Wikipedia:Reference desk/Archives/Science/2009 June 17

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June 17

Does TeVeS or STVG explain LIGO?

Despite years of operation, LIGO has yet to have a single unambiguous detection event. Meanwhile, TeVeS and STVG have been developed, which can explain galaxy rotation curves without the need for dark matter, and which avoid some of the problems that plagued earlier alternative gravity theories. Does either TeVeS or STVG modify gravity theory at interstellar distances in ways that would explain why LIGO can’t seem to detect gravity waves? Or are TeVeS and STVG both close enough to unmodified general relativity that it shouldn’t affect LIGO? Red Act (talk) 00:16, 17 June 2009 (UTC)

All these modified gravity theory have a hard time explaining some of the evidence for dark matter such as the Bullet Cluster, so they may be part of an explanation but don't preclude the need for some form of dark matter. Dauto (talk) 00:38, 17 June 2009 (UTC)

I don’t know about TeVeS, but the STVG article says that STVG successfully explains the gravitational lensing in the Bullet Cluster, using this as its reference. Red Act (talk) 00:51, 17 June 2009 (UTC)

Does anyone know the answer to Red Act's question abut the gravity waves? I'd be interested also. --Trovatore (talk) 09:43, 17 June 2009 (UTC)

I've just learned that I mispoke a bit in my question, although my intended meaning was clear from context. My question about LIGO is of course referring to gravitational waves, not gravity waves. Red Act (talk) 18:40, 18 June 2009 (UTC)

What is the resonant frequency of fingertips? Is it in ultrasound?

Sagittarian Milky Way (talk) 01:26, 17 June 2009 (UTC)

I would expect it to be at the high end of the audible range, based on intuition. How would you define the resonant frequency? Where is the energy applied? Edison (talk) 02:22, 17 June 2009 (UTC)

A fingertip is a structure of the human body that is constructed of many different tissues. There is no uniform answer to you question. Medical ultrasonography only covers part. There are many other imaging techniques that rely on various resonance frequencies. Most of those do not consider Skin. 68.208.122.33 (talk) 05:29, 17 June 2009 (UTC)

Resting a finger lightly on a loudspeaker cone delivering bass tones may give an impression that the finger resonates slightly at some frequency. However the fingertips are so like rubber that any resonance would be so heavilydamped as to be probably undetectable. Cuddlyable3 (talk) 08:13, 17 June 2009 (UTC)

Edison, applied at the fingerpad, I guess. Cuddyable, true it does feel like that, but then again, I can't touch the wall soft enough to not hear it, so something's vibrating there, and not too obscurely at that. Very short, but not infinately damped.

Maybe because of my age. Old people like 40 or 80 can't hear as high a frequency so if people return negative findings with being able to hear that then it's pretty much confirms the range. Sagittarian Milky Way (talk) 14:15, 17 June 2009 (UTC)

"Resonant frequency" is probably the wrong term; the fingers are so highly damped that they don't resonate to any meaningful degree. If the point of the question is to ask what frequencies we can sense with our fingertips, the main sensors are Pacinian corpuscles and Meissner's corpuscles, which mainly respond to frequencies below 100 Hz, i.e., deep bass. Looie496 (talk) 17:18, 17 June 2009 (UTC)

Yes, they will not resonate, because they are not a nice acoustic simple harmonic oscillator. The frequency response is probably very wide. Nimur (talk) 22:36, 17 June 2009 (UTC)

Why does so little of the energy become sound when objects strike each other?

Sound power says that a jackhammer is only 1W of sound power. You make 2 orders of magnitude more than that just standing still. What is the efficiency ratio? (Joules of kinetic energy dissipated to joules of sound (all frequencies) produced) Sagittarian Milky Way (talk) 02:05, 17 June 2009 (UTC)

Take a look at transverse wave compared to longitudinal wave for help with your question. It looks like homework, so I won't say more other than you can probably get by with simple math. ZabMilenko^{How am I driving?} 04:56, 17 June 2009 (UTC)

If I attached the business end of a jackhammer to a flexible cone of plastic inside a properly designed sound enclosure, the sound output could be orders of magnitude higher. It is designed to break concrete, not to cause air vibrations. Edison (talk) 02:20, 17 June 2009 (UTC)

If you can find the watts of electrical power consumed by the compressor that feeds the jackhammer then you have its overall power ratio regarded as an unintended loadspeaker. Power is also released at supersonic frequencies and as heat. Cuddlyable3 (talk) 08:03, 17 June 2009 (UTC)

Maximum possible impact of one person

Is there any theoretical upper limit on how much of humanity, or of the universe as a whole, one person can ultimately impact in one lifetime? Any lower limit? NeonMerlin 01:52, 17 June 2009 (UTC)

If you're the guy who invented the self-replicating nanobots that end up malfunctioning and consuming first the entire planet for resources to increase their number, then spreading out from there, then 'lots'... ;) --Kurt Shaped Box (talk) 01:58, 17 June 2009 (UTC)

