Wikipedia:Reference desk archive/Science/2006 September 27

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[edit] Destroying the earth with high speed object...

Suppose a high-speed interstellar object (e.g. a iron-based chunk of rock), travelling at high speed (for the sake of argument, say 50% of the speed of light) were to collide head-on with the earth - what size of object, given the above, would be needed to completely shatter the earth? Just a topic raised in conversation with my father today - he figured that it wouldn't have to be very big at all, maybe a few metres across. He compared it to the 'watermelon scene' in The Day of the Jackal... --Kurt Shaped Box 01:15, 27 September 2006 (UTC)

You might ask on the Usenet newsgroup alt.destroy.the.earth, where they talk about this stuff all the time. Or you could calculate the Earth's gravitational binding energy, and work out the mass needed to get that much relativistic kinetic energy; that won't be an exact answer but could give you a ballpark figure. --Trovatore 01:21, 27 September 2006 (UTC)

We have an article on impact events which seems like it might be helpful. It also has a number of links to other discussions. --Fastfission 02:37, 27 September 2006 (UTC)

Why don't you ask "How fast does an 8mm speeding bullet have to be in order to destroy the entire earth in a head on collision?". 202.168.50.40 02:55, 27 September 2006 (UTC)

You need 2 × 10³² joules of energy to blow an earth-sized planet apart. Firing a standard 5.56 x 45 mm NATO round, which weighs about 4.5 grams, at 4.7 × 10¹⁵ m/s. That's about 15 million times the speed of light. Which is to be expected since the required energy is about the output of 10²³ kilograms of matter and antimatter annihilating simultaneously --⁪froth^{T C} 03:21, 27 September 2006 (UTC)

Not so. Because as the object approaches the speed of light 1. its mass increases and 2. its energy increases indefinitely (see kinetic energy, particularly the relativistic part). A bullet could therefore, if accelerated to a high enough velocity, destroy the Earth. The problem is that you would need a fantastic (probably impossibly high) amount of energy to accelerate the bullet to that speed. Batmanand | Talk 09:38, 27 September 2006 (UTC)

I don't think that even The Jackal is that good. ;) --Kurt Shaped Box 10:47, 27 September 2006 (UTC)

From the article Kinetic energy:

$E_k = mc^2 - m_0 c^2 = m_0 c^2(\frac{1}{\sqrt{1 - (v/c)^2}} - 1)$ .

Putting $v = 0.5c\,$ and solving for $m_0\,$ gives:

$m_0 = (3+2\sqrt{3})E_k/c^2 = \gamma E_k, \mbox{ where } \gamma = 72 \cdot 10^{-18} \mbox{m}^{-2}\mbox{s}^2\,.$

Using froth's $E = 2 \cdot 10^{32}~\mbox{J}$ results then in $m_0 = 14 \cdot 10^{15}~\mbox{kg}.$ . --Lambiam ^Talk 13:27, 27 September 2006 (UTC)

That's all fine but don't you agree that a bullet at relativistic speed would just zip through the earth, leaving a hole? You have to make sure that the energy gets absorbed in the earth, i.e. the projectile has to be stopped. So, no matter how fast it is, if the diameter is too small, it won't work. Better suggestions please. Simon A. 15:25, 27 September 2006 (UTC)

That's not my intuition, no. Eight thousand miles is a long way to drill a hole, even at relativistic speed. I think most of the energy would be absorbed, or perhaps reflected back (that is, a lot of it might go into the ejecta from the crater, headed back into space at high velocity in the direction whence the bullet came).

This is just an intuitive response, though. If anyone's done a genuine justifiable simulation, I'm not aware of it, but I wouldn't be too surprised; if anyone can find one, please post. --Trovatore 15:55, 27 September 2006 (UTC)

More intuition: when a hypervelocity bullet hits a solid object, it bores a conical hole (a large "entrance wound") where the shape is caused by the expanding shock wave coming from the bullet's path. (When forces are huge, all objects behave as liquids.) But with a relativistic bullet, the speed of the expanding shock wave would be very small when compared to the speed of light. Therefore the cone-shaped hole would be very long and narrow, and then would continue to expand wider, depending on how much momentum the bullet managed to deposit as it went past. On the other hand, the speed of light inside solid rock is pretty high, so radiative heating caused by the bullet would probably spread the energy much wider, creating a line-shaped explosion inside the Earth. When the bullet tried to penetrate the Earth's iron core, things would be different, and again we'd get a narrow tunnel which keeps expanding after the bullet had passed. Now if the relativistic bullet was not able to push solid matter to the side as it moved forward, the bullet would break apart. It would probably form an expanding disk of relativistic matter, depositing its energy into a fairly large area before stopping entirely. We'd end up with a disk-shaped explosion taking place inside the Earth. If this happened in the crust, then no doubt most of the energy would reflect upwards as high-speed ejected gases. So the question is ...should a bullet having a particular mass be made of fluffy powder, or should it be made of neutronium? :) You could choose the bullet size/density in order to make it travel to the Earth's core before it halted (and exploded from the thermal energy.) --Wjbeaty 01:35, 28 September 2006 (UTC)

If Lambiam's "bullet" where made of stone, it would be about 17 km on a side. This would require displacing at least ~10^19 kg of material on its way through the Earth, suggesting it's momentum would drop my more than a factor of 1000, which suggests the whole thing could still exit at a few hundred km/s. Given that this is still large compared to the speed of sound in rock (a few km/s), I'd agree that the object described above would mostly likely penetrate all the way through. However, with those figures the exiting mass would carry only about 1% of the total energy with it, leaving most of the energy associated with the shockwave of ripping a gigantic hole through the Earth to tear us all to shreds. By the way, at these speeds and energies there would also be a great deal of nuclear fusion in the shockwave directly in front of the impactor. What difference that makes, I don't know. Dragons flight 01:58, 28 September 2006 (UTC)

It may work, assuming, that is, that the earth has no atmosphere, that we have the technology to accellerate something 15 times the speed of light, that no one had any objections to us bloxing up our home planed, and that you were crazy enough to kill billions of people with a pebble. Ilikefood 20:10, 1 October 2006 (UTC)

By the way I found that number from the article on the Death star which links to a page that has some maths on the subject --⁪froth^{T C} 19:52, 27 September 2006 (UTC)

[edit] Pseudoscience

I read that chiropractic practice is a pseudoscience. are there any explanations to why this would be based on false science or logic? Thanks

perhaps you should start with chiropractic? Xcomradex 02:15, 27 September 2006 (UTC)

So let me first point out that many people claim to receive enormous benefit from chiropractic, and for all I know, they really do. Still, one of my favorite smirking pleasures is H. L. Mencken's spirited defense of chiropractic, which includes the line

If a man, being ill of a pus appendix, resorts to a shaved and fumigated longshoreman to have it disposed of, and submits willingly to a treatment involving balancing him on McBurney's spot and playing on his vertebrae as on a concertina, then I am willing, for one, to believe that he is badly wanted in Heaven.

You can see the whole essay at [1]. --Trovatore

There is not much good published research on chiropractic methods; here is one study: A Randomized Trial of Chiropractic Manipulation and Mobilization for Patients With Neck Pain: Clinical Outcomes From the UCLA Neck-Pain Study. --JWSchmidt 02:45, 27 September 2006 (UTC)

Quackwatch has a nice section on chiropracty ont their front page! http://www.quackwatch.org/] — X [Mac Davis] (SUPERDESK|Help me improve)06:50, 27 September 2006 (UTC)

In addition to the section regarding your question on the Chiropractic article, you should also take a look at Pseudoscience. Notice how the definition of psudoscience itself is not a clear-cut black-and-white matter.

