Science desk
< February 9	<< Jan \| February \| Mar >>	February 11 >

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

February 10

Why do things "inflate" when their velocity gets closer to the speed of light or "c"?

In Stephen Hawking's book "A breif history of time",

it says that as one has the velocity of 10% speed of light,it would be 0.5 times more it's normal mass

and as it approaches 90% ,it is at least 2 times more.

let it be negligible....but could you pls tell me , is it possible to trap the energy of ordinary light we get from our bulbs....also tell me is it possible to construct an artificial but long lasting circuit to trap the energy of visible light...Bhaskaran 88 10:34, 10 February 2007 (UTC)[reply]

When you say "trap the energy of ordinary light", are you refering to things like solar panels? These can collect energy, but unfortunately, they are very uneffective (only about 10% of the energy which hits them is trapped". As for the inflation effect, it is a result of special relativity. For full info see Mass in special relativity, but in effect, because E=mc², as E (the energy of the object) increases, m (the mass of the object) also has to increase to balance out the equation. Giving the object more energy by making it move faster also gives it more mass. Laïka 15:56, 10 February 2007 (UTC)[reply]

Not entirely true. The best tandem solar cells to date have a conversion effiency around 31%. The best crystalline Si cells are pushing 25% effiency (pretty darn good considering that the theoretical maximum effiency for an Si quantum conversion PV cell is around 30%). Compared with other forms of electrical energy conversion, solar cells are pretty efficient. -- mattb @ 2007-02-10T18:43Z

trap the energy of visible light

let it be negligible....but could you pls tell me , is it possible to trap the energy of ordinary light we get from our bulbs....also tell me is it possible to construct an artificial but long lasting circuit to trap the energy of visible light...

This kind of device is called a solar cell. It is not 100% efficient, or very low cost, but it is useful in isolated or portable electrical items. This electricity can charge a battery. Most of a light bulb's energy comes out as heat rather than light. GB 12:14, 10 February 2007 (UTC)[reply]

A black object will absorb energy from a light bulb. The absorbed energy will cause it to become hot. An "artificial but lonfg lasting sircuit to trap the energy of visible light" might be a black object surrounding a light bulb. Most of the electricity used by a light bulb is emitted as invisible infrared light at too long a wavelength to be seen. Edison 07:25, 11 February 2007 (UTC)[reply]

Random junk.

here are a few sciency questions I don't understand. So i decided to put them all here and see if anyone else can understand. Some of them probably don't make any sense, but any help with those that do will be appreciated.

Why does helium float? What is it that makes it move upwards?
How much does helium weigh?
What is it that prevents a muscle from contracting when trying to move something that is too heavy?
Why does everyone look the same? Most people have two legs, two arms, one head &c, but DNA is just a list of proteins, so where does the rest of the information come from?
Why do things break if you drop them?
If a hollow ball could be made so that all of its surface was exactly the same thickness, and the pressure inside it increased, where would it break?
Why do the speakers on my computer make a noise when I touch the wire that should plug into the computer?
If I had a lump of iron, what would I have to do to turn it into a magnet?
How much could someone grow in one day before they ran out of all the chemicals they need to make more of themselves, and how fast could they grow if all their cells were dividing as fast as possible?
What happens to a birds feathers around its elbows and wrists when it folds up its wings? Shouldn't they get screwed up or damaged or something?
How much energy could someone respire to produce one litre of carbon dioxide?

Hidden secret 7 12:05, 10 February 2007 (UTC)[reply]

Helium is less dense than air. It is the same reason rocks don't float.
Helium has an atomic mass of 4.002602 grams per mol. (Air has a mass of 28.97 g/mol)
The muscle does contract, there simply is not enough force to move the thing!
All the information that make us look the same come from DNA. Proteins can do marvelous things!
Because they are not strong enough to resist the fall?
There is no way to tell. If it does actually break, yhe probability that it would break at any given point would be equal for all points on the ball.
I've wondered the same myself.
See Magnet#Magnetization of materials
If they kept eating, would they ever run out of the necessary nutrients?
I don't think feathers grow in such a pattern that this matters.
The average person breathes in about 500 mL per breath, and the average amount of CO₂ in exhaled air is 4.5%, or 22.5 mL. This would take 44-45 breaths to do, and at a rate of 15 breaths per minute, this would take 3 minutes.

