Wikipedia:Reference desk/Archives/Science/2011 November 19

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

November 19

More force by pedaling

When pressing a bicycle pedal we press it with our weight on the pedal (x kg). What if we had some back support? Would we be able to put more pressure onto the pedal? Quest09 (talk) 00:49, 19 November 2011 (UTC)

Not with a regular bicycle. If you had something holding your shoulder's down, perhaps. StuRat (talk) 01:51, 19 November 2011 (UTC)

You have down on your shoulder? You silly goose. Clarityfiend (talk) 05:33, 19 November 2011 (UTC)

A recumbent bicycle has back support, and one was used to set the world speed record (though I infer this was due to reduced wind resistance). Clarityfiend (talk) 03:07, 19 November 2011 (UTC)

There's only a very brief discussion under Recumbent bicycle#Disadvantages (section Uphills), where it's observed that even on a normal bike you can still pull against the handlebars, and that recumbents are generally thought to be harder to pedal uphill, although this may be because they tend to weigh more. My thought is that although you could put more pressure on the pedal if you have something behind your back, it wouldn't be more efficient, because needing that much pressure would just mean you were in too high a gear for the task.  Card Zero  (talk) 03:14, 19 November 2011 (UTC)

Note that this is one reason why even semi-serious performance riders use clips and straps, or, nowadays, clipless pedals and matchings shoes. This allows you to exert force both on the up and on the downstroke, and thus in particular to exert more on the downstroke (since your other foot is keeping you down). --Stephan Schulz (talk) 09:25, 19 November 2011 (UTC)

Just from inference, the angle of the back to the seat, partly supported by hands on the handlebars, changes the pivot of the momentum of the foot on the pedal. ~AH1 ^(discuss!) 21:32, 20 November 2011 (UTC)

Acrobats demonstrate that a foot can put more pressure than a body weighs. Cuddlyable3 (talk) 19:28, 22 November 2011 (UTC)

Photon engine

Is it possible for photons to do work directly instead of converting it to heat or electric current? ScienceApe (talk) 03:29, 19 November 2011 (UTC)

Sure. Photons have momentum, and if they bounce off something then they do work. See, for example, solar sail and radiation pressure. TenOfAllTrades(talk) 03:35, 19 November 2011 (UTC)

The Radiometer article is in pretty rough shape, but I've added the illustration to this question. You can find these things in novelty shops. APL (talk) 03:47, 19 November 2011 (UTC)

A Crookes radiometer is not driven directly by radiation pressure, though this is a common misconception. The radiometer relies on greater absorption of photons by the dark-colored vanes and the conversion of those photons to heat (which in turn heats the adjacent air, generating thrust from the air's thermal expansion). As such, it's not a good response to the original poster's question. Indeed, if the Crookes radiometer were driven by radiation pressure, then it would turn in the opposite direction—there is twice the transfer of momentum when a photon is reflected as when it is absorbed, so the vanes would have a greater force on their white face than on their black face. TenOfAllTrades(talk) 04:05, 19 November 2011 (UTC)

Ah, you're right. I've removed the illustration. APL (talk) 04:11, 19 November 2011 (UTC)

Has anyone produced a radiometer in a vacuum bulb so that it does turn the other way? Sorry, the answer is in Nichols radiometer. Dbfirs 12:30, 20 November 2011 (UTC)

There have actually been proposals for a photon rocket (what, no article?), which would use the reaction force from an intense beam of photons to propel itself at speeds close to the speed of light. The only problem (aside from finding a suitably powerful energy source) is that light energy of such intensity can vaporize all known reflecting materials. So at present this is entirely in the realm of science fiction. 67.169.177.176 (talk) 07:49, 19 November 2011 (UTC)

I just now created a redirect, so that photon rocket is no longer a red link. Red Act (talk) 19:27, 19 November 2011 (UTC)

See IKAROS. Gandalf61 (talk) 10:29, 19 November 2011 (UTC)

Photons themselves have no mass but carry energy. Also examine for example the workings of a charge-coupled device. ~AH1 ^(discuss!) 21:28, 20 November 2011 (UTC)

cooling in vaccum

suppose any hot plate in vaccum space, in which gradient or ratio its cooling happens ?consider there is not any conductor except radiating.--Akbarmohammadzade (talk) 05:16, 19 November 2011 (UTC) I want to discuss about any star which has continues body such as t-tauri star comparing with spherical normal star such as sun.Too cooling regime of planets such as Earth with molten volcanic hot core .--Akbarmohammadzade (talk) 10:33, 19 November 2011 (UTC)