Well, if chaos theory says that the flapping of a butterfly's wing can change the course of a hurricane on the other side of the earth a year later then the amount of change that the least noticable, laziest couch-potato can make in a lifetime is WAY more than that! The theoretical upper limit is determined by the speed of light. If you live for 100 years - the theoretical limit of your influence during your lifetime is a sphere 200 light-years in diameter. But beyond your lifespan...there is no theoretical limit. I strongly suspect the upper and lower limits of influence are pretty similar. But a lot depends on what you mean by "impact". Genghis Khan had a pretty wide-spread influence - he's known for a lot of very specific influence. But the total number of atoms he rearranged as a result of his actions are pretty similar to the "influence" of anyone else. It's a matter of notability. SteveBaker (talk) 02:15, 17 June 2009 (UTC)

I think Steve loves to bring Chaos theory into the picture every opportunity he gets :-)Rkr1991 (talk) 11:04, 17 June 2009 (UTC)

but if you think about it genetically rather than physically Khan is more influential. some ridiculous number of people are descended from him on account of his prodigious reproduction. --173.66.250.169 (talk) 03:21, 17 June 2009 (UTC)

(That's actually the reason I picked him as my example!) SteveBaker (talk) 12:41, 17 June 2009 (UTC)

The theoretical impact would indeed be limited, by cosmic inflation outpacing light speed. --Sean 12:51, 17 June 2009 (UTC)

Taking "impact" literally, presuming a person massing 120kg (because they want to make as big an impact as possible), and travelling near light speed (for the above reason), they'd deliver an impact approaching (0.5 x mass x speed x speed) 5.4 EJ. That's quite an impact. --Polysylabic Pseudonym (talk) 07:44, 17 June 2009 (UTC)

Such a person might well cry "I'll show them all who has guts." Cuddlyable3 (talk) 07:51, 17 June 2009 (UTC)

Very, VERY briefly...yes. SteveBaker (talk) 12:41, 17 June 2009 (UTC)

Superconducting Monkey Collider loses funding. --Sean 12:51, 17 June 2009 (UTC)

Wouldn't their mass increase without limit as their speed approaches the speed of light? — DanielLC 14:38, 17 June 2009 (UTC)

Mass is not a useful consideration, but their energy would certainly increase without limit. --Tango (talk) 17:23, 17 June 2009 (UTC)

An unsourced bon mot by Peter Ustinov gives a hint of the maximum impact to date: "The jews are remarkable for having produced Jesus Christ and Karl Marx who have influenced more people than any others, but had the sense to believe neitherr of them." Cuddlyable3 (talk) 07:49, 17 June 2009 (UTC)

It has been argued that at their peak there were more fans of The Beatles than followers of Jesus...but "influence" is a slippery word and almost any interpretation is possible. SteveBaker (talk) 12:41, 17 June 2009 (UTC)

With 1/3 of the Earth's population being Christian, and counting the Muslims as well (Jesus has an important role in Islam as well) I would disagree with the above sentence. --131.188.3.20 (talk) 22:22, 17 June 2009 (UTC)

Well, you would be wrong. It definitely has been argued. Steve made no statement on whether the argument was correct or not. --Tango (talk) 23:49, 17 June 2009 (UTC)

Is telepathy possible through technology? What is this called?

And how is it done? —Preceding unsigned comment added by 24.118.246.158 (talk) 04:54, 17 June 2009 (UTC)

Take a look at brain waves for older examples, and possibly brain-computer interface. All of this, I believe, falls under emerging fields like cognotechnology. ZabMilenko^{How am I driving?} 05:05, 17 June 2009 (UTC)

It's called techlepathy. —Preceding unsigned comment added by 24.118.246.158 (talk) 05:15, 17 June 2009 (UTC)

Following WP:RS the answer is No. Cuddlyable3 (talk) 07:37, 17 June 2009 (UTC)

What about this? It looks as if synthetic telepathy may be another useful search term. ZabMilenko^{How am I driving?} 08:04, 17 June 2009 (UTC)

Some day, cell phones could be so small that we would be able to have them inside our ear. Does it count as telepathy?--80.58.205.37 (talk) 10:38, 17 June 2009 (UTC)

"Telepathy" is a pretty wide out term. Are you looking to be able to talk to people brain to brain? Because you can't do that. But there, are interesting technologies that allow you to control computer games (Or other computer programs) with your brain. [1] And there's this toy from Mattel that sort of gives you telekinesis. Sort of. APL (talk) 13:49, 17 June 2009 (UTC)

Yes, "telepathy" is not a very precisely defined term. In the sense of direct brain-to-brain communication, it isn't possible to any useful degree with present technology, but there is nothing to rule out future developments making computer-mediated non-linguistic brain-to-brain communication possible. Looie496 (talk) 17:11, 17 June 2009 (UTC)

"Possible" is also poorly defined. Any "Is xxx possible through technology" could be answered with "maybe in the future". Can pigs fly?: maybe in the future! Even proposals that break the laws of physics can be answered so, as there is no way to predict the far future. To my mind, that makes the whole line of enquiry non-scientific, it is instead purely philosophical.YobMod 09:50, 18 June 2009 (UTC)

Anything will fly as long as you give it a means to generate sufficient thrust. Think pig with Cruise missile strapped to back. Large boar ammunition. 65.121.141.34 (talk) 13:12, 18 June 2009 (UTC)

Oils and fluids

What is the difference between an oil and a fluid?

