Wikipedia:Reference desk/Archives/Science/2010 May 28

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May 28

Songbird Study

In one of Roger Penrose's lectures (video here: http://www.youtube.com/watch?v=f477FnTe1M0 , part in question at 1:12), Penrose talks about some studies done on birdsongs. The studies supposedly had humans give an aesthetic rating the songs of male birds that were then followed in order to determine their reproductive success, and whether it had any statistical correlation with the humans' ratings.

Does anyone know this study (or these studies)? I'd appreciate a citation or journal link! Inasilentway (talk) 22:21, 1 June 2010 (UTC)

Satellites and relativity

If you know the height of a satellite above the Earth (h) and you also know the velocity with which the satellite rotates around the Earth (v) what calculation do you perform to determine the offset of the clock aboard the satellite due to the combined effects of special and general relativity?--Wikinv (talk) 02:26, 28 May 2010 (UTC)

I don't think there are any general relativity effects. The satellite is in free fall, so it's experiencing no acceleration (force). All you have is velocity, and of course that only has meaning in comparison to something, presumably the earth. The interesting part is that the earth is experiencing general relativity effects due to it's gravitational field, not the satellite. Ariel. (talk) 03:21, 28 May 2010 (UTC)

The offset I'm talking about is relative to a clock on the surface of the Earth, meaning that the effect of general relativity on board the satellite will be less than that on the surface of the Earth, so I think it will still have an effect. How do you do it for special relativity then?--Wikinv (talk) 03:36, 28 May 2010 (UTC)

The general relativistic effect is real, and measurable. See Gravity Probe A. I don't know what the equation is, but maybe you can find it the referenced paper. Someguy1221 (talk) 03:50, 28 May 2010 (UTC)

According to Seeber, G. (2003) Satellite Geodesy for a satellite transmitting to a ground station there are two effects:

• the transmitted frequency is observed to be lower due to the relative motion (special relativity), and
• the transmitter operates in a field of different gravitational potential; the Earth bound observer receives a higher frequency (general relativity).

$\Delta f_{s_{rel}}=f_{s}\left({\frac {1}{2}}{\frac {{v_{s}}^{2}}{c^{2}}}+{\frac {GM}{c^{2}}}\left({\frac {1}{|\mathbf {r} _{s}|}}-{\frac {1}{|\mathbf {r} _{i}|}}\right)\right)$

$f_{s}$ frequency of satellite transmitter

$v_{s}$ relative velocity of the transmitter with respect to the receiver

$\mathbf {r} _{s}$ position of satellite transmitter

$\mathbf {r} _{i}$ position vector of receiver

—eric

Watch this video [1]. What I want to know is what calculation the presenter uses to arrive at his conclusion for the offset of the clock aboard the satellite.--Wikinv (talk) 04:32, 28 May 2010 (UTC)

How about this $\Delta t'={\frac {\Delta t}{\sqrt {1-v^{2}/c^{2}}}}$ ? 04:40, 28 May 2010 (UTC)

That's special relativity only, which could still be useful. How would you use that formula to determine the offset of the clock aboard the satellite relative to the clock on the surface of the Earth given the velocity with which the satellite travels around the Earth?--Wikinv (talk) 04:43, 28 May 2010 (UTC)

Perhaps with a tick counter and identical clocks being synchronized (started) at some (identical) point in time and the counters then compared at some time in the future. 71.100.8.229 (talk) 05:14, 28 May 2010 (UTC)

(ec)So according to the video the clock will speed up by 45µs per day due to the difference in gravitational potential. Plugging values into the above formula you get:

${\frac {398600.4418}{299792.458^{2}}}\left({\frac {1}{26560}}-{\frac {1}{6378}}\right)*60*60*24$

=-0.00004565 s/day. At 3.87 km/s slow down by 7µs per day:

${\frac {1}{2}}{\frac {3.87^{2}}{299792.458^{2}}}*60*60*24$

= 0.00000719 s/day.

—eric 05:22, 28 May 2010 (UTC)

There's also a lot more going on, the relative velocities are constantly changing, the orbits are not spherical, etc. so there is also a periodic adjustment throughout the orbit, works out to between +70 and -70 nanoseconds.—eric 05:28, 28 May 2010 (UTC)

Why are the relative velocities constantly changing?--Wikinv (talk) 07:17, 28 May 2010 (UTC)

The satellite and receiver are moving along independent circles at different rates. -- BenRG (talk) 20:12, 28 May 2010 (UTC)

You can get a decent approximation using the Schwarzschild metric, which is $ds^{2}=(1-2M/h)dt^{2}-dh^{2}/(1-2M/h)-h^{2}d\Omega ^{2}\!$ (using h instead of the usual r). If the orbit is circular (or approximately so) then $dh=0$, which leaves $ds^{2}=(1-2M/h)dt^{2}-h^{2}d\Omega ^{2}\!$, or

$ds/dt={\sqrt {1-2M/h-(h\,d\Omega /dt)^{2}}}={\sqrt {1-2M/h-v^{2}}}\approx 1-M/h-v^{2}/2$.

That's the clock rate compared to a "stationary clock at infinity". To get the ratio between two clocks at finite heights, you compute clock₁/clock₂ = (clock₁/clock_∞) / (clock₂/clock_∞), or

${\frac {1-M/h_{s}-v_{s}^{2}/2}{1-M/h_{r}-v_{r}^{2}/2}}\approx 1+M(1/h_{r}-1/h_{s})+(v_{r}^{2}-v_{s}^{2})/2$

where s is the satellite and r is the receiver. With factors of G and c put in, that's

$1+{\frac {GM}{c^{2}}}\left({\frac {1}{h_{r}}}-{\frac {1}{h_{s}}}\right)+{\frac {1}{2}}\left({\frac {v_{r}^{2}}{c^{2}}}-{\frac {v_{s}^{2}}{c^{2}}}\right)$.

This is equivalent to the formula from Seeber if you take $v_{r}=0$ (but even for a "stationary" ground receiver, $v_{r}$ is really nonzero because of the rotation of the Earth). This formula gives the average time discrepancy of the satellite and ground clocks over a long period of time. At any given moment, the ratio of the ground clock rate to the received signal from the satellite will be somewhat larger or smaller than this average, because of redshift/blueshift. -- BenRG (talk) 05:54, 28 May 2010 (UTC)

Look at the article Gravitational time dilation. That's the name of the effect you're asking about. From that page:

Circular orbits

In the Schwarzschild metric, free-falling objects can be in circular orbits if the orbital radius is larger than ${\frac {3}{2}}\cdot r_{0}$. The formula for a clock at rest is given above; for a clock in a circular orbit, the formula is instead

$t_{0}=t_{f}{\sqrt {1-{\frac {3}{2}}\cdot {\frac {r_{0}}{r}}}}$

This is a consequence of the equivalence principle of general relativity (not special relativity). One related fact is that a monochromatic source of radiation will be observed with a lower frequency (longer wavelength, relative to the source) if the receiver is at a higher altitude (gravitational potential) and will be observed with a higher frequency if the receiver is at a lower altitude, due to the photons' losing (gaining) energy overcoming (having work done on by) the gravitational potential (gravitational redshift)Inasilentway (talk) 22:06, 1 June 2010 (UTC)

dam people

Paraphrasing Ronald Regan as having "...seen one tree, you've seen them all." where would be the best places to dam up the Grand Canyon and how much energy from fossil fuel would be replaced? 71.100.8.229 (talk) 02:31, 28 May 2010 (UTC)