Further more, the article with a list of pseudoscientific theories has an entry for chiropractic practice under the medicine section --Yaksha 07:32, 27 September 2006 (UTC)

Many people claim benefit, but then lots of people claim benefit from placebos, and they also benefit from getting the practitioner's attention.--Shantavira 07:46, 27 September 2006 (UTC)

In the province of Ontario, Canada, chiropractic treatment is recognized by the healthcare system (partially). There are parts of chiropractic practice (e.g. treatment that relaxes the muscles in your back) that can be helpful to a patient with back pain, but a regular doctor will similarly suggest some sort of physical therapy that will be more or less as effective. However, the actual "back cracking" thing that they do is quite debatable. There have been (very rare) cases where doing so has unblocked some passage in the body, or something like that, but for the most part that part of what they do doesn't really seem to do anything, and it may actually be dangerous (your chiropractor will ask you to sign a waiver). - Rainwarrior 16:22, 28 September 2006 (UTC)

Even a broken watch is right twice a day. Clarityfiend 22:53, 28 September 2006 (UTC)

Also, there's this: http://www.chirobase.org/01General/chirosub.html , which lends much support to my opinon, derived both personally and professionally, that chiropractors are, by and large, just a bunch of sharlatans out to fleece the unsuspecting public. Mattopaedia 05:24, 30 September 2006 (UTC)

[edit] How many digits of pi for the known universe?

If I wanted to measure the circumference of the known universe to the accuracy of a planck length, how many digits of pi should I use?

PS. I'm assuming that the universe can be modelled by a very large circle.

202.168.50.40 02:47, 27 September 2006 (UTC)

It's impossible to make such an precise measurement, and even if you could, it would take a sophisticated experimental setup, not any number of digits of some mathematical constant. Melchoir 02:54, 27 September 2006 (UTC)

That's a pretty important assumption- see Shape of the universe. At very small and very large distances, we tend to have trouble modelling shapes and distances, and the universe almost certainly can't be modelled by a simple circle. --⁪froth^{T C} 02:56, 27 September 2006 (UTC)

all of them. anything less simply won't do. Xcomradex 03:18, 27 September 2006 (UTC)

The original question seems pretty reasonable to me. According to Observable universe#size, our universe, modeled as a sphere, is between 14 and 78 billion light-years in radius. I'm not going to try to figure out the answer, at least not tonight, but it should be doable. --Allen 03:38, 27 September 2006 (UTC)

I'm assuming, though, that the questioner is really talking about calculating the circumference of the universe, not measuring it... so that it's a math problem, not a physics problem. --Allen 03:43, 27 September 2006 (UTC)

With that data, it's easy: you have at most one significant digit to work with, so "pi = 3." suffices. It won't get you Planck-level accuracy, but neither will any other method without better data. Melchoir 04:21, 27 September 2006 (UTC)

Please see Pi#Numerical value for a start to answering the question. — Knowledge Seeker দ 04:13, 27 September 2006 (UTC)

Your error is going to be far larger than one Planck length, unless you make the assumption from the start that the measurements you're using are perfectly accurate. -- Consumed Crustacean (talk) 04:16, 27 September 2006 (UTC)

Radius = 78 billion light years = 78E9 * 9.461E15 = 7.38E26 metres

Diameter = D = 2 * 7.38E26 metres = 1.476E27 metres

Let C be the circumference

$C = \pi * D \,$

thus

$C + \Delta C = (\pi + \Delta \pi) * D \,$

$C + \Delta C = \pi * D + \Delta \pi * D \,$

$\Delta C = \Delta \pi * D \,$

$\Delta \pi = \frac{\Delta C}{D} \,$

$\Delta \pi = \frac{\mbox{planck length}}{D} \,$

$\Delta \pi = \frac{1.6 * 10^{-35}}{1.476 * 10^{27}} \,$

$\Delta \pi = 1.08 * 10^{-62} \,$

So I say you need about 63 or 64 digits of PI.

That's a pretty precise 78 billion light years you've got there. Can you be sure of that figure? freshofftheufo ΓΛĿЌ 04:24, 27 September 2006 (UTC)

Sorry, but you missed the most important part of the error. It should read:

$\Delta C = (\Delta \pi) D + \pi \Delta D, \,$

And since ΔD is literally astronomical, for small values of ΔC there is no solution for Δπ. Melchoir 04:24, 27 September 2006 (UTC)

I still agree with the anon calculator, because I think the original poster meant to ask about the number of digits of pi given a known radius of the universe. And as long as the universe's radius is in that tens-of-billions range, the answer is going to be 63 or 64 digits. And it's an interesting question, too... insofar as using pi to calculate circumferences is concerned, we will never ever need more than 64 digits for any practical problem. I bet that's what led the questioner to ask the question. --Allen 04:30, 27 September 2006 (UTC)

If I remember correctly, some versions of inflation theory produce sizes of the universe in the range of $10^{10^{200}}$ (ref. The Whole Shebang), which throws everything out the window (try getting 10²⁰⁰ digits of pi...). —AySz88 \^-^ 04:44, 27 September 2006 (UTC)

The point of the question is that we long ago calculated pi to far more digits than would be needed to calculate the diameter/circumference/radius of the observable universe to subatomic uncertainties. The had it to 100,000 decimals by 1968, if I recall correctly. I believe Isaac Asimov pointed this out several decades ago. So going from 100 digits to 100,000, to 100,000,000 perhaps does not have any practical purpose. Edison 05:26, 27 September 2006 (UTC)

pi's used for a lot more things than calculating circumferences. In which one of his 300 books did asimov say this?

Perhaps "Asimov on Numbers" but I read it decades ago.Edison 14:48, 27 September 2006 (UTC)

While this is true, you need about three times as many digits to compute the volume to the same precision. So, there could feasibly be a "practical" need for a bit over 200 digits. Of course, we don't have good data on the global curvature of the universe... -- Fuzzyeric 04:46, 28 September 2006 (UTC)

In curved space of course, the circumference of a circle is NOT equal to pi D. And depending on the curvature, you could have any value for the ratio of circumference to diameter ( as long as its greater than pi. ) What do we call this new 'constant' which is variable?--Light current 15:14, 28 September 2006 (UTC)

While we have no practical use for all of these digits, the science of calculating them has been quite beneficial to computer science. The principles learned from attacking the pi problem have applications in many other places. - Rainwarrior 16:33, 28 September 2006 (UTC)

[edit] What pressure is Hydrogen stored at?