I am an apprentice fitter & turner, 2nd year. I have just started to learn about hydraulic fitting, and my tradesman wants me to find out the difference between an oil and fluid. I have used google and yahoo, but can't find anything. Everyone seems to say they are the same thing, but they are not. So I want to know the difference. All I know so far is that a fluid is used to transmit power, whereas an oil is purely a lubricant. —Preceding unsigned comment added by Thenickoff (talk • contribs) 05:34, 17 June 2009 (UTC)

I have no particular technical training or knowledge, but in terms of hydraulics "hydraulic fluid" and "hydraulic oil" mean the same things - they even point to the same wikipedia page. Hydraulic fluid is generally made of mineral oil. More generally, see oil and fluid - outside the field of hydraulics these terms are very, very, very general. --Polysylabic Pseudonym (talk) 07:32, 17 June 2009 (UTC)

Oil is a fluid, so is water. Thus not all fluids are oil. You seem well aware of the application of oil in particular. There are many applications of fluids in general, including washing, irrigating, drinking, swimming, floating boats on, putting out fires, thermometers (mercury or alcohol - both are fluids), riot crowd control, eye/nose/ear drops, steam engines,... Hydraulic systems are not my field but the article Hydraulic fluid says it may or may not be an oil. Cuddlyable3 (talk) 07:33, 17 June 2009 (UTC)

Scientifically speaking, all gasses, most liquids and a few solids (eg silly putty) are "fluids". Therefore oils are also fluids.

However, in the automotive world, I don't think many people would think of gasses as fluids. People talk about "windshield washer fluid" - which is most certainly not an oil. I don't agree with your idea that fluids transmit power - that's certainly not true of windshield washer fluid! We also tend to use terms like "hydraulic oil" and "hydraulic fluid" interchangeably - so not all oils are for lubrication. The definition of an 'oil' is a bit fuzzy - basically it's a fluid, and it's one that's "hydrophobic" (won't mix with water). But we don't call gasoline an "oil" so that definition isn't precise enough...I think oils have to be more viscous than that. It used to be that all oils were derived from natural biological sources (ie crude oil or vegetable/nut oil) - but with synthetic engine oil - that definition is falling apart.

In your field, I would offer the following simplified definitions:

• Fluid - Any liquid.
• Oil - Any viscous fluid which does not mix easily with water.

SteveBaker (talk) 12:31, 17 June 2009 (UTC)

The on-line etymology dictionary gives:

OIL c.1175, "olive oil," from Anglo-Fr. and O.N.Fr. olie, from O.Fr. oile (12c., Mod.Fr. huile), from L. oleum "oil, olive oil" (cf. Sp., It. olio), from Gk. elaion "olive tree," from elaia (see olive). O.E. æle, Du. olie, Ger. Öl, etc. all are from Latin. It meant "olive oil" exclusively till c.1300, when meaning began to be extended to any fatty, greasy substance. Use for "petroleum" first recorded 1526, but not common until 19c. The verb is c.1440, replacing O.E. besmyrian. The artist's oils (1663), short for oil-colour (1539), are paints made by grinding pigment in oil. Cuddlyable3 (talk) 21:22, 17 June 2009 (UTC)

The above answers seem to be forgetting that this is a domain-specific terminology. The original poster has clearly stated that he wants to know the difference with regard to metal-working. We have an article: Cutting fluid. There is not a significant difference, and the terms are often used interchangeably. (Take a look at Metalworking Fluid Magazine's recommended reading list for some example usage). However, "fluid" is more technically correct (more general), because not all metal-working fluids are petroleum-based (or oils at all, in the chemical sense). Fluids include silicones, petroleum derivatives and true oils, soy-based and organic chemicals, mists, etc. etc. etc. For example, if you were going to be working on a metal fitting joint for an oxidizer system, never use an oil - you must use an oxygen-clean, safe working fluid - because there is a very real risk that residues left behind will combust (catch fire). Krytox is a safe alternative, it is often used for sealing, but it can also be used while working the part. Some machinists will suggest that a good toothbrush cleaning removes all oil residues, but they probably never worked with very strong oxidizers... Nimur (talk) 22:43, 17 June 2009 (UTC)

Determining the Credibility of Research Journals

Until recently I was very naive about research journals, sort of blindly accepting their published results as being peer-reviewed and trustworthy, even if I'd never heard of the journal before. As a writer who is now frequently tasked with reporting on advances in cancer research, this is admittedly foolish. But then I came across Regulatory Toxicology and Pharmacology, and recognized the editor's name as a notorious one in his field, and later read that it receives funding from RJ Reynolds.

