) near busy roads had lung problems which were sometimes very severe. It was said that their lungs were like those of a long time chain-smoker. I can't remember if that was just the worst cases, though. If I remember correctly, they spoke of a reduction in lung functionality of 10%.

However, that's the Netherlands, where most people live near the sea (Randstad). In the UK, you've got London, a metropolis that exceeds anything we have in the Netherlands in terms of size and congestion, and in the centre of which you are not likely to get much relief from a sea-breeze. Cities have always been an unhealthy surrounding. I just wonder if it isn't getting worse. DirkvdM (talk) 16:26, 24 February 2010 (UTC)

what is the most likely avenue for curing cancer?

What, in specific terms, is the most likely route being pursued for curing cancer? 84.153.231.223 (talk) 00:52, 24 February 2010 (UTC)

Every type of cancer is different, and there isn't going to be a single approach that works for all of them. The most promising approach is usually some combination of chemotherapy, radiation, and surgery. Once a cancer has metastasized, though, it seems to be generally incurable by any approach that is currently envisioned. Looie496 (talk) 01:34, 24 February 2010 (UTC)

Come on, Looie -- certainly the inquisitor was not asking for an explanation of current methods -- being pursued suggests a look into the future. So while we do not make predictions here at the ref desk, I would say the phasing out of all three methods mentioned by Looie would be quite welcome for pretty much the same reason: the target is too large. Chemotherapy works by targeting speedily growing cells, which certainly includes malignant cells, but also unfortunately includes those found in hair follicles and reproductive organs, among others. The effects of the medication are also embraced by unspeedily growing cells. Radiation therapy targets any and all cells, and the focus in this realm has been to narrow the beam and decrease the effective dose so that only the most targeted cells die -- but this again is not a perfect method. While surgery is great at removing the entire lesion assuming the lesion hasn't metastasized, clean margins are necessary and resections can often leave the cancer patient severely disfigured, although still alive. If I'd have to say what the pursuit of cancer research is in terms of defined therapy, I'd think it would be a more refined target derived from the specific type of cancer cell, so that the therapeutic agent would be a poison for only that group of cells but as harmless as sodium Na⁺ for the remainder of the body's cells. DRosenbach ^{(Talk | Contribs)} 01:51, 24 February 2010 (UTC)

You really think sodium metal is harmless for human cells? :-) 24.23.197.43 (talk) 02:06, 24 February 2010 (UTC)

You got me -- I was too lazy to find the <"sup"> <"/sup"> button :) DRosenbach ^{(Talk | Contribs)} 05:14, 25 February 2010 (UTC)

I took being pursued to mean being actively worked on, as opposed to being fantasized about. Regards, Looie496 (talk) 02:12, 24 February 2010 (UTC)

Only very recently has medical science discovered the connection between viruses and cervical cancer as well as at least one other type (I read about it recently, but can't remember which). The 20th Century bias toward looking for environmental, genetic, psychological and "life-style" causes of cancer led to an absence of reserach into viruses and bacteria as causes of cancer (or, for that matter, of all other chronic illnesses). (Remember when ulcers were caused by a bad attitude? Thanks, Sigmund. Meet my friend Dr. Pasteur.) It may be that the most fruitful preventative measure against cancer will eventually be innoculation, anti-biotics, and the like. See the book (circa 1999) Plague Time, by an Amherst College professor of evolutionary virology whose name escapes me. 63.17.65.39 (talk) 02:46, 24 February 2010 (UTC)

It's odd that people still talk about finding "a cure for cancer". We already have several cures for cancer. A very large proportion of people diagnosed with cancer these days recover fully (exactly what proportion depends on the type of cancer). As with any disease, we can expect our cures to improve over time or be replaced by entirely different cures (more effective, fewer and less serious side effects, cheaper, etc.). There is no way to predict what the improved or new cure would look like. --Tango (talk) 02:59, 24 February 2010 (UTC)

As Looie points out, the fact that pretty much every cancer is different means that different strategies are being pursued for different types of cancers, and each has different chances of success. A few examples:

• for cancers that are highly associated with viral infection, vaccines hold great promise. The National Cancer Institute says, "Widespread vaccination has the potential to reduce cervical cancer deaths around the world by as much as two-thirds..." which is pretty promising (though is dependent on the usual vaccine caveats).
• Another use of vaccines is against markers of the cancers themselves, see Stimuvax as a promising example of this.
• The rapid decrease in cost, and development of third generation DNA sequencing, means we are approaching the time when it may be feasible to sequence the genome of individuals. Thus instead of being told "you have liver cancer", your doctor may be able to determine the exact mutation that has caused your liver cancer. This will make targeted therapy more effective and opens up the door to personalized medicine. It could also identify those at high risk of certain cancers, permitting earlier screening and detection, leading to higher survival rates.
• Some companies have tried using viruses to kill cancer cells specifically, or use viruses to carry targeted chemotherapeutics. One of the early examples, Onyx-15, was not very successful but the concept seems to be working and other systems are in development.

There are many, many more (see Experimental cancer treatment for some examples), but comparing them is a bit like comparing apples and oranges and asking which is better for you. And if anyone knows for sure which is going to prove to be most successful, then they should invest in the company that is developing it and wait for the money to roll in. Rockpocket 03:31, 24 February 2010 (UTC)

"Plague Time" (referred to above) was written by Professor Paul W. Ewald. A reviewer from The Science Advisory Board writes: "Though there has been much investment in studies of genetic causes of disease, the most significant returns were generated on investments made in the studies of infectious diseases. Polio, measles, hepatitis, liver cancer, ulcers and cervical cancer were all controlled or shown to be controllable during the last half of the twentieth century through the control of infectious agents. This track record provides a sense of how to invest in our future: focus on the germs." http://www.scienceboard.net/resources/bookreviews.asp?cat=1&book=159 63.17.65.39 (talk) 05:08, 24 February 2010 (UTC)

I keep referreing to this comic: [12] for a quick explanation of the issue. It gets the point across EverGreg (talk) 09:22, 24 February 2010 (UTC)

It's a question of inputs versus outputs. Less noxious gases breathed in, less questionable food and drink, more fresh air and fresh food. That will be the avenue to cancer disappearing. In a lab? Oh please! Vranak (talk) 01:57, 25 February 2010 (UTC)

How would doing those things prevent infection by the viruses correlated with cervical cancer and liver cancer? (It took a long time to persuade the mainstream that stress doesn't cause ulcers ...) The "life-style" theories may be a post-Freudian, puritanical 20th century bias, now moving toward a dead end ... as viruses, bacteria, and other infectious agents are ignored until, as in cervical and liver cancer, they become too obvious to ignore. 63.17.57.56 (talk) 02:35, 25 February 2010 (UTC)

I will simply state that the human body is an extremely capable machine. It fights off degeneration for ages and ages and ages. It takes a lot to bring down a man -- about 80 years of sucking in nasty houses gases, most notably. Vranak (talk) 04:04, 25 February 2010 (UTC)

Whether healthy living is the "avenue to cancer disappearing" is very controversial. The reality is pretty much every environmental factor - even so-called "healthy ones" - can have mutagenic potential when you add up exposure over a lifetime. You may be able to combat some cancers by shutting yourself in a controlled, sterile room for most of your life away from mutagens and infectious agents, but good luck convincing anyone to do it. You will certainly be able to decrease your personal risk of some cancers by adopting a healthier lifestyle and avoiding risky behaviours, but that is hardly going to abolish all cancer. Moreover, with our increasing population and pollution levels, it simply isn't realistic to expect that human population can address cancer by returning our planet to an idyllic garden of Eden, spending out time in the fresh air eating organic food and avoiding pollutants. Ironically enough, if we did that rates of skin cancer would increase (unless we all used strong sun blocks which, incidentally, are developed in the lab). Like it or not, lab researched therapeutics, in co-ordination with education on healthier lifestyles, is the most realistic chance we have to combat cancers.

Finally, I take issue with your suggestion that our body "fights off degeneration for ages and ages and ages". It doesn't. Degeneration (cellular, genetic, physiologic) is a continuous process that occurs pretty much throughout our lifetimes, certainly from our twenties onwards. Its called aging and no amount of healthy eating and fresh air will stop it. Cancer is the ultimate conclusion of that process. You pick up mutations in the very process of living your life, and eventually you will get one or two that hit a tumor suppressor gene or an oncogene. Unless something else gets you first, everyone on this earth will get a cancer eventually. It is completely inevitable, which is why it is so difficult to "cure" cancer. Rockpocket 20:59, 25 February 2010 (UTC)

bleach cover up

there is an employee of Clorox editing the bleach articles trying to minimize the risks of bleach and the carcinogenic and caustic nature of it. can someone stop him and revert his edits? —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 03:29, 24 February 2010 (UTC)

Try asking here: Wikipedia:Conflict of interest/Noticeboard. --Tango (talk) 03:39, 24 February 2010 (UTC)

it would also help for you to give their user name so that we can check it out. --Ludwigs2 05:17, 24 February 2010 (UTC)

Does gasoline float on water? Will it dissolve sugar?

Will water, for example in a gas tank, float on top of the gasoline or sink to the bottom (and why)? Also, does sugar dissolve in gasoline, or will it stay granular? I think sugar will not dissolve due to the non-polar nature of sucrose and gasoline. —Preceding unsigned comment added by 161.165.196.84 (talk) 08:32, 24 February 2010 (UTC)

Gasoline floats on water, and sugar does not dissolve in gasoline. Read the Wikipedia article on solubility for more information on this. 217.158.236.14 (talk) —Preceding undated comment added 11:11, 24 February 2010 (UTC).

Snopes.com: Sugar in the Gas Tank might be of interest to you. AlmostReadytoFly (talk) 11:42, 24 February 2010 (UTC)

Snopes says "No", but The Straight Dope claims to have run the experiment and gotten a "Yes". Followup: are you sure sugar in the gas tank will wreck a car engine? APL (talk) 16:31, 24 February 2010 (UTC)

So we need Mythbusters to break the tie... --Tango (talk) 18:30, 24 February 2010 (UTC)

I note that the Straight Dope article notes that it clogs the fuel filter sock, exactly the result described by Snopes. They agree that sugar won't destroy an engine, and they agree that sugar can stop a car from operating. So I don't see a need for a tiebreaker, although giving the Mythbusters new excuses to destroy stuff is always entertaining. — Lomn 18:57, 24 February 2010 (UTC)

The Mythbusters did do "sugar in the gas tank" (I think it was episode 15) - and it didn't work. The engine ran just fine. They tried a bunch of other things too. What did finally kill the engine was bleach. SteveBaker (talk) 03:46, 25 February 2010 (UTC)

Electrolysis and Photolysis of Water

If you use electricity to split saltwater into hydrogen into oxygen, what would happen to the salt in the saltwater? Would it also split into sodium and chlorine or would it remain as salt?

If you use light or radiation to split saltwater into hydrogen and oxygen, what would happen to the salt in the saltwater? Would it also split into sodium and chlorine or would it remain as salt?

An Unknown Person (talk) 10:07, 24 February 2010 (UTC)

When salt is dissolved in water, it already is split into sodium and chlorine ions. See the articles Ion and Solution. DVdm (talk) 10:59, 24 February 2010 (UTC)

WIth electrolysis you can get chlorine gas formed and sodium hydroxide at the other electrode. Hydrogen is formed in preference to sodium metal. Graeme Bartlett (talk) 11:21, 24 February 2010 (UTC)

If you use electricity, heat, light, or radiation, etc, to split saltwater into hydrogen and oxygen, then what happens to the sodium and chlorine in the saltwater?

An Unknown Person (talk) 09:09, 25 February 2010 (UTC)

The above answers and electrolysis of water explain what happens when you use electricity (the sodium in particular will remain in the water, although you may get some chlorine and sodium hydroxide forming at the electrodes). Using heat or light or most forms of electromagnetic radiation will not split saltwater into hydrogen and oxygen (when you boil water you just get steam). (I'm not sure what high doses of ionizing radiation would do, but I wouldn't recommend you try it.) If you use the heat/light/radiation to generate electricity (in a steam turbine, photocell, nuclear power station, etc) then the answer for electricity applies. --Normansmithy (talk) 11:48, 25 February 2010 (UTC)

very hot water + some cold water = just warmed water?

If I want to heat a pot of water to a certain "quite warm" temperature, but overshoot my target and get a raging boil, will adding some cold water, and mixing, produce the equivalent "quite warm temperature" water as if I had just heated to that temperature directly? Or will the cold water "ruin" some aspect of the water? Please answer from both a scientific and practical standpoint. Thank you. 82.113.121.93 (talk) 12:41, 24 February 2010 (UTC)

Practically speaking, it can be a very bad idea to have hot and cold things together in glass or ceramic containers as thermal shock can cause them to break, but for a metal pot, addition of cool water to hot water will change nothing but the temperature and mass of the whole. Googlemeister (talk) 13:57, 24 February 2010 (UTC)

Adding to the practical warning, it's not so much an issue in this case. You're likely to encounter thermal shock issues if you plunge a raging hot container into an ice bath, or dump boiling water into a frozen glass, but adding cold water to a hot pot full of hot water will avoid the effect -- there's enough thermal inertia there to avoid the shock.

On the other side of practicality, some people claim that their boiled tap water tastes different from their unboiled tap water. They might consider such mixing as you suggest to be "ruining" the water, and from their subjective standpoint, that's fine. Note, however, that it's strictly a case-by-case basis. If mixing the water bothers you, don't do it. An alternative option would be to dunk a plastic bag full of ice water into the hot water; that will generate the cooling effect without mixing the water. — Lomn 14:02, 24 February 2010 (UTC)

I have no idea what you mean by 'ruining' the water (do you mean for making tea or something?).

But the temperature-thing is easy. If you add an equal amount of water then the resulting temperature will be the average of the two. For example, if you have boiling water that'll have a temparature of 100 C (a 'raging boil' just means that it is working harder at losing the heat added to it by the heat-source). Suyppose it's 1 l. If you add 1 l of water at room temperature, say 20 C, then the resulting temperature will be (100 + 20) / 2 = 60 C. If you add just 50 cl, then you get three parts, two of which are the boiling water, so it will be (2*100 + 20) / 3 = 220/3 = 73,8 C. If you add just 10 cl, it'll be (10*100 + 20) / 11 = 1020/11= 92,7 C. In other words, if you want just 'quite warm' water, say about 40 C, then you'd have to add more water at room temperature than the water in the pot.