[edit] Answered

I need to know a rough pressure H2 is stored at (or what pressure it's unsafe at in a pipe). If you know any sources, please cite them, sorry I'm not too good with google. Thanks.

i use H2 up to 100 psi without incident in an appropriate setup. and the hydrogen we buy is sent out at at least 1000 psi (just read the gauge, may be higher when new). Xcomradex 05:08, 27 September 2006 (UTC)

ok good. I was worried about 5 atm (73.5 psi) flowing in a pipe but I guess this is quite small. THanks.

bear in mind my "appropriate setup" is a reactor made of ~1 cm thick stainless steel Xcomradex 12:04, 27 September 2006 (UTC)

What pressure is safe for a pipe is a property of the pipe, not the gas. --Lambiam ^Talk 10:35, 27 September 2006 (UTC)

Storing gas at 1000psi is one thing, but in a typical lab set up, there would be a regulator attached directly to the tank with no transitional piping. This is just a hunch, but if you need pure H2 you probably don't have a direct feed, but a feed with heated copper to scrub the O2. If that heated copper mesh is in a glass tube, then 5atm may be too high. The glass tube may be able to handle it, and it would be relatively safe (because a pipe dissection with a non-flammable gas such as air or CO2 would not be all that big of a deal) with another gas, but 74psi is probably not a good idea with an explosive gas. In general, you really should know the maximum capabilities of your piping and stay well below them with flammable/explosive gasses. Also, what's with the "anwered" thing at the top, never seen that before...Tuckerekcut 13:38, 27 September 2006 (UTC)

That's something new we are trying, to mark questions that no longer require answers, so we don't have to keep reading thru them to figure it out. StuRat 14:18, 27 September 2006 (UTC)

Great idea Stu. I think I'll start doing that. Should we put it in bold or as a sec header? — X [Mac Davis] (SUPERDESK|Help me improve)16:21, 27 September 2006 (UTC)

Just like the one at the top of this question. We've been debating this on the Ref Desk Talk Page, so may end up changing things, but I'm trying it this way for now. StuRat 16:40, 27 September 2006 (UTC)

[edit] natural bleach source

In the 1700s or 1800s, what natural sources were used to bleach natural fibers?

Seaweed ashes, sour milk, sunlight, and time. ReproductionFabrics has a description of the process which seems to have taken forever - until chlorine's bleaching effect was discovered in the late 18th century.---Sluzzelin 06:56, 27 September 2006 (UTC)

I believe urine was used at one time, as well. StuRat 10:10, 27 September 2006 (UTC)

Urine is still used! In places you don't want to go. — X [Mac Davis] (SUPERDESK|Help me improve)18:09, 27 September 2006 (UTC)

I believe urine used to be collected from families in Britain during roman times (and maybe later) I thikn for use a bleach. A urine collector was quite a good postition to have but the wages were piss poor! 8-)

An early form of trickle down economics ? :-) StuRat 17:41, 28 September 2006 (UTC)

Then of course there were the night soil collectors. That was a crap job!--Light current 17:45, 28 September 2006 (UTC)

[edit] earths motions

What are the four main motions of the earth?

June

can you be a bit more specific? motions as in the earth as a planet moving, or motions as in things like wind and tides which are on earth and are always in 'motion'?

Also, please take a look at Planetary motion, Earth rotation and Polar motion first to see whether they have your answer. The List of basic earth science topics may also be worth browsing through. --Yaksha 07:21, 27 September 2006 (UTC)

Also, motions relative to what? There are components that are relative to the galaxy and to the local group of galaxies. Or you could surprise your teacher with observations about the Chandler wobble.--Shantavira 07:55, 27 September 2006 (UTC)

"Or you could surprise your teacher" lol...just assume it's a homework question. --Yaksha 08:39, 27 September 2006 (UTC)

Easy: Up,down, left, right--Light current 20:21, 27 September 2006 (UTC)

Here on Wikipedia, most of us don't view existance in only two dimensions. freshofftheufo ΓΛĿЌ 01:23, 28 September 2006 (UTC)

Sounds like original research to me. :--) JackofOz 02:51, 28 September 2006 (UTC)

"Sounds like" sounds like POV to me! freshofftheufo ΓΛĿЌ 05:39, 29 September 2006 (UTC)

" "Sounds like" sounds like" sounds like POV to me. DirkvdM 09:46, 29 September 2006 (UTC)

Don't forget internal motions. The tidal effect of the Sun and the Moon causes the Earth to be kneaded, which I believe is part of the reason the Earth has a molten centre. I don't know the name for the phenomenon, though. DirkvdM 09:46, 29 September 2006 (UTC)

Tidal forces? 8-)--Light current 00:36, 30 September 2006 (UTC)

[edit] Tarsola

Has anyone ever heard of a bird or animal called a "forest tarsola"? Such an animal is mentioned in the fictional novel Journey to the River Sea by Eva Ibbotson, where a stuffed specimen is part of a museum display in Manaus. Whatever it is, if it exists at all, should be indigenous to the Amazon Basin. I am looking for a Latin name or a synonym for use in an authorised translation of the book.

Another animal, mentioned in the same book, about which I have not been able to find an independent source of information is an "Amazonion river slug". Is there such a thing, or is it just a fanciful invention of the author? Here's another one: a "tabernid fly". Ring any bells?

Thanks, --woggly 11:07, 27 September 2006 (UTC)

I found nothing, except that there are slugs living in the Amazon river; most of these have very specific names though, and I couldn't locate an 'Amazonian river slug' as a species name. According to WP's article on Eva Ibbotson, she often features 'magical' creatures in her works. Is it possible that she just made up these names and species? Both she and her husband seem to have studied natural sciences, so I would assume she chose her names carefully. Tarsola reminded me of the (Asian) Tarsiers, or of the tarsus (insect foot or vertebrate bone cluster). Tabernid only reminded me of the silly Pseudolatin phrase 'situs vilate inisse tabernit' (which, when rearranged, is German for 'looks like Latin, but it isn't' - since she has Austrian roots this allusion is possible, but unlikely I guess). My suggestion for translation would be to keep the animal names as close to the original as possible while maintaining the 'scientific ring' they seem to suggest.---Sluzzelin 08:21, 28 September 2006 (UTC)

Thanks for looking into it. I wouldn't put it beyond her to have invented the names, but on the other hand she makes plenty of references in this book that seem to be quite authentic, so I feel I need to be careful. For instance, she also mentioned a plant named "mashohara" which only had about ten independent Google hits but what few hits there were seemed to confirm this is Justicia Pectoralis, a medicinal plant used by native tribes in Amazonia - which is how it is described in the book. So I can't help thinking she knows lots of stuff that I don't. "Tarsola" is also similar to "Tarsila", which is the name of a famous Brazilian painter, I doubt that's a coincidence. Your suggestion is a reasonable, if not ideal solution, which we may have no choice but to adopt.

That German/Latin sentence is pretty funny. Reminds me of a whole set of Hebrew/Japanese jokes: How do you say 'driver' in Japanese? - Ishimoto (looks Japanese, but is also Hebrew for "man with car"); How do you say 'diaper' in Japanese? - Sakimkaki (ditto for "sack of poop") etc. --woggly 10:17, 28 September 2006 (UTC)

The Tarsila reference sounds very likely to me - you obviously already did your research. I read that the author dedicated Journey to the River Sea to her late husband. Maybe knowing more about him could help you further. Btw, I like your Japabrew examples, and, on a sidenote, I wonder whether WP has an article/collection of this type of wordplay.---Sluzzelin 13:24, 29 September 2006 (UTC)

Well, yes, I try to do my own homework - posting a question to the reference desk was a way of covering all bases, not of evading my work! As to wordplay: I wouldn't know under what name such an article would be filed. I know there is a form of poetry that follows this same idea, wherein the same sequence of sounds creates two different poems in two different languages, but I don't know that this form of poetry has a name. Here is an example, the first line of such a poem (a dirge) written by Rabbi Yehuda Aryeh of Modena in 1584.

In Italian: Chi nasce muor: Oime, che pass' acerbo! ("All that is born will die; alas! How bitter this move!")