I'm aware of the more renowned journals, such as The Lancet, but the List of medical journals is extensive. I assume that over time, familiarity will breed the necessary discretion. Until then, are there methods of determining the credibility of research journals I haven't heard of? Wolfgangus (talk) 06:59, 17 June 2009 (UTC)

Your scepticism of journals funded by vested interests is evidence that you are no longer naive. In reports about a major research field such as cancer it would be wise to look for reliable, third-party, published sources similarly to the WP:RS guideline. Cuddlyable3 (talk) 07:14, 17 June 2009 (UTC)

On Wikipedia there is also WP:MEDRS and the reliable sources notice board, WP:RS/N. In real life, googling the journal and the editorial stuff may help. Looking for red flags is useful. And check Google Scholar to see how often and how widely a given paper has been cited. --Stephan Schulz (talk) 07:21, 17 June 2009 (UTC)

If the result of a study doesn't sound right, you will have to examine the methodology used and make your own conclusions (don't forget to also read the footnote containing any possible conflict of interests of the authors). For pharmacology this can be difficult and sometimes an error will be impossible to spot as it is not noted in the research (see: Retracted article on dopaminergic neurotoxicity of MDMA published in one of the big three journals (Nature, Lancet, Science)). --Mark PEA (talk) 09:20, 17 June 2009 (UTC)

OK- The guidelines in both WP:MEDRS and WP:RS seem sound, I can work with those. Google Scholar I hadn't given thought to, so I appreciate that as well. With regard to the reliable sources notice board here, that page is new to me as well. Does that concern only sources used on Wikipedia? It appears that way. (Oh and thanks so much for your time and assistance). Wolfgangus (talk) 09:39, 17 June 2009 (UTC)

For a relevant case study see the MMR vaccine controversy - research originally published in The Lancet was subsequently discredited, but not before widespread panic had been caused amongst parents fearing the vaccine would harm their child. --Lonegroover (talk) 14:50, 17 June 2009 (UTC)

It's sometimes easier, in my opinion, to gauge the value of an article than of a journal, if the article is a few years old. With high probability, if Google Scholar shows a bunch of citations, and the citations come from papers in journals that you know are good, then the article is a good one. This doesn't work too well with articles published in the last couple of years, though. Looie496 (talk) 17:06, 17 June 2009 (UTC)

Incidently, Nature News discusses a fake (nonsensical) paper submitted to and accepted by an online journal. Arguably this will hurt said publication's credibility. Normal peer review should get around this, but I'm skeptical of journals I've never heard of before. Reputable journals ask for authors to disclose potential conflicts of interest. -- Flyguy649 ^talk 17:43, 17 June 2009 (UTC)

Bentham Open also published a "peer-reviewed" paper by 9/11 conspiracy theorists which supports the notion that the World Trade Center was destroyed by a controlled demolition. The Chief Editor of the journal resigned saying that she never authorized its publication and did not consider it worthy of publication; other editors also resigned as a result.[2]. Bentham Open has been accused by academics of 'spamming' researchers with offers to publish or edit the journal, even where those researchers have no background in the field of study.[3][4]. Bentham Open comes up a lot on articles related to 9/11 conspiracy theories because they think it gives their conspiracy theories scientific credibility. A Quest For Knowledge (talk) 18:18, 17 June 2009 (UTC)

Corporate interests do not necessarily invalidate credibility - they just "modulate" it. Ultimately, the reliability of the research is independent of who paid for it and how it was published - what matters is whether the results were scientifically accurate, and the conclusions were reasonable, and the experimental data is repeatable. Nimur (talk) 22:51, 17 June 2009 (UTC)

The "credibility" of a journal is generally considered to correlate reasonably well with its impact factor (though this is not without criticism). Info on Regul. Toxicol. Pharmacol. can be found here, and that particular jounal appears to be of middling impact factor rank in its fields. — Scientizzle 23:18, 17 June 2009 (UTC)

I somewhat disagree here. Specialist areas may be more trustworthily covered by specialist journals that may have lower impact factors. There is a lot of prestige that goes along with getting in higher IF journals, which can result in rushing, or making exagerated claims. This is clearly seen when Science or Nature rushes to publish extroadinary claims (about cold fusion, homeopathy, human cloning) without good fact-checking, because they want to be first.YobMod 09:42, 18 June 2009 (UTC)

Which is why you consider IF within the relevant field. That's the comparison I linked to in my last link immediately above. IF is only an imperfect, but useful, proxy for determining whether a journal is generally considered credible. For someone completely unfamiliar with a particular subspecialty, IF is a reasonable jumping-off point (as is, say, determining whether the journal is indexed in MEDLINE, and looking at citations patterns). — Scientizzle 15:28, 18 June 2009 (UTC)

Quarternary Structure

I've looked around for this on here. What exactly holds the quaternary structure of a protein together. All I could find on here was that the monomers are not normally covalently linked, then the article talked about many methods of determining the quarternary structure. Any help is much appreciated, thanks...Oh, and while I may currently be doing an assignment on proteins and enzymes, this is actually a personal interest question that has cropped up while doing it. —Preceding unsigned comment added by Alaphent (talk • contribs) 09:53, 17 June 2009 (UTC)