But it would be easier to use ice-water (water in which some ice cubes have been floating for a while without completely melting). This is more practical because you can create both temparatures without a thermometer (one with a boil the other with ice). And it makes for easier mathematics as well because you've got a 'point zero' and the other number is 100 (note that this only works for Celsius, not for Fahrenheit). To get at a certain temperature, divide 100 by it and you get the proportion of boiling water you need in the mix. For example, to get 25 C, that has to be 25/100 = 1/4. So the proportion of ice water has to be 1 - 1/4 = 3/4. So 1 part boiling water, 3 parts ice water. If you want 40 C it's 40/100 = 4/10 and 1 - (4/10) = 6/10, so 6 parts boiling water and 4 parts ice water.

I'm sure there's an easier way to explain this, but I hope this helps. DirkvdM (talk) 15:50, 24 February 2010 (UTC)

Just a practical point: use only the water that had the ice in it. Don't add the ice; it counts as "below 0 °C" even if its temperature is exactly that because of the heat of fusion. --Tardis (talk) 16:41, 24 February 2010 (UTC)

Our water memory article is good reading. Comet Tuttle (talk) 17:51, 24 February 2010 (UTC)

For a sufficiently warped definition of "good"! --Tango (talk) 22:09, 24 February 2010 (UTC)

Avid tea drinkers claim that over-boiling the water drives out oxygen and perhaps other dissolved gasses and makes it taste 'flat'. There may be some truth to this...but shaking it up with some air ought to solve that pretty quickly so "ruined" is perhaps a bad choice. SteveBaker (talk) 03:23, 25 February 2010 (UTC)

Surface of Gas Giants

While reading 2010: Odyssey Two, I remember ex-David Bowman observing that Jupiter's core was a diamond the size of Earth, due to the intense pressure on the gases in that region. I, personally, don't believe there is enough carbon in the Jovian atmosphere to create a diamond, but is it at all possible that this theory could be true? MMS2013 14:19, 24 February 2010 (UTC)

Unlikely. ~ Amory (u • t • c) 15:32, 24 February 2010 (UTC)

But there are serious "diamonds in space" hypotheses: Neptune#Internal_structure, BPM 37093. -- Coneslayer (talk) 15:42, 24 February 2010 (UTC)

Aspirin from a tree?

I recently went on a jungle trip, on which my guide showed me a tree the sap of which was supposedly good for stomach-aches. He let me try a bit and it tasted very much like aspirin. At the aspirin talk page someone mentioned that "salicylic acid is similar to the acetylsalicylic acid in aspirin, and is found naturally in some plants, such as the willow tree." So is that all basically the same stuff? Or might a new source of a similar chemical still be useful for medicine? (In other words, can this make me and/or the locals very rich? :) ) DirkvdM (talk) 15:09, 24 February 2010 (UTC)

See salicylic acid. It is a well-known product, not a new discovery. Of course, you could get rich off it. There are a lot of people who sell plants and herbs that don't do much and make good money. All you need to do is find someone to buy it.

I don't know what plant you were shown, but the substance in willow bark essentially is asprin. Acetylsalicyclic acid is just a synthetic version - it is much cheaper to use fancy chemistry to make it than to grow lots of willow trees (and I think it is slightly more effective/has fewer side effects). Using willow to treat pain was well know long before modern chemistry. --Tango (talk) 16:44, 24 February 2010 (UTC)

Actually, no — that's what I used to think too. In fact it's what pretty much everyone used to think. But they set me straight on the talk:aspirin page.

Aspirin has a different mode of action from salicylic acid (the stuff in the willow trees). Aspirin irreversibly acetylates some enzyme, probably COX but I'm not sure about that. Obviously salicylic acid can't acetylate anything, as it has no acetyl group. --Trovatore (talk) 21:46, 24 February 2010 (UTC)

It's also not true that aspirin is easy to make than salicylic acid. Aspirin is made by acetylating salicylic acid. Aspirin is was preferred mostly because it attacks the stomach much less strongly. Algebraist 21:56, 24 February 2010 (UTC)

Well, no, it's preferred because it acetylates COX, whereas salicylic acid doesn't. Salicylic acid has some independent effect; I don't know what it is. I don't know whether it's an anti-inflammatory at all. --Trovatore (talk) 21:58, 24 February 2010 (UTC)

Sorry, I should've made it clear I meant that's the reason aspirin was preferred when it was first devised. I think you're right that salicylic also lacks the non-analgesic effects that were discovered for aspirin later. Algebraist 22:03, 24 February 2010 (UTC)

The "new source of a similar chemical" would have to be more effective, or have fewer side-effects (or preferably both) if you want to make your fortune out of it (without "quackery"). If you have found a new "wonder-drug", then you must take out world-wide patents as soon as possible. You should be aware, however, that most similar chemicals have already been tried and rejected long ago. Dbfirs 21:40, 24 February 2010 (UTC)

Ah, 'similar drugs' is what I was getting at. So there are variations on the drug. (Also see the polymorphism section, although I suspect that that gives just a limited range of variation.) Might there be a list somewhere of plants and trees that contain similar drugs?

I suppose one first question is whether this is a willow tree. Comparing my pictures with these, it may very well be, although I'm by no means an expert. Also, it had shoots that look rather willowish to me. I assumed willows didn't grow in the tropics, but they seem to grow just about anywhere (just mostly in moderate climates). But even if it is a willow tree, there appear to be many species of willow, with lots of variation (not surprising since they grow just about anywhere) and this might be an uncommon one (possibly even unknown to western science, given where I found it). Do they all have the same salicylic acid? If so, and if this is a willow tree, then I suppose that's the end of it.

One more thing, though. Which drugs taste like aspirin? Is it the salicylic acid that gives it the typical taste or the acetyl, or what? DirkvdM (talk) 09:25, 25 February 2010 (UTC)

You should bear in mind that it costs a pharmaceutical company like Bayer (very roughly) about $500,000,000 (yes, that's five hundred million US dollars) to take a "candidate molecule" all the way from discovery of its existence (or its invention), through all the various testing and trials and licencing processes required by governments, to being a marketed product. The subsequent profits it makes for the company also have to cover the costs of all the (many more) candidates that didn't make it all the way, a roughly comparable sum.

Because pharmaceutical companies are working with such vast sums they can afford to employ extensive research staffs who are well aware of the potential for new drugs in locally known remedies such as this; it's therefore very probable that this one has already been, or at best is being, investigated by one or more of them [Disclosure: I used to work at #12 on (both of) the above-linked lists].

On the very slim chance that you have stumbled upon something not yet investigated, you might consult (probably at considerable expense) a lawyer specialising in such matters about how to retain some interest in it, but consider also that most people and legal systems would probably consider that the indigenous people from whom you learned about it would have a far greater claim than you on the fruits of its exploitation.

There are of course less currently regulated and consequently less costly (but also less lucrative) areas of "hebal", "folk" and other "Alternative medicines." Again, it would be surprising, if less so, if this particular local remedy were not already known to such industries. It seems likely from recent trends and events [13] that regulation of these (in the "Western World") is going to be tightened up in future. 87.81.230.195 (talk) 16:23, 25 February 2010 (UTC)

r-tree structure for image retrieval

Hi

please, I have 16-dimension color histogram , i need to use r-tree indexing in order to speed up the image retrieval. how can I determine the MBR in the tree?, and How the overlapping happen? ,how many level I need to represent r-tree? please any help زينب —Preceding unsigned comment added by Dania2009 (talk • contribs) 15:15, 24 February 2010 (UTC)

Have you read the article R-tree? Cuddlyable3 (talk) 23:12, 24 February 2010 (UTC)

rebok

is castro wearing rebok sneakers in this pic?

http://en.wikipedia.org/wiki/File:Fidel_Castro8.jpeg  —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 15:22, 24 February 2010 (UTC) 

They are obviously trainers of some kind - but the photo was taken in 2003 and because Reebok change their designs at least several times a year - it would be very hard to find an exact match for them by searching for images on the web to get a match for the design. However, he clearly likes to wear sneakers here, for example. He's also not above advertising some western brand names either: Adidas!. So I doubt we can say that he was wearing Reeboks - but it's very likely some kind of brand-name sneaker. SteveBaker (talk) 00:57, 25 February 2010 (UTC)

why is the universe so dumb?

It's obviously a huge oversight that just be speeding around for a while relative to the other, two twins can end up with arbitrarily different ages. That obviously doesn't make much sense. Therefore, the Universe is very stupid. My question is: why is it so stupid? Why isn't it more sensible? 82.113.106.92 (talk) 16:32, 24 February 2010 (UTC)

Your argument is just an opinion, not a fact. What you are asking is "Why do I think the universe is stupid?" From your statement, the best answer that I can give is "Because you don't understand it."

Time dilation is an inevitable consequence of the speed of light being the same to all observers. There isn't really a reason for it, though, the universe is just the way it is. --Tango (talk) 16:45, 24 February 2010 (UTC)

well isn't it pretty dumb that if you are a photon of light going the opposite way of another photon of light, and you're both travelling at c, then you are not moving away from the other one any faster than if the other one were a brick wall? That seems really dumb to me, but if you say that it is only my opinion, why don't you give me ONE good reason why it's not dumb? I can't see any reason why it's not dumb of the universe to be such that hurling away at c from a brick wall doesn't move you away from it any faster than hurling away at an object going 186,000 miles per second in the opposite direction. I'm open to any reason why this shouldn't be a really dumb set of laws... (I don't mean that they don't apply, but that it's dumb that they should, that our universe should be so shoddily hacked together in this way). Thanks. 82.113.106.92 (talk) 17:09, 24 February 2010 (UTC)

Stupidity is a factor of intelligence, which means you're suggesting the universe is either a life form, or was created by one. Science can't answer those kind of questions. Vimescarrot (talk) 17:18, 24 February 2010 (UTC)

The universe is wise, which has no bearing on intelligence. --Ludwigs2 17:20, 24 February 2010 (UTC)

Is time dilation really that much less counter-intuitive than, say, the doppler effect or redshift? In other news, where do you want us to go with your assertion that you find the universe dumb, beyond "so what; get a clue"? --Tagishsimon (talk) 17:25, 24 February 2010 (UTC)

The universe is not dumb, and neither are the laws of relativity (or, at the other end, the ones of quantum dynamics). It's quite literally us, who only experience "the middle world" who form wrong assumptions by looking at a small part of the world with bad focus and then expect our assumptions to apply to all of reality. Newtonian physics is not the law and relativity the exception, rather, relativity is the law and Newton's laws of motion are an approximation that works in some limited case. --Stephan Schulz (talk) 17:28, 24 February 2010 (UTC)

(ec) Come on, obviously I'm not talking about 'intelligent' design in the Universe. I mean, in human terms, the way things are are pretty dumb. Actually 186,000 miles per second isn't that fast. It takes an easily discernable amount of time just to ping someone in China and get their response - it is physically palpable lag. And that's on just a local, Earthly basis. On a galactic basis, this universal speed limit is ridiculous. I'm not saying "SOMEBODY" made the speed limit be 186,000 miles per second. I'm saying, it's a stupid state of affairs, regardless of whether anything intelligent (or lack thereof) caused it. It's just stupid. But, for anyone who actually is taking the effort to understand what I'm SAYING here, I'm open to anything you know that makes the above aspects of the universe I mentioned actually be not-stupid, but pretty cool. Here is an alternative way of phrasing it: If reality really were that conceived by classical physics people thought we were living in in the 18th century, NO ONE, but NO ONE, would wish "sigh. If only there were a universal speed limit of 186,000 miles per second. If only you could never move, even in the vacuum of space, even close to that speed. If only twins could end up with different ages if one takes a fast trip." Why would anybody want that? Nobody would want that: it's dumb. Unless you know of some reason why somebody WOULD pine after the state of our universe, if they were like us but lived in a nonrelativistic place. Also, relativism is just one aspect of our dumb universe, don't even get me started one quantum mechanics. One thing at a time: is there anything good or nice about living under relativistic physics? Or, is it merely dumb for the reasons I outlined? Thanks. 82.113.106.92 (talk) 17:39, 24 February 2010 (UTC)

This thread should probably be collapsed for trolling, but I have a good answer. I like living in this awesome relativistic universe because if the speed of light constant and time dilation were any different, it would affect things like the formation of stars and galaxies in unpredictable ways, and human life would most likely not exist. Comet Tuttle (talk) 17:48, 24 February 2010 (UTC)

That's a very good answer, actually, despite the fact that you dismiss my question as a troll. I hadn't thought of that answer. However, that is not due to real stupidity on my part, but because of a lack of science education. All of the humanities (human affairs) are inconsequential spots in the formation of the stars, and so the fact that we are inconvenienced by ping times, for examples to a planet as close as Mars, is nothing compared with the benefit of existing. I guess it's like some really stupid human laws, that nevertheless serve an important purpose, and "but for" them, the place would go to hell in a handbasket. 82.113.106.92 (talk) 17:54, 24 February 2010 (UTC)

It seems that the OP is equating "counterintuitive" with "dumb." This is a huge fallacy. First of all, things are only ever intuitive because you have daily experiences with them, and can perceive events and judge generally what you expect should happen. But physics is the quantitative analyis of the mechanisms of the universe at many different scales. Relativity in particular is concerned with the physics of very large masses, very high energy, very fast speeds (and similar). Since humans are small compared to the scales necessary to observe many relativistic effects, we have no daily experience with them; nor have we evolved biological sensors which can make meaningful sense of those relativistic effects. The same applies to quantum mechanics - which deals with very small energy scales, length scales, and time scales. Again, the behaviour of the universe is very different at such scales - so it seems to contradict your "gut sense" of what should happen. But if you spend a lot of time observing things at quantum or relativistic scales (which means learning to use the mathematical machinery and understanding the experimental observations that are available) - then you will see that the universe actually is quite ordered and follows well-defined rules. Nimur (talk) 18:50, 24 February 2010 (UTC)

It sure seems to follow rules given the current level of sensitivity of equipment. Is it possible that finer analysis may reveal that it does not, in fact, follow any rules at all? 82.113.106.89 (talk) 19:23, 24 February 2010 (UTC)