Oooh! I know - they could call it the "Hoover Dam"...Oh...wait, did someone already use that name? Anyway, it produces 2080 MegaWatts. If I have my math right (and someone should check!) - that's equivalent to about 80,000 barrels of oil per hour. SteveBaker (talk) 04:03, 28 May 2010 (UTC)

Yeah but that is just one site where a large reservoir might be located. Take another look at the expanse of the Grand Canyon and you will see that if you are able to sacrifice the senic wonder in line with Regan's philosophy that you might be able to build another dam or 100. 71.100.8.229 (talk) 04:10, 28 May 2010 (UTC)

Lake Mead, which lies above Hoover Dam at the base of the Grand Canyon, has a water level of 1200 feet and a drop of about 500 feet. Lake Powell, at the other end of the Grand Canyon, has a base level of about 3100 feet. So that gives about 1900 feet of altitude to work with, meaning potentially around four times the output of Hoover Dam could be generated, assuming you dammed the entire Grand Canyon. Looie496 (talk) 04:28, 28 May 2010 (UTC)

Assuming there is enough water to work with. The Colorado River already doesn't reach the Gulf of California anymore; it hasn't for decades. Lake Mead's and Lake Powell's levels have dropped in recent years, there has been some serious speculation that their levels may drop below usable levels in the not-to-distant future. Additional dams are a veritable impossibility. There are similar problems on most western rivers; we've literally almost run out of usable dam sites in western North America; its why hydroelectric isn't seriously discussed anymore as a viable alternate energy source; there's no where else to put dams. --Jayron32 04:38, 28 May 2010 (UTC)

Indeed - there is more talk these days of removing old dams than of building new ones. The issues of the region behind the dam silting up - and the river in front of it moving too slowly to sustain native wildlife have really put dams out of favor. You can buy a lot of windmills for the price of a major new dam! SteveBaker (talk) 02:56, 30 May 2010 (UTC)

How do Astronauts performing spacewalks deal with an itch?

Suppose the Astronaut has an itch at the tip of his/her nose and just began a 6 hr spacewalk, how would they handle that situation? I can't imagine them being able to slip their arm up through their spacesuit just to scratch an annoying itch. Thanks!Drummerdavid (talk) 03:58, 28 May 2010 (UTC)

I believe there is a little gizmo that sticks out into the helmet that the astronaut can turn his head around to in order to scratch against. It's put there for just such a reason - there is also a tube for sucking a little water or juice and some kind of an energy bar stick to chew on. SteveBaker (talk) 04:06, 28 May 2010 (UTC)

Mind control and adding nitrous oxide to the air can make an itch go away. The problem is the crossover. 71.100.8.229 (talk) 04:17, 28 May 2010 (UTC)

Thank you for the quick reply!Drummerdavid (talk) 04:27, 28 May 2010 (UTC)

"The problem is the crossover?" What's that mean? --Anonymous, 16:55 UTC, May 28, 2010.

detergent

There are detergents specifically designed to remove oil and grease (hydrocarbons) from eating and cooking utensils by one end of the molecule attaching to the oil and the other to the water. Is there a detergent that will attach one end specifically to water and the other end to just soot or pure carbon? 71.100.8.229 (talk) 04:59, 28 May 2010 (UTC)

Not that I know of -- but detergents that remove oil and grease should in principle work pretty well to remove soot or coal dust. FWiW 67.170.215.166 (talk) 07:06, 28 May 2010 (UTC)

Incidentally, you don't need special detergents to do what's described by the OP. That's how regular old soap works (for non polar grease) Nil Einne (talk) 07:40, 28 May 2010 (UTC)

You mean you do not classify soaps and Surfactants as detergents? In any case I'm looking for a "detergent" where one end binds only with or specifically with carbon or carbon monoxide or carbon dioxide but with a hydrocarbon and it might not be known specifically as a "detergent". 71.100.8.229 (talk) 10:02, 28 May 2010 (UTC)

I don't think that detergents bond with carbon. They bond with nonpolar molecules, and CO is polar. --Chemicalinterest (talk) 10:57, 28 May 2010 (UTC)

You said "There are detergents specifically designed to remove oil". Soap isn't 'specifically designed'. It's something that can occur naturally and people have been making before anyone had any understanding of the chemistry involved. (In addition, our article does say a distinction is sometimes made between soap and other surfactants as detergents, but that wasn't my point.) Nil Einne (talk) 12:50, 28 May 2010 (UTC)

Soap is made from fat and sodium hydroxide with sodium at one end of the molecule and hydroxide at the other same as many synthetic detergents. I recall a "detergent" with different ions at the end which had a greater affinity for various oils while the other end had a greater affinity for water. My memory is failing so maybe I'm just confused. 71.100.8.229 (talk) 03:53, 29 May 2010 (UTC)

Soap chemical structure

Typical liquid detergent structure (Sodium lauryl sulfate)

Your description isn't quite right - I've put images of the chemical structures in - so you can see the difference between what you remember.77.86.47.199 (talk) 09:33, 29 May 2010 (UTC)

Okay I see. It was the sodium ion that was replaced with a hydroxide ion with the hydrocarbon chain remaining the same. Is ther a hydrocarbon chain then that will attach to soot or pure carbon specifically, assuming the sodium or hydroxide end is the one with affinity for water? 71.100.8.229 (talk) 03:17, 30 May 2010 (UTC)

(It's not hydroxide - in the diagrams it's carboxylate or sulphonate an organic sulphate)

It's the sodium end that attachs to water , yes

I'm not aware of something that is specific to soot or carbon - there were mentioned some possibilities below.83.100.138.38 (talk) 15:06, 30 May 2010 (UTC)

You want a detergent that bonds specifically to carbon in the form of soot - As far as I know there is no such thing yet.77.86.125.207 (talk) 14:30, 28 May 2010 (UTC)

Since like dissolves like a surfactant with a napthalene or anthracene at the end of the non-polar part might be a good choice for graphite based soot. Other soots are considerably oxidised, and contain many OH and C=O bonds - for a substance encouraging the suspension of soot particles you might consider a strong sugar solution - such as golden syrup.77.86.47.199 (talk) 14:42, 28 May 2010 (UTC)

Orbital stability

How would one go about showing that an inverse-sqaure force produces stable orbits (or how to check whether a given central force produces the like)? I tried googling, but most of the sites I was linked to dealt with mathematics that was beyond me (eigenvalues and so on). Are there simpler, calculus-based or, better yet, qualitative methods of answering such questions? 173.179.59.66 (talk) 05:37, 28 May 2010 (UTC)

Stability means decay of small perturbations. A small perturbation of a Kepler orbit will not decay, but will not grow either (to put this in the simplest terms, in the 1/r potential, gently nudging an orbiting body moves it from one closed orbit into a slightly different closed orbit). Therefore, it may be argued that a closed orbit of the two-body system with 1/r interaction potential exhibits a marginal stability. Actually, this is a far more general property of a broad class of so-called conservative systems (we don't have an article, but reading Conservative vector field may help anyway). Such systems don't normally have stable limit cycles; instead, depending on the initial conditions and the type of interaction, the behavior may be ergodic, or the system may be in a closed orbit, or the system may collapse into a singular state (see e.g. Coulomb collapse). --Dr Dima (talk) 07:22, 28 May 2010 (UTC)