Secondary structure is the general 3D form form of local segments of polypeptides, formed when hydrogen bonding occurs between hydrogens of an amino group and lone pairs of a carboxy group. Disulfide bonds can also contribute to secondary structure. Tertiary structure is the 3D form of the entire polypeptide/protein. Quaternary structure is when multiple tertiary structures come together to form a working complex. Examples include insulin (in some states) and haemoglobin (a tetramer with an iron ion bound). --Mark PEA (talk) 11:15, 17 June 2009 (UTC)

Mark, you didn't exactly answer the question. The OP didn't ask "what is the difference between the structures?", he asked for the force that is holding the quarternary structure together. The answer is: Van der Waals force. In chemistry (and also biology), if it's not covalent or ionic, it is in most cases a van der waals interaction. Even hydrogen bonding is a very strong van der waals interaction, so most biological molecules "assemble" the way they do because of van der waals attractions. Btw: most secondary and tertiary structes are also formed because of van der waals forces, with the exception of covalent disulfid bonds. --TheMaster17 (talk) 12:45, 17 June 2009 (UTC)

Sorry, I think I only skimmed over the question, but I assumed that Alphaent didn't really understand what kept secondary structures together, thus once knowing what kept secondary structures together would know what keeps quaternaries together. TheMaster17, are you sure that the Fe²⁺/Fe³⁺ ion in haemoglobin doesn't contribute to holding the tetramer together using ionic forces? --Mark PEA (talk) 15:47, 17 June 2009 (UTC)

Any of the forces that hold the tertiary structure together can also be found linking subunits in quaternary structure. So Van der Waals, Hydrogen-bonding, ionic interactions, hyrophobic effect. I work with an antibody made of 3 units, 2 of which are linked by disulphide bridges (to the central unit). The important part of the definition is what is being linked - the separate subunits is what differentiates it from 3° structure.YobMod 09:34, 18 June 2009 (UTC)

You two are right, my answer was a bit exaggerated: It is not only van der waals forces, for sure there are all possible forces involved, including ionic bonds (between charged amino acids or other ions). I just wanted to point out that van der waals forces with water are usually the major force between different parts of a protein or a complex in aqueous solution. The protein has very many water molecules to interact with: hydrophobic parts will stay away from the water and hydrophilic parts will be "covered" with water. Without water it won't work in most cases, even if all ions and covalent bonds are in place. Water and its van der waals interaction are required for the parts to fit properly. --TheMaster17 (talk) 09:53, 18 June 2009 (UTC)

why do hurricanes slow down?

what stops hurricanes carrying on exponentially? if there is the energy for them to get to the size they do, why doesn't it carry on increasing? i am not a scientist at all, but i was thinking maybe it has something to do with friction, though i have no idea if this is relevant to air particles. is it to do with air pressure? as it moves into low pressure areas it kind of disperses? cheers

nick —Preceding unsigned comment added by 86.172.240.210 (talk) 11:17, 17 June 2009 (UTC)

Have you read hurricane, especially the topic mechanics? "When a tropical cyclone passes over land, it is cut off from its heat source and its strength diminishes rapidly." directly from the article's text. And concerning the growth of the initial hurricane: it gets larger as long as the feedback process can feed more energy per second into the system. If the cyclone moves into an area with less favorable conditions it will shrink, and grow again if there is enough moisture/temperature gradient in another place it passes through. It's a dynamic process with positive and negative feedback loops, and their balance at any time dictates growing or shrinking of the storm system. --TheMaster17 (talk) 12:24, 17 June 2009 (UTC)

There are three factors that impact hurricanes the most: land, water temperature, and wind shear. The land factor is described in the previous comment. The water temperature factor means that when the sea surface temperature is too low, there isn't enough evaporation to sustain a tropical system. This always happens sooner or later, because hurricanes have a strong tendency to move northward, where the water is colder. The wind shear factor comes into play when low-altitude and high-altitude prevailing winds blow in different directions -- this stretches the circular shape of a hurricane and reduces its ability to spin easily. Looie496 (talk) 17:00, 17 June 2009 (UTC)

Also, another reason hurricanes do not strengthen indefinitely is because they often go through eyewall replacement cycles, which temporarily weaken the hurricane even over warm water (sometimes as much as one category downward). Another inhibiting factor is the Saharan Air Layer, which pulls dry air into the hurricane, dramaticly weakening it. ~AH1^(TCU) 13:00, 18 June 2009 (UTC)

Sticky situation

To start with, I'm not considering doing anything that I talk about here. If a person eats a normal balanced diet and they are not ill. How long could they go without shitting if they delibratly held it in? Is there a point at which it would become dangerous? Heinzcreamofchickensoup (talk) 13:16, 17 June 2009 (UTC)

Sorry - we don't give medical advice. Consult a doctor. Exxolon (talk) 13:53, 17 June 2009 (UTC)

Not a medical advice question, consider it a human biology question, read the first sentence? —Preceding unsigned comment added by Heinzcreamofchickensoup (talk • contribs) 13:57, 17 June 2009 (UTC)