Also: I don't equate "dumb" with "counterintuitive" -- I call it dumb because no one would ask for them in their absence, but there are a lot of counterintuitive things that people DO ask for, in the absence of any such effect. Two great examples are replication and teleportation, neither of which make any sense on an intuitive level, yet both of which are commonly requested. In other words, every single one of the aspects of the universe"I've described is more readily described by its users as bugs, not features; meanwhile, actually requested features are totally absent. That's what I'm getting at: that what we get, is a wet blanket. I'm especially talking about relativistic effects. They are not useful, but on the contrary, dampen many ambitious plans (such as the trillion mile per second rocket etc). 82.113.106.89 (talk) 19:27, 24 February 2010 (UTC)

"My own suspicion is that the universe is not only queerer than we suppose, but queerer than we can suppose." J.B.S. Haldane. --TammyMoet (talk) 18:57, 24 February 2010 (UTC)

Why would you expect the universe to be how human science-fiction writers want it to be? --Tango (talk) 19:43, 24 February 2010 (UTC)

As you can see we already have a pretty long thread and we haven't even started answering your question yet mainly because of your poor choice of words. I'm sure there is a lesson somewhere in there... Dauto (talk) 20:32, 24 February 2010 (UTC)

I know you were exaggerating, but actually you have started answering the question, viz. Commet Tuttle's "if the speed of light constant and time dilation were any different, it would affect things like the formation of stars and galaxies in unpredictable ways, and human life would most likely not exist". That's the anthropic principle, and kind of a good answer. By the way, you said I used a poor choice of words, but I don't really have better ones for the question and feeling that I'm addressing. What would you suggest I say, given the clarification to the question I've since given? 84.153.235.131 (talk) 21:20, 24 February 2010 (UTC)

Words like 'frustrating', 'annoying', or even 'unfair' would have worked better than stupid and dumb. Dauto (talk) 22:49, 24 February 2010 (UTC)

A complaint that something is "obviously a huge oversight" should be addressed to the one you think is responsible. Unfortunately there Ain't Nobody Here But Us Chickens. Cuddlyable3 (talk) 23:09, 24 February 2010 (UTC)

Personification is not science. If you wanted the science, ask science questions. If you wanted to know why the Universe is stupid to you...that would be psychology, one of the Humanities? The question, as you asked it, seemed to be applying psychology (concepts of intelligence, or lack thereof) to physics. The two are incompatible. Vimescarrot (talk) 23:27, 24 February 2010 (UTC)

I once read a short sci-fi story (Far Centaurus by A. E. van Vogt, I think) where the means of travelling faster than light involved work in the field of "electron psychology". What this meant was never really explained... --Tango (talk) 01:02, 25 February 2010 (UTC)

The problem with the universe is not with it - but with us. We've evolved to clamber around in trees, chase after small furry animals, clonk them on the head so we can eat them and frolic through the grasslands picking delicious nuts and berries. Nothing we've evolved to deal with goes faster than maybe 100mph and no event that we ever care about takes less than the literal blink of an eye. Nothing weighs more than a smallish planet - nothing is (perceptably) larger than however far you can run in a day. So when we find that the rules at scales that our brains have evolved to cope with do not apply for anything that's very heavy, very large, very fast, very tiny or very brief, we're not really equipped to handle that. When we're exposed (through our own science) to things that are as downright weird as time dilation or quantum theory - we're inclined to the kinds of response that you're feeling. It's not at all a strange or inexplicable reaction to how the universe is...it's simply that (for most of us) the boundaries of our intellectual knowledge has outpaced our ability to truly internalize those things. The universe is actually rather cool (I wouldn't say "dumb" or "intelligent") - some of this weird stuff is really useful. Without all of that quantum theory, most of the fancy electronics that we love so much wouldn't be possible. The speed of light thing is a bit of a bummer for the science fiction fans who really wanted to go and explore other star systems - but you've gotta admit it's interesting. SteveBaker (talk) 00:41, 25 February 2010 (UTC)

The real question is, why do you care if the Universe is stupid? If you are so smart then it shouldn't trouble you in the slightest. Only if you were also stupid would other people's stupidity (or universal stupidity) be a hassle. Vranak (talk) 01:56, 25 February 2010 (UTC)

The OP writes "don't even get me started on quantum mechanics." Without quantum mechanics, the protons in the sun wouldn't fuse because they would invariably repel each other (both being positively charged; that's intuitive and sensible, right? -- for an "intuitive" but wrong analogy, think of trying to force "the wrong ends" of two magnets together). The hydrogen in the sun wouldn't produce helium, and so on. It would be very cold and very dark and none of us would exist. Fortunately, quantum tunneling and and velocity distribution allow hydrogen protons to fuse (after a few tens of millions of years of hanging out in the sun). Thanks, stupid quantum mechanics! 63.17.57.56 (talk) 02:56, 25 February 2010 (UTC)

Theology is adept at discussing vaguely phrased and confusing questions. In your question we see a parallell with the well-known Problem of evil (POE) in your Problem of stupidity (POS). Some of the answears to the POE can be easily amended to answear the POS, such as mankinds limited ability to assess the universe or the existence of free will. Or maybe the POS is a variant of the Omnipotence paradox? You could start with that and move on to the Euthyphro dilemma with some very interesting conclusions. (There must be a forum for such ideas somewhere :-) EverGreg (talk) 09:27, 25 February 2010 (UTC)

Adept at discussing - certainly. Able to come to a true, useful or even comprehensible answer? Never. SteveBaker (talk) 04:06, 26 February 2010 (UTC)

Salt ionizing in water

If salt is ionized in water, why does the water still taste salty? I know that sounds dumb, but if the salt gets separated into Na⁺ and Cl^-, wouldn't it stop being salt and stop having its properties? Maybe not all of the salt gets ionized? Or maybe I just don't understand the process fully. —Preceding unsigned comment added by 160.36.39.222 (talk) 16:50, 24 February 2010 (UTC)

Don't forget that any undissolved salt entering your mouth will dissolve soon enough in your saliva. So judging from that alone, it seems to me that all you ever taste is the ions. Vimescarrot (talk) 17:21, 24 February 2010 (UTC)

(edit conflict) It is the sodium ions that cause the salty taste - our article on taste says "Saltiness is a taste produced primarily by the presence of sodium ions". Other alkali metal ions produce a similar taste. I doubt it is possible to know what undissolved salt tastes like - before it gets anywhere near your taste buds, it will have dissolved in your saliva. Gandalf61 (talk) 17:22, 24 February 2010 (UTC)

Other alkali metals tasting roughly the same is why potassium is often used to replace the sodium in low-sodium salt. (Not that potassium is any better for you in large quantities than sodium, unless you have some medical condition that makes sodium really bad.) --Tango (talk) 18:08, 24 February 2010 (UTC)

I'd say very roughly. I can easily distinguish KCl from NaCl. KCl is subjectively much more "sour".

It's too simple to compare K to Na as "which one is better for you". The main issue is that most people eat far too much sodium. On the other hand it takes (IIUC) significantly less potassium to outright kill you (quickly, as opposed to via hypertension, which generally takes years or decades to be lethal). --Trovatore (talk) 23:39, 24 February 2010 (UTC)

Galactic Plane and Rotation

Relative to the equator (or ecliptic) what is the angle of the galactic plane? Assuming the north pole of the earth faces upwards does the galaxy rotate CW or CCW? Is there some rule determining which way a galaxy rotates? TheFutureAwaits (talk) 17:23, 24 February 2010 (UTC)

See Galactic coordinate system, I think it answers all your questions except the last. The way a galaxy rotates will depend on the random motion of the matter than collapsed to form it. That motion will, due to random chance, have had a slight net rotation when you average it out. As the proto-galaxy collapses, conservation of angular momentum means the rotation gets faster and the galaxy flattens out into a disk. Which direction it rotates will be the same direction as that tiny net rotation the original cloud had, which is random. The same principle is what results in all the rotations in the solar system (rotations of planets on their axes, orbits of planets around the sun, orbits of moons around planets, etc.) which are almost all in the same direction (anticlockwise when viewed from above the north pole, if memory serves). The exact mechanism for the formation of galaxies is still up for debate, but what I've described should be accurate as far as it goes. --Tango (talk) 18:06, 24 February 2010 (UTC)

Numbers and diagrams only get you so far in getting a real gut feel for this. So how about thinking about it like this: The photo at right of the Milky Way was taken at a Telescope facility in Paranal in Northern Chile (More info about the photo comes from here). It was taken in the middle of winter and Paranal is well south of the equator - so we're somewhere "underneath" the planet. The bright dot in the middle of the photo is Jupiter. The laser beam is pointing towards the center of the galaxy. It takes a bit of mental gymnastics to get your head around that. But since Earth and Jupiter both lie in the plane of the solar system's ecliptic - and the photo was taken in the middle of the night - so the sun is somewhere off the bottom of the photo beneath our feet - so if you imagine a triangle with one point where Jupiter is, one where we're standing and another point way below our feet - then you can get a feel for how the plane of the solar system ecliptic doesn't line up well with the plane of the galactic disk. Hopefully, this conveys the fact that the solar system is tilted at about 85 degrees to the plane of the galaxy. When you look at the Milky Way, it fills about 100 degrees of your field of view - if you put your arms out to try to grab it(!) they make an angle bigger than a right angle. Imagine you're holding a gigantic round disk in your hands while they are 100 degrees apart - and that should give you a feeling of just how far on the outer edge of the galaxy we really are. SteveBaker (talk) 00:15, 25 February 2010 (UTC)

Where does that 100 degrees come from? The Milky Way surrounds us on all sides as a belt. That's 360 degrees. How much of it you can see at any given time will depend on where on the planet you are. The bit towards the centre of the galaxy is much more dramatic, of course. --Tango (talk) 00:35, 25 February 2010 (UTC)

Yeah - of course you're right - the galaxy is all around us. The number I quoted is for the bright stuff - and it's very approximate - no science behind it. If you get someplace where you can see the Milky Way clearly - it just looks like you could grab it with outstretched arms at a bit more than 90 degrees. The number "100 degrees" is mentioned at the link I pointed to here. SteveBaker (talk) 01:23, 25 February 2010 (UTC)

Thanks guys, this explains a lot regarding the angle. The only part I don't get is why the gravity of the galaxy wouldn't be enough to cause stellar systems to align their planets with the galactic plane. If the gravity is strong enough to make everything rotate around the galactic core then why aren't stellar plane's aligned? TheFutureAwaits (talk) 14:15, 25 February 2010 (UTC)

Weather and Axial Tilt

What would the weather and seasons be like on Earth of the axial tilt was 90 degrees instead of 23? Would the change have prevented life from evolving? TheFutureAwaits (talk) 17:26, 24 February 2010 (UTC)

The more I think about it there could be two answers couldn't there? If the "south pole" of a 90 degree axial tilt was pointing along the orbit of the Earth (aka 90 degrees from the direction of the sun) then there would be no seasons, just a 12 hour day night cycle right? If the "south pole" was facing the sun then there would be extreme seasons resulting in 6 months of darkness for every location on the planet. I imagine that would be enough to cause catastrophic weather likely preventing any life. Is my understanding correct? TheFutureAwaits (talk) 17:41, 24 February 2010 (UTC)

Not quite. The axis stays put as the Earth orbits the Sun so, relative to the Sun, it rotates once a year. This is what causes the seasons. Your two scenarios are actually just different parts of the same scenario. At one point the north pole will be pointing at the sun, then 3 months later the axis will be pointing along the Earth's orbit, then 3 months later the south pole would point at the sun, then 3 months after that it is pointing along the orbit, just in the other direction, and then 3 months later the north pole is back facing the sun. During spring and autumn you would get normal 12 hour days, during summer you would get constant sunlight and during winter constant darkness. It's just like what happens inside the Arctic/Antarctic circles in real life, but the circles will now be the equator so the whole northern hemisphere is the Arctic and the whole southern hemisphere is the Antarctic. --Tango (talk) 17:51, 24 February 2010 (UTC)

Somewhere above about 70 degrees of tilt it is predicted that the poles would have an annual average temperature higher than the equator (due to many months of 24 hour sun at the poles) and the equator would start to form an ice belt due to the generally oblique sunlight it sees most of the year. Dragons flight (talk) 19:04, 24 February 2010 (UTC)

Average temperature is irrelevant to life. Far more important is the extremes. The equator may be colder on average, but it would be much more stable, which is what is important. --Tango (talk) 19:45, 24 February 2010 (UTC)

That's not true. Average temperature matters a lot when you put snow and ice in the mix. Whereas many forms of life, e.g. deciduous plants and hibernating animals, have adaptations to specifically deal with seasonal variability. If the equator had permanent ice sheets (which is likely at a 90 degree tilt), then I think it would be rather barren of life the same way our polar deserts are relatively barren now. Stability matters, but so does staying away from 0 C for us water based lifeforms. Dragons flight (talk) 22:19, 24 February 2010 (UTC)

If you have an ice belt, I would expect the life to be underneath it where there would be liquid water. If the equator is always frozen there will be belts on either side that are seasonal and life could migrate between. --Tango (talk) 00:02, 25 February 2010 (UTC)

As for the consequences for life, it is difficult to say since we only have a single example of a planet where life can evolve. You certainly couldn't have life like we have, there would need to be major changes. The equator would be fairly stable temperature-wise, so I suppose life could evolve there. Some very simple life might be able to survive the massive temperature changes elsewhere or complex life could migrate (as many species do now). Exactly how great the temperature variations would be would depend on whether winds can transfer heat from the day side to the night side effectively. The issues are very similar to those found with tidally locked planets, like many of the planets we've found around other stars are thought to be. See Hot Jupiter for some information. --Tango (talk) 17:56, 24 February 2010 (UTC)

As I understand it, the current best theories for abiogenesis involve white smokers underwater. For this, plate tectonics (and hence a large hydrosphere) are more important than climate. What happens after that is a lot harder to predict, but I would trust evolution to find ways of coping with the different scenario. --Stephan Schulz (talk) 19:03, 24 February 2010 (UTC)

I assume that life first formed in the oceans, in which case as long as you don't freeze the oceans solid, I'd say the existence of life is still quite likely. Life on the surface would have to deal with greater extremes, but the oceans are a pretty good buffer for many forms of life. Dragons flight (talk) 19:04, 24 February 2010 (UTC)

