Wikipedia:Reference desk/Archives/Science/2010 June 14

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June 14

Synthroid versus Armor thyroid

Synthroid synthetic thyroid replacement hormone is dosed in micrograms. Natural thyroid, such as Armour thyroid, produced by Forest Pharmaceuticals, made from porcine thyroid powder, is dosed in grains. Are there published equivalencies of efficacy of Synthroid micrograms versus Armour thyroid grains? How many grains of Armour would be equivalent to 100 micrograms Synthroid? Edison (talk) 04:07, 14 June 2010 (UTC)

Since they are fundamentally different (Thyrolar/Armour containing both T3 and T4) a comparison of efficacy per dose is particularly ineffective. (edit: I found the contents of Thyrolar here and it makes sense that efforts would be made to allow Thyrolar doses to line up with Armour but again it's synthetic vs porcine so IMHO there is still some room for error.) It all depends on how the patient reacts to the artificial sources, some people are better/worse at converting T4 (in levothyroxine) into T3, and the 'effective' amounts of either vary from person to person as well. If you want to take a very casual look at it, compare the available doses of Armour (1/4 grain to 5 grain) to Synthroid (25 mcg to 300 mcg) as those designing the drugs probably have a similar target audience. *This is advice is for research purposes only and not medical in nature, see your doctor for genuine advice on prescriptions* --144.191.148.3 (talk) 13:54, 14 June 2010 (UTC)

e/c The Desiccated thyroid extract article states that "One grain (about 60 mg) of desiccated thyroid contains about 38 mcg of T4 and 9 mcg of T3". But comparison may be difficult because of the T3 component which isn't a part of the Synthroid formulation. hydnjo (talk) 14:12, 14 June 2010 (UTC)

Rifling and slower bullets

If I understand the rifling article correctly, all sides of a rifle bullet continuously scrape against the inside of the barrel, along the entire barrel length; while in a smoothbore weapon, the bullet (or ball) is smaller than the internal diameter of the barrel, and the bullet basically ricochets a few times against the inside of the barrel before it exits. I assume the hugely larger amount of friction in the rifle would slow down the bullet a lot, compared to the smoothbore; though I might see how in a smoothbore weapon, the bullet wouldn't "capture" as much force from the gases expanding from the gunpowder explosion. So, in "equivalent" rifle and smoothbore weapons, how much slower is the rifle bullet immediately upon exiting the barrel? Comet Tuttle (talk) 04:23, 14 June 2010 (UTC)

I'm not sure a rifle would be slower. If the bullet continuously scrapes against the barrel, that means that the pressure wave from the explosion propelling the bullet stays entirely behind it, propelling it more efficiently. — DanielLC 05:59, 14 June 2010 (UTC)

Our article on internal ballistics has a section on energy transfer during the transit inside the barrel. Rifle rounds engage - they actually squish/expand/melt into the bore rifling, forming a metal-to-metal seal that is extremely precise. Virtually all of the pressure-volume work is transferred to the round. (Of course friction does cause some loss to heating the barrel, but this is much smaller in magnitude compared to the energy lost if there is a gas-escape from an improper round/barrel seal. It's hard to compare, because few rifles have an equivalent smoothbore version. Even those few firearm models that could be equipped with either barrel type are not "exactly" the same between rifled and smoothbore versions - the cartridges, calibers, propellant charges, and so on are different. Even the makeup of the bullet is different, because the materials and alloys that allow a rifle round to expand and engage the grooves are useless in a smoothbore. Typically, though, rifle rounds are faster than smoothbore rounds - this may be a design consequence, and not an effect of the rifling. Because rifle rounds can be more accurate and more stable in flight, it is possible to design them to fire faster, imparting more energy and resulting in more effective terminal ballistics (stopping power, penetration, or other desired ballistic property). Nimur (talk) 06:05, 14 June 2010 (UTC)

Interesting, thank you. Comet Tuttle (talk) 20:29, 14 June 2010 (UTC)