Turns out we don't have an article on Coulomb collapse (for some reason I thought we did). I guess I'll have to explain briefly what it is. Imagine a classical 3-body (or N-body, N > 2) system with 1/r pairwise interaction where at least some of the interactions are attractive. (Classical -- neither quantum-mechanical nor relativistic -- gas of electrons and ions interacting pairwise via Coulomb potential is an example, hence the name; or imagine a cluster of gravitationally interacting stars and planets). When an electron gets close to an ion, it has higher-than-average kinetic energy; that's because the vicinity of an ion is a deep potential well for an electron. Electrons with higher-than-average kinetic energy tend to lose energy in collisions with other electrons. The more energy our classical electron loses, the deeper it falls into the potential well around an ion. The deeper it falls, the higher its kinetic energy becomes. (Remember that, on average, in a Kepler orbit the kinetic energy is minus one half of the potential energy; see Virial Theorem). In a classical system this will go ad infinitum, with r going to zero and the potential energy of the electron-ion pair going to minus infinity. This is known as the Coulomb collapse. Quantum-mechanical phenomena stabilize atomic orbitals against Coulomb collapse. Finite size and internal pressure of the star prevents gravitational systems from going into collapse. When this fails and the gravitational system does collapse, a black hole is formed (however, the energy released is still finite). --Dr Dima (talk) 07:53, 28 May 2010 (UTC)

Spoke and Hub

Are there any two commercial airports that would require a minimum of 5 flights to get from one to the other? Please note I mean standard commercial flights, nothing chartered or private. TheFutureAwaits (talk) 08:39, 28 May 2010 (UTC)

I don't know that answer, but maybe this map of the world's most remote spots will help. Also, what if the airports are connected by a weekly flight? Does that count as a connection? Or do you mean daily only? Ariel. (talk) 08:52, 28 May 2010 (UTC)

Yes weekly would count although I would argue it would not be reasonable to wait more than a day for your next flight. TheFutureAwaits (talk) 09:54, 28 May 2010 (UTC)

Hmm. This sounds like the six degrees of separation problem. How about this for 7 flights?

Papa Westray Orkney, UK —(several pickup stops) — Kirkwall Orkney, UK — Glasgow, UK — London, UK — (Bangkok or Dubai to refuel) — Sydney, Australia — Christchurch or Wellington, NZ — Invercargill, NZ — Ryan's Creek, Rakiura, NZ

I wouldn't like to try it as Glasgow to Auckland is the best part of 32hrs, with 1.5hr stop-overs at each airport, I'd imagine Wellington and Christchurch are the same. CS Miller (talk) 11:47, 28 May 2010 (UTC)

As a general guide, I'd look for itineraries of the form

remote location → regional airline hub → major intercontinental hub → (new continent, change of airline) major intercontinental hub → regional hub → remote location

Bonus steps can be added if the intercontinental hubs are far enough apart that you need a fuel stop between them (as in London to Sydney). Good luck on your painfully long journey! TenOfAllTrades(talk) 13:58, 28 May 2010 (UTC)

I found one that would need ten, since it looks like Greenland does not like to use hubs. It is seasonal, but regularly scheduled while in season and would consist of

Qaanaaq, Greenland (Qaanaaq Airport), Upernavik, Greenland (Upernavik Airport), Ilulissat, Greenland (Ilulissat), Kangerlussuaq, Greenland (Kangerlussuaq Airport) Nuuk, Greenland (Nuuk Airport), Reykjavik-Keflavik, Iceland (Keflavík International Airport) Frankfurt, Germany (Frankfurt Airport) Johannesburg, South Africa (OR Tambo International Airport) Gaborone, Botswana (Sir Seretse Khama International Airport) Kasane, Botswana (Kasane Airport)

The inter-airport structure is analyzed in some detail in Guimera et al 2005. Basically, it fits a Small-world network model, which displays the popular Six Degrees of Kevin Bacon phenomenon. In most such networks, however, the usual "degree of separation" is significantly less than six. From Guimera, 56% of all pairs of cities are within 4 flights of each other, and the vast majority are within 5.

"The farthest cities in the network are RAF Mount Pleasant in the Falkland Islands and Wasu, Papua New Guinea: To get from one city to the other, one needs to take 15 different flights. From Mount Pleasant, one can fly to Punta Arenas, Chile, and from there fly to some hubs in Latin America. At the other end of the path, from Wasu one needs to fly to Port Moresby (Papua New Guinea), which requires a unique sequence of eight flights. In the center of the path, between Punta Arenas and Port Moresby, six different flights are needed. In contrast to what happens the ends of the path, in the central region of the path there are hundreds of different flight combinations, all of them connecting Punta Arenas and Port Moresby in six steps." - from Guimera et al 2005. SamuelRiv (talk) 04:44, 29 May 2010 (UTC)

Very nice! -Rajah (talk) 01:59, 30 May 2010 (UTC)

chemistry lesson plan for teachers

How to write an introduction for the subject changes in chemistry? —Preceding unsigned comment added by Kvjith (talk • contribs) 08:56, 28 May 2010 (UTC)

• The meaning of chemistry.
• The uses of chemistry.
• The properties of matter (its states, etc.)
• The scales of measurement in chemistry.
• Energy and its relationship to matter.

Here are some ideas for introductory lessons. --Chemicalinterest (talk) 11:00, 28 May 2010 (UTC)

We should have had an article on chemistry teaching, but chemistry education is for tertiary education only! Graeme Bartlett (talk) 11:02, 28 May 2010 (UTC)

Help With

please anyone who knows: Alkyl nitrites synthesized in the lab like? Thank you --I love chemistry (talk) 10:18, 28 May 2010 (UTC)

Alkyl nitrites says: "Organic nitrites are prepared from alcohols and sodium nitrite in sulfuric acid solution." Don't forget to look for an article first before asking.77.86.125.207 (talk) 10:38, 28 May 2010 (UTC)

As you see on the top of the reference desk page, it says that you can search for your applicable term in the search box on Wikipedia. If not try a Google search. Then, if you do not get your answers clearly you may ask. This is to prevent excess cluttering of the reference desk with basic questions that could be answered simply by a search.--Chemicalinterest (talk) 10:56, 28 May 2010 (UTC)

[2] Nitrosyl chloride can also be used to synthesise them from alcohols.77.86.125.207 (talk) 10:59, 28 May 2010 (UTC)

Quote

Can I have another simple meaning for the underlined phrase told by Einstein:

The precise formulation of the time-space laws was the work of Maxwell. Imagine his feelings when the differential equations he had formulated proved to him that electromagnetic fields spread in the form of polarised waves, and at the speed of light! To few men in the world has such an experience been vouchsafed . . so bold was the leap that his genius forced upon the conceptions of his fellow-workers

Indeed I was translating this into Arabic, but found it confusing in the last part.--Email4mobile (talk) 14:35, 28 May 2010 (UTC)

What he is saying is, "his idea was such a brilliant and unexpected one, that the fact that Maxwell was a genius was obvious to every other scientist once they heard of the idea." Does that clarify it? That is not a exact "translation" of what Einstein is saying, but should help you parse exactly what he's trying to indicate, I hope? --Mr.98 (talk) 14:47, 28 May 2010 (UTC)

Actually I don't think that's what it's saying at all - more like "His ideas were so advanced nobody understood them for years..."77.86.47.199 (talk) 14:57, 28 May 2010 (UTC)

You can read the full article here [3] p.489 left column (Einstein was quite a good writer)

There's some missing text where you have dots ".." - if you add that it makes more sense. I can't (work out how to) copy paste that article here - so you'll have to read the link.77.86.47.199 (talk) 14:48, 28 May 2010 (UTC)

I'll just type it in

"Meanwhile it took physicists some decades to grasp the full significance of Maxwell's discovery, so bold was the leap that his genius forced upon the conceptions of his fellow-workers" Science, May 24 1940, A. Einstein, article