The hot item will radiate energy following the Stefan–Boltzmann law. In other words, the energy lost is proportional to the surface area and to the 4th power of absolute temperature. It will asymptotically approach the temperature of the environment - for a spherical cow that would be either 0 K, or the temperature of the cosmic microwave background, about 2.725 K. There may be confounding factors, like differences in albedo. For a body like the Earth you also need to modell how much energy is flowing from the hot core to the surface - energy is only lost at the surface, but vertical heat transport in the Earth is very slow. In the case of Earth, the geothermal contribution to the energy flux is only about 0.025% of the total. --Stephan Schulz (talk) 11:08, 19 November 2011 (UTC)

hydrogen bonding

why dissociation of soap or detergent in water produces lather or foam? — Preceding unsigned comment added by Jyotiprakash hati (talk • contribs) 09:26, 19 November 2011 (UTC)

The soap and detergent molecules each have a part that loves to be in water, and another part that is repelled by water. This causes them to stay at the surface of the water. You will also need mechanical agitation of the water to form the bubbles. This ends up lowering the surface tension, and allowing the surface to curve without much energy. See foam detergent surfactant and Foaming agent Graeme Bartlett (talk) 12:05, 19 November 2011 (UTC)

Pseudo science or genunie plughole at equator

I have been musing about it and wondered if I could have a definitive view on whether this equator plughole stuff is fake science in this video I suspect this is a stunt for tourists; I don't reckon a few hundred metres is enough for it to make a difference on plugholes and it is probably all in the shape of the tub? (Of course his comment near the end about weight is wrong, the 3% versus the poles might be right though). However I don't really have a feel for how sensitive a nonlinear instability might be to pick up the tiny difference from moving a few hundred metres and the plug hole going straight down is impressive. Thoughts? --BozMo talk 09:29, 19 November 2011 (UTC)

Actually it is rubbish at any latitude. It is practically impossible to open the plug without causing some arbitrary lateral movement within the water. The coriolis force of the earth is far too weak at the scale of a tub of water to override any number of other influences - even thermal convection would be far stronger - http://www.snopes.com/science/coriolis.asp . Roger (talk) 09:54, 19 November 2011 (UTC)

The statement "In reality, this motion would not be seen with a small amount of water – a huge mass of fluid is needed – so the demonstrator is using some showmanship to simulate the effect." at BozMo's link seems to be a giveaway ;-). --Stephan Schulz (talk) 11:10, 19 November 2011 (UTC)

I heared it's not the lateral movement you cause when you open the plug that's really significant, but the imperfect shape of any bathtub. – b_jonas 18:16, 19 November 2011 (UTC)

Unless it's something on the scale of the Equatorial Counter Current, any association between Earth's rotation and the rotation of toilets is not really that significant. ~AH1 ^(discuss!) 21:10, 20 November 2011 (UTC)

There's something mystical about "plugholes" that is far beyond my comprehension. I still remember using a darkroom, almost twenty years ago, which had a huge circular basin with the drain at the middle. The water would stagnate and refuse to drain the last inch or so, so that if left to itself the chemicals would crystallize out in the basin. But if a tube was placed above the drain, not quite touching it, I could turn the tap full on, and all the water would go down the drain without any obstruction. I must have spent a full hour trying to understand that sink... I still have absolutely no idea at all! Wnt (talk) 00:47, 21 November 2011 (UTC)

The only way for all the molecules of the stagnant water to go down the conical basin is for some molecules to go up. It seems some asserted their democratic right not to do so. Cuddlyable3 (talk) 19:13, 22 November 2011 (UTC)

Superluminal neutrinos

I would like to know more about the newly found fact that neutrinos travel faster than light.. — Preceding unsigned comment added by Sreevidyaphysics (talk • contribs) 11:13, 19 November 2011 (UTC)

I wouldn't call it a "fact" quite yet. Our article on the topic is OPERA neutrino anomaly; you could start there and then follow the links in the references and the "External links" section to learn more. Deor (talk) 11:23, 19 November 2011 (UTC)

It's not a fact. It's just an anomaly - that is an unexplained and likely incorrect observation. Out of the many possible explanations for that anomaly, superluminal neutrinos is one of the least likely. Dauto (talk) 14:35, 19 November 2011 (UTC)

What are the other explanations physicists are throwing around? Are any of them taking hold? Aaadddaaammm (talk) 15:46, 19 November 2011 (UTC)

Well, the most popular explanation is simple experimental error. They're ruled out one possible cause of error with the recent re-runs (by using shorter pulses), but there are plenty more possibilities to be considered. Until another team using different equipment have replicated the results, scientists will continue to assume it's an error. --Tango (talk) 16:17, 19 November 2011 (UTC)

sametime , time gose backwared , thanks wate nosfim — Preceding unsigned comment added by 212.199.175.104 (talk) 06:35, 20 November 2011 (UTC)