And in Hebrew, the same pattern of sounds: קינה שמור, אוי מֶה כי פס אוצר בו ("Save your lament, alas how is it that no more is that which once encompassed")

Maybe someone at the language desk will know a name for this form of poetry. --woggly 21:44, 30 September 2006 (UTC)

In computer science, there is such a thing as a program that works in multiple programming languages. Such a program is called a polyglot program, so I suggest the term "polyglot poetry". --WhiteDragon 19:36, 5 October 2006 (UTC)

[edit] Medical

What you mean by Health&Safety in working place

Try reading Wikipedia's article on Occupational safety and health. --Shantavira 13:32, 27 September 2006 (UTC)

The (British) government agency, The Health and Safety Executive has a decent website ([2]). --Dweller 14:47, 27 September 2006 (UTC)

[edit] Solar wind/Gamma rays

My question is if earth's atmosphere & magnetic field reflect(& protect us) all the gamma rays,x-rays & solar wind how come it allows visible light ,which has much lower energy, to reach us? I guess my question is a simple one but i couldn t find an answer on the net. Thank you Abhijit

The magnetic field will only deflect ionized particles, like the solar wind. Some frequencies of radiation are reflected or absorbed by the atmosphere, while others (like infrared and visible light) pass thru. I believe that which ones are reflected, absorbed, or transmitted is related to the electron configuration of the atoms and energy quanta, but will let a physicist comment on that. StuRat 16:34, 27 September 2006 (UTC)

All elecromagnetic radiation is made of the same stuff (photons). EM radiation above a threshold frequency will get through - this is somewhere in the radio region. Gamma rays and xrays do get through. StuRat is correct about the solar wind. See atmospheric seeing

[edit] do you metabolize trans fats?

Hi I was wondering if you are able to metabolize all fats or do the trans fats stay within your body hardening your arteries. So the question is do you breakdown trans fats? thanks so much this will help

The article on Trans Fat may be of use to you. Benbread 20:26, 27 September 2006 (UTC)

The article on Trans fat may be even more useful to you. David D. (Talk) 20:31, 27 September 2006 (UTC)

There have been some studies suggesting that trans fatty acids can alter desaturase activity (example) resulting in altered levels of some fatty acids that might be important for normal health. I'm not sure that good studies have been done on humans. I think most studies have been concerned with effects of dietary trans fatty acid on levels of HDL-cholesterol and LDL-cholesterol, and other forms of circulating lipids and lipoproteins. Dietary trans fatty acids can accumulate in cell membranes of the body and it has been suggested that certain membrane-associated enzymes and receptors might have altered activity that contributes to disease (example: Dietary intake of trans fatty acids and systemic inflammation in women).

[edit] Relativity-: Theory, hypothesis ,conjecture or philosophy?

When Einstein formulated his Theory of special relativity, I believe he took as his only experimental evidence as that of the constancy of the speed of light. Einstein himself performed no experiments. In the light of this, was his 'Theory' (in modern scientific terms):

just philosophical musings
a scientific theory
a hypothesis or
a conjecture

THe underlying question is, of course, ' Can science be done without experiment'?--Light current 16:44, 27 September 2006 (UTC)

That depends on your definition of science of course, and we could go into the philosophy of science as well... --HappyCamper 17:06, 27 September 2006 (UTC)

MY defn of science is 'Knowledge of how the universe operates'--Light current 20:14, 27 September 2006 (UTC)

I'd say it was a hypothesis at the time of its formulation. There's a complicating issue with moderm scientific terms: lots of things in physics are called "X theory" even if they're just a class of mathematical tools (quantum field theory), conjectures without experimental support (string theory), or largely rejected (SU(5) grand unified theory). If relativity were invented today, perhaps it would be called "relativity theory" just for looking good! Melchoir 17:29, 27 September 2006 (UTC)

I feel that "postulate" is the best description of Einstein's work - unless I'm sorely mistaken on what his work was. As I understand it, scientists since Galileo were bashing their heads trying to find an absolute state of rest to use as a universal reference for relative motion. Einstein postulated that there is no absolute state of rest. Instead, there is an absolute state of motion - the speed of light. Everything is equally relative to that. The problem with his postulation is that it didn't fit with the already well known physical measurements of space and time. So, Einstein got around that with a second postulate that space and time can be bent, allowing the speed of light to remain constant. If both of those postulates are assumed true (which they must be or they wouldn't be postulates) the rest of his theories are just reflections on the ramifications of the absolute speed of light. --Kainaw ^(talk) 17:40, 27 September 2006 (UTC)

As for the underlying question, yes, science can be done without experiment. It cannot be done without observation, and experiment is one particular type of observation which is particularly valuable to science, which is why experiment is generally used when it's feasible to do so. With experiment, you can set up two apparatuses which are identical in every respect except for one. When experiment is not feasible--for example, we cannot do experiments in astrophysics, since we don't have the technology to do experiments with stars--we can still observe the subjects of the science; it's just that it can be harder to draw conclusions since you're not going to find two stars that are the same in every respect except one, so you have to take many possible variables into account in analyzing the data. But even though astrophysics is based only on observation, not on experiment, it's still a science. Chuck 18:01, 27 September 2006 (UTC)

Of course science can be done without the experiment, but it isn't science until the experiment works. It is only a protoscience. Today, special relativity is a theory. Then, a believe it would be a postulate or a hypothesis. The real scientific method (not the crap taught in high schools and science fair projects) of theory, experiment, theory, experiment, is not fufilled by only theory. Therefore, it is a protoscience, like string theories and sociobiology.

"The supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a single datum of experience." -- Albert Einstein (1933)

— X [Mac Davis] (SUPERDESK|Help me improve)18:06, 27 September 2006 (UTC)

I'm afraid that I don't think your categories are appropriate. First, let me complain about the use of "just philosophical musings." I'm sure what you meant to say was something like, "ideas which are unconstrained by fact," or something like that. But, please, don't call that philosophy. Bad philosophy, like bad science, is unconstrained by fact, but it not a feature of philosophy as a whole to be widely unconstrained. And certainly, I don't think Einstein imagined he was doing that. Second, I don't understand the distinction between a scientific theory, hypothesis, and conjecture. Do you mean, to what degree did Einstein think his theory confirmed by the evidence? If this is what you mean, its not so much a question of three categories, but a matter of degree. In such a case, I think the historical record is unclear. Although his theory explains the Michaelson-Morley experiment, Einstein says contradictory things regarding his prior knowledge of the experiment. I don't think it was determined that Einstein's theory could account for the advance of the parahelion of mercury, one if its standard triumphs. Experiments about the bending of light around the sun weren't done until sometime after. On the other hand, his theory fit well with other facts known at the time, perhaps better than Newtonian mechanics. Because it had other virtues, like simplicity, Einstein may have thought it more confirmed by available evidence. --best, kevin [kzollman][talk] 23:06, 27 September 2006 (UTC)

Einstein postulates the constancy of the speed of light, indistinguishability between acceleration and force, Galilean invariance, and a few other pieces. He then constructs the (falsifiable) theory that the speed of light is an invariant with respect to intertial reference frames and that the Fiztgerald contraction is physically real. He then hypothesizes several things: clocks appearing to move appear to run slow, clocks apparently accelerating appear to run slow, fast moving meter sticks can pass through 1/2 m doors, et al. Experiments to test these hypotheses did not refute the theory (yet). However, until the theory -> hypothesis -> experiment loop is closed, there isn't Science. Ideally, every scientific theory (1) fits all prior data, (2) produces hypotheses (predictions) that discriminate it from other theories of the same phenomena, and (3) survives experiments that test the predictions. Without both the production of theories and the mechanism to reject wrong ones, it isn't science. Relativity was a theory that made a wide range of predicitions that disagreed with the prevalent prior theory (-ies) and Relativity has survived every critical test of its predictions. (So much so that it's more likely from an a priori position that dark matter or dark energy causes a deviation from the predictions of relativity than that relativity is incorrect, although this is technically muddled reasoning in the scientific framework.) -- Fuzzyeric 05:01, 28 September 2006 (UTC)

