Wikipedia:Reference desk/Archives/Science/2008 February 3

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February 3

Video

Watch this video then try and answer my questions

1) Does his theory on how to cure cancer even make sense?

2) Is there alternate fuel even sensible? Will it ever be put to use? Does it use too much salt water to work well?

Thanks, schyler (talk) 00:43, 3 February 2008 (UTC)

1) There is Radiofrequency ablation, but he'd need a way to make his metal particles selectively enter cancer cells, which the video never explains.

2) Absolute bullshit. Saltwater is, chemically speaking, fantastically stable. The process of burning would necessarily consume more energy in the form of radio waves than it releases as the products are burned. At best, this is just an efficient way of turning electrical energy into mechanical energy, but I'm not sure of that. Someguy1221 (talk) 01:05, 3 February 2008 (UTC)

You should be able to (eventually?) create artificial viruses that can target cancerous cells, but if you can do that, you can also get the viruses to inject a toxin that kills the cells without the extra radio signal. — Ƶ§œš¹ _{[aɪm ˈfɻɛ̃ⁿdˡi]} 07:32, 3 February 2008 (UTC)

Reminds me a little of this therapy, which is real (because it solves the problem of how to associate the metal particles with the cancer cells): http://nano.cancer.gov/news_center/nanotech_news_2005-10-17b.asp 71.196.233.110 (talk) 17:56, 3 February 2008 (UTC)

The cancer application sounds very reasonable, you can coat nanoparticles with antibodies to target them to the cancer. The burning water is cool, but just another (probably very inefficient) way to hydrolyze water. Сасусlе 23:39, 3 February 2008 (UTC)

Conveying thought process in audio/visual context

On television etc, the idea that someone is thinking is conveyed by changing the sound of their voice-I think it gets a bit deeper and echoey. Exactly what parameters are changed to achieve this effect and how might I go about emulating them in Windows and/or Linux? —Preceding unsigned comment added by Seans Potato Business (talk • contribs) 02:07, 3 February 2008

Get a sound editing progam (Goldwave, Audacity), then boost the bass levels with the EQ and add some reverb? Trimethylxanthine (talk) 02:31, 3 February 2008 (UTC)

Are those the only changes normally used? ----Seans Potato Business 02:43, 3 February 2008 (UTC)

It depends really...if it's the effect I think you're talking about then yea that's mostly all. I mean you could add other effects if you wanted, but it's just about getting the right type of reverb. Your best bet is to just play around and see what happens. I should point out I'm not actually trained in this sort of thing...I just used goldwave and stuff quite a bit :) Trimethylxanthine (talk) 00:57, 4 February 2008 (UTC)

Magnetic field

There is an ideal n × n × n lattice of aligned magnetic dipoles, d units apart. How much energy would be required to rotate the central dipole 180°, in terms of n, d, and any other nessecary variables? Thanks *Max* (talk) 02:10, 3 February 2008 (UTC).

Homework? Looks like it to me. Still, let me give you a hint. Magnetic field at the central dipole location is the vector sum of fields produced there by all the other dipoles. Oh, and I suppose n is odd, otherwise the "central dipole" is not very well defined. Good luck with your studies! Cheers, --Dr Dima (talk) 14:00, 3 February 2008 (UTC)

Actually it's not homework. I could guess the vector sum thing but I have no idea how to calculate magnetic fields. Also, I was thinking of writing n odd, but wouldn't it be unstable as a square lattice? Would it be any different in quantum and classical physics (I need the more presice ie. quantum answer)? *Max* (talk) 21:54, 3 February 2008 (UTC).