One claim mentioned a week or two ago in the weekly New Scientist magazine, which is of course following these events, was that the team had neglected to correct for the relativistic effects of the movements of the GPS satellites used to calculate the exact distance between the neutrino emitter and detector. However, that argument was no longer mentioned in the latest article in Saturday 19th's issue concerning the re-run. {The poster formerly known as 87.81.230.195} 90.193.78.12 (talk) 18:59, 20 November 2011 (UTC)

It looks like that explanation was based on a mistake - the guy who made it, Ronald van Elburg, seems to have applied the Lorentz transformation incorrectly, and by chance that incorrect calculation produced a number that roughly cancelled out the anomaly. Smurrayinchester 12:31, 23 November 2011 (UTC)

Recent observations continue to suggest the validity of experiments, but issues are being raised into whether the margin of error was greater than the anomaly of the result. See for exaple this article in Discover Magazine's website. From tachyon#Speed:

In 1985 it was proposed by Chodos et al. that neutrinos can have a tachyonic nature

Chodos, Hauser and Kostelecký (1985): The neutrino as a tachyon {Abstract} ~AH1 ^(discuss!) 21:07, 20 November 2011 (UTC)

inorganic chemistry

why concentrated sulphuric acid appears like an oil? — Preceding unsigned comment added by Jyotiprakash hati (talk • contribs) 15:01, 19 November 2011 (UTC)

You might have a look at Sulfuric_acid#Physical_properties & Viscosity#Viscosity_of_various_materials. It's worth pointing out that this has nothing to do with Inorganic Chemistry.(+)H₃N-Protein\Chemist-CO₂(-) 19:17, 19 November 2011 (UTC)

To clarify, Sulfuric Acid of course is of course an inorganic acid, but this seems like a solution chemistry question (ie more in the realm of pchem or analytical chem) and thus is not really an inorganic chemistry question. Apologies for any confusion I may have caused with my initial reply.(+)H₃N-Protein\Chemist-CO₂(-) 19:24, 19 November 2011 (UTC)

inorganic chemistry (isomeric ethers)

why isomeric ethers have low boiling point than alcohols? — Preceding unsigned comment added by Jyotiprakash hati (talk • contribs) 16:32, 19 November 2011 (UTC)

Excuse me if I'm mistaken but it seems like you've asking a series of questions taken from your homework in which case the best place to find the answers would be your text book and/or class notes. Dauto (talk) 16:50, 19 November 2011 (UTC)

I added to the title so we won't have two Q's with the same title. StuRat (talk) 19:38, 19 November 2011 (UTC)

Take a read of Ether#Physical properties. Graeme Bartlett (talk) 22:50, 21 November 2011 (UTC)

inorganic chemistry (why water is a versatile solvent)

why water is a versatile solvent?Jyotiprakash hati (talk) 17:10, 19 November 2011 (UTC)

Welcome to Wikipedia. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our policy here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. 220 of ^Borg 18:38, 19 November 2011 (UTC)

I added to the title so it won't be identical to your earlier post. StuRat (talk) 19:40, 19 November 2011 (UTC)

I'll give you a clue: All the questions you've asked so far are variations on a single theme. That's all the help I'll give you for now -- you figure out the rest on your own. 67.169.177.176 (talk) 21:14, 19 November 2011 (UTC)

Try chemical polarity, if it helps. ~AH1 ^(discuss!) 20:59, 20 November 2011 (UTC)

Zion Nat'l Park stone tool?

I'm curious if I found a stone tool at Zion National Park. A photograph of the top and two sides can be seen here: [1]. The stone was the exact same color as the rock formations I found it on, which were near one of the entrances to the park. In the top picture, you can see how smooth the "handle" is (sorry for the out of focus-ness) and the tip of the tool looks like it was sharpened into a blade. I really couldn't believe this wasn't man-made. Any ideas? The article does mention "flaked stone knives", though I don't know what that is. Thank you!Reflectionsinglass (talk) 20:49, 19 November 2011 (UTC)

A flaked stone knife is a knife made by chipping off flakes of stone until you get a sharp tool. But this item looks more like it could be a scraper, which might be used to scrape flesh off of skins, so they don't rot quite so quickly (the best they could do before tanning). However, it could also be a natural rock. StuRat (talk) 21:35, 19 November 2011 (UTC)

IMO, natural. Fracture looks very fresh with no sign of usage wear. Compare with actual neolithic tools in our article on Stone tool.-- Obsidi♠n Soul 22:22, 19 November 2011 (UTC)

Hmmm, wonderful, thanks for the answers! The fact that it was just lying there out in the open may mean something too, tho I don't know what.Reflectionsinglass (talk) 00:15, 20 November 2011 (UTC)