Thanks to all respondents. Esp Eric who has clarified the 'scientific' position excellently. I didnt know that he postulated the constancy of the speed of light: I though he was aware of the Michelson-Morely results. So is it fair to say that Einstien's Theories are rapidly becoming 'science' even if they are not science at the moment.--Light current 16:54, 28 September 2006 (UTC)

If your interested in the distinction between science and non-science, see the demarcation problem. Almost all philosophers of science agree that something which is unconfirmed, but capable of being confirmed, counts as science (so long as people are actively seeking confirmation). Under most criteria SR is, and has always been, science. --best, kevin [kzollman][talk] 17:38, 28 September 2006 (UTC)

The Michelson-Morley experiment measured no variation in the speed of light. This is different from claiming the axiom "the speed of light is constant in all reference frames". One measures a property of an experiment, the other makes a grand fundamental statement about how the universe works. Michelson and Morley make the experiment and derive no further conclusions from it. Fizgerald explains the length contraction implied by the Maxwell equations "as if" it were real, but since he doesn't take it to be a fundamental feature of the universe, doesn't derive subsequent relativistic hypotheses. Einstein says it is real and fundamental, so get used to it, then derives consequences of the claim.

Einstein's theories were science when they were formulated. Newton's laws were not correctly predicting the precession of the orbit of Mercury, which had been measured and puzzled over. Relativity fit the Newtonian data and the Mercury data, made testable predictions (e.g. about the bending of light around the sun, clocks at different altitudes running at different rates, and so on) that differed from Newtonian predictions, and (unlike Newtonian theory) survived the experiments which tested the differences. -- 66.103.113.62 02:36, 29 September 2006 (UTC)

[edit] spirulina

I want to ask you that from where I get spirulina culture? I am residing at Anand,State-Gujarat,India.my e-mail ID is (removed for privacy) Please send me the regarding information as soon as possible to my e-mail ID.

Please send me the phone NO. of your office and contact person's name so I can contact & get all the necessary informations. I expect good ,positive reply from you.

The Wikipedia Reference Desk is not an organization and it doesn't have a contact person. It's an online bulletin board "staffed" by volunteers. If anyone has an answer (I regret I don't), it will be posted here. --Ginkgo100 ^{talk · e@} 19:16, 27 September 2006 (UTC)

Also, have you heard of Google? From a simple Google [3]. Of course, you could probably find someone in India fairly easily if you search a bit harder. Nil Einne 00:01, 28 September 2006 (UTC)

[edit] velocity

if i squeeze a spot what is the maximum velocity with which the spot goo exists the spot?

FAQ!--Light current 19:18, 27 September 2006 (UTC)

geez if I had a nickel for every time that was asked! --Deglr6328 22:53, 27 September 2006 (UTC)

Like for all matter, the velocity cannot reach the speed of light. -- --Lambiam ^Talk 23:38, 27 September 2006 (UTC)

[edit] Speed of light

If nothing can go faster then the speed of light, how come the force of gravity or lack of it is felt sooner? It takes the light from the Sun 8.5 minutes to get to earth, but if the Sun where removed the affects would be felt that very moment and the Earth would loose it orbit well before it would get dark.

is it possibale to travel faster than the speed of light, and if so, this means that travelling faster than the speed of light will make time move backwards according to the principle of relativity which states that time slows down as you travel closer to the speed of light, and since travelling at the speed of light is impossibale then time can never absolutley come to a halt, also if time comes to a stop or moves backwards then this must mean that objects moving at the speed of light or faster than it must have a length of zero or a negative value: Length of an object = Speed of light x time diffrence.

I hope someone could clear things up for me..

It is not currently believed to be possible for a particle with real mass to travel faster than the speed of light. See also Faster-than-light, Tachyon. JBKramer 19:33, 27 September 2006 (UTC)

For example, if an astronaut falls towards a black hole, (which spins faster than the speed of light) time to the astronaut would be normal. But to a distant observer, their time will slow and then stop altogether as he enter the black hole. To clarify this, pretend the asrtonaut had a watch that could send time signals to Earth. If you could pick up the time signals from the astronaut falling towards a black hole, the time from the signals would go slower and slower until, as he/she entered the black hole, it would stop altogether. However, like I mentioned before, to the astronauts, time would be normal. My friend think that someone travelling faster than light would see people moving slowly. I used to have trouble understanding it, but now I do understand it! And I'm only in grade 6! WARNING: Do not try this at home! Himanyo 19:46, 27 September 2006 (UTC)

Himayo!!! You gave edit conflict 3 times!!! argh! hehe, black holes don't spin, they're singularities, not plug holes. Philc _T^E_C^I 19:51, 27 September 2006 (UTC)

Not so! --⁪froth^{T C} 20:02, 27 September 2006 (UTC)

It is possible to travel faster than the speed of light, however it is impossible to accelerate (or decelerate for anyone not accustomed to the physics meaning of acceleration) from below to above the speed of light, or from above to below. As that would violate causality, not to mention, as we know, something that is travelling at the speed of light would have infinite mass, and therefore recquiring an infinite amount of energy to move. So yeh, it is impossible to travel at the speed of light, above and below (theoretically) your fine, but we can never get above it, as that would recquire traveeling at it. Philc _T^E_C^I 19:49, 27 September 2006 (UTC)

Um, no. The current theory is that one may take two observers some distance away from "the" Kerr black hole, the "rest" observer will watch the rest of the experiment and the "moving" observer will putter around. The moving observer accelerates into the ergosphere. At no time will the moving observer accelerate to a speed faster than the speed of light relative to test particles near himself. However, to the rest observer, the moving observer can appear to exceed the speed of light. I.e., the net effect of the acceleration and the frame dragging 1 in the ergosphere will produce the observation of superluminal velocity. It isn't yet decided if this is correct or not. I recall experiments planned for earlier this year using photons as the drag-inducing medium. I wonder whatever happened with that. -- Fuzzyeric 05:26, 28 September 2006 (UTC)

I agree with Philc_0780. And sorry, black holes don't spin (?what word can I use?!) faster than light, but have gravity strong enough to suck light in. A little mistake. And gravity can also affect time. Don't forget wormholes. Also you can get teleported into the past or future if travelling faster than light according to Einstien, I think. I forgot.Himanyo 19:58, 27 September 2006 (UTC)

Black holes do not spin faster than the speed of light. Nor is time travel through wormholes anything but science fiction at this point --⁪froth^{T C} 20:02, 27 September 2006 (UTC)

My computer is running slow today. And sorry for the edit conflict Philc_0780. Himanyo 20:00, 27 September 2006 (UTC)

I know wormholes are s.f. but some scientists think they exist. Also I wrote that the GRAVITY of the black hole affects time.