For magnetic field of a dipole, see Magnetic dipole. As for the stability of a two-dimensional quadratic or of a three-dimensional cubic lattice, with magnetic dipole interaction alone they would be unstable anyway, regardless of n being even or odd. You need an additional interaction to stabilize your lattice. Ferromagnetic condensed matter is stabilized by the electron pressure. That pressure is the result of a peculiar quantum-mechanical effect that prevents any two or more indistinguishable fermions (electrons in particular) from occupying the same state. Hope this helps. --Dr Dima (talk) 00:09, 4 February 2008 (UTC)

I don't really understand how to calculate the magnetic field or the amount of energy from that page. The stability part is not imortant to my question, but I meant any cubic lattice (as opposed to something like diamond). *Max* (talk) 03:15, 4 February 2008 (UTC).

Fried eggs

What is the minimum temperature required to 'fry' an egg? Article Fried egg doesnt seem to say.--TreeSmiler (talk) 02:23, 3 February 2008 (UTC)

According to Harold McGee

"...egg white begins to thicken at 63 °C and becomes a tender solid when it reaches 65 degrees". Furthermore, "The yolk proteins begin to thicken at 65 °C and set at 70 °C ...". (McGee, pp 85).

--hydnjo talk 04:19, 3 February 2008 (UTC)

Ah, so with a water bath it should be possible to cook the perfect soft-boiled egg! Skittle (talk) 13:52, 3 February 2008 (UTC)

I'm willfully misunderstanding here: Not a bath I'd want to take (70 degrees C = 158 degrees F). A small amount of 150 degree air is barely tolerable, but in water, it's intensely painful and then... you're dead.71.196.233.110 (talk) 17:51, 3 February 2008 (UTC)

At 70 °C, the yolk would set too. I'd want a much more reasonable 65 °C :) Skittle (talk) 01:51, 4 February 2008 (UTC)

Hi. Remember that when it's hot outside on a sunny day in a city, it can get hot enough to cook eggs even if it's under 63C. When it got just above 40C in Ontario one hot summer's day, the sun made the pavement hot enough to cook eggs and melt the soles of your shoes, and would probably give you a burn if you were for some reason walking barefoot on a day like that. Now let's hope global warming doesn't exceed its expectations or we'll have to fry eggs on the street. Hope tis helps. Thanks. ~AH1^(TCU) 02:33, 4 February 2008 (UTC)

Sounds too cool to fry an egg. Edison (talk) 03:27, 4 February 2008 (UTC)

Not so cool ! --hydnjo talk 07:35, 4 February 2008 (UTC)

As perhaps the previous comment refers to, the temperature of the air should not be confused with the temperature of the pavement; the latter can be higher due to absorbed radiation.--Patrick (talk) 11:50, 4 February 2008 (UTC)

Quantum Physics (again)

When I try to calculate this equation, it keeps giving me Hertz + Hertz + Joules = hc/λ. This is frustrating me and I don't know why it keeps doing this. I know about unit conversions and all that, but I'm typing in exactly what is given and it consistently comes out as hertz + hertz + joules. Could someone please explain why it's doing this? (all of the values are given above in the original question: Quantum Physics)

$E={\frac {\hbar ^{2}n^{2}\pi ^{2}}{2m_{e}R^{2}}}+{\frac {\hbar ^{2}n^{2}\pi ^{2}}{2m_{h}R^{2}}}+E_{g}={\frac {hc}{\lambda }}$

${\frac {\hbar ^{2}n^{2}\pi ^{2}}{2m_{e}R^{2}}}+{\frac {\hbar ^{2}n^{2}\pi ^{2}}{2m_{h}R^{2}}}$ is being given as hz + hz and then bandgap energy is given in joules.

Thanks in advance, Zrs 12 (talk) 03:07, 3 February 2008 (UTC)

I don't know what you're talking about, because the units work out perfectly for me. $n$, $\pi$, and $2$ are all dimensionless, so we can forget about them. $\hbar$ has units of $L^{2}MT^{-1}$ where $L$ is length, $M$ is mass and $T$ is time. $\hbar ^{2}$ has units of $L^{4}M^{2}T^{-2}$, $m$ has units of $M$, and $R$ has units of $L$, so $\hbar ^{2}/mR^{2}$ has units of $L^{2}MT^{-2}$, which is the same as energy. Where's the problem? —Keenan Pepper 07:29, 3 February 2008 (UTC)