− Twas Now ( talk • contribs • e-mail ) 12:37, 10 February 2007 (UTC)[reply]

Might I suggest a collaborative effort for this question, since I think it will be clearer. I've copied Twas Now's answers below, with edits as I think they should be. Could other's improve them? Skittle 18:02, 10 February 2007 (UTC)[reply]

Helium is less dense than air. It is the same reason rocks don't float.
Helium has an atomic mass of 4.002602 grams per mol. (Air has a mass of 28.97 g/mol) At atmospheric pressure, at 0^oC, helium has a density of 0.1786 g/L, which means a litre weighs 0.1786 grams.
The muscle does contract, there simply is not enough force to move the thing!
All the information that make us look the same come from DNA. Proteins can do marvelous things!
When things fall, they convert their gravitational potential energy to kinetic energy (they go from being motionless high up, to moving quickly low down). When they hit the ground, that kinetic energy can't just vanish. It can be converted into a lot of things: sound energy, heat energy, kinetic energy in the other direction (if the thing bounces), deformation energy... That last is the thing that breaks or bends things. Another way of looking at it is to think of the object going from falling quickly to being still in a very short time. This means it has a large negative acceleration. From F=ma, you can see that the force on the object will be large, and that force can break it.
There is no way to tell. If it does actually break, the probability that it would break at any given point would be equal for all points on the ball.
If it was completely uniformly strong, it would break simultaneously at every point. In practice there will be thin or weak points that stretch more and fail first. A completely uniform material with no defects would be very strong - eg nested buckyballs, diamond, they could withstand pressures over 100 gigapascals (one million atmospheres). GB 20:59, 10 February 2007 (UTC)[reply]
I disagree. I think it would break at wherever it was hit, like at the bottom if it's dropped to the floor. – b_jonas 10:23, 11 February 2007 (UTC)[reply]
Sure, but the question was about it breaking from internal pressure alone. For which, Graeme's answer is right. --Anonymous, February 11, 23:51 (UTC).
Oh yeah. It's the previous question that said "drop". – b_jonas 23:47, 18 February 2007 (UTC)[reply]
I've wondered the same myself.
You may be putting a static discharge into the cable, you may be jostling a loose connection. There may be a piezoelectric effect in the cable insulator. It does not happen on my speaker cables! GB 20:59, 10 February 2007 (UTC)[reply]
See Magnet#Magnetization of materials
If they kept eating, would they ever run out of the necessary nutrients?
Feathers grow in cunning patterns that fold neatly into place when a bird folds its wings in the proper way.
The average person breathes in about 500 mL per breath, and the average amount of CO₂ in exhaled air is 4.5%, or 22.5 mL. This would take 44-45 breaths to do, and at a rate of 15 breaths per minute, this would take 3 minutes. According to our article Respiration (physiology), aerobic respiration of glucose produces 6 moles of CO₂ and 2830 kJ of energy for every mole of glucose used. Now CO₂ has a density of 1.6 kg/L and each mole weighs about 44g. So there's about 36 moles of CO in a litre. This means about 16980 kJ produced for every litre of CO₂ exhaled.

note* 16980 kJ is approximately 71 food calories. --Wirbelwindヴィルヴェルヴィント (talk) 18:14, 10 February 2007 (UTC)[reply]

(edit conflict)

1. Helium floats up because the less dense want to be above. It's the same reason when you try to hold a balloon under water, the balloon wants to force itself up above water, because water is more dense than air.

It's not so much that what is less dense wants to be higher, but what is more dense wants to be lower. Gravity pulls everything down. But if it pulls a set volume (say 1 L) of helium down, it has to move 1L of air out of the way first. It's a lower energy situation to have the more massive thing lower, and the lighter thing higher, so that's what happens - the air goes down, and the helium is pushed upwards by the air coming downwards. See Buoyancy -- 20:16, 10 February 2007 (UTC)

5. Because the potential energy is being converted into kinetic energy, so there's a downward force caused by gravity.

7. There are electric signals in you, which is why EKGs work. I've been using an instrumentation amplifier, such as ones used for EKGs. Before we filtered noise, the output amplified signals changed significantly just from our hands being near, much less touching it. Using a multimeter, you can actually get a reading of how much resistance it is from hand to hand.