It depends what you are talking about.The main purpose of rifling is to spin the bullet so that it will be gyroscopically stabilized.The rifling in a barrel could be compared to a screw.As the bullet travels through the barrel, the rifling causes the bullet to spin thus making it stable(Gyroscopes.Earlier guns did not have rifling on them and thus suffered a lack of gyroscopic stabilization on their projectiles.Thus the projectiles had short ranges and these weapons were extremely inaccurate.Rifling was added to combat this.Even though the friction caused by rifled weapons is greater that those of smooth bore weapons,the gyroscopic stabilization caused the bullets to travel farther due to their increased stability than of those of smooth bore weapons.However nowadays smooth bore weapons are being used again.The issue of stability is combated using stabilizing fins on the projectile.Although the smooth bore concept is being used extensively in big guns its usage in smaller weapons tend to be limited. --Matrix747 (talk) 02:18, 17 June 2010 (UTC)

If you're interested, most of our articles on particular rifles cartridges list muzzle velocities for typical loads. See for example the slow .30-30 and the fast .22-250. Friday (talk) 15:38, 18 June 2010 (UTC)

Why did SI standardize the mole?

The SI unit of amount of substance is the mole. But there existed already an SI unit, the joule per kelvin, J/K, as the Ideal gas law relates amount of substance n to pressure p, volume V and temperature T by pV = nRT where R is a constant conversion factor, the gas constant. If n is measured in mole then nR is measured in J/K. So I wonder why the mole is standardized as an SI unit? Using the J/K as unit for amount of substance would simplify all formulas involving R. Bo Jacoby (talk) 07:20, 14 June 2010 (UTC).

The Ideal Gas Law only relates to gases though, and as most substances manipulated or calculated aren't gases, that wouldn't be all that much use. --John (talk) 07:29, 14 June 2010 (UTC)

Well, the Ideal Gas Law in its derivation actually applies to the simplest distributed system in statistical mechanics, which in the real world turns out to be warm gases where collisions are rare. Thus using that as the basis for deriving a unit is completely justifiable a priori. Note Planck Units in particular set $k_{B}=1$, which is related to what OP suggests, though it still doesn't give a value for the unitless Avogadro's Number (in physics where we need Planck Units, we just count particles individually until the very end when we convert to real-world values using Avogadro). SamuelRiv (talk) 08:29, 14 June 2010 (UTC)

This is nineteenth century physics with no reference to atomic physics. The gas constant is quoted with 6 decimal digits (even if many substances are not gases). Perhaps this accuracy is insufficient? Bo Jacoby (talk) 13:07, 14 June 2010 (UTC).

The mole makes a convenient standard in that it also allows for one to relate atomic mass units (aka Daltons) to grams, in that 1 dalton-mole = 1 gram. (or 1 gram/mole = 1 dalton) The importance of Avogadro's number is that it is basically the number of particles that will allow that conversion to occur. In a very approximate sense, one mole of nucleons (protons or neutrons) weighs one gram, which is why the mole is so useful as a measure of amount. Specifically, to standardize the mole (since protons and neutrons don't have the same mass, and the mass of a nucleus is also not exactly the total mass of the individual nucleons due to mass-energy equivilances) we use the standard that exactly 12 grams of Carbon-12 contains exactly one mole of atoms. Yes, there are other hypothetical numbers which may be somewhat useful in counting particles in other applications, but the usefulness of Avogadro's number makes it a far more ideal number if you have to pick just one for the SI system. --Jayron32 06:07, 15 June 2010 (UTC)

Thank you for the explanation. I do not find it satisfactory however. The idea behind standardization of units is to clean up the mess, such that there is only one standard unit for each kind of quantity. But there are two SI units for amount of substance: the joule per kelvin and the mole, connected by a conversion factor R. One mole equals 8.31447 J/K. An ideal gas at p pascal and T kelvin contains p/T joule per kelvin per cubic meter. There are (1/k=) 7.24296×10²² molecules in a J/K. The dalton is not an SI unit for mass, and I still do not understand why the mole redundantly has been made an SI unit for amount of substance. Each extra unit gives rise to tiresome conversion factors and blocks the understanding of the subject matter. Bo Jacoby (talk) 09:19, 15 June 2010 (UTC).

You know that R=Lk (where k is the boltzmann constant) ..