No matter how the planet spins or points, there have to be some places that get a bearable amount of sunlight for a bearable amount of time. When the south pole points towards the sun, it cooks and the north pole freezes - but around the equator, there is a nice belt that gets a reasonable amount of sunlight. When the north and south poles line up along the path of the orbit, then at the equator, you have a fairly normal day/night cycle - so living on the equator would be kinda like living at the poles for us with months of perpetual twighlight followed by months of more normal conditions. The third extreme is when the poles point at right angles to the plane of the orbit...which is more or less what we have. Even if the planet isn't spinning at all, there are still places that get a reasonable amount of sunlight. Probably the worst case is not spinning but not tidally locked so that the nominal poles of the earth point toward the sun for months and then along the orbit for months - but even then, there are two points on the equator that get reasonable sunlight all year round. There ought to be liquid water no matter what (although not necessarily everywhere). So long as life has a way to get started, it's hard to imagine that between migration, hibernation and simply living in the right places, it could not evolve and continue. The most significant issue is what these peculiar arrangements do to weather and water - if it's enough to cause crazy energetic stuff to happen - then life might have a hard time of it. SteveBaker (talk) 23:51, 24 February 2010 (UTC)

I could imagine very strong currents in either the atmosphere, the oceans (under the ice) or both. Whenever you have localised heating of a fluid, you get convection currents. They could be really strong. --Tango (talk) 00:02, 25 February 2010 (UTC)

This is a really interesting subject. Steve, I'm having a hard time visualizing the two points on the equator you mentioned:"Probably the worst case is not spinning but not tidally locked so that the nominal poles of the earth point toward the sun for months and then along the orbit for months - but even then, there are two points on the equator that get reasonable sunlight all year round." Is there any chart or map which would explain this more clearly? In fact any graphic of any of these scenarios would be most appreciated. TheFutureAwaits (talk) 11:11, 25 February 2010 (UTC)

OK - so for some months of the year, (let's say around January) the planet's North pole faces the sun. Any point on the equator sees the sun on the horizon for months at a time whether the planet is spinning or not. The same for the months when the South pole is facing the sun (July). This is the same whether the planet is spinning or not. But in the intervening months, as the north-south axis becomes parallel to the direction that the planet is moving around it's orbit (April and October), then (if it's not spinning on its axis) there will be a circle of points running around the planet from one pole to the other via the equator that see the sun on the horizon. So during the course of three months - we go from one pole cooking (December) and the other freezing with the equator being in partial sunlight and therefore potentially livable - to a situation in April where (let's say) the Eastern hemisphere is cooking and the Western hemisphere is freezing with a circle of points going through both poles that is in partial sunlight. OK so now, imagine - as the planet moves between those two extremes, that circle of "reasonable temperature" gradually rotates from one of these positions to the other. However, there are two points on the equator where the April circle of reasonableness crosses the equator that are in partial sunlight all year round Everywhere else gets cooked and frozen alternately.

But if the planet is spinning about its axis - then in December and June, half the planet is frozen and the other half cooks - but in April and October, everywhere sees a 24 hour day/night cycle. In that scenario, anywhere on the equator gets normal days for six months out of the year - and perpetual twilight for the other six.

SteveBaker (talk) 04:00, 26 February 2010 (UTC)

Joseph Jenkins

Original post removed.

This isn't really a science question. I'm trying to give you the benefit of the doubt, but it seems that your post is an effort to troll the desk so that people will search for shock sites. Little do you realize that the Ref Desk regulars are savvy internet-jockeys who will not be taken in by such antics. If you disagree with this point of view, and have a valid reason why you posted this to the Science Desk, please elaborate. Nimur (talk) 18:54, 24 February 2010 (UTC)

put my question back up. i was not trolling, your paranoid. humanure is something i do. its been around since 1990 and jenkum is a new thing. i wanna now if theres a correlation. —Preceding unsigned comment added by 67.246.254.35 (talk) 13:01, 25 February 2010 (UTC)

Black holes

Every black hole will try to pull object towards it's center. Now the same force will be be from (far end) to its center at both the sides meaning that any object it pulls cannot come out from other side as it will be attracted towards the center. So then will the object will remain always at center and not come out from other end? Is there any way to measure the pull of the Black hole? —Preceding unsigned comment added by Itsrohit (talk • contribs) 18:14, 24 February 2010 (UTC)

what? —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 18:22, 24 February 2010 (UTC)

I don't think this has anything to do with your question, so I've given it a new section heading. --Tango (talk) 18:29, 24 February 2010 (UTC)

See the answer provided at the section below, and in the future, please only ask the question once. — Lomn 18:48, 24 February 2010 (UTC)

is this a rigorous procedure?

what do you think of this methodology for debunking the idea of plants responding to prayer or bioenergy. I think the easiest would be something like buying a bag of potatoes, putting each one in a separate paper bag with a number on it, placing them along on a table in order (this configuration to be retained throughout, no touching them or the tables until after the experiment) then, say there are 50 numbers. Then I would with a program randomly partition each one into one of two lists, like with a random binary number, if it's 0, it goes on the first list, if it's a 1 it goes on the second list, and at the end a coin flip determines if I'll be praying and bioenergating up the first or the second list. I print the two sheets of paper twice, once to be put on the table inside an envelope but not touched again (one of each list), and the other copy is the one I use. Of the other copy, I flip a coin at the start of the experiment to see if I will be praying up and bioenergating the first or the second sheet of paper. The one I'm not bioenergating/praying up I discard. Then every day, for my remaining key, the ones that are listed I individually go to and pray and bioenergate up for 5 minutes, giving the ones that aren't on the list absolutely no love or attention. (However, I do not touch them or the table or interfere in any way, they are literally just splayed out, before they were even assigned to the first or second list).

Then, after an amount of time that is normally enough for sprouts to grow (however I don't look inside the paper bag! I still don't touch them, I simply discard the key I had been using (randomly either the first or the second sheet of paper). Then I invite a statistician student to help with my 'science project' showing him the envelope that I never touched, and telling him that it has two lists of potato numbers, one of them is the ones I fed with Miracle-Gro, and the other ones I didn't. I don't tell him anything else, but let him go to work.

If he comes back with high statistical confidence that he's determined which list is the miracle-gro group, and it matches the group I've been praying for, then uh-oh, the prayer and bioenergy must have done something, or I picked a bad statistics student :(( :((. If, on the other hand, he has no statistical confidence as to which one had been miracle-grown, then Euroka! Prayer + bioenergating debunked.

Is this a correct procedure? Thank you. —Preceding unsigned comment added by 82.113.106.92 (talk) 18:19, 24 February 2010 (UTC)

Your research student shouldn't be given a key, you just ask him to look in each bag and write down how many sprouts it has (or how long they are, or whatever). Someone that knows a bit of statistics then compares his list with you key and sees if there is a statistically significant correlation. There is no point lying to anyone about what the experiment is about. As long as the research student doesn't see the key, he can't bias the results. --Tango (talk) 18:27, 24 February 2010 (UTC)

What if I get someone else to rate each potato on a subjective scale, 1-10, for how "healthy" and "sprouty" and "energetic" it looks (third obviously very subjective). If they don't see the key, and there are enough potatoes, will it still be rigorous? For example, the statistitician then just gets a list like:

1-5/5/7 2-3/5/7 and they aren't told what the three factors are, just that the scale is 1-10. Also, there would be no evaluation at the beginning, only the end, and obviously the evaluator doesn't get to see the key. In that case, is that enough information for the statistician to say whether there is statistical confidence in differentiating the two lists based on one or several of the factors (without knowing what they are)? Thank you. 82.113.106.92 (talk) 18:38, 24 February 2010 (UTC)

One hole I see in this procedure is that since you have already decided you are "debunking" the prayer idea, your prayers are unlikely to be sincere. You should locate a person who really believes they can affect the potatoes with their bioenergy, and have them do the prayers. Hey, I'm with you on the likelihood of this one; I'm just sayin'. Comet Tuttle (talk) 18:41, 24 February 2010 (UTC)

Oh no, I have very strong prayer and bioenergy: it just doesn't do anything. 82.113.106.92 (talk) 18:45, 24 February 2010 (UTC)

Or more open-mindedly I should say: I would just like to show rigorously if it does anything to potatoes that is statistically discernible. :) 82.113.106.92 (talk) 18:46, 24 February 2010 (UTC)

By using the term "debunking" you have already invalidated the experiment. --TammyMoet (talk) 18:52, 24 February 2010 (UTC)

Actually, I think the opposite thing will happen, that there will be statistical effect from personal bioenergy. The reason I used "debunking" was so I wouldn't be called a troll/crank/all manner of other things here... :) 82.113.106.89 (talk) 19:18, 24 February 2010 (UTC)

Yes, the statistical effect will be the opposite of what you are doing precisely because you have already set your intention. I hear what you're saying about being called a crank - I'm probably the only person here who holds cranky beliefs! And it is generally held in the metaphysical community that your intention affects the outcome. Therefore, you have already set your intention and the outcome is therefore assigned. --TammyMoet (talk) 20:52, 24 February 2010 (UTC)

Such criticism only goes to show that prayer is not scientifically definable. How can you measure intent? In order to make a scientific definition of prayer, we need a set of observables - for example, a critical number of specific words must be chanted; a specific number of hand movements must be performed; etc. Any set of actions which meet that definition, whatever it is, are prayer. Since sincerity is not measurable or well-defined, it is silly to put it as a required criteria for defining some set of actions as a "valid" or "invalid" prayer. Without a rigorous operational definition for prayer, I think it is impossible to decide whether a plant has been "prayed at" or not. (How could you deal, for example, with a corner case of somebody unconnected with the experiment who has prayed that science will prove, or disprove, the efficacy of prayer? If their prayer changes the outcome of your experiment, the resulting conclusion might contradict itself.) If something as subtle as subconscious intent affects the definition of "prayer", then we need some way to measure that so that we can make the experiment repeatable. Since it is impossible to come up with a widely-acceptable objective definition of prayer, the experiment cannot be expected to attribute any measurable effect to such a hazy, ill-defined cause. Nimur (talk) 22:12, 24 February 2010 (UTC)

To maximise the Signal-to-noise ratio of your results use potatoes that have been grown by atheists (but not in holes) and do the experiment well away from churches and casinos. Cuddlyable3 (talk) 22:53, 24 February 2010 (UTC)

Hmmm - the trouble with that is that you can't tell whether atheist potatoes are responding to the prayer or benefitting from the humor of watching you do it! SteveBaker (talk) 23:37, 24 February 2010 (UTC)

Making an experiment totally rigorous is very difficult. Suppose, for example, that your mere presence near the plant makes it grow (let's say maybe the CO2 from your breath helps it out). You'd pray to half the plants and they'd do better than the ones you ignored. So that's not a rigorous experiment at all! So maybe you have to do a 'blind' experiment: Recite 'fake prayers' in front of one half and 'real prayers' in front of the other. But the experimenter might be the cause of the problem here. Maybe you get more excited when doing the 'real' praying and accidentally exhale more CO2? To fix that, you need a double-blind experiment...but that's kinda tough because you know what you're saying. Perhaps you need to find someone who doesn't understand a word of english to do the reciting - so they can't tell which random-seeming words are a "real" prayer and which are fakes. But if that fails to show a result - then maybe the problem is that the person doing the reading these words has to really believe in it. As you can see, it's exceedingly hard to get this right. HOWEVER, you can first do a very simple, poorly controlled experiment and just see if there is a massive difference to be observed. If there is, you can't make direct conclusions - but you can at least see if it's worth going to the next step. If your simple experiment shows no difference (as seems to be overwhelmingly likely in this case) - then you may not wish to proceed with the difficult stuff. SteveBaker (talk) 23:34, 24 February 2010 (UTC)

Ha! I caught Steve Baker not understanding something!!! Yay :) :) :). So, what you don't understand Steve Baker, is the meaning of "blind". You mean a placebo (fake prayers). It doesn't make sense of a potato experiment being single blinded or not, as a potato can't be told or not told whether it is the control. However, a person can be: if I am not a blind subject, I know if I am being given medicine under evaluation or just the current gold standard medicine for the piercing headache I have. I can then report my results to my researcher. In this case, the self-reported headache lengths and intensities will be skewed by the idea of having received a super-new drug being tested. (you can test this effect by giving the subjects the same old gold standard drug, but just telling one half of them that it is super new and being tested - they will not report exactly the same effects). now if the doctor doesn't tell the subject if she is getting the old or the new drug (here, fake or real prayers), then that is single-blind (which obviously isn't relevant to a potato - since they can't be told, all experiments on non-sentient objects are automatically blind). However, there is still a problem as in cases where it is very important to the researcher (say, in an aids vaccine the researcher personally helped develop) to show an effect, the researcher might consciously or unconsciously affect the behavior or reporting of the control group. Say, by just mentioning them casually a few factual pieces of information about the risks of unprotected sex with stranges, perhaps just a casual reminder that the drug is not effective and the common saying that for highly contagious diseases, from the disease's perspective, when you sleep with someone, you sleep with everyone they've slept with and so on. This could be totally subconscious, yet the brief mention could so affect the control group that they are simply disgusted by that idea; maybe they still sleep around just as much as before, but out of the pool of people they could be sleeping with, they just take ONE second to choose the ones that are less obviously slutty or shady, the ones who at least make a tiny effort to judge the other person and maybe don't say yes right away, but after 2 minutes. That SLIGHT change in behavior could, depending on the demographics and so on, TOTALLY change the epidimiology, maybe the control and test group would have both had a lot of sex, but only been infected by people who have averaged more than 100 sexual partners a year, but none of the subjects the doctor makes his careless warning to will choose the people averaging 100 sexual partners anymore, since this is pretty obvious to tell, and disgusting to them. So, if you don't want to end up with a "miracle" drug that is nothing more than a casual remark the scientist happens to make more often to one group than another (because subconsciously they don't want their test group sleeping around, increasing their risk, and "outweighing" the vaccine effect the researcher really hopes is there), then you have to make the researchers who interact with the patients have no knowledge of which medicine they are giving. They can just say: "okay, here is either the status quo drug or a candidate, I don't know which one either", and so on. This, double-blind, you can do with inanimate objects (though I guess it should just be called blinded), by not kinowing which treatment you're giving to something. How would it be possible to pray for plants without knowing whether you are currently praying or not-praying? Clearly this is impossible, and so it is not possible to make this particular experiment fully blinded... (unlike say, testing miracle-gro, in which case it is easy to make is so you yourself don't have a clue if you are putting miracle-gro or water into the soil at the moment). 82.113.106.97 (talk) 15:43, 25 February 2010 (UTC)