I've chosen to answer under Kainaw's criterion, which I find sensible. --Sean 14:09, 17 June 2009 (UTC)

Probably long enough to give themself a fecal impaction, which if untreated could lead to their never having a bowel movement again. There have been cases where drug mules or others who have swallowed contraband and then been apprehended have tried to avoid having a bowel movement in order to withhold evidence, but I don't know how long they held out or how successful that strategy is. --Sean 14:07, 17 June 2009 (UTC)

I'm not even sure it's possible to "hold it in" indefinitely. I once read that there is nothing that varies so much from one human to another as defacation frequency. For some people, once a week seems to be perfectly normal[5] while for others it's several times a day.--Shantavira|^{feed me} 15:31, 17 June 2009 (UTC)

A 19th century circus freak called the "Windbag Man" had a huge protruding abdomen due to feces retained in the colon.He died in 1892 at the age of 29. He supposedly had only one bowel movement per month. "Holding it in" may have led to a massive dilation of the colon. He may also have suffered from Hirschsprung's disease, a congenital nerve problem lmiting bowel contractions. His colon had 40 pounds of stool in it when he died. His colon, with contents, can be viewed at the Mutter Museum of medical curiosities. Edison (talk) 18:59, 17 June 2009 (UTC)

I once saw a photo of a preserved megacolon. It looked to be about the size of an Alsatian dog. --Kurt Shaped Box (talk) 19:27, 17 June 2009 (UTC)

If it had to be surgically resected, would it leave a semicolon? Edison (talk) 22:11, 17 June 2009 (UTC)

Hahaha, that's REALLY funny!!! ROFLMAO!!! 76.21.37.87 (talk) 05:54, 18 June 2009 (UTC)

Many years ago, when I was about 12 or so, I went to visit some relatives who only had an outhouse. Needless to say, the smell was mighty ripe in the middle of July. The nearest flush toilet was 30 miles away! Being a fussy lad, I refused to use the "rural facility." To make a long story short: I refused to poop for a week and a half. Darn near exploded. Not so fussy any more . . .

human weight

I weigh myself several times a day on the same scale and have noticed that I almost always weigh less in the morning then I do at other times of the day, generally by 1-3%. Do people really fluctuate in that kind of a range, or is it more likely a measurement error because the scale is usually cooler in the morning then at other times? 65.121.141.34 (talk) 14:45, 17 June 2009 (UTC)

Short-term weight fluctuation is well-documented and normal. This article specifically discusses day-to-day measurements, but the same principles hold for morning-to-evening measurements. A couple of simple possibilities include time since your last meal (likely highest at your morning weigh-in) and time since your last toilet use (possibly lowest at your morning weigh-in, depending on your ritual). — Lomn 15:35, 17 June 2009 (UTC)

I would suspect your scales and suggest you try weighing something else (such as a full suitcase) at the same time. Bathroom scales are not very accurate. To ensure consistency, make sure the scale is on a hard level surface (not carpet) and don't move it between weighings.--Shantavira|^{feed me} 15:37, 17 June 2009 (UTC)

That wouldn't explain the measurements being consistently lower in the mornings. Lomn's response is the more likely explanation. --Tango (talk) 15:53, 17 June 2009 (UTC)

Just remember that 1 kg = 1 liter. If you weigh 50 kg and you drink a couple of cups of anything, that already makes 1% more weight.--Mr.K. (talk) 16:31, 17 June 2009 (UTC)

I've experienced the same thing. I assume it was because your body continues to burn calories while you sleep and the fact that you probably haven't consumed too much water in the middle of the night. A Quest For Knowledge (talk) 17:49, 17 June 2009 (UTC)

I don't buy this. I agree you will burn some calories while asleep and thus lose some mass as CO₂, but I'm pretty sure it would be a negligible quantity and within the measurement error of your bathroom scale. Assuming you weigh yourself at night after you've urinated/drunk water/whatever and then reweigh yourself in the morning prior to urinating/drinking water/whatever, the reading should be the same. If it's not, I'd look at the scale (unless you sweat a lot at night). Why might it not be reading the same? I'd bet there's a change in ambient temperature of a couple of degrees C that affects the accuracy/calibration of the scale. The only way to verify that the change is not due to some error of measurement is to calibrate the scale with a fixed mass as suggested above. -- Flyguy649 ^talk 20:38, 17 June 2009 (UTC)

I weighed myself after urinating for both the morning and night. The difference between the two is that you typically don't drink much water while you sleep (at least I don't). So your body processes water you already have in your system before it is replenished in the morning. A Quest For Knowledge (talk) 22:12, 17 June 2009 (UTC)

Don't trust your intuition on this one, even giant redwood trees are literally made out of thin air. However, my guess ist that in humans water loss due to breathing is the main form of mass loss at night. —Preceding unsigned comment added by 84.187.114.219 (talk) 21:56, 17 June 2009 (UTC)