That makes more sense with the rest of the sentence does it not?77.86.47.199 (talk) 14:51, 28 May 2010 (UTC)

• Bold leap - is metaphorical, his ideas were completely different to what was understood (to be true) before
• forced upon the conceptions - challenged what they thought was true (conception/conceive can mean what you think is true, as well as pregnancy. See the wiktionary entry, meaning 2)

CS Miller (talk) 15:00, 28 May 2010 (UTC)

Thanks to all of you :). That was great help!--Email4mobile (talk) 15:07, 28 May 2010 (UTC)

Evolution

Someone told me that Charles Darwin corresponded with Karl Marx, and that he had copies of Das Kapital and The Communist Manifesto. Is this true? --J4\/4 <talk> 15:56, 28 May 2010 (UTC)

sort of.. Marx sent Darwin his book . http://friendsofdarwin.com/articles/2000/marx/ 77.86.47.199 (talk) 16:12, 28 May 2010 (UTC)

Darwin definately had a copy of Das Kapital, not sure about the other book - here's an image of Darwin's copy of Das Kapital with a dedication from karl.. http://www.englishheritageimages.com/pictures_464127/das-kapital-k030651.html 77.86.47.199 (talk) 16:14, 28 May 2010 (UTC)

A little more info here http://www.guardian.co.uk/science/2009/feb/09/charles-darwin-museum-exhibition Darwin tried to read it, but never finished it.. The book was inscribed "your sincere admirer Karl Marx"

As a learned man, he may have had those books. I see no mention of an association in the Charles Darwin article. Keep in mind that some people make an effort to discredit Darwin for their own reasons.. they apparently think that attacking the man himself somehow renders modern scientific findings invalid. See also Creation–evolution controversy. Friday (talk) 16:10, 28 May 2010 (UTC)

There is no evidence that Darwin corresponded with Marx. Apparently Darwin sent a letter to someone else asking not to be mentioned in a book's dedication, and for some time it was thought this letter was to Marx when in fact it was not. See here and here and here for details. As for books, Darwin did indeed own Das Kapital, as Marx himself sent Darwin a copy. That copy now resides at Down House. Hope this helps. --Sean 16:21, 28 May 2010 (UTC)

I'm not sure how your question relates to the section title you gave it - but back then, being well-read and having a rounded education stood for a lot - and reading ideas by people you don't agree with is one excellent way to get that kind of education. As the son of a wealthy doctor and financier, he would certainly have owned a large and diverse library - such was the mark of a well-to-do intellectual man of the mid-1800's. So we don't know that Darwin necessarily agreed with Marx - and even if they corresponded, that would not be considered unusual between intellectuals of the day when there was more of a spirit of open debate than we're (sadly) seeing these days. Darwin lived for 73 years - it would be exceedingly strange if the only thing he did in his entire life was to formulate the ideas behind evolution!

See the talk page. Not Directly Relevant. Buddy431 (talk) 01:14, 29 May 2010 (UTC)

However, one thing is for 100% certain and that is that no effort to claim that Darwin was a pinko commie or a flaming gay or a religious fanatic (all of which I've seen claimed here by various religious nuts, young-earth creationist crazies and intelligent-design fanatics over the past year or so) will make the slightest difference to the scientific principle of evolution. The anti-evolution nutcases like to refer to believers in evolution as "Darwinists" in the hope that by pulling down the "Father of Evolution" they can end the belief in the scientific principle. Sadly, while that might have worked in the first few years after publication of "On the Origin of Species", we're way beyond that now. Science is an evidence-based practice - the people involved in finding that evidence don't matter beyond some small historical curiosity. The evidence for evolution is utterly overwhelming and only the most close-minded or ill-educated individuals could possibly be blind to that fact. So maybe Darwin was a pinko, god-fearing, gay, child-molesting, lying, cheating, occultist (did I miss any?)...but that doesn't change the scientific fact that species change over time in reaction to their environment and on the basis of well-established genetic principles. We have tons of solid proof of that that are completely independent of Darwin. For what it's worth, I don't think Darwin was any of those things - he was a "gentleman naturalist" - a quiet contemplative man who didn't hold strong views about much beyond what he discovered. But that really doesn't matter a damn except to historians.

SteveBaker (talk) 18:33, 28 May 2010 (UTC)

Responses to collapsed section above

This screed and Chemicalinterest's response are off-topic and inappropriate. Opie asked a simple question about an interesting factoid in Darwin historiography (the case of the misfiled letter) and doesn't deserve this kind of knee jerk response. --Sean 20:34, 28 May 2010 (UTC) Solid proof? I do not stand for attacking people who believe in evolution (calling them names), but I do not hesitate to attack the philosophy. Anyone who attacks people (Darwin) while missing the subject (evolution) is like trying to kill a bear by shooting its leg: It weakens it, but it makes it much madder and more defensive. --Chemicalinterest (talk) 18:47, 28 May 2010 (UTC)

Marx did read Darwin, and wrote to Engels that "Darwin’s work is most important and suits my purpose in that it provides a basis in natural science for the historical class struggle."[4] Which is historically pretty interesting.

As for Darwin's correspondence, it has been meticulously categorized as part of the Darwin Correspondence Project, which is still a work-in-progress. Darwin did correspond with Marx in 1873, thanking him for sending him a copy of Das Kapital, and expressing that he wished he understood more of "the deep & important subject of political Economy."[5] The full digitized version of the letter appears in the link above. It does not appear they had an extensive correspondence and it appears that they would have corresponded long after Darwin came up with the ideas and even execution of The Origin of Species. Which is understandable—Darwin certainly had an interest in political philosophy (Malthus was a major inspiration), but he wasn't much of a heavy reader of such things. After 1869 he was a major British intellectual figure, so it's no surprise that Marx read him and perhaps vice versa (though I doubt it). As for any implications on his own politics, Darwin was many things, but a Communist he was not. He was rather conservative by most political standards of his day—he read the British equivalent of Fox News as his regular newspaper (for details on this, see R. Colp, Jr., "Charles Darwin: Slavery and the American Civil War," Harvard Library Bulletin 26 (1978), 471-489), which occasionally led him to rather retrograde opinions (he was extremely anti-North for most of the Civil War, even though he was a passionate abolitionist). --Mr.98 (talk) 00:08, 29 May 2010 (UTC)

Training your body to not be lactose intolerant

Someone I know said they were diagnosed as a child to be lactose intolerant, but then as an adult they are no longer lactose intolerant. Then a friend of hers said that she trained her body into not being lactose intolerant anymore by gradually introducing milk products into her body over a long period of time. Is this possible? Is what her friend saying true? ScienceApe (talk) 15:58, 28 May 2010 (UTC)

Different people have different problems with Lactose. But it seems like in some cases what you describe is possible. Lactose_intolerance#Rehabituation_to_dairy_products. APL (talk) 16:18, 28 May 2010 (UTC)

There are a few papers that point toward such a thing, but a more important point is that numerous studies show that the majority of people who think they are lactose-intolerant aren't really, except in a psychological sense. (In many people who think they are lactose intolerant, milk with the lactose removed produces the same symptoms as whole milk.) Looie496 (talk) 16:28, 28 May 2010 (UTC)

Syrup

1. 1 Hi. More of a cooking question than science but here goes .. Does corn syrup taste different from golden syrup (I know what golden syrup tastes like, but haven't seen corn syrup in the UK. I would be comparing the light corn syrups with golden syrup. Also what does 'karo' taste like.