Eh? That's exactly my belief - except that you are assuming that the potatoes are not capable of "understanding" (well, perhaps: "reacting to") the stimulus we're testing - but that's pre-judging the result. If we're actually going to do this rather silly experiment, we have to take the possibility that it might work as a given. It's "possible" that the potatoes do indeed react to being breathed on or talked to...and if so, then that might skew the results either in favor of - or against - the hypothesis we're testing. Hence we DO have to "blind" the potatoes by randomly giving them the "gold standard" (talking to them) or the "experimental drug" (prayer). That's a blind experiment. But (as you correctly say), the "doctor" (the person who 'administers' the prayers) has to be blinded too just in case he does something to inadvertently give the potatoes what they need just because he knows which ones are supposed to "win". Everything you say applies perfectly well to what I said. I didn't misunderstand a thing. SteveBaker (talk) 03:38, 26 February 2010 (UTC)

Future citizens of Earth demonstrate (Video) a 10-fold prayer-free regime for processing Solanum tuberosum. Cuddlyable3 (talk) 18:04, 25 February 2010 (UTC)

Object at center of Black hole

Every black hole will try to pull object towards it's center. Now the same force will be be from (far end) to its center at both the sides meaning that any object it pulls cannot come out from other side as it will be attracted towards the center. So then will the object will remain always at center and not come out from other end? —Preceding unsigned comment added by Itsrohit (talk • contribs) 18:32, 24 February 2010 (UTC)

More or less correct. Anything that passes inside the black hole's event horizon is never passing back outside the event horizon. As for the "passing through the center" bit, that needs a little more examination. Your premise for "why" is flawed -- moving aside from black holes, there are plenty of scenarios where we can do thought experiments about dropping items through the center of some massive object. Those items don't stop right at the center even though the gravitational force is balanced, and that's because they've still got a lot of velocity. It's not until they've gone past the center of gravity that they slow down and eventually return. Back to black holes, though, it's possible that something hitting the exact center (the gravitational singularity) might instantly stop -- I'm not fully up on the weird math that takes place there. However, it's not necessarily a meaningful discussion. From an outside observer's perspective, once an item passes the event horizon, it's gone. We don't know what happens to it. Worse yet, the outside observer doesn't even observe the object pass the event horizon, due to time dilation. — Lomn 18:45, 24 February 2010 (UTC)

My understanding is that the singularity doesn't exactly experience time — that it is the future in that region of space. So things hitting it stop, but not in the normal sense because they aren't experiencing time anymore at all. --Tardis (talk) 19:09, 24 February 2010 (UTC)

Yes, if you look at the Schwarzschild metric, the radial coordinate is time-like inside the event horizon, so you cannot move outward. Icek (talk) 19:24, 24 February 2010 (UTC)

The OP refers to the black hole's "center." This is usually called the singularity. In non-rotating black holes (and probably all black holes), all objects that pass the event horizon reach the singularity, where they have already ceased to be "objects" due to spaghettification. So it is not meaningful to ask "what happens to an object" at the center, because no object remains an "object" by the time it gets there; instead, it is crushed to infinite density and simply adds to the black hole's mass. (So, to answer the OP's specific question: everything that enters eventually reaches the "center" in a different form, and "remains" there in the sense that it becomes part of the hole's mass.) This is probably also true of all black holes, but the current state of theory allows for the possibility that in some rotating black holes an object which passes the horizon might avoid the singularity; that would be a rare event in any case, and will likely be shown to be impossible as the theory progresses. Note: some information does, however, escape from black holes, though "objects" as such do not (see Black hole information paradox). 63.17.57.56 (talk) 03:44, 25 February 2010 (UTC)

"Crushed to infinite density" doesn't make sense - when an infinity appears in physics like that it is mathematics way of telling us we've made a mistake. Something happens at the centre of a black hole, but we don't know what. --Tango (talk) 17:37, 25 February 2010 (UTC)

Supplementary question: When an object is attracted towards a black hole is the black hole attracted towards the object? When the object accelerates towards the black hole are the Conservation Laws of momentum and energy conserved by proportional movement of the black hole? Cuddlyable3 (talk) 17:33, 25 February 2010 (UTC)

Yes. At large enough distances, a black hole behaves just like any other object of that mass. --Tango (talk) 17:37, 25 February 2010 (UTC)

What is that mass? Cuddlyable3 (talk) 19:27, 25 February 2010 (UTC)

It may be any mass. There is no theoretical limit on how heavy or how light a black hole may be. Dauto (talk) 21:41, 25 February 2010 (UTC)

If 1gm of material falls into a black hole does the mass of the black hole increase by 1gm? Can a black hole's mass be as small as a subatomic particle? Cuddlyable3 (talk) 22:56, 25 February 2010 (UTC)

Yes. Maybe. Really small black holes evaporate in a fraction of a second by Hawking radiation. Working out exactly what happens to the smallest black holes would require a theory of quantum gravity, which we're still working on. --Tango (talk) 03:26, 26 February 2010 (UTC)

Tango states that "'Crushed to infinite density' doesn't make sense." Neither does the quantum leap (how can something go from one place to another without crossing the intermediate area?), but it's real. When the overwhelming consensus is "A," simple standards of citation and authority make "B" incorrect; SO, it is incorrect to say that the singularity does not have infinite density. It may eventually be shown that it doesn't, but as of the last 40-plus years (since it was demonstrated by Penrose), it has been the overwhelming consensus of all citable authority that the singularity has infinite density. Simply google "black hole singularity" and you'll find dozens of authoritative sources stating exactly that. Tango writes "when an infinity appears in physics like that it is mathematics way of telling us we've made a mistake," but this is an opinion supported by no citable authority and actually disproven to the extent that general relativity describes the final stages of massive stars. "A black hole is what you get if you compress so much mass into a region of space that it collapses, under its own weight, to an infinitely small, dense, point called the 'singularity.'" -- Leonard Susskind at http://calitreview.com/790 . See also http://www.scribd.com/doc/9517358/Michael-Good-The-Black-Hole-Singularity ... and about eleventy zillion other sources. Yes, it's true we don't know what happens in the singularity -- and in fact it is unobservable by definition, so any theory will be strictly mathematical. But the singularity has infinite density, whether or not that offends someone's sense of colloquial or semantic logic. —Preceding unsigned comment added by 63.17.46.122 (talk) 03:35, 26 February 2010 (UTC)

Liquid-mixing scintillation effect

Sometimes when two miscible liquids are mixed, you can see a hard-to-describe scintillation effect (sort of like you can see the two liquids mixing, even when they're the same color). It works when pouring cold water into a cup of hot water, if that helps. What is this called, and what causes it? 76.204.127.175 (talk) 21:28, 24 February 2010 (UTC)

It's caused by the two liquids having different refractive indexes: light bends "differently" in each. See Schlieren photography. DMacks (talk) 21:44, 24 February 2010 (UTC)

Subject catgeorization

The University of Edinburgh Library has shelved some books in strange categories. When this was pointed out they gave the excuse that sometimes books have more than one possible category. That may be a valid reason sometimes but I don't think so in this case. I can't figure out why these books have been categorized in the way they have so I'm asking here in the hope that someone will be able to explain what these books have to do with the subjects they have been put in. "Measure, integration, and functional analysis‎" by Robert B. Ash was in the geophysics section, as was "The elementary process of Bremsstrahlung" By Eberhard Haug, Werner Nakel, and a book on the evolution of binary stars was also in the geophysics section. The book "Quantum Field Theory on Curved Spacetimes" by Christian Bär, Klaus Fredenhagen was in the biophysics section inbetween a book on zoological physics and a book on insect populations. I took these books to the library desk to enquire about this. The next day the books had been put back in the same place. Upon taking the "Quantum Field Theory" book back to the desk, I was told that the librarian had checked and this book has been categorized the same way in other places as well. I reckon the librarian is talking bs but I would love to be proved wrong. —Preceding unsigned comment added by 217.44.34.55 (talk) 21:53, 24 February 2010 (UTC)

Somebody, somewhere, has clearly screwed up. It may well not be at that library, though. Library often get their classifications from some central source. If that central source has screwed up, then the librarian could well be right that other places have the same problem. That doesn't mean the librarian shouldn't do something about it, though... Does the physics department have a designated library liaison? If so, it might be better if they talked to the librarian about the problem. --Tango (talk) 22:08, 24 February 2010 (UTC)

See the article on Dewey Decimal Classification in case the library uses that system of categories. You may find the librarian to be more receptive if you can point out the correct categorisation in Dewey terms. Cuddlyable3 (talk) 22:38, 24 February 2010 (UTC)

Looks like the University of Edinburgh Library uses the Library of Congress classification. 75.41.110.200 (talk) 23:23, 24 February 2010 (UTC)

I don't know why libraries have so much trouble over such a relatively simple data organisation problem. If you have all your books listed on the Internet along with their shelved position - then the library can be classified in any and all ways imaginable - books can be in multiple categories without problems. The only reason shelf order matters in an era of near-universal computer access is for people who browse looking for books in a general category. But even that is well handled by things like "Other people who borrowed this book also borrowed..." kinds of search criteria. The biggest problem is when a book gets put back in the wrong place by accident - so if I were organizing a system, I'd put computer-generated colored stickers on the spines so that all of the books on one shelf should have the same combination of colored stickers - if a book is on the wrong shelf, you can spot it in seconds. SteveBaker (talk) 23:22, 24 February 2010 (UTC)

First, I have spent a long time working on the "Other people who XXX this..." algorithms and I think a proper algorithm would be "Other people who borrowed this book then borrowed...". Time ordering plays a role in which books you may want to read. Second, There are libraries that use color coded stickers. I've seen many (ie: the public library in Charleston County, SC). I've also seen work on using barcodes. A robot can scan shelves very quickly at night and take note of all incorrectly shelved books. It would be optimal if it could also correct shelving. Finally, as for categorizing books. Some libraries shelve books in multiple locations. It was difficult to manage when it was all done by hand, but computers make it easy to manage multiple copies of a book sitting in multiple locations (even multiple libraries). —Preceding unsigned comment added by Kainaw (talk • contribs)

February 25

salt in water

since i got my wisdom teeth out recently ive been drinking warm water in half a glass with half a teaspoon of salt to clean the mouth. anyway today i heated up the water for 30 secs in the microwave, then put the half teaspoon of salt in the glass. i then stirred the glass with the teaspoon. as i was stirring, the spoon made a low scrapping sound, and as the salt dissolved, the sound grew louder. when all the salt was dissolved, stirring the glass sounded normal.

i was wondering what was happening with the sound. was the salt absorbing the sound? it was really cool.--Minor330 (talk) 01:16, 25 February 2010 (UTC)

I would think it would be perfectly obvious: so obvious in fact that I will resist the urge to explain. I think you are testing the reference desk to see just how stupid people can be. But if you are not, well, the sound ceased when the salt disappeared, because the salt was making sound as it scraped the glass. Come on. Vranak (talk) 01:52, 25 February 2010 (UTC)

Is that really an appropriate tone to take in answering a question that appears to have been asked in good faith? Particularly since you seem to have missed the key part: that the sound got louder as the salt dissolved, which is what the OP is querying. Possibly related to the change in pitch as you stir a hot chocolate? 131.111.248.99 (talk) 02:16, 25 February 2010 (UTC)

We had a very similar question before - (someone should check the archives - I had a quick search but couldn't find it) I'm 99% sure the salt and the heat has nothing to do with it. What I think makes a big difference is that when the liquid is already swirling it makes a dramatically different sound than when it's stopped or moving slowly without turbulence. SteveBaker (talk) 03:59, 25 February 2010 (UTC)

This question was similar. Cuddlyable3 (talk) 17:24, 25 February 2010 (UTC)

Yeah - that's the one I was thinking of. Thanks! SteveBaker (talk) 03:19, 26 February 2010 (UTC)

Good faith has its limits. Even so I have accounted for the possibility that the questioner did not know what was happening even though he already explained exactly what was happening. Groan. Vranak (talk) 04:00, 25 February 2010 (UTC)

How do you propose to explain why the sound grew louder as the salt dissolved? If the salt was responsible, shouldn't the sound become quieter? --99.237.234.104 (talk) 04:54, 25 February 2010 (UTC)

Related : The Straight Dope : When I stir my coffee, why does the sound gradually change pitch? APL (talk) 15:41, 25 February 2010 (UTC)

I would surmise that it is due to the changing speed of sound in different strata. Vranak (talk) 18:49, 25 February 2010 (UTC)

After the last time we were asked this (Thanks Cuddlyable!) our OP claimed that (s)he could reliably "reset" the sound by stirring the liquid. If that's true, it busts the dissolved gasses theory - so I think "The Straight Dope" guy is guessing. SteveBaker (talk) 03:27, 26 February 2010 (UTC)

Chemical looks.

I have six out of: 1-aminobutane, benzaldehyde (according to wikipedia - colourless liquid), benzoic acid (according to wikipedia - colourless solid), butanone (according to wikipedia - colourless liquid), benzophenone (according to wikipedia - white solid), ethanamide, ethylbenzene carboxylate and benzonitrile. Two of my substances are white flakey powder. Two are clear liquids. One is a clear solid in small wet-ish picces like powder. One is a slightly yellowy liquid. Could you please help work out the which would be which? Particularly which the clear solid is and the yellowy liquid is? Also, one smells absolutely vile, which is it? All help is greatly appreciated. —Preceding unsigned comment added by 81.157.96.6 (talk) 02:00, 25 February 2010 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. --ColinFine (talk) 08:59, 25 February 2010 (UTC)

Sorry, I forgot my login details before.

It's not a homework question but a question for mock coursework practical. We're allowed to do as much research as we want and take in notes, so I've tried to find out elsewhere but I can't; this is far from my first port of call. It would be extremely useful to find out which the yellowy liquid is. Thank you for any help you could possibly provide. Chocolate muffins in a basket 11:12, 25 February 2010 (UTC)

Right, I strongly suspect the stinky stuff is 1-aminobutane (there's an article here on n-butylamine, I might put in some redirects later so it's all IUPAC'd up). Amines in general are fishy or ammoniacal as far as smell goes. It should also be the slightly yellow liquid. You could probably work out which one is benzoic acid with universal indicator (or, to show off, an acid-base titration). As for the others, I'm sure you can come up with something. Brammers (talk) 11:26, 25 February 2010 (UTC)

Thank you very much. I've looked at previous experiments and it looks like it is 1-aminobutane that smells. I also have which is benzoic acid. And I can easily work out the other two solids using Brady's reagent. Thanks. Chocolate muffins in a basket 11:33, 25 February 2010 (UTC)

You're welcome! Also, just remembered that benzaldehyde smells strongly of almonds, which could be handy too. Good luck with the coursework! Brammers (talk) 16:29, 25 February 2010 (UTC)

Nonrenewable Energy

Coal, oil, natural gas, and nuclear fuels such as uranium are nonrenewable. So if we continue to use them at the current rate, when will they be used up?