Years ago, I let myself go and was getting fairly chubby. For my News Year's Resolution, I decided to lose about 25 lbs. I went on a diet and worked out regularly. I kept daily records and always used my morning weight because it was a pound or two heavier lighter than my nightly weight - except if I ate something salty which I assumed resulted in water retention. My hypothesis is easy enough to test if you have some weights. A Quest For Knowledge (talk) 22:08, 17 June 2009 (UTC)

Through the magic of Google, searching "overnight human mass loss water", I found this recent study published in "Nature Precedings". In this small study, the subjects lost 300 +/- 68 g overnight, or roughly 3/4 lb. My scale won't reliably see that difference, but I suspect others might. But still a very small difference. -- Flyguy649 ^talk 22:31, 17 June 2009 (UTC)

It's possible the scale's bias changes with temperature, which may partly account for this. Dcoetzee 12:03, 18 June 2009 (UTC)

If you habitually urinate before weighing yourself in the morning then since the bladder holds around 400 to 600 mL of fluid - you could easily see an overall 500g drop. Add to that the water you lose due to sweating and that you exhale in your breath - and the carbon you lose in converting oxygen to CO2. That's easily at the lower end of the "1% to 3%" range that our OP sees. The rest of the variation is probably due to inaccuracies in the weighing machine. Just altering where you stand on the machine can get you a kilogram of difference. SteveBaker (talk) 13:09, 18 June 2009 (UTC)

Prediction market and sport betting

If the mob is almost always right, betting on what the mob chose will be a pretty sure way of making money, isn't it? What about if I go betting for results that the mob consider have odds of 99% of happening? I would earn 1.01 (1%) for every time I bet (2 hours?), much more than any bank account.--80.58.205.37 (talk) 16:23, 17 June 2009 (UTC)

Betting on results that have odds of probably 99% and pay 1% are only a good deal if they happen more than 99.1% of the time or more. It is certainly not a "pretty sure way" of making money. --Mr.K. (talk) 16:35, 17 June 2009 (UTC)

Don't forget the vigorish, which would swallow up your 1% profit. Bookies don't work for free. Clarityfiend (talk) 16:37, 17 June 2009 (UTC)

And how much would you lose when the mob is wrong? For this to be a worthwhile strategy, you need three things. One, the mob has to do better than the books over the long term. This might be the case, and in any event, should be verifiable. Two, you need sufficiently deep pockets to recover from inevitable losses. Three, you need a book that allows large enough bets to recover those losses. Points two and three are unlikely, and comprise the flaw in the Martingale system. As such, books are more than happy to let you try this. — Lomn 16:37, 17 June 2009 (UTC)

Your premise is that the mob is almost always right. I would encourage you to go and find evidence of this claim. Tempshill (talk) 16:46, 17 June 2009 (UTC)

Actually, bookies set the line or the odds in considerable measure exactly by appealing to the wisdom of the mob. They look at where the money is being bet and adjust the terms so that there is roughly equal payout expectation on both sides (plus the house's cut of course). So, the available betting propositions are likely to already track the mob's opinion, and consulting the mob is unlikely to appreciably improve your odds. Dragons flight (talk) 16:55, 17 June 2009 (UTC)

Also, how often do 99% certain bets come along? Certainly not every two hours. Clarityfiend (talk) 18:40, 17 June 2009 (UTC)

Can anyone clarify this ([6]) for me? Quote:

Coral have hailed Sunday's defeat of Rafael Nadal at odds of 1/100 in his French Open match against Robin Soderling as the biggest shock in living memory. Soderling was a 14/1 chance to beat Nadal and Coral laid just a single five pound bet online on the Swedish player, with no recorded bets in the shops or on the phones.

How can the odds be 1/100 (for Nadal to lose) and 14/1 (for Soderling to win)? Anyway, this is clearly an example where the mob was very wrong, and the bookmakers look to have made a very nice profit from it. --Mark PEA (talk) 20:20, 17 June 2009 (UTC)

If you are wondering why the probabilities don't add up to 100%, that's where the bookmaker's profit comes from. --Tango (talk) 22:42, 17 June 2009 (UTC)

The odds weren't 1/100 on Nadal to lose. They were 1/100 on him to go through. I.e. he was a shoe-in. Basically they had thousands of bets on Nadal to go through at 1/100 (awful odds but a considered dead-cert, maybe used in accumulators or by high-volume betters) and so before the game they were standing to lose (probably because they couldn't 'balance' the Nadal-win bets with Soderling-win bets). This continued with the in-game betting where gamblings were expecting a turn-around that never came. Coral made bucket-loads because the favourite-lost. Bookies often make the most money when the favourite loses because they have X-thousand betting on the favourite at low-odds and only X-hundred betting on the outside at high-odds. ny156uk (talk) 22:17, 17 June 2009 (UTC)

Forgot to add - read Mathematics of bookmaking, in particular the intro-section on 'notion of a book and overound' ny156uk (talk) 22:19, 17 June 2009 (UTC)