1. 2 Does anyone have enough expertise to say what flavour chemicals are present in these syrups, if any. I guess it's lower concentrations of whatevers in molasses/treacle that makes golden syrup golden.. ? ? 77.86.47.199 (talk) 17:10, 28 May 2010 (UTC)

Corn_syrup#Commercial_preparation and Golden_syrup#Production may help. Regards, --—Cyclonenim | Chat  17:16, 28 May 2010 (UTC)

there doesn't seem to be an answer to any of my questions there (apart from the possibility of a salt trace in there - depending on method) - obviously I don't know what if any taste differences there are between glucose, fructose and sucrose - I thought there was something else in there beyond sugar, in low concentrations that gives it a different taste to say - pure glucose?77.86.47.199 (talk) 17:21, 28 May 2010 (UTC)

I'd be somewhat surprised if anyone here can give you a definitive answer on the relative taste of golden syrup and corn syrup, but you never know. As a practical matter, though, no one (or almost no one) uses corn syrup in a way that you'd be likely to notice a distinctive flavor. It's a cheap sweetening agent — you put it in rather than on things, and the things you put it in should have enough of their own flavor to overwhelm any from the syrup. --Trovatore (talk) 18:44, 28 May 2010 (UTC)

"no one (or almost no one) uses corn syrup in a way that you'd be likely to notice a distinctive flavor" - so you have never poured Karo over your pancakes then. Especially dark Karo on cornmeal cakes, mmm. 75.41.110.200 (talk) 19:22, 28 May 2010 (UTC)

I would have said that golden syrup has a pretty distinctive taste, while corn syrup, especially light, non-vanilla flavored corn syrup, is relatively tasteless. Just my non-scientific opinion, though. Buddy431 (talk) 21:19, 28 May 2010 (UTC)

How do these compare with honey? 92.15.4.237 (talk) 10:03, 2 June 2010 (UTC)

Decipher Karl Marx's handwriting?

What does the handwriting here http://www.englishheritageimages.com/pictures_464127/das-kapital-k030651.html say? I'm particularly curious what the address is, and where it would be or if it still exists in modern times. Thanks 92.15.30.36 (talk) 18:03, 28 May 2010 (UTC)

see Jenny von Westphalen 1 Modena Villas, Maitland Park, Haverstock Hill, London, NW (Humanities Desk next time please)77.86.47.199 (talk) 18:10, 28 May 2010 (UTC)

It was knocked down [6] , the street was renamed Maitland Park Villas [7] 77.86.47.199 (talk) 18:22, 28 May 2010 (UTC)

Its ironic that Marx, of all people, should marry into the aristocracy. None of his descendants appear to have survived into the present time. How did Marx support himself and his family while writing Capital? 92.15.30.36 (talk) 20:24, 28 May 2010 (UTC)

a. Use the humanties desk, and b. Read Karl Marx as the answer to your question is in that article: "Marx's major source of income was from the support of Friedrich Engels, who was drawing a steadily increasing income from the family business in Manchester." 77.86.47.199 (talk) 20:55, 28 May 2010 (UTC)

Probiotics

not sure if it is the same thing, but what other foods have live bactiera in it besides yogurt?Reticuli88 (talk) 18:56, 28 May 2010 (UTC)

Unpasteurized milk and cheese - if you can get legally them. 75.41.110.200 (talk) 19:12, 28 May 2010 (UTC)

There's a list of products here Fermented_milk_products#Comparison_chart many of which are not pasturised - many of them yoghurt like in fact.77.86.47.199 (talk) 19:14, 28 May 2010 (UTC)

also if you don't mind sorting out these yourself - look at Category:Fermented foods , not all have live bacteria, but many do. 77.86.47.199 (talk) 19:15, 28 May 2010 (UTC)

(ec) Blue cheese. "Probiotic" is a marketing term rather than a scientific one, so it isn't particularly well defined (or defined at all, really). You can decide for yourself whether the bacteria in blue cheese count as probiotic or not. --Tango (talk) 19:17, 28 May 2010 (UTC)

Probiotic isn't a marketing term (we have a rather detailed and well-referenced article on it), and the word is actually quite well defined. ~Amatulić (talk) 19:22, 28 May 2010 (UTC)

(Unpasteurized) beer will have live yeast in it. Buddy431 (talk) 21:16, 28 May 2010 (UTC)

A tiny bit, maybe. The yeast is supposed to be removed before bottling, for bottled beer, or it being put in a barrel, for lager. Real ale is put in the barrel with yeast still in it, but you are supposed to leave barrels to settle after tapping them before serving, so there shouldn't be any yeast in the actual served beer. --Tango (talk) 22:34, 28 May 2010 (UTC)

Not true... even after allowing the beer to clear, there is still a small amount of yeast in suspension, even in very bright beer. Exactly how much depends on the yeast's flocculance character (I'm a 10th level beer nerd). – ClockworkSoul 22:37, 28 May 2010 (UTC)

Like I said, you may (ok, will) get a tiny bit. It's an insignificant amount, though (both in terms of digestive health and continued fermentation). --Tango (talk) 00:38, 29 May 2010 (UTC)

It has enough yeast that it can be used as a leavening agent. It's clearly not an "insignificant amount" in certain situations. Buddy431 (talk) 00:45, 29 May 2010 (UTC)

I concur. Some British and many Belgian bottled beers (for example) contain a very noticeable quantity of yeast in order to cause a secondary fermentation in the bottle; one may either pour carefully to leave this at the bottom of the bottle, or deliberately mix it into the beer, according to taste: although much of this yeast may have died (especially if the bottle is well matured) enough usually remains alive to enable re-cultivation.

Cask beer (as opposed to filtered keg beer) typically contains an even higher proportion of live yeast than bottled beer, and although finings are added to make this flocculate and settle out, much remains invisibly in suspension (and knowlegeable drinkers don't object to a degree of cloudiness due purely to yeast). Having worked at scores of beer festivals, I have often observed glasses of visually clear beer, left undrunk overnight, having by morning a couple of millimetres' thickness of settled out yeast at the bottom. 87.81.230.195 (talk) 02:36, 29 May 2010 (UTC)

Intentionally soured beer styles (lambic and similar brews) often contain Brettanomyces, Lactobacillus and/or Pediococcus bacteria. In days gone by these were the result of "wild" fermentation, but these days they're typically cultured and sold commercially. Take a look here: [8]. – ClockworkSoul 22:37, 28 May 2010 (UTC)

Anthropology/ early hominids

I am looking for an author ( possibly an anthropologist, maybe a professor from the Seattle area ( Pacific Northwest )) who wrote a book called " Second Genesis " theorizing about brain growth in early hominid during the drying of the Mediterranean Sea following the closing of the Gibraltar Strait. Men were separated in " Terrariums " ( his word ) created by the rivers flowing into the Mediterranean as the sea receded lower into its basin, depositing more salt at the bottom.This book is probably 30 or 40 years old and dated the time of the discovery of a Nile Canyon now submerged, which proved the drying and high salt content of the Mediterranean. Daniel —Preceding unsigned comment added by 96.50.111.4 (talk) 19:00, 28 May 2010 (UTC)

Sounds like Genesis Revisited: A Revolutionary New Solution to the Mystery of Man's Origins (1979), by Glenn G. Strickland (apparently an engineer rather than an anthropologist). Description here—scroll down to the post by "Morphane". Deor (talk) 19:51, 28 May 2010 (UTC)

Unpleasant materials

I have an aversion to some textiles (don't know exactly which ones), that give me the creeps. When I touch them long enough (especially directly with bare hands), I experience very creepy feelings and the hands nearly sweat. Particularly, I had a jacket that nearly tormented me. Maybe someone has the same. Why is that? 213.154.25.253 (talk) 19:18, 28 May 2010 (UTC)