(h / (2 * pi)) / ((1 (m^2)) * (1 kg)) = 1.05457148 × 10^(-34) hertz

Like there. What did I do wrong to make it come out in hertz? What should I change? (I used the google calculator). Zrs 12 (talk) 18:28, 3 February 2008 (UTC)

Looks like a typo—you didn't square the h-bar term. TenOfAllTrades(talk) 18:39, 3 February 2008 (UTC)

Oh my gosh! How could I make such an elementary mistake so consistently! Thank you all. That was the problem. Zrs 12 (talk) 18:48, 3 February 2008 (UTC)

what/is/the/resistance/of/humanbody/

Italic text —Preceding unsigned comment added by 59.93.198.63 (talk) 06:08, 3 February 2008 (UTC)

It's quite variable, depending on where you measure, skin condition, fat/lean content, the connections used, and other factors I can't think of offhand. This article should be illustrative. — Lomn 06:39, 3 February 2008 (UTC)

It also depends on what you're trying to resist.--Shantavira|^{feed me} 09:43, 3 February 2008 (UTC)

Presumably electricity (electrical resistance). —Pengo 14:22, 3 February 2008 (UTC)

Maybe Shantavira meant what type of signal? I doubt skin is an ohmic conductor. Trimethylxanthine (talk) 04:28, 4 February 2008 (UTC)

1200 Ohm was published on some obscure website.--Stone (talk) 13:02, 4 February 2008 (UTC)

That is clearly wrong. Although we're not supposed to, here's some original research. I found my ohmmeter and a box of resistors. Measuring from arm to arm, after having licked my fingers to reduce resistance at the surface, gave a reading of slightly over 100 kOhm. To verify this, I checked against various resistors, the closest being 130 kOhm. With dry skin, the resistance is considerably higher, and I was unable to get a consistent reading, but it is certainly higher than 500 kOhm. --NorwegianBlue ^talk 14:03, 4 February 2008 (UTC)

I had the same experience when measuring with an ohmmeter, but I think that it's lower at higher voltages (if it weren't then it would be safe to touch household power supply - you need about 50 mA to die or so I learnt). BTW, I've heard rumors that someone killed himself with a 9 V battery by inserting the contacts into the veins in his right and left hand .... Icek (talk) 02:03, 6 February 2008 (UTC)

Wow! Do you have a source? Googled it with no luck. Should qualify for a Darwin Award! --NorwegianBlue ^talk 09:10, 6 February 2008 (UTC)

Unfortunately not - I read it somewhere on the internet a few years ago. What is the electrical conductivity of blood and lymph? With a salinity of 0.7% it's maybe about 1 S/m (seawater's is 5 S/m according to our article, but other ions like phosphate will probably make blood's conductivity larger). If the current is 50 mA, then the conductance should be 1/180 S. If the distance between the contacts is 1.5 m, and we assume equal thickness along the conductor, its cross section should measure 83 cm², e. g. a cylinder about 5 cm in radius. At least it looks as if it could be true. Icek (talk) 14:41, 6 February 2008 (UTC)

Doubts

I'm going to study Telecommunication engineering in uk.After completing my degree can i get a job(Telecommunication engineer)easily&Cani earn High salary? —Preceding unsigned comment added by 124.43.214.206 (talk) 10:16, 3 February 2008 (UTC)

Depends on whether you'll be good (the best) at what you do, and whether there'll be demand for your line of work. I presume the answer to the latter is yes, now it depends on you how you handle the former. Cheers, Ouro (blah blah) 18:41, 3 February 2008 (UTC)

Species

I've heard it said that the largest group of organisms is insects. Is this true? Because I thought bacteria was the largest group. KarateKid101 (talk) 10:23, 3 February 2008 (UTC)