If you connect to an amplifier and speaker you get a popping sound as the nerves fire. The electrode has to be over a muscle - eg the thumb pad. GB 20:59, 10 February 2007 (UTC)[reply]

9. I'm not sure about this one, but aren't there cases of cancer growing uncontrollably fast?

10. Correct me if I'm wrong, but feathers by the elbows and wrist fold in a way that it overlaps each other. Sort of like cards. You have your cards fanned out when you're playing, but they still fold up nicely into a deck afterwards.

-Wirbelwindヴィルヴェルヴィント (talk) 18:07, 10 February 2007 (UTC)[reply]

I actually meant to ask how much helium weighed relative to the air arround it, and therefore how much weight a helium balloon &c could lift:) Apart from that I think I have all the answers I wanted, and more than I expected, thanks:) Also are you sure you didn't mean 16980J:?HS7 21:04, 10 February 2007 (UTC)[reply]

Okay, under ordinary temperature and pressure 1 mole of any gas occupies the same molar volume of 22.4 liters -- I'll say 22 liters to work in easier numbers. The molecular weight of helium is 4. Air is 21% oxygen (molecular weight 32), 78% nitrogen (mol.wt. 28), and 1% argon (mol.wt. 40) for an average mol.wt. of just about 29. So 22 liters of helium weighs 4 grams while the same volume of air weighs 29 grams. Therefore 22 liters of helium in a balloon will lift 29 - 4 = 25 grams. To lift 100 grams you need 22 × 4 = 88 liters, to lift 1 kg you need 880 liters. Of course the weight of the balloon itself must be deducted from the lift. Note incidentally that using the only available gas that's lighter than helium, namely hydrogen, does not improve the lift very much (and of course does create a significant fire hazard). 22 liters of hydrogen will lift 29 - 2 = 27 grams instead of the 29 - 4 = 25 grams for helium. --Anonymous, February 12, 2007, 00:00 (UTC).

Oops, I did it in relation to joules. I assume he meant joules too, else that's too much energy. --Wirbelwindヴィルヴェルヴィント (talk) 22:05, 10 February 2007 (UTC)[reply]

Only if our article on respiration (physiology) has got J and kJ confused. And here we see the dangers of self-reference... Skittle 22:56, 10 February 2007 (UTC)[reply]

We still haven't really answered #7. What sort of noise were you hearing when you touched the speaker wire? And were you touching just the wire itself, or the metal tip of the connector? And were these plain or amplified speakers?

I assume (since you said you were plugging them into your computer) that these are powered speakers, and I assume you were in fact touching the connector. But I'm not 100% sure what noise you heard.

If the noises were single clicks or pops, as other posters have suggested, they're likely static electricity discharges, or momentary flows of current due to the capacitance of your body. (Either some stored charge on your body is flowing into the speaker circuit, or an electrical potential in the speaker circuit is flowing into and charging you.)

But if -- as is more likely -- the noise was a continuous, low hum or buzz, that's the 60Hz (or 50Hz if you're in Europe) frequency of the AC electric power supply that's ubiquitous in the developed world. Electricity is everywhere, and your body acts as an antenna to pick it up. If your speakers are powered, their amplifier is sensitive enough to pick up the tiny amounts of radiated energy which your body is picking up, and amplify it so that it can be heard.

I just turned on my own speakers and touched the connector, and got a loud 60Hz buzz, just as I expected. (It was a no-brainer, as I hear that sound whenever I grab that connector to connect it to my iPod or computer.) Then I held my hand near the room lights, and the sound got louder. Then I held my hand near an outlet, and the sound changed. Then I touched the grounded metal screw on the outlet cover plate, and the sound diminished. (By grounding myself, more of the signal I was picking up drained into the ground, and was unavailable to the speakers.) Then I turned off the room lights, and the sound decreased quite a bit. Then I turned the lights back on, and played with the dimmer, and the sound changed some more. Because of the way they "chop" the AC sinewave, dimmers are notorious for injecting buzzing noises into inadequately shielded audio circuits.