Could it be what it's made of - do you have the labels - a lot of people don't like polyester, also fleeces/corduroy/others feel unpleasent to some since the ends of the fibre point up (like tiny brushes). Or maybe the jacket was rubbery , some people done like that - even a small percentage of lycra to make the material more stretchy can impart a rubbery feel. 77.86.47.199 (talk) 19:30, 28 May 2010 (UTC)

How odd. Do these same people dislike the feel of other furry things, such as kittens? Are you implying that the ends of the fibers stab into delicate skin and cause pain, or what? 81.131.68.87 (talk) 19:50, 28 May 2010 (UTC)

Are kittens made out of fleece or velvet ? No. Am I implying anything ? No.77.86.47.199 (talk) 20:10, 28 May 2010 (UTC)

I've experienced a similar reaction - so, no, you're not alone. It's hard to describe. Artificial fabrics that cling to my fingers kind of creep me out. Cheaply made fake fur, for example, always seems to have too much friction and the oils from your hand sometimes make weird squeaking noises when you wipe them on it. Yuck. Matt Deres (talk) 00:12, 29 May 2010 (UTC)

I'm stroking a teddy bear right now (presumably polyester fur) in an effort to work out what you mean, and I really don't get it. Sure, it doesn't feel quite like real fur, and it has slightly more friction, and I guess it makes a bit more rustling noise (it doesn't squeak!) ... so all in all it feels slightly different from real fur. So why is that disturbing? Is it an uncanny valley effect? That relies on our inbuilt instincts for identifying humans, though, and it's not like we have an instinctive affinity for the feel of real fur - or maybe you guys do? 81.131.23.148 (talk) 04:17, 29 May 2010 (UTC)

Yes, looks like it's some artificial textiles which make my palms wet after stroking. Particularly, a grainy sofa casing, brr:( 213.154.5.40 (talk) 05:23, 29 May 2010 (UTC)

I dislike the feel of cotton wool. 92.28.242.45 (talk) 09:16, 29 May 2010 (UTC)

Experimental design

I'm designing an experiment to measure the effect of a treatment on the composition of substance. Of course I want do replications, but the right or most sensible way to go about this is less obvious that it might seem.

I could:

1. Apply the treatment to 5 samples of the substance, and then measure the composition of each treated sample once
2. Apply the treatment to one sample of the substance, and then measure the composition of the treated sample five times
3. Apply the treatment to 5 samples of the substance, and then measure the composition of each treated sample five times

Repeating the treatment is much more 'expensive' that repeating the composition measurement. Although I want to be thorough, I need to make efficient use of my resources. Can you help me understand how I should be thinking about these different alternatives? If you can point me to somewhere that I could read about this issue, that would help. I've searched, but I must be using the wrong terminology because I haven't found much. ike9898 (talk) 19:48, 28 May 2010 (UTC)

ok Two relevant articles are sampling error, Margin of error - you have at least two possible errors here:

• The error of measuring the composition
• The variance in the treatment of the substance

If you don't do the 5x5 experiment you won't know anything about one of the two possible errors.

Experiment 2 gives you some indication of the error of measuring the composition. You can't really say much about the experimental error in treatment of the substance until you measure this.

If you are certain within yourself that one of the two errors is likely to be small (eg you think the treatment process is reliable and consistent, or you think the measurement of the composition is so reliable that you only need to do one measurement) then you could do experiment 1 or 2. but you have no statistical knowledge about the error at all.

There should be an article experimental error but I can't find it. I don't know of a good read on this subject but the search http://www.google.co.uk/search?hl=en&q=experimental+error&meta= gives pretty reliable hits on the sort of pages you might want to read - if you aren't already at least get to understand the different between "statistical" and "systematic error", and get an idea of how errors propagate.77.86.47.199 (talk) 20:42, 28 May 2010 (UTC)

Straight answer: What I'd suggest is do experiment 2 once (maybe with more than 5 measurements) - so you have an idea of the statistical error in the measurement - this should then give you enough information to know how many times you need to do the measurent for future samples to get a reliable answer:77.86.47.199 (talk) 20:47, 28 May 2010 (UTC)

Process 1 is valid, and process 3 probably won't be much better. Process 2 is not valid unless you are sure that all samples are the same. The crucial point is that when you calculate a mean and standard error, the samples that go into the calculation have to be completely independent of each other, and they have to be chosen randomly from the distribution. That means if you apply process 3, you would have to calculate the mean separately for each of your 5 samples, and then use the calculated means as input to a 5-sample check. But in any case you're putting the cart before the horse: you need to have a well-defined hypothesis to test in order to properly design an experiment, and you didn't state what your hypothesis is. Looie496 (talk) 20:49, 28 May 2010 (UTC)

OP here. Well, I'm not sure what my hypothesis is, but let me explain what I am trying to do, which is slightly more complex than what I described. There's not just one treatment; the treatment is a continuous independent variable, and I intend to perform experiments with treatment variable set at 5 different values. I want to produce is a figure that shows the composition at the various settings for the treatment. I think I'd also like to be able to fit a curve to the results. ike9898 (talk) 21:29, 28 May 2010 (UTC)

Suggest following my straight answer above - do 5 (or 10) measurements with one sample - this gets you an error bar for that measurement. For the others if you don't have time(/don't want) to do repeat experiments you can use the same error bar (probably best to scale as a percentage error) for the other measurements (assuming you do only one measurement per sample) - if plotting this as a graph you should clearly state and distinguish the proper and extrapolated error bars (eg solid for measured error, dotted for extrapolated) - though there is no substitute for actual measurements, and some people may take issue with extrapolated error bars...

As for curve fitting - It helps if you have a hypothetical equation first (ie a hypothesis) - do you have one, otherwise you could guess the curve - (see also Curve fitting) - though the problem here is that logarthymic/quadratic/exponential curves can look much like a straight line if the range of points is small. Not sure how much info you need on curve fitting. A quick look at this [9] suggests it's a good introduction though searching for "curve fitting" turns up many results of use - often the URLS that end with .ac. are useful since they are from universities.77.86.47.199 (talk) 22:11, 28 May 2010 (UTC)

"Dichroic liquids" / dyes

Has anyone ever seen a phenomenon like this before? It is quite remarkable imo. Does anyone have any ideas as to what might be causing it? Perhaps it is a colloid with suspended particles being of different color than the solvent they are suspended in; whereby transmitted light is absorbed by the solvent at selective wavelengths but absorbed at all wavelengths by the dispersed solid particles, which also simultaneously scatter light at selective wavelengths (green).

http://www.youtube.com/watch?v=7jA7DRFDr70 —Preceding unsigned comment added by 128.151.32.169 (talk) 20:58, 28 May 2010 (UTC)

Thank you very much that is fascinating - this article [10] suggests that methanol / chloroform mixtures, though miscible can show localised regions where hydrophobic and hydrophilic ends of molecules agglomerate - ie like micelles (I would assume that dyes contain both hydrophilic and hydrophobic parts) - could a micelle like structure explain the optical properties?