• L has clear meaning, and is directly measurable, though somwhat abitrary (12g of Carbon?)
• R appears to be an experimental constant

... clearly there's a relationship between R and k

The origins of k are somewhat hairy to say the least, but if you have already got k , then you can derive R

I think the reason is that constants need to be abitrary rather than experimental (though k is experimental as far as I know it's obtained from a broader range of experiments and is not necessarily dependeant on L); if the value of k can be 'explained' then the situation changes.87.102.18.94 (talk) 10:27, 15 June 2010 (UTC)

The whole point of SI unit is to provide for the most accurate standards of measurements using currently available technology. It turns out that in practice we cannot use many of the fundamental physics relations/identities to do accurate measurements. So, we have ended up with quite a few "redundant" units. Defining the mole to be some precise number and thus effectively removing it from the SI sysem would amount to redefining the Kilogram, but this will only be done if this makes measurements of mass more accurate.

Compare this to the redefinition of the meter in terms of the second. Einstein could have suggested getting rid of the stupid factors of c and measure distances and time intervals in the same units in 1905, but it was only in the 1980s that this was also better from an experimental point of view. Count Iblis (talk) 23:32, 15 June 2010 (UTC)

Old medical terms

Partial question copied from WP:VPP by Gwinva (talk) 08:52, 14 June 2010 (UTC)

"I recently watched the old movie "Bell, Book and Candle" with Jimmy Stewart. In that movie there is a sign outside an herb shop listing various conditions that can be treated by the herbs. These names (as used in that time) were obviously common knowledge at the time (why else would they be used on public signage?) but some of them have fallen out of common usage or been replaced by more precise terminology. I wanted to know what diseases they meant so I went to Wikipedia and found very few answers. Here are the names I did not know, of which only two were actually helpful:

• Milk Leg <-- [redirects]
• Blood Disease <-- What medical conditions did this commonly refer to back then?
• Whites <-- I found no medical use of this term.
• Spleen Trouble <-- ?
• Catarrh <-- This is still called by the same name so this was just a word I didn't know.
• Hollow heels <-- ?
• Wobbles <-- I could only find an animal disease for this name. Was there a human one?
• Thrumps <-- ?

66.102.204.25 (talk) 08:02, 14 June 2010 (UTC)

• Whites = Leucorrhea. DuncanHill (talk) 08:53, 14 June 2010 (UTC)

You might do better on the language desk. I'm pretty sure that wobbles will be a folk term for movement disorders such as Parkinson's disease.--Shantavira|^{feed me} 09:17, 14 June 2010 (UTC)

Wobbles might be an abbreviation for collywobbles. Mitch Ames (talk) 12:23, 14 June 2010 (UTC)

It's possible that they are fictional diseases meant to parody outlandish patent medicine-style claims to cure anything. Nimur (talk) 14:44, 14 June 2010 (UTC)

It's also possible they were words used in that particular district and nowhere else. In the UK, many dialects have their own words for medical conditions and parts of the body. This page gives an example from close to my home patch: Staffordshire medical dialect --TammyMoet (talk) 15:20, 14 June 2010 (UTC)

These were in a mainstream film contemporary to circa 1958 New York City. At best the terms might have been "quaint" for that era but certainly would not have been obscure to the film's audience. 66.102.204.25 (talk) 18:49, 14 June 2010 (UTC)

• Hollow heels in humans - see Pes cavus. Could it also means something horse-related? Those old west drugstores would bunch human, horse and cattle ailments together, wouldn't they? East of Borschov (talk) 19:11, 14 June 2010 (UTC)

Very doubful it is a horse issue as this was set in 1958 Greenwich Village NYC, NY. :) 66.102.204.25 (talk) 19:18, 14 June 2010 (UTC)

Doubtful indeed :)) Good catch, I had to check the film article first. East of Borschov (talk) 19:28, 14 June 2010 (UTC)

• A complicating factor for figuring out modern names for historic diseases is a tendency for multiple diseases to be lumped together under their major symptom. For example, pancreatic cancer, appendicitis, kidney stones, and ovarian torsion might all be covered by the local name for "severe abdominal pain". --Carnildo (talk) 00:49, 16 June 2010 (UTC)