I wouldn't dismiss it out-of-hand as not authentic. Stone tools and arrowheads are shockingly common in some areas. I am not familiar with Zion in particular, but my wife's grandfather was something of an amateur archeologist; he would comb through construction sites near where he lived in Wisconsin, and had collected several thousand arrowheads and other tools. So, while not every chipped rock is a man-made tool, it still could be. --Jayron32 03:51, 20 November 2011 (UTC)

I suppose then that I would have to find more, maybe. Is there an ethics thing about picking up/touching/removing stone tools from places? I didn't go into it, but I do have a twinge of guilt because I thought the scraper was cool (and man-made).`Reflectionsinglass (talk) 18:27, 20 November 2011 (UTC)

Removing archeological items from a national park is certainly illegal. Taking even things like rocks or flowers is typically not allowed. The rock that you have found looks entirely natural to me. — Preceding unsigned comment added by 148.177.1.210 (talk) 21:42, 21 November 2011 (UTC)

Ok, I wondered. I'll in good faith return it where I found it. It's been the source of fun discussions, though. Thanks all.Reflectionsinglass (talk) 21:03, 22 November 2011 (UTC)

Facial hair growth hormone?

i know that the Head-hair hormone is "DHT". what about facial hair hormone?, have we discovered it yet?.

thanks. — Preceding unsigned comment added by 109.67.12.102 (talk) 21:11, 19 November 2011 (UTC)

DHT is not a "head-hair hormone". DHT is dihydrotestosterone. DHTs role in baldness is complex; it appears that the hormone is responsible for development of secondary sex characteristics, such as facial hair growth. Some males have a genetic predisposition towards baldness, whereby DHT apparently deactivates the hair folicle in some way; but this is not a primary role of DHT, it is a complex hormone that does lots of things, many of which are unrelated to baldness. Also, the role of DHT in hair loss is not entirely accepted as described, at least according to the Wikipedia article Androgenic alopecia. If you read that article, so-called "male pattern baldness" is not simply due to DHT, but associated with a whole lot of hormonal effects. --Jayron32 22:30, 19 November 2011 (UTC)

and what about facial hair growth in males?. what could a man who has a sparse growth there do?. thanks. 79.183.13.71 (talk) 08:35, 20 November 2011 (UTC)

Well, some form of testosterone would be used to increase facial fair growth, as it is in those who have a female-to-male sex change. However, hormone treatments have serious side effects, so should certainly not be used just to get a thicker beard. Some type of cosmetics, something like mascara, might make more sense, to both thicken and darken the hairs they do have. Or just hair dye could be used, if the beard is too lightly colored. Just for Men is one such product. StuRat (talk) 17:14, 20 November 2011 (UTC)

The Just for Men range also includes dyes specifically for beards, though fewer outlets stock them than the hair dyes. I myself use one of the hair dye range to even up my rather piebald moustache and beard, as one can contrive several applications from the same pack, but I'm consciously contravening the manufacturer's reccommendations, so don't take that as advice ¦;-{))>. {The poster formerly known as 87.81.230.195} 90.193.78.12 (talk) 19:13, 20 November 2011 (UTC)

Genetics, androgen hormone availability and other factors determine facial hair growth. ~AH1 ^(discuss!) 20:55, 20 November 2011 (UTC)

what are this other factors?. do you guys know any bio-chemist who researched on this issue?. thanks.

Cancer

Hi, I would like to know: 1)What is the deadliest cancer?

2)Why do cells of pre-cancer get some properties that they didn't have.

Exx8 (talk) 23:18, 19 November 2011 (UTC)

See also: Cancer. →Στc. 00:00, 20 November 2011 (UTC)

Define "deadliest". Lung cancer kills the most people,[2] but pancreatic cancer is generally considered to be the deadliest in terms of prognosis at time of diagnosis (see http://www.helium.com/items/1993804-deadliest-types-of-cancer-with-the-worst-prognosis , which I can't link to normally due to a spam filter.) Glioblastoma multiforme is up there, too. Red Act (talk) 00:04, 20 November 2011 (UTC)

There are many potential definitions, for example: rapidity of onset, severity of illness, shortness of time elapsed between diagnosis (or metastasis, or first symptoms) and death of the patient, prevalence, earliest childhood cancers, etc. ~AH1 ^(discuss!) 20:38, 20 November 2011 (UTC)

For your second question, I'm no expert, but see articles glycolysis, tumor progression and metastasis. ~AH1 ^(discuss!) 20:41, 20 November 2011 (UTC)

Better yet, malignant transformation and carcinogenesis. TenOfAllTrades(talk) 23:38, 20 November 2011 (UTC)