An Unknown Person (talk) 09:13, 25 February 2010 (UTC)

Our fossil fuel article gives the estimates below.

Years of production left in the ground with the most optimistic proved reserve estimates (Oil & Gas Journal, World Oil)

• Oil: 43 years (or 43 years using proven levels and flows in the fossil fuel article)
• Gas: 167 years (or 61 years using proven levels and flows in the fossil fuel article)
• Coal: 417 years (or 148 years using proven levels and flows in the fossil fuel article)

but it's a big assumption to say we continue to use them at the current rate. Currently our use is growing, but Hubbert peak theory claims that use will decline as reserves run out and prices get higher.

Estimating how long uranium reserves will last is also tricky, because it depends on whether breeder reactors are used (and because the industry is currently experiencing a regrowth). World energy resources and consumption gives an estimate of 70 years and then says most industry observers disagree (which is helpful). AlmostReadytoFly (talk) 11:38, 25 February 2010 (UTC)

The French authority NEA gave 100 years based on 2006 consumption rates.[14] AlmostReadytoFly (talk) 11:48, 25 February 2010 (UTC)

This link World_energy_resources_and_consumption#Nuclear_fission gives the reserves of nuclear fuel as 2500ZJ. With a worldwide total energy consumption of 474EJ (your first link) I calculate more than 5000 years reserves of nuclear fuel even if we would stop using any other energy sources completely. 95.115.141.196 (talk) 13:40, 25 February 2010 (UTC)

Does this presume 100% energy recovery from the 2500ZJ,or is that already factored in? Googlemeister (talk) 17:29, 25 February 2010 (UTC)

Dunno, that's just what the article says. Let it be pathetic 10% and it still will be enough for a good 500 years. (Don't get me wrong, I'm not into soapboxing today (I said: todoay) and not saying anything about nuclear waste.) 95.115.141.196 (talk) 18:06, 25 February 2010 (UTC)

For the fossil fuels (coal, oil, gas), we can't run out because if we burned all that there is, the greenhouse gasses produced would make the earth virtually uninhabitable. Uranium is a much bigger unknown. If we manage to get fusion working reasonably - then there are truly vast reserves of hydrogen to work with...although a lot depends on the final technology. While you're worrying, you might want to consider the world reserves of copper, helium and the "rare earth" stuff from which high powered magnets are made. All three will run out long before fossil fuels - and at least copper and rare-earth magnets are essential to the very energy reduction efforts in things like electric cars - and in renewables such as wind turbines. Several other rare metals that are frequently used in batteries and high-tech electronics come only from single sources in places that are politically unstable. Not good! SteveBaker (talk) 14:14, 25 February 2010 (UTC)

From Rare earth element: "rare earth elements are found in relatively high concentrations in the earth's crust". 95.115.141.196 (talk) 14:51, 25 February 2010 (UTC)

They are called "rare" for a reason. These concentrations aren't generally high enough to be economically viable. See this, for example or this. SteveBaker (talk) 03:08, 26 February 2010 (UTC)

So the problem is not the world reserves as such but the ore quality. It takes more energy to concentrate and extract the metals. So it boils down to the availability of energy. Is China politically unstable? 95.112.185.232 (talk) 08:47, 26 February 2010 (UTC)

I clearly remember when I was still at school (about 1976?) reading an earnest newspaper report saying that the world's oil reserves would be exhausted in 1984. Prediction is not a precise science. Alansplodge (talk) 17:32, 25 February 2010 (UTC)

There was a very obese American pundit who around that time was well known for saying that the world would get increasingly materially wealthy. Who was he, and was he right? 78.147.93.182 (talk) 21:21, 25 February 2010 (UTC)

We could use all the fossil fuels very slowly without global warming being an issue. The half-life of CO2 in Earth's atmosphere is, perhaps, a few thousand years (it is unclear), so if we take 50,000 years to use it all the fossil fuels, we should be ok. --Tango (talk) 03:23, 26 February 2010 (UTC)

We've had 40 years worth of oil left for at least the last 50 years. Take all such estimates with a tablespoon of salt. They are usually based on known reserves accessible with current technology, so are just a lower bound. As we search more and our technology improves, we find more oil we can access. We will never actually run out, of course, since as we get near the price will go up and people will switch to alternatives that will be cheaper. --Tango (talk) 03:23, 26 February 2010 (UTC)

The price is already going up. Haven't you been living in this planet the last few years? Dauto (talk) 03:44, 26 February 2010 (UTC)

moon mission

why is it that no other country other than us has been able to sent a man on moon. while us had done it almost 50 years ago. do all other countries cant create such a mission even after so many years.....piyush (talk) 09:15, 25 February 2010 (UTC)

They probably didn't think it was worth the cost. Watch an expert explain it.

Ben (talk) 09:44, 25 February 2010 (UTC)

There was a lot more prestige involved in a Cold War space race. Clarityfiend (talk) 10:17, 25 February 2010 (UTC)

Could it be done at all today? 95.115.141.196 (talk) 11:53, 25 February 2010 (UTC)

It is worth mentioning that some people think it didnt happen Moon_landing_conspiracy_theories. If it did happen 50 years ago, it should be orders of magnitude cheaper and easier to do now, due to advances in technology and industrial processes. Therefore, a billionaire could easily do it himself. —Preceding unsigned comment added by 194.196.95.89 (talk) 11:58, 25 February 2010 (UTC)

Well, this is not a place for soapboxing, so I leave it like that. 95.115.141.196 (talk) 12:16, 25 February 2010 (UTC)

Computers have been getting cheaper because the components have shrinking and mass production has been encouraging research, (and probably because computation is a fundamentally easy thing to do, with the laws of physics we have). Even if we were mass-producing moon rockets, that wouldn't change the fact that the only way to get to the moon is to strap yourself to a thirty-story tower of explosives. (the Space Shuttle has a comparatively easy job, since it only goes to low earth orbit.) Paul Stansifer 14:35, 25 February 2010 (UTC)

The reason other countries didn't bother is the same reason why the US stopped going there and has never returned...there was prestige value to being the first (and the US was really desperate for the Soviet Union not to get that prestige) - there was (and still is) no prestige value in being second. Aside from that - there is little reason to go to the moon. Until we have the technology to create robotic factories that could do something interesting with the moon's resources, it's essentially an entirely boring place. With robotic factory technologies, there are a few interesting projects:

1. Build massive solar power generation facilities at the lunar poles and beam power back to earth from them. (Although, arguably, doing that at a suitable Lagrange point might be easier).
2. Build a telescope on the back side of the moon where it could see without the earth being in the way - and a radio telescope would not pick up all of the radio pollution from here on Earth.
3. Mine Helium3 and ship it back to Earth to make it easier for us to build fusion power plants.
4. Use solar power and water from deep craters near the poles - make hydrogen and oxygen for deep space missions - and to provide for an eventual human colony on the moon.

But none of those things could usefully be done by a handful of people going for a few days as in the Apollo era. It takes massive construction equipment - and that means either a large group of humans (which would be ruinously expensive) or fancy autonomous robots (which we don't yet have the technology to provide).

So there is literally no reason to go there. It's a very dead, boring place. We have moon rocks to study and we have really detailed photos...what more do we need? 14:05, 25 February 2010 (UTC)

A French expedition to the Moon found it occupied by an alien civilisation. Cuddlyable3 (talk) 17:18, 25 February 2010 (UTC)

Hmmm - good point. A very dead, boring place...with Frenchman - that's an even better reason not to go there! :-) SteveBaker (talk) 19:30, 25 February 2010 (UTC)

50 000 000 != wrong. Cuddlyable3 (talk) 20:18, 25 February 2010 (UTC)

It is important to distinguish between not being able to go to the Moon and not trying to go the Moon. The US is the only country to ever fail to land on the Moon (see Apollo 13). --Tango (talk) 01:37, 26 February 2010 (UTC)

So they say... ;-) --Mr.98 (talk) 04:20, 26 February 2010 (UTC)

The truth is getting to the moon was exceptionally difficult in 1969 and had not a huge amount of payoff other than propaganda. Could the US do it again? Probably, but it would take a lot of specialized work to do it. Sending up satellites and even ISS missions is a very different sort of work than landing on the moon. You don't immediately go from sending unmanned probes to making manned craft again in a short working order. A space shuttle can get people and things into space and back again (with still some difficulty), but it is not the same thing as landing on a totally different body with different gravity and etc. It's a non-trivial task, even today. The reason no one else has bothered is because there is great risk, great cost, little reward. --Mr.98 (talk) 04:20, 26 February 2010 (UTC)

Steam

I was given two questions, to which I'm pretty sure I know the answer to, but I would like to confirm them.

Q1: "When given a bowl of chicken soup, which way does the smoke go, and why?" My answer would be that it travels upwards, because the water vapour rising off the surface of the bowl is hotter, and therefore less dense, than the surrounding air. However, I have an auxillary question (this is my own): would the fact that this steam has more water vapour significantly affect it's relative density?

Q2: "When a cold box is opened, which way does the smoke go, and why?" My answer would be that it goes downwards, because the vapour is now colder than the surrounding air. Auxillary question: why is there vapour in the first place? Is it because air trapped inside the box when it's closed gets cooled down, which causes the water in the air to condense? —Preceding unsigned comment added by 173.179.59.66 (talk) 09:44, 25 February 2010 (UTC)

First vapor is not smoke. What you see when you open a cold box, vapor apparently going out, is in reality cold air condensing water vapor that was outside the box. Non Zero-sum Ed (talk) 11:33, 25 February 2010 (UTC)

Q1: See the article Steam. What you see as smoke consists of hot water vapour (invisible) plus a visible white mist of water droplets where the vapour condenses in contact with external cold air. The mist is an Aerosol that is slightly denser than air and eventually falls as it cools.

Q2: What you see as smoke is invisible cold air plus a visible white mist of water droplets where external water vapour condenses in contact with the cold air. Otherwise your answers are correct. Cuddlyable3 (talk) 16:41, 25 February 2010 (UTC)

So, to confirm: in Q1, the smoke will first rise, due to higher temperatures, but then fall as it cools due to higher density; in Q2, the smoke will fall due to the combination of being both cooler and denser than the surrounding air? —Preceding unsigned comment added by 173.179.59.66 (talk) 05:13, 26 February 2010 (UTC)

Donating plasma

According to the American Red Cross [15], referring to plasma: The "best blood type to donate: AB+, AB-, A+, A-" Why are these blood types better?--Non Zero-sum Ed (talk) 11:30, 25 February 2010 (UTC)

According to blood type "Type O plasma, containing both anti-A and anti-B antibodies, can only be given to O recipients. The antibodies will attack the antigens on any other blood type. Conversely, AB plasma can be given to patients of any ABO blood group due to not containing any anti-A or anti-B antibodies." This indicates why AB is good and O is less useful. I'm not sure why they prefer A over B --Normansmithy (talk) 12:00, 25 February 2010 (UTC).

According to blood type type A is more common - therefore type A plasma can be used to transfuse more peoplem and is therefore more useful. --Phil Holmes (talk) 12:15, 25 February 2010 (UTC)

In my fantasy world, where everyone who can would donate some blood product, I would want especially O to donate whole blood rather than "just" plasma, since universal-donor is particularly useful itself (as opposed to "O plasma is not as useful as others'"). Totally speaking from my own head only here. DMacks (talk) 21:10, 25 February 2010 (UTC)

milk ph

milk is a basic ph but i heard when it is drunk it is converted by the body to a acid, is this true? is drinking milk beneficial or detrimental to raising the bodys ph ? —Preceding unsigned comment added by 67.246.254.35 (talk) 15:40, 25 February 2010 (UTC)

You are probably talking about lactic acid. Some are affected more by it than others. It isn't really beneficial or detrimental to the body's ph level. -- kainaw™ 15:46, 25 February 2010 (UTC)

im not referring to lactic acid —Preceding unsigned comment added by 67.246.254.35 (talk) 16:26, 25 February 2010 (UTC)

Milk isn't basic pH, it's slightly acidic at around 6.4-6.8. I doubt it would have either a detrimental or beneficial effect on the body with respect to the pH. Someone feel free to prove me wrong. Regards, --—Cyclonenim | Chat  17:53, 25 February 2010 (UTC)

The body is strongly buffered. I don't think you could drink enough milk, even if it were converted to acid, to change the body's pH. As an aside, acid lowers pH (bases raise it). DMacks (talk) 18:03, 25 February 2010 (UTC)

We are mammals. We've evolved to drink milk. We're capable of spending the first year of our lives living on nothing else whatever! If you have the gene for lactose tolerance (as a good majority of humans do) then your digestive system should work just great with stuff that has whatever pH milk has. Why would you think otherwise? SteveBaker (talk) 19:27, 25 February 2010 (UTC)

Actually Steve, a good minority of humanity has the gene for lactose tolerance; the majority become lactose intolerant as they grow up, like most mammals. A good majority of European humans have the gene, relatively recently evolved, for lactose tolerance. 86.177.121.239 (talk) 20:04, 25 February 2010 (UTC)

yes i understand milk is about 6.8 ph but what i heard is that for some reason the body coverts it to about 4.0 or lower is this true? —Preceding unsigned comment added by Thekiller35789 (talk • contribs) 19:32, 25 February 2010 (UTC)

I still don't get where you thought milk was basic then, if you understand that milk is slightly acidic and you thought it went even more acidic. Anyway, no, it won't be as low as 4.0 because all that is happening during digestion is the bonds are breaking and new products are forming, mostly protein and lipids. Neither would be at pH 4.0, I don't think. Regards, --—Cyclonenim | Chat  20:55, 25 February 2010 (UTC)

I was always told milk was basic when I was younger, and that it can be used to neutralize battery acid if a battery leaks. It wasn't until later that I found out that it was acidic. Falconus^{p t c} 02:47, 26 February 2010 (UTC)

Yes, I used to think milk was alkali... anyone know where that misconception comes from? --Tango (talk) 03:02, 26 February 2010 (UTC)

Milk is buffered, which is a fancy chemical way for saying that it resists changes in pH. Essentially, regardless of whether you add an acid or a base to milk, it tends to rebound back to near its native pH level, which is how buffers work. Add a base, and the pH snaps back to the pH of milk. Add an acid, and the pH snaps back. Which is why people have vague recollections of being told to drink milk to treat either acid or base poisoning. Also, the buffering effect of milk is why drinking too much milk can make you throw up. The classic "you can't drink an entire gallon of milk in one hour" is because your stomach expects a very low pH. There are biofeedback mechanisms which, if your stomach pH is out of whack, causes you to throw up. Because milk is a buffered solution, when you drink a lot of it, it causes your stomach to think you've ingested something which is bad for you, and causes your vomit reflex to kick in. You can easily drink a gallon of plain unbuffered water in the same time period, because it isn't buffered, and so will not drastically change your stomach's pH as much as milk will; even though pure water is at a more basic pH than milk. --Jayron32 05:41, 26 February 2010 (UTC)

Fascinating - thank you. --Tango (talk) 06:15, 26 February 2010 (UTC)

Articles about plants and animals

Well, this is a question that might sound like a complaint. If so, it's against the world as such, not against the contributors of wikipedia. And it's hard to put it in a question.