Understood. As an encyclopedia however we ought to be able to provide readers with some useful information even if it is to that effect. Perhaps a dab-type article that says "The term blood disease was used in the early half of 20th century America to ambiguously refer to one of the following conditions: ...". I would suspect on these there might be various medical writeups (perhaps from medical schools?) from the era that could support these facts. 66.102.198.18 (talk) 18:41, 16 June 2010 (UTC)

"Blood disease" and "Spleen trouble" are probably holdovers from humorism (which was still active in scientific medicine into the 19th century, and in folk medicine a good bit longer), and might refer to any of an assortment of conditions (from anemia to fevers to stress in the first case, and from dyspepsia to ulcers to insomnia or irritability in the second). --Ludwigs2 19:01, 16 June 2010 (UTC)

why water form fountain as it goes up?

Answer: water follows a parabolic trajectory

Try this(if u had never tried before): while watering tour garden hold pipe in such away that its mouth is towards sky(or just perpendicular to ground). Water coming out of the pipe will make fountain, it gets spread.

Now hold pipe's mouth towards the ground, u will notice that water gets stream lined as it falls. It makes a cone like structure whose base is mouth of pipe.

The Question Is

Why does this happen? Why not water forms fountain while falling and why not it becomes streamlined while going upwards? -IIT question [--Myownid420 (talk) 09:23, 14 June 2010 (UTC)]

When you point the hose up, the water coming down falls onto the water going up and they scatter each other. This doesn't happen when you point down since the water is all going in the same direction. Staecker (talk) 11:52, 14 June 2010 (UTC)

Water should stay in Laminar flow rather than turbulent flow regardless of whether the hose is pointing up or down (unless you tweak the nozzle when it is travelling upwards). The key variable is how long it stays in laminar flow whilst travelling upwards, primarily as a result of gravity overcoming the upwards force exerted when the water leaves the hose.FramingArmageddon (talk) 12:06, 14 June 2010 (UTC)

Yes, and having two streams of water intersect each other is a sure-fire way to create turbulence, meaning water goes every which way. One stream going up and another falling back down into it matches the bill, nicely. StuRat (talk) 16:58, 14 June 2010 (UTC)

If the droplets of water in the stream did not interact with each other, each one would follow a trajectory that traces part of a parabola, as shown in the picture. Just think about what happens to droplets that start upward along slightly different parabolas, as opposed to starting downward on slightly different parabolas. The upward-oriented ones give a lot more divergence. Looie496 (talk) 19:20, 14 June 2010 (UTC)

(Interesting question!!) The previous answers are excellent - I'd just add that for a given nozzle velocity, the water takes longer to reach the ground when it's aimed upwards than downwards - so any divergent effect will be greatly increased just because the droplets have more time to spread apart. But this is just a contributory factor - I think the previous answers are 90% of the reason. SteveBaker (talk) 00:00, 15 June 2010 (UTC)

Assuming a circular cross section of the water jet, the radius $\scriptstyle r$ will increase upwards as the velocity $\scriptstyle v$ decreases. $\scriptstyle \pi r^{2}v$ is the constant rate of flow of water $\scriptstyle =\pi r_{0}^{2}v_{0}$ where $\scriptstyle r_{0}$ is the radius of the pipe and and $\scriptstyle v_{0}$ is the initial velocity of the water. So $\scriptstyle r=r_{0}{\sqrt {\frac {v_{0}}{v}}}.$ The velocity relates to the height above the mouth of the pipe, $\scriptstyle h$ , by the energy conservation law $\scriptstyle gh+{\frac {v^{2}}{2}}={\frac {v_{0}^{2}}{2}}$ where $\scriptstyle g$ is the gravitational acceleration. So $\scriptstyle v={\sqrt {v_{0}^{2}-2gh}}$ , and $\scriptstyle r=r_{0}{\sqrt {\frac {v_{0}}{\sqrt {v_{0}^{2}-2gh}}}}=r_{0}{\sqrt[{4}]{\frac {v_{0}^{2}}{v_{0}^{2}-2gh}}}.$ The denominator becomes zero, and so the radius of the water jet becomes infinite, at $\scriptstyle h_{\max }={\frac {v_{0}^{2}}{2g}}.$ This marks a breakdown of the assumption that the cross section of the water jet is circular. The water splits into drops when accelerated outwards. It has nothing to do with turbulence. See surface tension. Bo Jacoby (talk) 10:10, 15 June 2010 (UTC).