If they couldn't balance the bets, why didn't they just change the odds to reflect how people were betting? ie. if lots of people thought it was a good idea to bet on Nadal at 1/100, change it to 1/200, then 1/300 and so on until people bet for the two players in the appropriate proportions so that the bookie breaks even (well, makes the amount of profit they always factor into the odds). I thought that was how it worked... --Tango (talk) 22:39, 17 June 2009 (UTC)

That's the theory - you set the odds to drive the customers to end up balancing your books, but that's not necessarily always going to happen. If people are betting at 1/100 in droves putting it to 1/200 might drop-off volume but it's not going to get them betting for the no-chancer. The no-chancer had 14/1 odds, that might sound not very generous but in some events 14/1 is the equivilent of a horse at 100/1. Betting on the outcome of a single game of tennis isn't (if my memory 'serves') will never get you a 100/1 outsider because it's a 2-player, 2-outcomes only game. It's likely that the odds that were offered 1/100 (for Nadal to win) and 14/1 (Soderling) were about as wide as the odds go but still the bookie couldn't balance. This is all a bit of rationalisation, but we can say with certainty that a professional book-making company will have tried balancing the bets within the best of their limits. 15:35, 18 June 2009 (UTC) —Preceding unsigned comment added by 194.221.133.226 (talk)

If people aren't betting on the no-chancer then surely the bookie needs to offer better odds on them. I can't see why a bookie wouldn't be able to balance their books if they tried to. Perhaps they decide to accept some risk in order to get better volume of bets and, thus, better (expected) absolute profit? The odds necessary to balance the books might have been odds that most people would have chosen to simply not bet at all on (an irrational decision, most likely, but humans are often irrational). --Tango (talk) 17:12, 18 June 2009 (UTC)

I think the original questioner is using "mob" to refer to the "Mafia" and is assuming that organized crime has rigged the event. This might not be a correct assessment. Nimur (talk) 23:07, 17 June 2009 (UTC)

I don't think so. "Mob" is a fairly common term to describe the large body of betters. --Tango (talk) 23:45, 17 June 2009 (UTC)

I have but few equals and no betters. Or did you mean "bettors?" Edison (talk) 01:58, 20 June 2009 (UTC)

The OED accepts either spelling. --Tango (talk) 02:15, 20 June 2009 (UTC)

White dwarf stars

Is white dwarf always white, or it can be blue sometimes. Then what is a blue dwarf?--69.229.243.248 (talk) 23:25, 17 June 2009 (UTC)

They are always called "white dwarfs" but I believe they can be hot enough to appear blue. Our article talks about white dwarfs with effective temperatures well above 10,000K, which is about where blue-hot begins. We have a disambiguation page, Blue dwarf, which lists some things that can be called "blue dwarfs". One is a type of galaxy, not star, one is hypothetical and I'm rather suspicious of the remaining one, "An early-type main sequence star.". I've never heard of a blue dwarf as a type of main sequence star - the colour depends, roughly, on the size. Small stars are cool and red, medium sized stars are yellow and big stars are blue. A blue dwarf seems to be a contradiction in terms... --Tango (talk) 23:44, 17 June 2009 (UTC)

A star's color more directly depends on its temperature, though it often corresponds with size as well. Red giants are enormous in size but cool, and according to our article on them, are .5-10 solar masses. Main sequence stars are like our sun—average size and average temperature. White dwarf stars are small in size but hot, and according to our article, are around 1 solar mass (with about 1.4 being the maximum, since they would supernova if they became more massive than that). —Pie4all88 ^{T C} 22:38, 19 June 2009 (UTC)

Sorry, I was talking just about the main sequence. Red giants and white dwarfs are not main sequence stars and behave very differently. On the main sequence, size and temperature (and, thus, colour) are very strongly correlated. --Tango (talk) 22:50, 19 June 2009 (UTC)

Ah, gotcha. My mistake. —Pie4all88 ^{T C} 22:16, 22 June 2009 (UTC)

• Do white dwarf just go straight to black or they slowly fade from white to orange, then brown to black?--69.229.243.248 (talk) 01:31, 18 June 2009 (UTC)

I think that the universe is not old enough for that to have happened yet. Presumably, though, they will slowly fade, becoming redder until they are too cool to produce visible light. Assuming the universe lasts long enough for that to happen. --Trovatore (talk) 02:12, 18 June 2009 (UTC)

We have an article black dwarf. Algebraist 02:15, 18 June 2009 (UTC)

The color of the star is just due to incandescence of the surface. Like any white-hot object that cools, its color will shift through orange and red before it fades to black. --Anonymous, 05:28 UTC, June 18, 2009.

I don't think incandescent bodies are ever brown. The go from blue to white to orange/yellow to red to black (notably, they are never green, although that isn't relevant to this discussion). Brown is kind of a dark orange, but we normally look at these things against the backdrop of a black night sky, so there is nothing for it to be dark relative to. Brown dwarfs are a different thing entirely, and are actually red, I think. I guess the name comes from them being a kind of inbetween star/planet and brown is a kind of inbetween colour in some sense. --Tango (talk) 13:49, 18 June 2009 (UTC)