I was looking at Jerusalem artichoke and would have liked to know plants that grow in similar climate/soil. No way to search for them before I know the names already?

I was looking at Rock samphire and would have liked to know how it manages to grow practically on stones.

When looking at articles about animals I'm generally not much interested in their dental formulas but in their ecological niches and, for example, what a lynx does better or worse than a competing fox in the same wood.

Am I somehow perverted to be interested in such things, or why is wikipedia lacking such information? 95.115.141.196 (talk) 16:25, 25 February 2010 (UTC)

Curiosity is healthy and Wikipedia is still a work in progress with room for improvement. Cuddlyable3 (talk) 16:45, 25 February 2010 (UTC)

The questions are great and when I have similar questions, and I don't have the resources to find the answers, I go to the "discussion" page of the article and add a new section asking for a knowledgeable editor to add a section with the information. Some day someone may do it. Comet Tuttle (talk) 18:00, 25 February 2010 (UTC)

I agree entirely with that - but people should recognize that there are limits to the depth of information that an encyclopedia can offer. I absolutely guarantee that the information that's being sought here isn't in (say) Encyclopedia Britannica. There comes a point when searching for very deep knowledge when you have to say "Well, I need to get a proper textbook on that subject". If we wanted to say everything there was to say about (say) Foxes - then the article would probably be 1000 pages long - about the length of a handful of books and a few dozen scientific papers about the animal. There is little likelyhood of that much information being written about every single animal, plant and Japanese railway station in existence (well, maybe there is a chance for the railway stations!). SteveBaker (talk) 19:25, 25 February 2010 (UTC)

I agree that an article cannot contain everything. But have you had a look at Rock samphire? Can you tell me seven articles about animals that refer to their ecological niche in comparison with their competitors? In the previous millennium (exaggeration intentional) Encyclopedia Britannica and dental formulas were the state of art, and a hand full of people making celluloid pictures of African animal wildlife became the avant-garde of zoology. (And finally I can't avoid soapboxing: we have fallen far behind our possibilities, in many aspects; pluck lost, all lost.) 95.115.141.196 (talk) 19:48, 25 February 2010 (UTC)

Steve Baker is conscious of the Information explosion. But Wikipedia has presently 3 200 000+ articles (English version), it's still growing and we are told WP:DWAP. Moore's law seems eternal so what can stop Wikipedia ìncluding everything? Software bloat? Search engine overload? Vandalism? Editors departing to jobs that pay real Money? Cuddlyable3 (talk) 20:42, 25 February 2010 (UTC)

There's more between client and server than a linear search algorithm could imagine. Disk space lost, little lost. Information lost, much lost. Pluck lost, all lost. 95.115.141.196 (talk) 21:06, 25 February 2010 (UTC)

What the pluck? Cuddlyable3 (talk) 22:48, 25 February 2010 (UTC)

I've always thought that a free online database and Wiki about garden flowers (and vegetables) would be very useful. There must be around twenty different pieces of information that a gardener would like to know when choosing flowers to grow in their garden. Even the best gardening books are incomplete and only give some of the information you need. 78.151.155.128 (talk) 01:00, 26 February 2010 (UTC)

There are lots of kinds of information that I'd love to have in Wikipedia too - but wishing it were here and actually getting it done is a very different matter. Category:Garden_plants links to about 300 articles about garden plants, List_of_garden_plants appears to link to several hundred also. Researching, referencing and adding all of that information would a very considerable effort. If someone wanted to undertake that, I doubt there would be any objections to creating an infobox to collect the relevant stuff in a uniform manner. There are a lot of subjects that would benefit from that treatment - but it takes some dedicated enthusiasm to make it happen.

I often joke about articles about Japanese Railway stations - but just marvel at List of railway stations in Japan - there are by far more articles about Japanese railway stations than about garden plants. Each one has a photo, a list of other stations on the same line, the history of the place, what bus stops there are there. It's crazy! I doubt that those articles get one visitor a year each! There are articles about all of the railroad companies, all of the rolling stock - you name it, if it's anything remotely to do with Japanese railways - and there is a really good Wikipedia article on it! Wikipedia:WikiProject_Trains_in_Japan is an entire user group set up entirely to create and administer these articles and standards for quality for them.

I completely agree that keeping all of that information about what kinds of soil, light, watering and feeding each kind of garden plant needs is vastly more useful than having 500 articles about Japanese railway stations in an English-speaking encyclopedia. But it's a labor of love. A small group of editors does that (and probably very little else) and it's an incredibly detailed record. If some person (or small group) were to attack the garden plant articles with the same enthusiasm as the Japanese railway folks - the encyclopedia would be better for doing that. But we can't possibly do anything to make it happen.

If someone with the knowledge and enthusiasm comes along, we'll get it. If not...not. But again, compare us to other encyclopedias. Aside from specialist gardening encyclopedias - I doubt most general purpose encyclopedias have half the coverage we have at half the depth we have.

SteveBaker (talk) 02:54, 26 February 2010 (UTC)

Mood Rings

Please explain in layman's terms how the stone on the mood ring changes color. Thanks --12.170.106.12 (talk) 18:28, 25 February 2010 (UTC)

Have you tried reading Mood ring? Is there something specific you don't understand? --Tango (talk) 18:34, 25 February 2010 (UTC)

It said something to the type of crystal it is but how does this crystal change color? What makes it different say when you touch a quartz crystal? --12.170.106.12 (talk) 18:36, 25 February 2010 (UTC)

The Liquid crystal article explains this in a reasonable amount of depth. APL (talk) 18:50, 25 February 2010 (UTC)

They use the same principle as one of those plastic-strip thermometers - it uses a liquid crystal that changes color as a function of temperature. The theory (and it's a terrible one) for how they tell your "mood" is that your body temperature is supposed to change when you get angry, etc. The trouble is that to the extent that this is true (which is to say "not much") is far FAR less than the color changing chemical will require to change color. By far the most significant thing that determines the temperature (and hence color) of the ring is how warm the air is around it. Proponents of these pieces of junk claim that in women, their "time of the month" affects their body temperature - and also their mood - but even that is really hard to justify. Basically, mood rings are junk. SteveBaker (talk) 19:11, 25 February 2010 (UTC)

At least they're less gaudy than a hypercolor shirt. APL (talk) 20:06, 25 February 2010 (UTC)

I hear they are really good at telling you the mood of your pet rock though. SteveBaker (talk) 02:27, 26 February 2010 (UTC)

Ah! Then they're obsolete! Modern pet rocks are USB compatable. APL (talk) 06:14, 26 February 2010 (UTC)

Killing those fun guys.

Fungi are annoying, often pathogenic, and because they're eukaryotes they're a bitch to treat. Therefore, when treating, presumably we have to develop drugs which primarily disrupt a fungus' unique characteristics. One such characteristic would be the presence of hyphae, and I can think of several very prevalent diseases which use them such as oral candidiasis. Why, then, is thrush so hard to treat? If we could target the mechanisms by which hyphae are used, or prevent them from growing at all, why haven't drug companies exploited this fairly obvious difference between humans and fungi? Is it simply that there isn't a known drug which can disrupt hyphae activity without harming humans (due to a similar protein or such things)? I'm not a pharmacist or pharmacologist so there must be a decent reason why this has been excluded from drug companies checklists? Regards, --—Cyclonenim | Chat  19:06, 25 February 2010 (UTC)

To answer your specific question, hyphae are not clinically useful antifungal targets for several reasons. First, hyphae, if anything, act as protective structures that insulate the fungal cell to a certain degree (similar to the bacterial capsule of certain species such as the one that causes gonnorrhea), and the fungus is perfectly able to get along without it. I should also note that most fungi that parisitize humans do not grow as molds. Candidiasis is caused by candida albicans, which grows as a yeast. Yeasts by definition do not grow as hyphae. Currently available antifungals do exploit differences between human and fungal cells. Most antifungals work by inhibiting the production of a molecule incorporated into fungal cell walls, called ergosterol. Some have other mechanisms, though the cell wall is a handy target being that it is chemically very different from human cell membranes. It is true that there is a small minority of fungi that causes some degree of human grief, however I will remind you that, in addition to being very useful in our food supply, a fungus gave us the first clinically useful antibiotic: penicillin. Tuckerekcut (talk) 02:54, 26 February 2010 (UTC)

Despite what you might infer from some Novartis advertisements, drug companies are motivated by revenue. They thoroughly enjoy marketing drugs that treat (but do not cure) widespread, chronic, perhaps mildly degenerative conditions that are at least somewhat life-threatening. This way, many patients will stick to their drug regimens for the remainder of their lifetime. Oral candidiasis does not fit well into this category because of low morbidity and mortality related to infection and relatively low incidence (such as in comparison to diabetes). Moreover, current forms of medication (such as clotrimazole troches and various other gels and rinses) are pretty good at reducing fungal levels to normal, allowing bacterial oral flora to re-establish their usually more prominent levels -- so why spend time, money and effort to try to develop better medications? DRosenbach ^{(Talk | Contribs)} 05:10, 26 February 2010 (UTC)

Fascinating, thanks. Though I've heard that candidiasis will effect 75% of women once, 50% twice and 25% reoccuringly, though I don't have a statistic to back that up, just heard it in a lecture yesterday. If someone found a cure for thrush, they could make billions of it straight away and then continue to make money as newborns will still get it. Regards, --—Cyclonenim | Chat  10:23, 26 February 2010 (UTC)

What is A and what is AH2?

There are several articles with the generic format:

In enzymology, a Delta12-fatty acid dehydrogenase (EC 1.14.99.33) is an enzyme that catalyzes the chemical reaction

linoleate + AH₂ + O₂ $\rightleftharpoons$ crepenynate + A + H₂O

The 3 substrates of this enzyme are linoleate, AH2, and O₂, whereas its 3 products are crepenynate, A, and H₂O.

Notice that those articles (listed below) link to A and AH2, which are not chemical substances!

The articles, as far as my search could go, are:

• Delta12-fatty acid dehydrogenase - from where I extrated the above quote
• Progesterone 11alpha-monooxygenase
• Steroid 9alpha-monooxygenase
• Taxadiene 5alpha-hydroxylase
• Estradiol 6beta-monooxygenase
• Carotene 7,8-desaturase
• Ecdysone 20-monooxygenase
• Kynurenine 7,8-hydroxylase
• Linalool 8-monooxygenase
• Thiophene-2-carbonyl-CoA monooxygenase
• Glycine dehydrogenase (cyanide-forming)
• etc

What is A and what is AH2? Albmont (talk) 20:08, 25 February 2010 (UTC)

I've seen AH2 applied to enthalpy change (no idea why) and to ascorbic acid (see here). Regards, --—Cyclonenim | Chat  20:58, 25 February 2010 (UTC)

Adenine. It looks like the usual cofactor for this class of enzymes is NADH or NADPH, which acts as a hydrogen donor to form NAD(P)+ as byproduct. DMacks (talk) 20:58, 25 February 2010 (UTC)

That'd probably make more sense than my suggestions... :) Regards, --—Cyclonenim | Chat  20:59, 25 February 2010 (UTC)

Ascorbate is a reasonable possibility for a redox-active item as you found. I searched for these specific enzymes (using the links in the infobox for the first example), which gave me a slightly more explicit reaction. Man, biochem is hard enough without having a pile of undefined and mis-wikilinked terms unless the reaction really does take place on a highway in Asia. DMacks (talk) 21:03, 25 February 2010 (UTC)

Are we all immortal?

Hear me out on this. When you are born you can first be observed by the universe. When you die you no longer can be observed. However relativity only permits information to travel at the speed of light. Therefore (assuming the universe is infinite) there's a wavefront heading away from you at the speed of light from the moment your born and it only ends when you die. Yet that wavefront will propagate forever. A wavefront that contains all the information that is you. A shell maybe 80 light years thick forever expanding out across the universe. Anywhere in that shell you will always exists. TheFutureAwaits (talk) 20:33, 25 February 2010 (UTC)

No, I think you would not exist, only the photons bouncing off of you would exist, or perhaps a radio signal or similar with your voice on it. Googlemeister (talk) 20:37, 25 February 2010 (UTC)

See that initially seems like the easy answer. But consider to an observer hundreds of lightyears away I won't exist until that light reaches them. TheFutureAwaits (talk) 20:41, 25 February 2010 (UTC)

Your image is not you--it's neither the complete information content of you nor the actual embodiment of that info. There's some plausibility to the idea "if there was a completely precise and accurate description of you, you could be recreated exactly as you are using that dataset". The photons bouncing off you are not that complete dataset (although they are influenced by some/much of it beyond the skin surface). DMacks (talk) 20:46, 25 February 2010 (UTC)

This seems like it's just a semantic argument about what it means to exist at a particular time and place. If you want to define existing at a particular time as still having an impact on events, then sure you exist forever everywhere inside of your future light cone. Is that a useful way to define it? Rckrone (talk) 20:50, 25 February 2010 (UTC)

From any given point of view you will exist for only a finite period of time.