B₂O₃

how do I get [[B₂O₃]] from Borax ?--אנונימי גבר (talk) 11:26, 14 June 2010 (UTC)

React the borax with hydrochloric acid until you have a slightly acidic pH. Boil the solution of boric acid and sodium chloride produced and cool. The boric acid should precipitate. Heat the boric acid crystals strongly with a blowtorch. They will dehydrate, leaving amorphous boron trioxide. --Chemicalinterest (talk) 12:56, 14 June 2010 (UTC)

Sliver nano

How can we produce a Siliver (Ag) nanoscale fibers (fiber diameter of less than 20 times that of a human hair)--אנונימי גבר (talk) 11:36, 14 June 2010 (UTC)

The article Silver nanoparticles refers to nanoscale particles rather than fibres, along with some production methods although I'm not sure if you were specfically after fibres, rather than particles. FramingArmageddon (talk) 12:08, 14 June 2010 (UTC)

http://www.google.co.uk/search?hl=en&q=nanowire+ag&cts=1276644607250&aq=f&aqi=&aql=&oq=&gs_rfai= this search turns up a few methods. 87.102.18.94 (talk) 23:31, 15 June 2010 (UTC)

(Cr - Pt)

• You can separate chromium from chromium alloy - Platinum (Cr - Pt) How?
  

I think you should give this alloy into a powerful disinfectant, then Platium (Pt) acts as a positive, Chromium (Cr) serves as the cathode (dissolves), then separated chromium salt!

• [Currently, I do not know what the appropriate reagents for reaction!]
  

--אנונימי גבר (talk) 11:57, 14 June 2010 (UTC)

I am not wealthy so I do not have platinum. If I wanted to separate that, I would use a nonoxidizing acid such as hydrochloric acid. The chromium would dissolve, leaving the platinum behind.

I'm sorry, but a disinfectant is used to kill bacteria and viruses, not to separate metal alloys. --Chemicalinterest (talk) 13:00, 14 June 2010 (UTC)

I think he was talking about oxidants, which he somehow confused with disinfectants. John Riemann Soong (talk) 22:04, 15 June 2010 (UTC)

A good way to separate is by electrorefining. Make the alloy the positive terminal, use a dilute acid solution, chromium should be deposited at the negative terminal, with Pt separating out as a solid.

Chemical alternatives include dissolving both, and selectively precipitating one or the other from the solution. Both elemental articles give selective methods for precipitating the elemental ions from solutions.87.102.18.94 (talk) 12:49, 15 June 2010 (UTC)

Relativity

Sir, I am a Higher secondary student.i am very interested in highly advanced theories of physics sush as relativity,Black holes,Galaxies,Time,General relativity etc.I have already referred many articles on Wikipedia but the problem is that every article contains many complex terms which are very difficult for me to understand.Please suggest an article or a website that would help me understand the basic concepts. —Preceding unsigned comment added by Vishnuthelegend (talk • contribs) 11:58, 14 June 2010 (UTC) Changed layout of question. Cuddlyable3 (talk) 12:21, 14 June 2010 (UTC)

Articles on advanced physics assume that the reader know about elementary physics. You cannot really understand Einstein before you understand Newton and Maxwell. Bo Jacoby (talk) 12:56, 14 June 2010 (UTC).