This of course depends on what you mean by 'group' (there are more animals than there are insects). It also depends what you mean by 'largest'. According to bacteria, there are about 5 nonillion bacteria on earth, making up much of the total biomass, but according to insect, insects make up the majority of known (and probably unknown) species, so presumably that is what is meant. Algebraist 12:50, 3 February 2008 (UTC)

Just to add, the concept of "species" often gets hazy with bacteria. —Pengo 14:20, 3 February 2008 (UTC)

Bacteria (and Archea, but there are less of them) form a kingdom (Monera), on the same level as Animals (Animalia). Insects (Arthropoda) form a phylum, a more specific classification. Monera is the largest kingdom and Arthropoda is the larget phylum. *Max* (talk) 22:00, 3 February 2008 (UTC).

If you follow Carl Woese's cladistic taxonomy, Bacteria and Archaea are two domains, and Animalia are but one of thirty or so kingdoms in the third domain, Eucarya. Monera does not exist as a taxon in this system. --ColinFine (talk) 00:50, 4 February 2008 (UTC)

General Paper essay question: "Boys are smarter than girls. How far do you agree?"

One of my arguments will be that in some areas, boys are smarter, but in others, girls are smarter. I recall reading somewhere that boys do better in maths and science tests while girls do better in languages. But I need hard facts and statistics, especially from scientific studies. Could someone give me a few links to hard facts and statistics and websites which are useful starting points for research? I tried Googling but because I did not know what search terms to use, I could not find much. —Preceding unsigned comment added by 59.189.60.87 (talk) 13:12, 3 February 2008 (UTC)

You might start with the articles on intelligence, gender, gender role, and gender identity and the links from those articles. If you are Googling, make sure your search terms specify "gender" rather than "sex"!--Shantavira|^{feed me} 13:28, 3 February 2008 (UTC)

Why? Sex is a biological concept. Do you have any good scientific basis for assuming that biology does not play a role in a child's linguistic/mathematical abilities? --72.94.50.76 (talk) 16:22, 3 February 2008 (UTC)

Why search for "gender" rather than "sex"? The latter will result in countless pornography links on Google, diluting the percentage of useful websites. --Bowlhover (talk) 21:24, 3 February 2008 (UTC)

Well, the role of gendering starts so early that disentangling the two is pretty much impossible. Go to a baby store sometime and look at what the options are. For boys it is "I LIKE DIRT AND TRUCKS" and for girls it is "I AM A PRETTY PRINCESS" (this is not, by the way, an exaggeration, but a direct quote. I was in a baby store just recently helping to buy some outfits for a friend's upcoming baby shower and was appalled at the choices. We ended up with "I LIKE DOGS" because it didn't seem to make strong assumptions about behaviors or inclinations, and both my wife and I like dogs and think that children should as well.) Assuming a biological difference in the face of overwhelming culture influence is not very scientific. --24.147.69.31 (talk) 16:27, 3 February 2008 (UTC)

The scientific approach to the problem is not to assume, a priori, that biology plays no role, but to actually try to measure the influence of biology empirically, and to conclude that biology has no effects on a child's linguistic and mathematical abilities only when empirical evidence supports such a conclusion. This is not the first time scientists have to deal with confounding variables. --72.94.50.76 (talk) 18:04, 3 February 2008 (UTC)

Who would assume it plays no role? Anyway, all modern scientists are well aware of the way in which the nature/nurture dichotomy is a false one. But for something like performance on standardized tests and in educational institutions, both of which have been heavily gendered for centuries in this country, anyway, it is foolish to assume that differences one sees are biological in nature. The idea that nature and nurture can be disentangled at all is a false one, as is now well known. Gender itself has biology as a component of it, but makes no pretense of getting rid of culture (or thinking that such a thing would make a lot of scientific sense, anyway—humans are cultural animals). As for scientists dealing with confounding variables—in studying human differences scientists have shown themselves over and over again to be unable to deal with such confounding variables in an objective fashion, hence most do not pretend today that the studying of human intellectual performance is anything close to pure biology. --24.147.69.31 (talk) 18:15, 3 February 2008 (UTC)