If you have an oscilliscope handy, you can touch its input connector with your finger and see a nice 60Hz sine wave, confirming the above.

If you had some battery-powered speakers, and if you took them 'way out in the country, away from any human habitation, and as long as there wasn't a cross-country transmission line nearby, you might be able to touch the connector and get no buzz at all. —Steve Summit (talk) 22:30, 10 February 2007 (UTC)[reply]

Per 8) You could magnetize a lump of iron simply by hitting it with something hard while it was in the Earth's magnetic field or by placing it in a stronger magnetic field produced by a permanenet magnet or a coil of wire with DC current going through it. Edison 07:20, 11 February 2007 (UTC)[reply]

Density of protein crystals

Attempting to answer a question on the reference desk of the Spanish wikipedia, led me into doing some calculations that left me rather confused. My a priori assumption was that the density of a crystalized protein would be somewhere in the vicinity of 1g/cm³. The PDB entry corresponding to human erythrocyte catalase, 1DGB, includes the following:

Unit Cell: Length (Å) a=83.50, b=139.93, c=227.89. Angles (°) alpha=90.00, beta=90.00, gamma=90.00.

Question 1: Does this imply that one molecule of crystalline human erythrocyte catalase occupies the space corresponding to a cuboid with sides 83.5Å, 139.9Å and 227.9Å?

If the answer is yes, and if I'm not making some stupid error in my calculations, the molecule would occupy a volume of 2662131 cubic Ångströms, corresponding to 2.66 × 10^-18 cm³. One mole of crystalline catalase would then occupy 2.66 x 10^-18 cm³ × Avogadro's constant = 1597279 cm³, and given the fact that the molecular weight of catalase is approximately 250000 g/mol, the density of crystalline catalase should be approximately 250000 g/mol / 1597279 cm³/mol = 0.16 g/cm³.

Question 2: Where is the error?

Is my a priori assumption about the density wrong, is my understanding of a "unit cell" in the PDB wrong, or am I making some silly mistake in the calculations? --NorwegianBlue^talk 17:03, 10 February 2007 (UTC)[reply]

I had a look and I don't think you've made an error - the volume seems right. Is the molecular weight right? The explanation I'd come up with (if I too haven't made simple mistake) is that proteins typically contain a lot of space in between the chains - no matter how folded - this would give the low density.87.102.9.117 17:49, 10 February 2007 (UTC) Consider the space filling model of the protein - there are many places small molecules (such as water) could go - so the structure is far from close packed - hence the lower density than say water or diamond..87.102.9.117 17:51, 10 February 2007 (UTC)[reply]

I'm reasonable sure about the molecular weight being somewhere between 230 and 250 kDa, see for instance this source. --NorwegianBlue^talk 18:20, 10 February 2007 (UTC)[reply]

I guess so - I'm not a enzyme expert - did the 'space between protein strands' explanation seem plausible?87.102.9.117 18:57, 10 February 2007 (UTC)[reply]

Well, the problem is that the calculated density is only a sixth of what I expected it to be, but if that indeed is correct, your explanation would of course be plausible. My initial assumption about the density is based on

The density of the human body is approximately 1 g/cm³.
I expected the density of a crystallized protein to be approximately equal to that of a compact carbohydrate, since the atomic weights of carbon, nitrogen and oxygen are the same order of magnitude, and since carbohydrates and proteins have similar hydrogen content. Glucose is 1.54 g/cm³. Paper can be close to 1 g/cm³.