Try plain old physics. --Chemicalinterest (talk) 13:02, 14 June 2010 (UTC)

Try here: http://hyperphysics.phy-astr.gsu.edu/hbase/hph.html Ariel. (talk) 00:29, 15 June 2010 (UTC)

C L I

Is there any way one can fool Caller Line Identification on the landline or mobile phone ? —Preceding unsigned comment added by Jon Ascton (talk • contribs)

From the article you linked to: Most service providers however, allow the caller to block caller ID presentation through the vertical service code *67. --Dismas|^(talk) 13:48, 14 June 2010 (UTC)

Yeah, that's what I am asking - if the service provider does not allow such facility. Is there some software or hardware hacking type trick one can do ? —Preceding unsigned comment added by Jon Ascton (talk • contribs)

We have an article all about this: Caller ID spoofing. SteveBaker (talk) 23:54, 14 June 2010 (UTC)

I know about the article, but what I want is some practical straight forward and fool-proof easy way that one can actually do !—Preceding unsigned comment added by Jon Ascton (talk • contribs)

Is it just me or are you being deliberately confusing? In your first post you asked for a method of "fool" caller ID, so I gave you a way to block it. Then you added an additional requirement, which wasn't in your original question, about what happens if the carrier doesn't allow for *67. And you asked for some software or hardware suggestions. Those are spelled out at the article that SteveBaker pointed out to you. Now you tell us that you already read that article and, for whatever reason, those solutions still don't work for you. So, what about the options in the caller ID spoofing is it that you don't care for? Dismas|^(talk) 04:37, 15 June 2010 (UTC)

The web page below needs to be updated with the correct new information regarding the list of SVHC's.

Substance of very high concern

Please update the web page with the most current list of SVHC's. Thanks Rick Morrison —Preceding unsigned comment added by 63.97.59.73 (talk) 13:42, 14 June 2010 (UTC)

I have copied this non-question to the discussion page of said article. Caesar's Daddy (talk) 13:51, 14 June 2010 (UTC)

Noted on behalf on WP:CHEMS, it's on my list of things to do in the morning. Physchim62 (talk) 23:24, 14 June 2010 (UTC)

 Done Physchim62 (talk) 09:44, 15 June 2010 (UTC)

How does pre-birth gender selection work?

I read someplace that nowadays, parents are able to choose the gender of their unborn child. How does that work? More importantly, how much does it cost? Since it's most likely too expensive in the US, in what countries could it be done for the lowest prices? --Let Us Update Wikipedia: Dusty Articles 14:19, 14 June 2010 (UTC)

Another important question is "is it legal?". In many countries, it isn't. Sex selection answers that, and how it works. You can probably find costs by googling. --Tango (talk) 14:50, 14 June 2010 (UTC)

Looks like it is legal, here is a clinic offering such a procedure in the US. Price is stated as around $18K. Link. Regards, --—Cyclonenim | Chat  17:05, 14 June 2010 (UTC)

It is legal in the US. It isn't elsewhere, eg. most of Europe, China, India, etc.. --Tango (talk) 23:19, 14 June 2010 (UTC)

There are two different things to discuss here: There are many (fairly cheap) techniques that can bias the probability of you getting a male or a female child - simple things like subtle pH variations at the moment of conception can change the statistics. But to absolutely guarantee a male or a female child is more likely to require serious medical intervention - which is much more ethically difficult (eg you might test the sex of the fetus and abort when the gender is not what you want - that is practiced (often illegally) in several places in the world) - or perhaps much more costly (eg in-vitro fertilization). SteveBaker (talk) 23:48, 14 June 2010 (UTC)

So what other countries is it legal in, where anyone would perform it for a far lower price than in the US? --Let Us Update Wikipedia: Dusty Articles 11:32, 15 June 2010 (UTC)

Birdsong 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) 14:34, 14 June 2010 (UTC)

Some good links (including studies) on this Google search. Not sure if it's helpful, but it's a start. Regards, --—Cyclonenim | Chat  17:02, 14 June 2010 (UTC)

How hot am I ?