I also think it may be some sort of colloid or emulsion - the green colour looks 'diffuse' as if it is particulate, whereas the purple color is clear. I'm not sure if it is coincidence that the green colour is the complement of the purple colour or not (ie green+purple=white)

Also towards the end of the video he says that the transmitted light (ie the light going through the liquid and out the bottom) is still purple - so that suggests no chemical change and that the green light is backscattered. Also when pouring the liquid it looks like thin films and the edges of the liquid look purple - suggesting that the green colour is cause by a bulk volume of liquid - again suggesting a colloid or emulsion or similar.77.86.47.199 (talk) 21:11, 28 May 2010 (UTC)

I think is a combination of reflectance and absorption. If you have a material that absorbs and reflects green light it would explain this. When the liquid is shallow, you see the green reflection. Little light is absorbed because there isn't much liquid (so it's mainly white with a tinge of magenta). However the human eye is much more sensitive to green, so the small amount of green light that is reflected is noticeable. When the liquid is deep a lot of green light is absorbed, leaving behind the magenta light. This mixes with a small amount of green that is reflected, but there is enough magenta, that that is what you see. On top of that the reflection is directional - so the green is reflected away from you. If you have a youtube account, link to this page in the video comments. Ariel. (talk) 23:36, 28 May 2010 (UTC)

I posted a comment on his blog, except I'm not sure comments are working. My suggestion is reabsorption by the competing molecules - the blue light reflected off the methanol is absorbed by the red chloroform and re-emitted as green (because the red dye is a reflection of white light - depending on the black body model, it'll look somewhat greener when a bluer-color light is shone). The converse occurence also happens, such that the net result is green. This occurs with magnitude not seen in other solutions I think because both chloroform and methanol are linear-polar, where ethanol is bent. Thus I think the chloroform and methanol align in the mixture and thus re-absorb each other's light much more effectively. But I do physics, not chemistry. SamuelRiv (talk) 04:25, 29 May 2010 (UTC)

2 gallons

i drink 1 gallon water a day. sometimes i drink 2 gallon water a day. when i drink 2 gallon water a day it feels like all the vitamins gets flushed out of my body. is this common occurrence. —Preceding unsigned comment added by Tom12350 (talk • contribs) 22:56, 28 May 2010 (UTC)

Drinking too much water can be very dangerous - people have died from doing that. Check out our article on Water intoxication. Daily intake recommendations for water depend on how much you exercise and how much body weight you have. Most web sites say that a typical person should drink eight 8oz drinks per day - that's just a half of a US gallon - others say 1.2 liters - or a third of a gallon per day. But this depends on body weight and exertion levels...you might well need more if you do heavy work. Drinking about one liter per hour is considered to be most a healthy person should consume because that's the fastest a pair of healthy kidneys can process the stuff into the bladder. 2 gallons is 7.5 liters - so if someone were to drink that much over (let's say) an 8 hour period - then they would be pushing the limits and entering into life-threatening territory. Those are the facts.

However, we're not allowed to offer medical advice here - so if you are concerned, you should consult a doctor.

SteveBaker (talk) 23:23, 28 May 2010 (UTC)

BTW, the 8 cups a day thing has no scientific basis at all. Someone just made it up. The only recommendation is to drink when you are thirsty. Drinking more than that just makes you more likely to get dehydrated (since your kidneys are accustomed to a lot of water, and if you don't constantly drink you will get dehydrated, since the kidneys are still excreting water at the usual pace). It takes a little while for the kidneys to get used to a new water level. See Drinking water#Requirements. Ariel. (talk) 23:31, 28 May 2010 (UTC)

Let's cut out the alarmist health crap. A healthy human can easily handle two gallons (~8 Liters) of water a day (source: [11]) (Note, though, that there are a number of diseases/disorders/etc. that can hinder the body's ability to process water. Echoing Steve, if you're concerned, see a doctor). Buddy431 (talk) 00:40, 29 May 2010 (UTC)

Well, using Steve's own number we find that that 2 gallons is fine. I don't know why Steve is using 8 hours as the length of a day... As long as you drink the 2 gallons spread out over the whole day and there are no exceptional circumstances (that's the bit we can't cover here and you need to see a doctor for), you should be fine (in the short term, at least - I have heard from reliable sources that there is a possibility that people drinking too much water "wear out" their kidneys over years. --Tango (talk) 01:00, 29 May 2010 (UTC)

Thirst is a very bad way to determine when to drink. If you are thirsty, you should definitely drink, but that isn't enough. A lot of people aren't good at noticing thirst, so they would only be drinking when they are already approaching dehydration. The colour of your urine is a better measure - it should be pretty much clear. If it is green/yellow, you need to drink more. --Tango (talk) 01:00, 29 May 2010 (UTC)

It's not "alarmist health crap". If you drink two gallons of water as fast as you possibly can - it could easily kill you. If you drink two gallons over 7 hours then you'll be consuming it at a higher rate than a healthy pair of adult kidneys can handle it - and it's likely that the resulting dilution of your blood will make you feel very strange - kinda like being intoxicated. If you drink that much over 24 hours, you should be perfectly OK. However, how do any of us respondents know whether the OP has healthy kidneys or unusually low body mass - or is a child? Are these "US Gallons" - because if not, then the risks are even higher than I estimated. Over how much time is the OP consuming this amount? We don't know any of those things - and because this is a potentially fatal situation, we MUST err on the side of caution. Two US gallons per day is an awful lot...and it's most certainly in the range where side-effects are possible. Since our OP explicitly expresses noticable symptoms from drinking that much - we have to consider the strong possibility of water intoxication. That's a potentially fatal condition, so we must not dismiss the possibility out of hand - and Buddy431 is taking an exceedingly irresponsible action by doing so. This is a situation where bad advice given on the ref desk could literally kill our questioner! Caution is therefore strongly advised here. Since we're most certainly not allowed to diagnose a medical condition, we should explain the facts in general terms and advise our OP to discuss this with a doctor - which is precisely what I did. SteveBaker (talk) 18:22, 29 May 2010 (UTC)

I don't quite understand the words "should", "enough", and "need" here. What advantage or disadvantage is at stake? 81.131.23.148 (talk) 04:36, 29 May 2010 (UTC)

Let me echo the anon. If one is drinking whenever one gets thristy, and hence staying comfortable, then what physiological benefit is there to drinking more than that? Obviously, the color of urine can indicate how much water was excreted with the urine, but is the person who drinks more and has light urine actually measurably healthier than the person with darker urine by any other objective measure? Dragons flight (talk) 09:00, 29 May 2010 (UTC)

"If [mild to moderate] dehydration is chronic (ongoing) it can affect kidney function and may lead to the development of kidney stones. It can also cause:

• harm to your liver, joints and muscles,
• cholesterol problems, and
• constipation." [12] --Tango (talk) 15:36, 29 May 2010 (UTC)

From your link, "Mild to moderate dehydration: The first sign of dehydration is thirst." So again, if one consistently satisfies ones thirst, what evidence is there that drinking more beyond that matters? Dragons flight (talk) 19:38, 29 May 2010 (UTC)

The problem is that a lot of people don't notice thirst (or mistake it for hunger). That's why the standard advice for checking you are drinking enough is to check the colour of your urine. If you follow the "Diagnosis" link at the top of that page you'll see it talks a lot about urine and doesn't mention thirst once. --Tango (talk) 20:45, 29 May 2010 (UTC)

I certainly don't welcome kidney stones. I notice though the diagnosis page says if "it is unusually dark in colour, you are probably dehydrated." Which is vague, of course, but it doesn't say "it should be almost clear" or "it shouldn't be yellow". I appeal to the fact that everybody knows urine is greenish yellow. 81.131.66.87 (talk) 00:54, 30 May 2010 (UTC)

Mine isn't. Mine is almost clear. The reason a lot of people "know" urine is greenish yellow is because a lot of people don't drink enough. --Tango (talk) 22:10, 30 May 2010 (UTC)

i live in a very hot place thats why i drink 1 gallon a day. my question is when i drink 2 gallon water a day it feels like all the vitamins gets flushed out of my body. is this possible.