We have an article on sex and intelligence. —Pengo 21:37, 3 February 2008 (UTC)

brain activity

Which side of the brain is typically believed to control the ability to read? —Preceding unsigned comment added by 76.252.17.101 (talk) 14:26, 3 February 2008 (UTC)

Both. See Lateralization of brain function. —Keenan Pepper 16:33, 3 February 2008 (UTC)

(ec) Reading is a very complicated function that takes place in a number of places in the brain; this page gives a nice overview of all of the different faculties it engages. As for left vs. right, it depends on a number of things, included handedness, see Lateralization of brain function. --24.147.69.31 (talk) 16:34, 3 February 2008 (UTC)

Proposed article: Sensory Illusions on the Ocean

Analogous to the Sensory Illusions in Aviation article but dealing with various problems of perception encountered by sailors.

Possible inclusions: How the mind effectively uses the detail gradient of the water to estimate distances and related problems with doing so in darkness and fog. The problem with estimating distance to light sources due to the eye's adaptation to light levels. Perceived motion between blinking buoys. The mind's tendency to be drawn toward features in relatively featureless surroundings. Human tendency to follow a dog curve- failing to take into account the motion of wind and current, or the motion of the target object and therefore taking the ship out of a direct line route and into a constant angle curve of constant adjustment. The perception of the dome of the sky as being flattened (perceiving the sun and moon to be larger on the horizon, and how, when people are asked to point to halfway between horizon and zenith, they tend to point to around 38 degrees instead of 45 degrees). It's a psychological phenomenon, but I don't know if it causes any problems. How broken clouds can appear to be an unbroken bank when viewed from a low angle. How objects are judged to be larger than they actually are when seen alone in an otherwise featureless field. How white noise (wind, waves) contains all the frequencies found in speech, and are thus raw material for hallucinated voices when a person is fatigued. How humidity affects the speed of sound and thus the perceived distance that sound has to travel through it. How low frequencies travel farther than high frequencies, and thus can be used as a yardstick for estimating how far a sound has traveled (assuming one knows what it sounded like originally). Similar phenomenon with colors- the bluing of distance. How the smaller of two objects appears to the one that's moving when both are seen moving relative to each other. Limits of attention span. The phenomenon of radar-assisted collision (Andrea Doria vs. Stockholm). Seasickness. That's all I can think of. 71.196.233.110 (talk) 17:44, 3 February 2008 (UTC)

This ain't _really_ the place to put this, how about WP:AFC? --Ouro (blah blah) 18:38, 3 February 2008 (UTC)

Thanks. I didn't know there was such a thing, so you answered my question. 71.196.233.110 (talk) 20:50, 3 February 2008 (UTC)

Click here: Sensory Illusions on the Ocean and start to write the article - that's how it works here, it's a wiki. :-) Сасусlе 23:22, 3 February 2008 (UTC)

Voice

What is it that distinguishes a male voice from a female voice? Why do they sound different? Black Carrot (talk) 19:58, 3 February 2008 (UTC)

Length of vocal cord is the short answer, see Human voice. SpinningSpark 20:26, 3 February 2008 (UTC)

You might also find Castrato interesting. SpinningSpark 20:32, 3 February 2008 (UTC)

I was looking for a longer answer. Black Carrot (talk) 02:14, 4 February 2008 (UTC)

Is this l-o-n-g enough? --hydnjo talk 08:39, 4 February 2008 (UTC)

I think Black Carrots question is a good one, which deserves a far better answer than it has received so far. If it were a mere question of vocal cord length, which basically translates to frequency, it only begs several new questions:

• Why do children that have the same vocal cord length as women sound different from women, even if they speak in a grown-up way?
• Why does a song played fast sound like the chipmunks?
• Why is it usually easy to distinguish an Afro-American male from an American male of European descent, even when they use exactly the same words?

I'll try my best at answering, but this is far away from my areas of expertise, so if someone who actually knows something about this comes along, I shall gratefully stand corrected for any mistakes that I might have made. This is from the top of my head.