More to the point (I think), you will only ever being observed having a finite number of interactions with the world around you. If you don't learn to ride a bicycle now in your (locally observed) life time, no one in the Andromeda galaxy will ever observe you riding a bicycle. APL (talk) 20:55, 25 February 2010 (UTC)

True, you can't change things but to an outside observer you will be making those decisions in realtime. TheFutureAwaits (talk) 20:59, 25 February 2010 (UTC)

When you talk about your existence do you mean just the image of your warm body that a camera can capture? If so then by your understanding "you" are indeed an expanding shell. The catch is that some of us think we are not just images. You can't see me so do you think I exist? Cuddlyable3 (talk) 20:57, 25 February 2010 (UTC)

We aren't just images but we ARE all information. Your actions can only have an impact within their light cone. So until a place intersects that lightcone you won't exist. TheFutureAwaits (talk) 21:01, 25 February 2010 (UTC)

(after ec) "A wavefront that contains all the information that is you." Ah, but that's not you. That's just a total encyclopaedian record of you, a dead thing, unable to act by itself and unconscious of itself. (I'm always fond of an intellectual discussion where I postulate that a candle flame is alive and squash away those counter arguments like not having a soul by asking what would be a proof for anything/anyone to have a soul.) 95.115.141.196 (talk) 20:58, 25 February 2010 (UTC)

Only the soulless need that truth proven. Cuddlyable3 (talk) 21:13, 25 February 2010 (UTC)

Quantum immortality is far more interesting. --Tango (talk) 21:17, 25 February 2010 (UTC)

I think the OP is reaching for something more holistic (along the lines that each of your movement has a subtle gravitational impact on everything in the universe...). arguably true, and karmically interesting, but hardly constituent of any realistic form of immortality. --Ludwigs2 21:30, 25 February 2010 (UTC)

I'd rather agree if you'd say we are all eternal (leaving aside all possible as well as unprovable religious metaphysics). 95.115.141.196 (talk) 21:45, 25 February 2010 (UTC)

Well, there's provability, and then there's truth. Which are you really more interested in — whether it can be proved that your consciousness can exist forever, or whether your consciousness will in fact exist forever?

If you're genuinely more interested in whether it can be proved, then fine, you can probably ignore the question. But I doubt that's what most people really want to know. -Trovatore (talk) 21:54, 25 February 2010 (UTC)

I'm really more interested in provability, as an intellectual exercise, for I know about truth already. 95.115.141.196 (talk) 21:58, 25 February 2010 (UTC)

There is a whiff of arrogance hopefulness about assuming immortality from a mechanical argument. The OP's prized shell of existence gets tenuously thin walled as it expands. Given the size of the Universe our OP gets stretched down to something thinner than a balloon, then down to a membrane of Nanoparticles and eventually down to subatomic particles that are unknowably adrift in the background radiation of the Universe that certainly won't stop expanding just so the OP can catch up. Cuddlyable3 (talk) 22:22, 25 February 2010 (UTC)

Doesn't one continue to exist after death even if their body is in a mausoleum or some such place? Bus stop (talk) 22:31, 25 February 2010 (UTC)

The wall would not get thinner. Let's say you lived 80 years. The shell would be 80 light years thick, always. The physical volume of space it contained would grow but the thickness would be the same.TheFutureAwaits (talk) 23:14, 25 February 2010 (UTC)

actually, that's not true - relativistic effects would ensure that the width of the "wall" would expand/contract/bend in interaction with gravitational wells... just saying...--Ludwigs2 23:20, 25 February 2010 (UTC)

You've got the right idea, but a bit backwards. The first fact is that you exist -- the universe is only tertiary to your consciousness. When you dream, your mind is imagining things, but those imaginings mean something, while all the goings-on outside your mind are totally irrelevant until you awake. Anyway we may be all theoretically immortal, but when you die, you lose all your memories, which is not preferred! So it's a yes-but-no kinda answer. Vranak (talk) 00:24, 26 February 2010 (UTC)

Tallow

where can i buy Tallow or Suet ?

A decent supermarket? --Tango (talk) 21:23, 25 February 2010 (UTC)

Suet you can get at any birding store - it's a common element of winter birdfeed. tallow is odder - it only has industrial uses in the modern world, and I don't know of anyplace to get it as a commercial product. if there's a rendering plant in your vicinity, you might give them a call and ask. or you can probably shop for it online. --Ludwigs2 22:12, 25 February 2010 (UTC)

Tallow is (was) used for caulking in wooden boats. Try asking at a chandler. CS Miller (talk) 22:20, 25 February 2010 (UTC)

In the UK you can find suet in most supermarkets, both beef suet and vegetarian 'suet'. Look by the baking supplies. As CS Miller says, tallow will be more difficult. 86.177.121.239 (talk) 22:23, 25 February 2010 (UTC)

I'd just like to caution you that bird-grade suet and industrial-grade tallow aren't made with human hygiene in mind, so don't eat them. If they were made hygienically then they'd be safe (they are just purified fats), but probably wouldn't taste that great. Should be fine for candle making tho. Tallow was used for candles, not sure about suet. CS Miller (talk) 22:38, 25 February 2010 (UTC)

I think suet can be used for candles as well (it's not that different from tallow) but I suspect it would smoke and stink badly... --Ludwigs2 23:05, 25 February 2010 (UTC)

Is this Edge Peak?

Hello, I live in Langley, BC. I saw this mountain to the North. Is this Edge Peak? --The High Fin Sperm Whale 21:06, 25 February 2010 (UTC)

This shot, from a slightly different angle, is still clearly the same mountain and is called Mount Robie Reid, and that article is in need of a photo. Mikenorton (talk) 21:43, 25 February 2010 (UTC)

Messing around with Google Earth, if I approach Mount Robie Reid (using the article's coordinates) from the south-southwest at a suitably low elevation, I can get a view that looks convincingly like your photo. Mikenorton (talk) 23:10, 25 February 2010 (UTC)

Edge Peak lies North-East of Langley. Does the OP's picture fit the profile? Cuddlyable3 (talk) 22:39, 25 February 2010 (UTC)

Thanks a lot guys, that would be it! --The High Fin Sperm Whale 03:50, 26 February 2010 (UTC)

Fog

Does fog occur worldwide? Thanks in advance. Rimush (talk) 23:12, 25 February 2010 (UTC)

I would think so, and there's nothing in our article on Fog to suggest that it doesn't. —Steve Summit (talk) 23:25, 25 February 2010 (UTC)

all fog requires is sufficiently high humidity, a temperature below the dew point and above freezing, and condensation nuclei. I can't think of anyplace that would preclude those conditions (except possibly in the heart of a dessert, if there is a dessert where humidity is always negligible). --Ludwigs2 23:35, 25 February 2010 (UTC)

As our article states, some deserts are in fact quite well known for their dense fogs. Some animals are keenly adapted to that phenomenon, indicating that, in some deserts at least, it's a very regular thing. Matt Deres (talk) 04:25, 26 February 2010 (UTC)

It occurs with varying frequency, but it can occur anywhere. Some deserts may get fog only once every 10,000 years, or something, though. --Tango (talk) 00:42, 26 February 2010 (UTC)

According to this info, the highest recorded temp at the south pole is 7 degrees Fahrenheit. It would have to get quite a bit warmer to permit fog. Looie496 (talk) 02:04, 26 February 2010 (UTC)

You don't have to have liquid water for fog: ice fog. (As well, even with sub-freezing temperatures you can still have supercooled liquid droplets — small water droplets can remain liquid down to thirty or even forty degrees below zero.) TenOfAllTrades(talk) 04:16, 26 February 2010 (UTC)

February 26

Turning a switch backwards

I don't know how standard these types of switches are around the world, so I'll just preface this by saying that I'm in the US.

What happens if I turn the twist type switch, the one up near the light bulb, on my lamp backwards? Does the little knob (similar to a watch crown) just unscrew? Since all my lamps work, I don't want to risk breaking one by testing this out. And I'm certainly not going to take one apart. Thanks, Dismas|^(talk) 04:30, 26 February 2010 (UTC)

I doubt there is any standard for the construction of twisting switches. It could turn freely, doing nothing. It could unscrew. It could refuse to move until you use enough force to break it. I expect there are switches out there that do each. --Tango (talk) 04:33, 26 February 2010 (UTC)

As Tango said... there are many types of twist switches. For any switch, there are many types. When I recently replaced a pull-chain switch, I was surprised to find four completely different types of pull-chain switches to choose from. -- kainaw™ 05:17, 26 February 2010 (UTC)

I have accidentally turned a twist switch backwards. The knob unscrewed from the switch (and returned to normal when I twisted it forwards again). As the last person said, this may not be the same for all of them. --Anonymous, 11:52 UTC, February 26, 2010.

Lorentz transformations

Why do Lorentz transformations have to be linear? My teacher mentioned something about one-to-one correspondence (whatever that means), but could someone be more specific? Thanks. 173.179.59.66 (talk) 07:00, 26 February 2010 (UTC)

We have an article on One-to-one correspondence (actually under the more formal title of "Bijection" but the two terms mean the same thing, and the former redirects to the latter). --Jayron32 07:04, 26 February 2010 (UTC)

Alright, so why is one-to-one correspondence important, and why does linearity conserve it? —Preceding unsigned comment added by 173.179.59.66 (talk) 07:48, 26 February 2010 (UTC)

One-to-one correspondence is important because it is desirable for the Lorentz transforms to express some sort of group structure. Without one-to-one correspondence, there would exist transforms without a well-defined inverse transform. It is desirable to have a group structure because then the transforms are universal - they're the same (structurally) for every reference frame and can transform from any reference frame to any reference frame. A linear function is an "easy" way to obtain a one-to-one correspondence that has an inverse map of the same form. It may even be the only way (perhaps a proof could start with the inverse function theorem). 118.209.163.175 (talk) 08:07, 26 February 2010 (UTC)

Unfortunately, my knowledge of linear mapping is pretty non-existant. Is there a more physics-oriented explanation? —Preceding unsigned comment added by 173.179.59.66 (talk) 08:50, 26 February 2010 (UTC)

I think you should tell your physics teacher that you have no idea about what one-to-one correspondence means. I'm sure he will have a long chat with your math teacher. DVdm (talk) 08:55, 26 February 2010 (UTC)

Mistake in Textbook?

I believe I found a mistake in my physics textbook, and Introduction to Mechanics by Kleppner/Kolenkow. I wanted to confirm that my assessment is correct.

Example 7.3 in Chapter 7 goes as follows:

Consider a particle rotating in a verticle plane as shown in the sketch. [The sketch consists of a three-dimensional Cartesian coordinate system with a circle representing the particle's plane of rotation. This plane is perpendicular to the xy plane, with the ω vector making a 45° angle with the x- and y- axes. The position vector of the particle, r, is said to be at an angle θ from the z-axis, with θ being in the clockwise direction]

First we shall calculate v directly from the relationship v = dr/dt. To find r, note that z = r cosθ, x = -r sinθ/√2, and y = r sinθ/√2. Hence,

$\mathbf {r} =r({-\sin \theta \over {\sqrt {2}}}\mathbf {i} +{\sin \theta \over {\sqrt {2}}}\mathbf {j} +\cos \theta \mathbf {k} ).$

Differentiating, we have, since r = constant,

$\mathbf {v} =\omega r({-\cos \theta \over {\sqrt {2}}}\mathbf {i} +{\cos \theta \over {\sqrt {2}}}\mathbf {j} -\sin \theta \mathbf {k} ).$

Next, we shall find the velocity from v = ω × r. Assuming that ω can be resolved into components,

${\boldsymbol {\omega }}={\omega \over {\sqrt {2}}}\mathbf {i} +{\omega \over {\sqrt {2}}}\mathbf {j} ,$

we have

${\boldsymbol {\omega }}\times \mathbf {r} =\omega r({-\cos \theta \over {\sqrt {2}}}\mathbf {i} +{\cos \theta \over {\sqrt {2}}}\mathbf {j} -\sin \theta \mathbf {k} )$

as expected.

However, unless I've made a mistake in evaluating the cross product, I get the negative of their answer, so there does appear to be a discrepancy! Is this a mistake on my part, or because they defined positive θ to be in the clockwise direction (and dθ/dt would be one, which was tacitly assumed in this example but should be -1 due to how they defined θ)? —Preceding unsigned comment added by 173.179.59.66 (talk) 07:47, 26 February 2010 (UTC)

difference between distance and displacement

What is difference between distance and displacement —Preceding unsigned comment added by NADEEM BHAT (talk • contribs) 08:22, 26 February 2010 (UTC)

Distance is the absolute value of displacement. When you go from a place with coordinate x=4 to a place with coordinate x=1, your displacement is -3 and you covered a distance 3. See our articles Distance and Displacement. - DVdm (talk) 08:47, 26 February 2010 (UTC)

Countering momentum

Suppose you are playing football (association football or soccer if you will) and you receive pretty strong pass from player exactly in front of you. If you take a shot without stopping the ball (back towards the player that sent the pass), the speed/strength of the shot feels substantially more powerful then if ball was resting. Obviously, the added strength comes from kinetic energy other player invested, but what is the exact mechanism behind this? To me, logical thing is that you would spend part of kinetic energy you invest on actually countering other player's kinetic energy, thus stopping the ball before sending it back, resulting in weaker shot overall, but opposite is true. Can you shed some light on this phenomena? --124.148.229.154 (talk) 08:57, 26 February 2010 (UTC)

LSHS

WHAT IS LSHS & FO —Preceding unsigned comment added by 117.204.85.94 (talk) 09:43, 26 February 2010 (UTC)

They could be many things. Could you give some of the context that they are being used in? --Phil Holmes (talk) 10:07, 26 February 2010 (UTC)

Seeing as you were quite vague I didn't have much to go on, but this is the science reference desk so that gives us a hint. Running a good search here for "LSHS" "FO" gave me a lot of results for two types of hydrocarbon in oil. Regards, --—Cyclonenim | Chat  10:27, 26 February 2010 (UTC)

fuel oil

what is hsd,fo,lshs? what are thire advantages and dissadvantages? is this all are commersially available fuels like petrol,diseal etc. —Preceding unsigned comment added by 117.204.85.94 (talk) 10:24, 26 February 2010 (UTC)

Animal tastebuds

Hi

1. What animal's tastebuds are similar to a human being's? 2. What type of animal's tastebuds are more complex or has a better sense of taste then a human being's

Thanks, NirocFX

41.193.16.234 (talk) 11:14, 26 February 2010 (UTC)