Nah, the edconflict thing is cool! It was just seeming less and less funny as it happened again, and again, hehe!! I dont see how black holes can be wormholes, as anything that went into a black hole would be well and truly wrecked by the time it got to the centre (urr, lots of gravity) so all the wormhole would be spitting out at the other end would be a chunk of neutronium at best. Philc _T^E_C^I 20:14, 27 September 2006 (UTC)

I know that the astronaut would become like a spaghetti as he got closer to the black hole and would be toast when he's in the center, but it's just an example. Wormholes connect different parts of space-time. Scientists think they can be used as time machines and I wrote before that... Himanyo 20:42, 27 September 2006 (UTC)

Another edit conflict! Ahh! *rips hair off head* Himanyo 20:42, 27 September 2006 (UTC)

Actually time doesnt slow down if u travel faster than the speed of light, because travelling at speed of light would mean that time reaches zero and completley stop at 300,000,000 meters per second (speed of light), therfore moving faster than the speed of light would mean moving back in time at a very slow rate say 400,000,000 meters per second, thus i guess that traveling at double the speed of light would be like normal time but backwards.

P.S:- it would be really kewl if your parents went on a trip to a nearby blackhole for 2 weeks then you will be 20 years older than your parents when they return --RedStaR 20:55, 27 September 2006 (UTC)

Why do you think that is likely and why would it be 'kewl'?--Light current 21:05, 27 September 2006 (UTC)

He didn't say it was likely, but all space travel involving black holes is inherently kewl. Hyenaste ^(tell) 00:30, 29 September 2006 (UTC)

The principle of relativity says that there is no preferred reference frame for constant motion. If one were to travel faster than light the maths does not say time would flow backwards - the passage of time would be measured as imaginary (some multiple of i).

The Lorentz transformation was only designed to work up to velocites of 'c'--Light current 00:08, 30 September 2006 (UTC)

[edit] Negative Kelvin Temperatures?

How can such temperatures be obtained? Its not like you can slow atoms that are already stationary... 152.163.100.74 20:21, 27 September 2006 (UTC)

Negative Kelvin temperatures cannot be obtained. 0K is the lowest theoretically possible. —D a niel (‽) 20:26, 27 September 2006 (UTC)

Negative Kelvin? Where did you get that from? Himanyo 20:27, 27 September 2006 (UTC)

You might want to read negative temperature. Absolute zero is in fact an impassable discontinuity in temperature space, and infinity (in the projective reals sense) a lesser one. It is still a trick to surpass (or even reach) infinite temperature, but with certain systems it is possible. Something with a very large negative temperature is only "slightly hotter" than something with a very large positive temperature. In a sense, temperatures range from 0K to -0K (or ε to -ε). --Tardis 20:50, 27 September 2006 (UTC)

Yup. And to clarify for the original question: you're right, the thermal motion of atoms cannot achieve a negative temperature. The only systems that can achieve negative temperatures have bounded energy spectra, such as spin ensembles. Now, if a system X at a negative temperature is brought into thermal contact with a gas, the gas will absorb heat from X until finally the temperature of X drops below infinity to a positive number; at equilibrium the two systems will have the same positive temperature. So a gas thermometer, no matter how small or unobtrusive, is incapable of measuring negative temperatures. Same goes for any other kind of material thermometer that relies on achieving equilibrium with its target. Melchoir 23:24, 27 September 2006 (UTC)

A classical example of a negative temperature system is a lasing medium in an inverted state. There is a great deal of potential energy in the system, causing the system to be disordered, and we can extract that energy and send the system to an ordered (grounded) state by kicking off the laser emission. At thermodynamic temperature we find the common equation 1/T = dS/dE. Since the entropy of the inverted state (mix of excited and grounded atoms) is greater than the entropy of the ground state (all atoms grounded) and we can induce a decrease in entropy by adding energy, we find that the temperature is dS/dE < 0, so T < 0. -- Fuzzyeric 05:34, 28 September 2006 (UTC)

[edit] belostomatidae or giant water bug (or beetle)

I found one and I am raising it. It is two inches long. I need to know what it eats.

Read our page please!

They are fierce predators which stalk, capture and feed on aquatic crustaceans, fish and amphibians

--Light current 21:10, 27 September 2006 (UTC)

Small fish and tadpoles, try tuna or sardin see if that works --RedStaR 21:15, 27 September 2006 (UTC)

And don't put your toe in the water. They ain't called toe-biters for nothing. Their bite is ... widely considered the most painful that can be inflicted by any insect. --Lambiam ^Talk 23:46, 27 September 2006 (UTC)

[edit] Wetness

Is the human skin capable of detecting 'wetness'? Or is the sensation imagined from a combination of temperature etc.--Light current 21:19, 27 September 2006 (UTC)

Actually it doesnt on condition that the water you put your hands in are the same as your body temperature eg: when your in a swimming pool for a consedirable amount of time untill your body adapts to the temperature of the pool water, you cant tell the diffrence if your wet or dry --RedStaR 21:29, 27 September 2006 (UTC)

Pardon?--Light current 21:30, 27 September 2006 (UTC)

No, no such thing as a wetness receptor.Tuckerekcut 22:16, 27 September 2006 (UTC)

Actually, not even a proper temperature receptor. You may know the following experiment: Put one hand in cold water, the other in hot water, and the both in the same pan with medium-warm water. The temperature feels different. Hence, your skin measures not absolute temperature, but temperature change: If warmth is drawn out of your skin, you feel cold. And this is why cold water feels so much colder than cold air of the same temperature. Cold water, due to its higher heat capacity per volume can draw the heat from your body much faster. If the heat is then also dissipated (carried away from the point into the bulk of the stuff) quickly in the material, so that the temperature difference between hand and touched material (and hence the heat flow) is kept steady, it feels especially cold. This is why metals, with their very high heat conductivity, feel even colder. Simon A. 09:42, 28 September 2006 (UTC)

I think its the thermal conductivity primarily that makes things feel hot or cold ( assuming the heat capacity is sufficiently large for you body not to affect the obejcts temperature substantially). For instance, marble or iron generally feels cool if its lower than your body temp, but hot if its above.--Light current 15:23, 28 September 2006 (UTC)

[edit] When the sun goes red giant...

...and presuming that the earth wasn't consumed, would it be possible for any of the lifeforms that exist on earth at present to survive? I'd guess that some bacteria, viruses and the obligatory 'stuff that lives near the hydrothermal vents' might be okay - but what about the plants and animals? What would the progress of the transformation of the sun be like anyway? Does it take place over hundreds/thousands of years or would it be like 'Wooosh! Suddenly the sun changes colour and fills half the sky now'? --Kurt Shaped Box 21:57, 27 September 2006 (UTC)

What your saying wont take course before a few billions of years when humans wont probably exist or will be in another solar system--RedStaR 22:27, 27 September 2006 (UTC)

I'm sure he knows this. - R_Lee_E

(talk, contribs) 22:11, 27 September 2006 (UTC)

The parrots, the gulls, the magpies and quite possibly the ants may all have upped and left in their own spacecraft by that point too and have scattered across the galaxy (I would *love* to be around long enough to see what sort of spacecraft the ants would build - I don't know but I can guess that it would be a pretty cool sight)... ;) --Kurt Shaped Box 22:23, 27 September 2006 (UTC)

Well, for one, the Earth would be completely consumed. But if we are only to consider the temperatures involved, I believe the oceans, along with any water trapped in fissures beneath the surface, would be evaporated. The atmosphere, as well, would be blown away. Hence, I'd be confident in saying that that would be the official end of life on Earth. - R_Lee_E

(talk, contribs) 22:25, 27 September 2006 (UTC)

The red giant article itself suggests that this is not nescessarily the case. The gravitational pull of the sun will have weakened by then due to its loss of mass, and it is possible that Earth may escape to a wider orbit [9]. The fate of the Earth with regard to the size of the expanding Sun is still hotly debated in the scientific community. --Kurt Shaped Box 22:26, 27 September 2006 (UTC)