When rotating the 3D structure, I find it hard to see that only one sixth of the space is "occupied". --NorwegianBlue^talk 19:52, 10 February 2007 (UTC)[reply]

I agree it seems to low - here is something else - maybe the molecular mass is that only of the protein - I would expect considerable water of crystallisation in the crystal - bumping up the density.87.102.9.117 20:00, 10 February 2007 (UTC)[reply]

By the way one possible explanation for a low figure is that the unit cell contains more than one enzyme unit - in different configurations - this would increase the density you calculated obviously.87.102.9.117 19:14, 10 February 2007 (UTC)[reply]

Very true - 1DGB contains four peptide chains per asymmetric unit (Although the ~240 kDa figure appears to be for the tetramer). A much bigger reason for the error is that you have neglected to include the mass of the water in the asymmetric unit. Protein crystals aren't like salt crystals - they're more like set gelatin. Each protein molecule is surrounded by a large number of water molecules. If you look at the .pdb coordinate file for 1DGB, you'll see there are over 1000 water (HOH) molecules listed. This only includes those water molecules which are stationary enough to have significant electron density. There are many more which are too disordered to be seen distinctly. -- 20:00, 10 February 2007 (UTC)

It certainly would. How can one read what's in a unit cell from the PDB entry? The "space group" is listed as P2₁2₁2₁. If that means that there are 8 molecules in a unit cell, we would have linear dimensions one half of those I gave above, and a density of 1.3 g/cm³. To me, that seems more reasonable. --NorwegianBlue^talk 19:56, 10 February 2007 (UTC)[reply]

That would be my guess too - but I'm not familar with the meanings of each space group - a separate question would confirm what the space group describes.87.102.9.117 20:57, 10 February 2007 (UTC)[reply]

On checking it seems that the space group can have just one molecule per unit cell. If you wan't to ask about the space group the maths desk might be a good place to try as well..87.102.9.117 21:01, 10 February 2007 (UTC)[reply]

effect of reversing real and imaginary components in the Schrodinger Wave Equation

In the time-independent Schrodinger Wave Equation, I noticed that if you interchange the real and imaginary components of all wavefunctions, the value of the wave equation remains unchanged. Is this correct, and is it of any significance? The Mad Echidna 18:54, 10 February 2007 (UTC)[reply]

I'm not sure that it is correct - but someone else will no doubt correct me - are you sure you don't mean the complex conjugate of the wave function?87.102.9.117 19:02, 10 February 2007 (UTC)[reply]

For example in a very simple case were the wavefunction is

f(x) = e^ax then d²(f(x))/dx² = a² e^ax = a² f(x)

where as if you reverse getting

f(x) = e^aix then d²(f(x))/dx² = -a² e^aix = -a² f(x)

So there is a change of sign in this simple example - not exactly the same.87.102.9.117 19:08, 10 February 2007 (UTC)[reply]

No, I meant if you change a + bi into b + ai, for all wavefunctions in the time-independent wave equation, what happens then? The Mad Echidna 19:59, 12 February 2007 (UTC)[reply]

In general if you change a + bi into b + ai the eigenvalue changes.. If a and b are parameters in the wavefunction. (There might be a wavefunction than doesn't change it's eigenvalue but in general the eigenvalue changes)

Is that what you meant? I was thinking you might have a wavefunction such as e^a+ib or similar? ? 87.102.16.197 21:54, 12 February 2007 (UTC)[reply]

Hi, thanks very much for this. The reply is a useful one, and tells me something new, but I don't think I'm getting across precisely what I mean, perhaps because I don't have the background knowledge. I was referring to a wavefunction which is just in the form a + bi, not e^a+ib. The values a and b would both be functions in themselves, rather than parameters, so I am not talking about any specific wavefunction, just all wavefunctions generally. Then, as I have understood it, the time-independent wavefunction depends on the amplitude of the wavefunction only, not the specific values of the real and imaginary components. This would mean that they could be interchanged without altering the probability at any part of the wave. The Mad Echidna 22:48, 13 February 2007 (UTC)[reply]

I think I have a good explanation. Isn't this true of ANY equation? When I was learning about complex numbers, we were taught to plot them onto a chart with the real part running along the X axis and the imaginary part on the Y axis. By switching over real and imaginary parts, all you are doing is making a mirror image of the chart in the X==Y line. So isn't it the case that any equation whatever with real and complex parts works equally well if you swap them? In the end, the fact that we stick an 'i' after the 'imaginary' component is just a notational convenience. We could equally well have decided to put an 'r' after the real part instead. Arithmetic doesn't care either way. SteveBaker 01:20, 14 February 2007 (UTC)[reply]