Anatomical reasons: The vocal cords in themselves produce a reedy sound, rich in overtones, something like a square or triangular wave (not sure which). The sounds produced are shaped by the resonances of the vocal tract. These resonances have fairly equal frequencies in women and men, but vary between the different vowels we produce because we change the shape of the resonant cavity when speaking. These resonant frequencies are called formants. The first three formants are the most important ones. What distinguishes one vowel sound from another is not the ratio of the fundamental frequency to the formants, but the ratio between the formants themselves. Therefore, when a woman speaks, the ratio between the fundamental and the first formant is quite different from the ratio between the fundamental and the first formant in a male voice. When you speed up a song, the ratio between the formants is preserved, but they have the wrong frequency. Therefore, you recognize the words, but it sounds unnatural. Children have smaller heads, and lack fully developed sinuses. I would expect that this results in their formants being located at a higher frequency, but since the ratio is preserved, the vowels are easy to distinguish. This may be one of the reasons for the wonderful timbre of a boy soprano, the elevated frequency of the first formant is well above the frequency of the fundamental, making it easy to distinguish the vowels. (WARNING: WP:OR). In contrast, adult female sopranos have a problem in that their highest notes have a frequency similar to the first formant, making it difficult to distinguish vowel sounds at high frequencies.

Cultural reasons: It is my impression that women chose different words, and also intonate slightly differently. This may vary from culture to culture. The stereotype gay parody in TV shows comes to mind. I would also suspect that cultural reasons explain the relative ease in distinguishing a male Afro-American from a male American of European descent.

Disclaimer: I am not an expert in this field. The above may contain mistakes. If you know something about this, please correct the mistakes. --NorwegianBlue ^talk 13:14, 4 February 2008 (UTC)

My impression is that "stereotypical" gay and black speaking styles are nothing more or less than accents. --Sean 00:01, 5 February 2008 (UTC)

Agreed, and that was exactly my point - there may be male and female accents or manners of speach, which may be difficult to separate from the physical features of the male/female voice. --NorwegianBlue ^talk 00:44, 5 February 2008 (UTC)

Human hair growth rate

Hi there, I was just wondering how quickly human hair grows, ie if I wanted to grow my hair down to my shoulders, how long would it take (it's only about 1cm long at the moment)?

Also, is there any truth in the old rumour that hair grows faster if you cut it? GaryReggae (talk) 20:31, 3 February 2008 (UTC)

Have you looked at the Hair article? This gives some figures for growth rates. I don't believe cutting makes any difference, the hair is already dead when it is cut. SpinningSpark 20:37, 3 February 2008 (UTC)

The reason it may seem to grow faster when cut is because if you let it grow out, it will reach a point where hairs are falling out at about the same rate as they are growing, so it hits a kind of equilibrium. If you cut it, then you take it back from that equilibrium so it is more likely to grow fast again. Confusing Manifestation(Say hi!) 22:04, 3 February 2008 (UTC)

Hair as food

Could a chemical process render the protein in human hair and that of other animals, accessible to the human digestive system (and perhaps that of other animals) and is it worth it? What makes it so indigestible in the first place? ----Seans Potato Business 21:07, 3 February 2008 (UTC)

Keratin makes it indigestible. You would be better off trying tofind a way to make grass digestible (other than the machines known as cows) SpinningSpark 21:10, 3 February 2008 (UTC)

why not boil it with lemon juice to break down the protein - making soup?87.102.0.66 (talk) 21:19, 3 February 2008 (UTC)

This IS done to some extent. Lots of chicken feathers (made of a keratin similar to that in hair) are processed to produce a product called hydrolysed feather meal which is used in animal feed. Its use is limited by it's amino acid composition; most animals can not get enough of all the amino acids they need from feather meal alone, so it is mixed with other things. Feather meal is sometimes made even more bioavailable by treatment with a keratinase enzyme; I know of a company called BioResource International that markets a keratinase called Versazyme for just this purpose. ike9898 (talk) 21:10, 4 February 2008 (UTC)

Ashes to Diamonds?