---wow, an edit conflict with two other posters...---

I can't answer your question, but I can tell you that should the plants die, even the bacteria living near hydrothermal vents will perish. These bacteria (actually they are mostly Archaea) use iron in their respiration. This iron, after it is used by the bacteria, becomes soluble in water and diffused into the ocean. When this diffuse (reduced) iron meets the oxegenated water near the surface, it becomes oxidized and falls back down to the bacteria, and the cycle starts over. Thus if the plants aren't around to oxegenate the air and water, even the bacteria living on the hydrothermal vents will die. Also, and don't take my word for this part, I remember hearing that when the sun becomes a red giant, it will be so large that the Earth itself will be engulfed, because its central mass will no longer be massive enough to hold the outside in ( that is, the outward explosive and centripetal forces will no longer be tiny compared to the gravitational force).Tuckerekcut 22:14, 27 September 2006 (UTC)

uhhhhm where did you get the wild idea about archaea at thermal vents depending on FeO influx from plants above. honestly, I don't think that's even wrong. the amount of iron compounts spewed from the vent itself is immense! --Deglr6328 00:19, 28 September 2006 (UTC)

The back of my envelope suggests a surface temperature of like 1100 C. So I'd say no life on the surface or in what once were the oceans. Some bacteria that live deep underground might still be happy, but I'd say that life as we know it would pretty much need to find a new place to live. Dragons flight 01:32, 28 September 2006 (UTC)

So (assuming the human race, or one of our successors from another evolutionary line was still around and paying attenion), how much notice would we/they have in advance of the impending 'end of (nearly) everything'? Would it be observable for a long time beforehand that the sun was about to balloon and incinerate the planet's surface? How long would it actually take for the sun to become a red giant once the process was irreversibly initiated? Minutes? Hours? Days? Weeks? Years? --Kurt Shaped Box 01:47, 28 September 2006 (UTC)

Refer to the image above. It would be about a two-billion year process. - R_Lee_E

(talk, contribs) 02:03, 28 September 2006 (UTC)

Sorry, I was trying to find out how long it would take to go from sun-sized to super-size once the thing 'blew'. Are you saying it would take 2 billion years to expand, or two billion years to reach 'critical mass' and then 'blow'? Sorry if I'm being thick - most of my knowledge in this area comes from bad sci-fi... --Kurt Shaped Box 02:11, 28 September 2006 (UTC)

I think most of the transition might be accomplished in only a few 100 million years, but basically the transition time scale is going to be absurdly long compared to the life time of any organism that might be around to worry about it. Which I suppose could push evolution towards hyper-hyperthermophiles, but I'd still have trouble imagining anyway to survive that transition and be carbon based. Dragons flight 02:35, 28 September 2006 (UTC)

Since Deglr seems skeptical, let me explain my rationale furthur. Although reduced iron is copious at the vent surface, it must be in its oxidized form to be coupled to respiration. Fe(III) acts as a terminal e- acceptor with acetate (as acetate is one of few organic acids which has been shown to form abiotically in hyperthermic environments from the organic matter that floats down (yet another reason this life could not survive without terrestrial flora: it needs a carbon source)). Since the iron coming out of the vents is completely reduced, it makes a very poor e- acceptor, and would not be able to contribute to vent life as such. The bottom of the ocean is mostly anaerobic, so it is O2 at the surface that oxidizes it. Check out Tor, JM, Amend, JP, and Lovley, DR. 2003. Metabolism of organic compounds in anaerobic, hydrothermal sulfate-reducing sediments. Environmental Microbiology 5:583-591.. And try not to be such an assface in the future.Tuckerekcut 02:27, 28 September 2006 (UTC)

pfft hah. real mature, what are you, like 12? that paper does not at all support your idea.--Deglr6328 03:42, 28 September 2006 (UTC)

With all due respect, I am quite confident that vent communities existed quite happily before the invention of oxygen based metabolism. Whatever minimal impact terrestrial flora might have on them, I am certain that life can persist nearly indefinitely even without a terrestrial biosphere. Dragons flight 02:48, 28 September 2006 (UTC)

I believe the consensus is that, in the presence of such extreme temperatures, much, if not all, of the water on Earth would be evaporated. Thus, a terrestrial biosphere is a moot point. - R_Lee_E

(talk, contribs) 03:25, 28 September 2006 (UTC)

Every once in a while, someone comes around and says that they have discovered an organism that is completely uncoupled from the sun's energy. Look up SLiME (Subsurface Lithoautotrophic Microbial Ecosystem) for a well publisized example. The deep-sea hydrothermal vents are another example. It seems at first glance that they get all of their energy (that is electron donor, electron acceptor, and carbon source) from the vents, but everything is so well reduced that they must rely on oxidized materials from above. The iron coming out of the vents is no more useful to these bacteria as an electron donor than CO2 or HS is for us. So even though these organisms live far from the sun's rays, they still require the sun in an indirect way. If the terrestrial plants on the surface, which oxegenate the air with the sun's energy, were not around, these deep sea archaea would not be able to survive. There is also new talk of a photosynthesizing organism living on the sea floor which uses the dim illuminescence produced abiotically in the sea (I don't know how) to live. We will sea if this one pans out to be truly decoupled from the sun, but I'm betting it won't be either.Tuckerekcut 12:00, 28 September 2006 (UTC)

I read years ago that when this process starts, the sun would bloom to a red giant in a matter of hours. But it would be a matter of millions of years before that process started.

[edit] Brown noise

Brown noise is a pitch with a certian frequency that makes people lose bal control, in other words it makes you crap your pants, the french experimented with it in World War II, comment on this is appreciated --RedStaR 23:11, 27 September 2006 (UTC)

Try brown note Nil Einne 23:29, 27 September 2006 (UTC)

A blue note makes me lose ball control. --Lambiam ^Talk 23:59, 27 September 2006 (UTC)

What you're talking about doesn't really exist. (And yes, there were experiments done trying to find it, possibly by the French, but they weren't successful.) There is another thing called brown noise which is a kind of sound, but has nothing to do with your bowels (it sounds kind of like distant cars on a freeway maybe). And of course the brown sound so loved by Van Halen. - Rainwarrior 16:09, 28 September 2006 (UTC)

Mythbusters tried it. No such thing. Deltacom1515 22:06, 30 September 2006 (UTC)

Brown noise isn't pitched; although the sliding scale between a definite pitch and white noise is continuous and therefore subjective, one look at the frequency plot is enough to agree it's noise. It certainly sounds like noise - put through a very soft low-pass filter. Perhaps the brown note you're looking for does exist at extreme volumes, but personally I'd go with a frequency of about 13KHz at a ridiculous SPL if I wanted to fuck someone up. Might not work on really old people, mind. Magic Window 15:08, 1 October 2006 (UTC)

[edit] How many humans have ever lived?

What is the total population of humans that has ever lived?

I defined the function B(year) to be the number of humans born in that year.

B(2006) = number of humans born in year 2006

Next I define a new function

TotalPop(xxxx,yyyy) as B(yyyy) + B(yyyy-1) + B(yyyy-2) + ... + B(xxxx)

For example:

TotalPop( 2006 , 2006 ) = B(2006)

TotalPop( 2004 , 2006 ) = B(2006) + B(2005) + B(2004)

So my question becomes what is the value of TotalPop( -INFINITY , 2006)

If I assume that B(2006) = k P(2006) that is birth is a proportion of the actual population. And that P(2006) = r P(2005) where r > 1.