I'm probably not helping you much - but no - if the wavefunction is fn1(x)+ifn2(x) you are right that the magnitude is indepedant of swapping, but the solution to the shroedinger equation will change - though there may be possibilities were it doesn't. It really depends on what those functions are.. 83.100.158.13 08:22, 14 February 2007 (UTC)[reply]

When you say 'the value of the wave equation' I assumed you meant the eigenvalue, maybe you meant something else.?83.100.158.13 08:29, 14 February 2007 (UTC)[reply]

eg if FN(x) is the function a(x)+ib(x) and V(x) is the energy potential (this can be 0 if you want to simplify) (k is a constant) then

k d²
  --  FN(x) + V(x)FN(x) = E times FN(x)
  dx²

Now only certain functions give solutions to this - because E is just a number - mostly notably exponentials, and also sines and cosines.. It's a differential equation - I'd suggest trying this with different functions and swapping and see what happens.83.100.158.13 08:55, 14 February 2007 (UTC)[reply]

No, this is in fact helping me a lot. To clarify my understanding (if you're still reading, which I hope) I'll use the notation F(x) = a(x) + ib(x), and (D) means to take the derivative along x. Using V(x) = 0 for simplicity, the equation becomes: k(D)(D)F(x) = E*F(x). Let F(x) = a(x) + ib(x) be a solution. This is true if and only if k(D)(D)[a(x) + ib(x)] = E*[a(x) + ib(x)], which is equivalent to the simultaneous equations k(D)(D)a(x) = Ea(x) and ki(D)(D)b(x) = Eib(x). The "i" cancels on both sides in the last equation, so k(D)(D)b(x) = Eb(x). The equations for a(x) and b(x) are exactly the same, so swapping them will generate another solution, ie k(D)(D)[b(x) + ia(x)] = k(D)(D)b(x) + ik(D)(D)a(x) = Eb(x) + iEa(x) = E[b(x) + ia(x)], so the equation holds (assuming k and E are real). This would appear to confirm the whole thing for all cases with V(x) = 0. Have I mucked something up? Thanks again for all the help, since you've obviously put a lot of time and thought into this. I hope my notation isn't too messy, but I haven't checked how to do the prettier notation, and I didn't want to mess it up. Cheers! The Mad Echidna 02:17, 16 February 2007 (UTC)[reply]

ok First of all I should point out your assumption that you can separate the a(x) and b(x) components won't always be right - it almost always will be - that's a minor point you can ignor for now (though consider equations including sqrt(x) if x can be negative )

Otherwise yes what you have said seems right - as long as a(x) and b(x) are the same function - I didn't realise you meant this before. In fact if a(x) and b(x) are the same you could just write F(x)=a(x)+ia(x) and it's obvious that swopping real and imaginary components of F(x) gives the same result.. Was there any more?87.102.20.186 10:54, 16 February 2007 (UTC)[reply]

Hi, astute observation on the separability thing. You seem to have misread something I said: I said the equations were the same (meaning the differential equations), but not the actual functions. Take for example a(x) = cos(x) and b(x) = sin(x). Then F(x) = cos(x) + i*sin(x), which satisfies the SWE, but then so does G(x) = sin(x) + i*cos(x). I believe my proof shows this applies for all cases, provided the function a(x) + ib(x) can be separated. My understanding is that any function can be rearranged into one that can be separated into real and imaginary components, although maybe it cannot then be expressed in the form of elementary functions. If F(x) = sqrt(x), then a(x) = sqrt(x) for x >= 0, and b(x) = sqrt(|x|) for x < 0; both a(x) and b(x) are zero outside the stated domains. This is not a solution to the SWE, but it can be separated. Tell me if I'm doing any better, and thanks again for the time you've spent on this. I've enjoyed the discussion/ clarification. Cheers :-) The Mad Echidna 03:51, 18 February 2007 (UTC)[reply]