Hi. I was listening to a song (Blunt Ashes - Nas (Hip Hop Is Dead)), and in the very beginning, he talked about how a man had his son cremated when he died, and had the ashes made into a diamond ring (so he could see his son shine everyday, or something to that effect). I'd like to know if that's possible, making someone's ashes into a diamond. Does it depend on their size? What would the quality of the diamond be? Is it legal? Thank you. 70.105.164.43 (talk) 21:09, 3 February 2008 (UTC)

Yup. We have an article about LifeGem, a company that does this. (EhJJ) 21:17, 3 February 2008 (UTC)

:(edit conflict)Diamonds can be synthetically made from carbon. The common name for these is zircon, but not to be confused with the mineral of the same same. The proper name for synthetic diamond is cubic zirconia and our article will explain how this is done. As ash is largely carbon, I guess this is possible. Whether it is legal, we are forbidden to give legal advice (not that I know). SpinningSpark 21:19, 3 February 2008 (UTC) Sorry, that answer is completely wrong. SpinningSpark 21:27, 3 February 2008 (UTC)

Here is the correct article Synthetic diamond. SpinningSpark 21:33, 3 February 2008 (UTC)

And what is made into a Diamond is not actually ash, but rather carbon extracted from the corpse (which apparently is charred first, not burned, as that would convert the carbon into CO2). --Stephan Schulz (talk) 22:01, 3 February 2008 (UTC)

Bromelain and other digestive enzymes

Would protein digestive enzymes allow ones body to absorb and use more protein if large amounts of protein are consumed?

Also, would digestive enzymes reduce flatus caused by some foods? —Preceding unsigned comment added by 71.106.9.137 (talk) 21:28, 3 February 2008 (UTC)

I think to some extent, yes to both. I believe that in research, animal nutrtionists test for unabsorbed protein in manure as part of determining how bio-available the protein is. I think that most of the protein that humans eat is highly bioavaible and thus almost completely broken down and absorbed. Some of the really cheap stuff that people attempt to feed to livestock has poorly bioavailable protein. It is possible that this unabsorbed protein could be used by intestinal microbes as both energy and nitrogen sources to grow and possibly produce gas. This is at the periphery of my knowledge, so hopefully some others will chime in. ike9898 (talk) 21:03, 4 February 2008 (UTC)

P.S. If you're talking about humans taking doses of enzymes orally, that might not work. Chances are that they would get denatured in the low pH environment of the stomach before they had a chance to do much good. ike9898 (talk) 21:03, 4 February 2008 (UTC)

bonds between magnesium and flourine

How are bonds between Mg and F formed? I know that the compound resulting will be MgF₂ (magnesium flouride), but why and how exactly does that happen? —Preceding unsigned comment added by 76.214.199.203 (talk) 21:36, 3 February 2008 (UTC)

Because flourine's and magnesium's electronegativity difference is greater than ~1.7, they will form an ionic bond. An ionic bond usually forms between a metal (magnesium) and a non-metal (flouride). They must both first become ions by losing or gaining electrons; the electrons are "donated" to the other ion to form a shared, stable octet between both of the elements, thus bonding them. --Emery (talk) 22:03, 3 February 2008 (UTC)

I.e., it is not a stable bond, it is more an attraction. Сасусlе 23:17, 3 February 2008 (UTC)

Fasting

What are the reasons for fasting before surgery? --~~MusicalConnoisseur~~ Got Classical? 22:29, 3 February 2008 (UTC)

To prevent asphyxiation and pneumonia due to pulmonary aspiration caused by gastroesophageal reflux. Сасусlе 23:15, 3 February 2008 (UTC)