B(n) = r^1 * B(n-1) = r^2 * B(n-2)

B(n) + B(n - 1) + B(n - 2) = B(n) * ( 1/r^0 + 1/r^1 + 1/r^2 )

TotalPop( -INFINITY , 2006) = B(2006) * ( SUM( t=0 , t=INF, 1/r^t ) )

So what is the value of B(2006) and the value of r ?

202.168.50.40 23:20, 27 September 2006 (UTC)

WORLD POPULATION

   Year            Population       
        1700            600,000,000  
        1800            900,000,000 ~~> 50% increase rate/100 yrs     
        1900            1,500,000,000 ~~>66% increase rate/100 yrs    
        2000            6,000,000,000 ~~>300% increase rate/100 yrs

I'm not sure of this but if u can figure out a fixed ratio or equation with the rate of increase of the population relative to 1000yr unit multiplied by estimated human existance would get a pretty approximated number of actual history of human population, (This does not include war casulties, epidemics, plagues, or other life manipulating factors) --RedStaR 23:51, 27 September 2006 (UTC)

As a model, it's probably not very accurate - since I wouldn't think there'd be a constant ratio difference between the total populations in 2 years now and in prehistory. The Black Death reduced Europe's population massively in the 14th century for example. But using the assumptions we have here;

P(n) = r P(n-1) where r > 1.

Let's rewrite that as P(n-1) = s P(n), where s < 1

B(n) = k P(n), i.e. B(n-1) = sB(n)

ok, so what we now have is just the sum of an infinite geometric progression, which sums to $\frac{B(2006)}{1 - s} = \frac{k \times\ P(2006)}{1-s}$ . I'm sure there are figures for P(2006) and P(2005) to calculate s, there might be figures about B(2006), so estimate $k = \frac{B(2006)}{P(2006)}$ . Then put it in the sum above. As I said, probably a very crude estimate Richard B 00:07, 28 September 2006 (UTC)

The answer to your title question depends considerably on how you chose to define "human", and whether or you want to count, for example, millions of years of walking apes. For some reasonable definitions (such as saying modern humans arise only near the start of agriculture or cities), it is not a stretch to argue that a substantial fraction of all humans that have ever been born are alive today. Dragons flight 01:11, 28 September 2006 (UTC)

I got lots of hits for "How many people have ever lived". The Straight Dope said in 1987 that demographers estimate between 69 and 110 billion. Another article dated 1999 said 96.1 billion (love that precision). The latter provides equations used to arrive at that estimate [4]. Clarityfiend 01:23, 28 September 2006 (UTC)

Wow, that would mean that 1 out of every 15 or so humans ever to live is alive today. — Knowledge Seeker দ 01:46, 28 September 2006 (UTC)

This is a Frequently Asked Question: Wikipedia:Reference desk archive/Humanities/2006 August 19#How to calculate the total human population, Wikipedia:Reference desk archive/Humanities/2006 August 22#Total World Population, Wikipedia:Reference desk archive/Humanities/2006 September 4#Number of Humans Since the Beginning, and Wikipedia:Reference desk archive/Humanities/2006 September 7#Number of humans that have ever lived. See also How Many People Have Ever Lived on Earth? with an estimate of 106 billion. --Lambiam ^Talk 04:04, 28 September 2006 (UTC)

 #!/usr/bin/python
 from __future__ import division
 
 def br(year):
   if year >= 2000:
     return 0.030
   if year >= 1990 and year < 2000:
     return 0.032
   if year >= 1980 and year < 1990:
     return 0.035
   if year >= 1970 and year < 1980:
     return 0.038
   if year >= 1960 and year < 1970:
     return 0.040
   if year >= 1950 and year < 1960:
     return 0.042
   if year >= 1925 and year < 1950:
     return 0.040
   if year >= 1900 and year < 1925:
     return 0.040
   if year >= 1875 and year < 1900:
     return 0.040
   return 0.040
   
 def dr(year):
   if year >= 2000:
     return 0.014
   if year >= 1990 and year < 2000:
     return 0.014
   if year >= 1980 and year < 1990:
     return 0.016
   if year >= 1970 and year < 1980:
     return 0.017
   if year >= 1960 and year < 1970:
     return 0.020
   if year >= 1950 and year < 1960:
     return 0.024
   if year >= 1925 and year < 1950:
     return 0.031
   if year >= 1900 and year < 1925:
     return 0.036
   if year >= 1875 and year < 1900:
     return 0.039
   if year >= 1750 and year < 1875:
     return (0.040 - 0.0057)
   return (0.040 - 0.0004)
   
 def gr(year):
   return (1.0 + br(year) - dr(year))
   
 # Main program
 P = {}
 P[2006] = 6.5E9
 B = {}
 year = 2006
 total = 0
 while P[year] >= 10:
   B[year] = P[year] * br(year)
   total = total + B[year]
   print "year %d pop %9.7g birth %9.7g total %12.7g" % (year,P[year],B[year],total)
   P[year - 1] = P[year] / gr(year - 1)
   year = year - 1

According the the python program above. The total number is around 99 billion.

Sweet. I want my kid to be human number 100000000000. freshofftheufo ΓΛĿЌ 05:36, 29 September 2006 (UTC)

Reality check. The above program says there were between 10 and 11 people in 43727 BC, way low. Those birth rates and death rates are just guesses.

 year -43724 pop  10.01154 birth 0.4004617 total 9.852964e+10
 year -43725 pop  10.00754 birth 0.4003016 total 9.852964e+10
 year -43726 pop  10.00354 birth 0.4001415 total 9.852964e+10

Also, the line "return (0.040 - 0.0057)" did you intend 'return (0.040 - 0.00057)' ? --GangofOne 10:13, 29 September 2006 (UTC)

In defence of the routine provided, you can't expect realistic results for every year, especially far in the past where the figures become largely insignificant. In reality, there would be one year in the past where zero humans were born (because they didn't exist yet), and the following year (imagine a year where homos became sapien) would show the birth of probably a few thousand. Since we can't really guess at the exact year, it makes more sense to write a function that approaches zero the further back in time you go. I agree, though, that getting a result of 10 only 40,000 years back will skew the results quite a bit, and I have given up on giving birth to the worlds 100000000000th child. freshofftheufo ΓΛĿЌ 11:56, 29 September 2006 (UTC)

The program does illustrate the exponential takeoff; it's just not numerically realistic. If you give birth, why not try for something doable, like 'the most beautiful baby in the history of the world.' You are very likely to achieve that. --GangofOne 23:00, 1 October 2006 (UTC)

[edit] Where are the "Fulcher bands"?

Deuterium spectrum w/fulcher bands(?).

I have been trying to validate my annotations to the discharge spectrum of a deuterium lamp for quite some time (see pic for my marked up version) and I can not for the life of me find a concise definition or spectrum showing the entire range of the so called "Fulcher bands". I am confident of my labelling of the balmer lines in the spectrum and pretty confident of the continuum radiation range note but I just don't know where the fulcher bands (are conventionally accepted to) begin. I have searched for hours through many many papers written through the last century on "fulcher bands" "fulcher system" and "secondary hydrogen emission/lines" and all I have found are refrences to the so called "q-branch" of the band, only above 600nm which is used along with the balmer lines to determine the ratio of molecular to atomic hydrogen in a plasma (only molecular H emits continuum and fulcher radiation). Can anyone here help? --Deglr6328 23:31, 27 September 2006 (UTC)

Not even a single comment?? :( --Deglr6328 13:51, 29 September 2006 (UTC)

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