How can you tell? You can't feel vitamins. Ariel. (talk) 00:02, 29 May 2010 (UTC)

i can feel them. when i drink 2 gallon water a day it feels like when i dont take my multivitamin for a few days —Preceding unsigned comment added by Tom12350 (talk • contribs) 00:21, 29 May 2010 (UTC)

I believe people who take a lot of multivitamins tend to end up with strange colour pee from all the vitamins being excreted. Perhaps when your pee is more dilute since the strange colours aren't so noticeable this is making you think there's something wrong. In addition see placebo. Nil Einne (talk) 00:35, 29 May 2010 (UTC)

It isn't vitamins you feel, it is salt. As a former desert resident myself, I know that it's quite difficult to keep your electrolytes in balance when you consume that much fluid. Drinking even a part of it as Gatorade or another sports drink reduces the problem quite a bit. Even something like ice tea causes less of that feeling than drinking straight water. When I did midsummer bike rides in Tucson, I would regularly down a gallon or more of unsweetened unchilled ice tea afterward, and it worked pretty well for me. Looie496 (talk) 00:38, 29 May 2010 (UTC)

Multivitamins don't really do anything (unless you have a vitamin deficiency, which you won't have as long as you aren't pregnant and have a good diet), so you won't really be able to tell the difference. It is all in your head. (Yes, there have been studies that show a benefit to multivitamins beyond placebo. There have also been studies showing a benefit to homoeopathy beyond placebo. You need to look at more than one study to draw a conclusion.) --Tango (talk) 00:43, 29 May 2010 (UTC)

Let's be honest though. There are plenty of people, even in the West, who don't eat a terribly balanced diet and could benefit from a multivitamin. We shouldn't be making any assumptions about Tom's eating habits, health, or nutrient situation. That's exactly what our medical advice guidelines are for; we haven't examined Tom, and we don't know his his history. It's irresponsible to recommend either taking or not taking a multivitamin. Buddy431 (talk) 00:50, 29 May 2010 (UTC)

it is not placebo. i dont eat vegetables or fruit. so if i dont take a vitamin i feel it. i also think "placebo" is a scam by lying psychiatrists —Preceding unsigned comment added by Tom12350 (talk • contribs) 00:51, 29 May 2010 (UTC)

In that case, it is almost certainly more important that you start eating fruit and vegetables than that you change your water consumption. A multivitamin is not a good substitute (it is better than nothing, but far far worse than a good diet - it doesn't contain any fibre for one thing). Placebos are definitely real - they are used in an enormous amount of medical research (and some treatment) that has nothing to do with psychiatry and a lot of people would have noticed if the effect didn't exist. --Tango (talk) 01:00, 29 May 2010 (UTC)

no Placebos are not real. i am part of the anti psychiatry movement. in addition you are derailing my original question. —Preceding unsigned comment added by Tom12350 (talk • contribs) 02:02, 29 May 2010 (UTC)

Actually, it is you who have derailed the question, because here on the Reference Desk, other editors generally never just let a comment like that pass, whether you like Anti-psychiatry or not. You weren't actually being told that your feeling had anything to do with the placebo effect. So, on your placebo comment, our placebo article makes it clear that there is definitely a placebo effect. The article also mentions at least one study that concluded that placebos had no clinically important effect, though these studies have been controversial. Comet Tuttle (talk) 02:36, 29 May 2010 (UTC)

If you could find multivitamins with relatively little taste and placebo pills that look (and taste) the same [13] you could test this yourself. (The great difficulty here would be getting multivitamin pills and placebo pills that taste and look the same.) Get a friend to toss a coin, and decide whether to put the real pills or placebo into a container. Then either leave them for you or hand them over without saying anything or exchanging looks. Try these for a few days. If you can genuinely 'feel' the difference, you should have no problem working out if these are the genuine pills or the placebos. Don't talk to your friend about this. When you've done, ask your friend for another batch (using the same or a similar container), tossing a coin or whatever to choose whether to give you the real pills or the placebos, and again without talking in any way about the brief or current batch. Again decide whethere they are the genuine multivitamin pills or placebos. Repeat 6 more times.

After these 8 repetitions, ask your friend for list of when the container had placebos and when they had genuine multivitamin pills. (8 repetitions isn't really enough but hey I'll be generous.) If in all 8 repetitions you correctly identified when you had real pills or placebos (which should be no problem if you can feel the difference) then people would be more willing to accept perhaps you really can feel it when you don't take your multivitamins (although I'd be more inclined to believe the pills didn't actually taste and look exactly the same) and you can be more confident in your believe that you really can feel the difference.

Note that the placebo effect has been observed in many cases outside of the medical field. E.g. people who are convinced they can hear the difference between various types of speaker wires.

Nil Einne (talk) 06:29, 29 May 2010 (UTC)

Er, placebos are an important and well-established part of scientific medicine. (Mostly in regards to double-blind drug research.) They're not really connected with psychiatry. Even if every psychiatrist in the world suddenly admitted they were making their entire field up and were nothing more than a pack of liars the fact of placebos would be unchanged because our knowledge of placebos doesn't come from psychiatrists, it comes from medical researchers. APL (talk) 06:44, 29 May 2010 (UTC)

Getting back to the original question, vitamins A, D, E and K are fat soluble. It is difficult to see how they could be 'flushed out' through the kidneys. This implies that the feeling you are getting is not related exactly to the 'lack' or otherwise of vitamins. Caesar's Daddy (talk) 07:08, 29 May 2010 (UTC)

And also back to the original question, I have kidney problems and have to drink a certain amount each day and no more. If that happens, my electrolyte balance is thrown out, and I feel quite sickly. I guess that's what's happening to you: you've drunk more than your body needs, and the balance of your constitution has been shaken. So in a sense you're right, but it's not the vitamins you're feeling the loss of. (Apologies if this constitutes medical advice, if it is can someone more experienced that I am delete it.) --TammyMoet (talk) 07:54, 29 May 2010 (UTC)

That would only be the case if the OP also has kidney problems (healthy kidneys should be able to deal with the extra water, as long as it isn't drunk over too short a period of time). So, if you are right, it is very important that the OP go and talk to a doctor. --Tango (talk) 16:20, 29 May 2010 (UTC)

couldent it flush out water soluble vitamins like vitamin c or b 12 ? —Preceding unsigned comment added by Tom12350 (talk • contribs) 18:10, 29 May 2010 (UTC)

All water soluble vitamins will be excreted, the level generally dependent on how much you consume. However interesting enough the level of vitmain B12 excretion may be dependent on urine output [14] Nil Einne (talk) 19:01, 29 May 2010 (UTC)

Ask a doctor if you suffer from acid reflux, which may cause you to feel the need for water to soothe the throat. 67.243.7.245 (talk) 12:07, 30 May 2010 (UTC)

This is getting dangerously close to our no medical advice guideline so feel free to remove it if you feel it necessary but if you are able to feel it when you don't take your multi vitamins, it's more likely to be a general 'poor'/'unwell' feeling then anything specific therefore in line with some of the above answers, I wonder if you're getting to the level where you're taking too much water with 2 gallons which in itself may lead to such a feeling and may also negativelly affect the ability of your body to excrete other stuff like vitamins (i.e. you may have too high a level), which could also lead to such a feeling. So anyway, yeah I agree with people above you may want to see a doctor. Nil Einne (talk) 18:12, 30 May 2010 (UTC)