It is common for someone under anaesthesia to vomit. While this is usually immediately cleared by using a suction device, it is possible for the patient to inhale the vomit resulting in choking or, I believe more frequently, aspiration pneumonia. By fasting before surgery, this potential complication can be minimized.(Pretty much what Cacycle said, except for the gastroesophageal reflux disease part which I think is an imprecise redirect.) (EhJJ) 00:17, 4 February 2008 (UTC)

Earth's orbit and time dilation

In theory, time dilation makes time go by slower at higher speeds, and conversely, time go quicker at lower speeds. A person on Earth, moving at 107,218 km/h per our planet's average orbital speed, would normally last ± 75 years. So, if one person was brought to outer space in a space ship, freeing itself from any kind of orbit, and then the space ship slowed down to a complete hault (0 km/h), would that person age and die much quicker due to time going by quicker? -- Leptictidium (mammal talk!) 23:24, 3 February 2008 (UTC)

If by "much quicker" you mean 2.37 11.8 seconds sooner, with respect to the sun, then yes. (I think I did my math right) Someguy1221 (talk) 23:29, 3 February 2008 (UTC)

Does that mean the difference between going a 107,218 km/h and standing still is only 3.15 seconds per century? -- Leptictidium (mammal talk!) 23:32, 3 February 2008 (UTC)

Oh, I made a slight error (factor of five disappeared somewhere). It's an extra 15.8 seconds a century (11.8 seconds for 75 years). This is a simple matter of applying the lorentz factor. Someguy1221 (talk) 23:38, 3 February 2008 (UTC)

It's not immediately clear (to me at least) that you can use the Lorentz factor here because the orbit itself is due to gravity. The speeds involved are small, but the value we care about is also small; we might be deep in the general relativistic regime here. Assuming the Schwarzschild metric and two test particles, one in a circular freefall orbit and one stationary at one point on the orbit, I get an elapsed time ratio of exactly ${\sqrt {1-{\frac {\beta ^{2}}{1-{\frac {2m}{r}}}}}}={\sqrt {\frac {1-3{\frac {m}{r}}}{1-2{\frac {m}{r}}}}}$ where $m$ is the mass of the sun (about 1.5 km), $r$ is the radius of the orbit, and $\beta ={\sqrt {\frac {m}{r}}}$ is the orbital speed. Using the Lorentz factor you get instead ${\sqrt {1-\beta ^{2}}}={\sqrt {1-{\frac {m}{r}}}}$, which... is almost identical when $r\gg m$. Oh well. If the "orbiting" particle is actually riding on the Earth's surface, you also have to consider the effect of Earth's rotation and its gravity. I think the former is negligible but the latter isn't; it contributes a factor of ${\sqrt {1-2{\frac {m_{e}}{r_{e}}}}}$, which is comparable to the orbital factor. -- BenRG (talk) 15:33, 4 February 2008 (UTC)

And just remember Einstein's great catchphrase, "It's all relative!" May not be actual catchphrase - when you say "complete halt", theoretically you mean relative to the Sun. Of course, there are then other issues that complicate things, including the fact that if your space ship is anywhere near the sun but not orbiting it it's going to fall in, and the results of general relativity that say that being in a gravitational field has its own type of time dilation involved. Confusing Manifestation(Say hi!) 06:27, 4 February 2008 (UTC)

But if a spaceship was programmed to compensate for any force applied to it by applying an equal force in the opposite direction, then it could be truly static, couldn't it? -- Leptictidium (mammal talk!) 12:10, 4 February 2008 (UTC)

If you are thrusting against gravity that would be an accelerated reference frame and thus general relativity applies. Even if we pretended the sun didn't exist, it would still be a problem for general relativity because we would then be comparing frames between the person in space that is in a non-accelerated reference frame to the person on the earth who now would be moving in a circular path which is an accelerated frame. But the important thing to note is that each person notices no difference in the passage of time; barring any tragic accidents they both live to be roughly 75 years in their respective frames. Simple calculations using special relativity would only apply if there were negligible gravity around and both parties move in straight-line motion, non-accelerated frames. -- Altered7th —Preceding comment was added at 14:01, 4 February 2008 (UTC)