I've noticed that I can't accurately judge if I'm hot or not. I certainly can tell if objects are hot, and if the air is hot, and if my forehead is hotter than my hand, but the only method I have to tell if I am overheating is if I'm covered in sweat. (The sweating means that my body is able to tell that it's hot, even if I can't.) This system doesn't work when in a hot tub, and the first sign I have that I'm getting hot is that I become listless and find it hard to breath enough air. So, am I unusual or does everybody lack an ability to judge their own temperature accurately ? StuRat (talk) 17:27, 14 June 2010 (UTC)

You're normal (well, as normal as a Wikipedian can be! ;)). Thermoception is relative. All it can do is tell you if something in contact with your skin is hotter than your skin or colder than it (and how much so). You can compare your symptoms in a hot tub with Hyperthermia#Signs and symptoms. An added complication is that the symptoms of hyperthermia are quite different to the symptoms of fever, despite both involving your body temperature being above normal (the cause is very different). --Tango (talk) 17:46, 14 June 2010 (UTC)

Funnily when I was working in West Africa and contracted Plasmodium falciparum Malaria the first inkling (and immediate self diagnosis) was turning off the aircon and switching on the heating in a car parked in full sun with an outside temp of 37C. I found myself wondering why I had never switched the heating knob in the car before and then it sunk in. With a core temperature steaming upwards the car seemed cold and I was shivering. --BozMo talk 18:09, 14 June 2010 (UTC)

A simple answer is that your sweat is cooling you down so you don't feel hot. If you feel hot that means your cooling mechanism (sweating) is malfunctioning or overpowered. --Chemicalinterest (talk) 18:28, 14 June 2010 (UTC)

Sweat doesn't work in a hot tub. Obviously sweat on those parts of your body that are underwater can't evaporate, and sweat on the rest of your body won't evaporate much because the air around you will be very humid. --Tango (talk) 19:07, 14 June 2010 (UTC)

There are medical issues that inhibit the brain's ability to sense if the body is hot or cold. As this is a medical issue, I will not make any attempt to diagnose this problem. However, I feel that it is important to point out that this (and pretty much any "Am I normal" question) is asking for a diagnosis of normality. -- kainaw™ 19:14, 14 June 2010 (UTC)

Medical issues aside - mostly the reason we can't tell whether we're hot or cold is because body temperature is well regulated. You can feel whether you are gaining or losing heat to the environment (which is how you know whether the air is hot or cold) - but it's likely that your core temperature is close to whatever is normal for you in all but fairly extreme circumstances. When the environment overpowers your thermoregulation system, you're already in some distress - and you feel the symptoms of that. Your hot tub experience is obviously a case like that. SteveBaker (talk) 23:42, 14 June 2010 (UTC)

Reminds me of a Dilbert in which the boss wakes up and, to his surprise, finds that his underwear, coffee mug and desk are all clammy -- finally, Dilbert suggests that maybe his hands are clammy. I forgot the rest. DRosenbach ^{(Talk | Contribs)} 12:00, 15 June 2010 (UTC)

Sweathog

Thanks. To follow up, if I can't tell when I'm getting hot, how does my body know when to sweat ? StuRat (talk) 15:24, 16 June 2010 (UTC)

Explosion

In a powerful explosion, how long is there between when the explosive detonates and you die? --76.77.139.243 (talk) 19:20, 14 June 2010 (UTC)

At the risk of stating the bleedin' obvious, it depends on the relative positions of the explosive and your body. Even a low power explosive could kill you instantly depeif it goes off on your head or chest. --TammyMoet (talk) 19:29, 14 June 2010 (UTC)

It depends on the time the ₎)) shock wave takes to hit you. Once it hits, then you die. --Chemicalinterest (talk) 19:45, 14 June 2010 (UTC)

People have been blown to a red mist and tiny bits by an explosion. Death is in milliseconds. At the other extreme, someone might be fatally injured by an explosion but linger for any long period before succumbing to the effects, which might include, for instance,sever and ultimately fatal burns, being in a persistant vegitative state, or paralysis leading to fatal complications a long time after. Edison (talk) 20:13, 14 June 2010 (UTC)

As Chemicalinterest says, it depends how far away you are. My grandparents all survived the nuclear bombings of Hiroshima and Nagasaki quite easily, because they were in the eastern USA when it happened. Nyttend (talk) 05:51, 15 June 2010 (UTC)

Shock wave in air travels at several hundred meters per second (more than a speed of sound but less than a thermodynamic limit, which for an ideal gas is 4 times the speed of sound). Fragments from the explosion may travel faster than the shock wave and further than the shock wave. Divide the distance (in meters) from you to the explosion by roughly 1000 m/s, and you will get the order-of-magnitude time (in seconds) before you get hit. (Order of magnitude means that the estimate may well be wrong by a factor of 2 or 3 either way). How long you stay alive after getting hit depends on the nature of your injuries, as Edison explained above. Massive brain injury may be considered instant; anything else may take a few seconds or a few years to take effect. --Dr Dima (talk) 20:33, 14 June 2010 (UTC)

My father survived a direct impact of a bomb in World War 2 - it hit his house. Dad himself had taken shelter under the stairs. He died 64 years later. So this is a bit of an unanswerable question.--TammyMoet (talk) 09:42, 15 June 2010 (UTC)

That must have been a spectacularly slow bomb! – ClockworkSoul 02:51, 16 June 2010 (UTC)

soy

are the estrogen's in soy; fat or water soluble ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 23:02, 14 June 2010 (UTC)

Well, [1] says: "Phytoestrogens are estrogens contained in plants. They have a chemical structure similar to the human hormone estrogen. They have a weak estrogen effect when eaten. The most commonly studied are the isoflavones...". Our articles on Phytoestrogens and isoflavones have much additional information...but I couldn't see any direct statement about solubility. I guess we'll have to wait for one of our expert chemists to swing by with an answer. SteveBaker (talk) 23:34, 14 June 2010 (UTC)

Natural estrogens are fat-soluble, as are pretty much all natural steroids. Physchim62 (talk) 00:18, 15 June 2010 (UTC)

so does soybean oil contain estrogen's ? —Preceding unsigned comment added by Alexsmith44 (talk • contribs) 20:42, 15 June 2010 (UTC)

Yes, see this. 86.7.19.159 (talk) 21:20, 18 June 2010 (UTC)

Definition of Horology???

I was looking at the Horology article and found it to be inconsistent, horology is defined as "the art or science of measuring time.", but then only talk about mechanical clocks and watches. To me this seams rather much like an article on transportation only discussing different kinds of bags, no ships, trains,trucks and so on.

Is horology only the study of historical/mechanical watches and clocks or does it include modern electronic clocks, GPS-clock synchronization, atomic clocks, astronomical observations of for example radio pulsars and so on??? Gr8xoz (talk) 23:10, 14 June 2010 (UTC)

Wiktionary (and several other dictionaries that I looked at) says: Horology: The art, science and technology of timekeeping and timekeepers, such as clocks, watches and sundials. - which certainly includes modern stuff like digital clocks. However, I would bet good money that almost all actual, practicing horologists are really only interested in mechanical clocks and sundials. The people who care about modern electronic/atomic timekeeping are in the fields of electronics and physics. That being the case, I think our article does a reasonable job of covering the practical nature of horology. Remember - the article isn't about clocks themselves. It's about the nature of the study of clocks. I agree though that we could at least mention more modern timepieces - IF we can find some reference to that kind of thing in a horology journal or whatever. At any rate, this discussion should really be held on the Talk:Horology page, not here on the reference desk - but I see you've already added a comment there with no response. I think you should go to Wikipedia_talk:WikiProject_Time. Of course if you feel strongly about this - you can always fix the article yourself...but I strongly encourage you to provide references for any statements you include. SteveBaker (talk) 23:24, 14 June 2010 (UTC)

The modern and precise measurement of time (eg, "atomic clocks") is usually seen as a subbranch of metrology, because it affects and depends on many other areas of physics. The one exception might be the network of observatories which keeps UTC in time with the Earth's (slightly irregular) rotation, but I would bet that they consider themselves astronomers and not horologists: horologists are people who can actually make a working clock or watch, and deserve every respect for that skill! Physchim62 (talk) 00:27, 15 June 2010 (UTC)

Again, I agree that's what practicing horologists actually do - but that's not what the word means. Also, your interpretation would include people who fabricate atomic clocks, digital watches or crystal oscillators for computers - which is not what people who'd describe themselves as horologists actually do - nor is "horology" what people who make such things describe what they are doing. What we have here is a disconnect between what dictionaries say the word means - and it's actual modern day usage. This is not an uncommon problem because dictionaries tend to lag decades behind changes in usage. SteveBaker (talk) 11:43, 15 June 2010 (UTC)