(Sorry ignore the bit about square roots - such functions aren't solutions here - my comment was irrelevant)

Otherwise yes,

If

(1) F(x)=a(x) has eigenvalue E

and

(2) F(x)=b(x) has eigenvalue E

then sums of the function

(3) F(x)=a(x)+b(x) has eigenvalue E

and in general

(4) F(x)=Aa(x)+Bb(x) has eigenvalue E , where A and B are any real,imaginary or complex numbers

eg A or B can be 1,i,0, 1+4i, 0.7+2i etc independantly

in your case A and B are 1 and i, or i and 1 and the situation still applies.

It's easy to prove that equation 4 and 3 are true if 1 and 2 are true. It took me a long time to understand what you were asking.87.102.9.240 15:26, 18 February 2007 (UTC)[reply]

Thanks again. It took me a long time to explain myself properly *grin*. I had forgotten the wave equation, since I'm not a physicist, and it's a long time since I've seen it, and I didn't understand it from the WP article (the notation threw me). My curiosity was based on the fact that the imaginary component in quantum mechanics and relativity always seems to represent time. I wondered then what happened to imaginary numbers in the time-independent wave equation. In keeping with the idea that they usually represent time, their special significance vanishes in the time-independent equation. If the real and imaginary components could be reversed without consequence in the time independent equation, then they are not "special" compared to real numbers in that setting. It seemed like a kind of circumstatial justification of the idea that imaginary numbers represent time. The Mad Echidna 16:43, 19 February 2007 (UTC)[reply]

Personality disorder causes

Are personality disorders considered to be caused by the strictly environment one grows up in, and not genetic causes or brain damage? I remember suffering from Obsessive compulsive personality disorder ever since I was a child, though I can't think of anything that happened to me as a child that could have caused it.--70.244.121.88 19:31, 10 February 2007 (UTC)[reply]

Outrigger Canoe

I am not sure if this question should be posted on this desk but here it is anyways. I have heard of people trying to circumnavigate the world in an outrigger canoe but has it ever been acomplished? Thank You for any answers.68.120.80.76 19:44, 10 February 2007 (UTC)[reply]

MP3 player

Hi, I wasn't sure whether to put this on the Misc. help desk or this one, but I put it here anyway. I want to buy an MP3 player (not an Ipod). I've got two on my list to choose from so far.

Philips HDD6320 30GB for £100. Reviews on sites such as amazon seem to be a bit iffy: problems such as freezing and long gaps between songs
Archos Gmini XS 202s 20GB £110 - reviews seem to be good but the Archos page says that the produced goods are low quality.

I only have about 6GB worth of songs so far so capacity doesn't matter much. I want a bigger capacity so I can add more songs.

Which do you think I should buy? Has anyone bought either of the above MP3 players and are they any good? Thanks very much for your help. Bioarchie1234 20:29, 10 February 2007 (UTC)[reply]

My Archos is an older model, but barring one issue with the line-in jack (which I don't use) it's survived four years, including my physically upgrading several components. Seems robust enough... Shimgray | talk | 14:59, 11 February 2007 (UTC)[reply]

Thanks for your help, Shimgray!Bioarchie1234 10:38, 17 February 2007 (UTC)[reply]

Why would FTL communication violate causality?

It is easy to understand why time travel to the past would violate causality (grandfather paradox), why traditionally accelerating matter past the speed of light is impossible (infinite energy required, etc), but why does faster-than-light communication violate causality? (the question is not about why is it impossible with current technology) --V. Szabolcs 21:07, 10 February 2007 (UTC)[reply]

From my point of view it doesn't - at least in terms of communication between two already known objects eg earth and moon. The info. would of course arrive earlier than expected based on a maximum speed of communication of 300,000,000m/s and that is all. (Are there any logically consistent references that state it does?)87.102.9.117 21:17, 10 February 2007 (UTC)[reply]

(edit conflict) I'm saying that faster than light doesn't violate causality - it just violates any law that states that speeds faster than light are impossible.87.102.9.117 21:34, 10 February 2007 (UTC)[reply]

Simple way to explain it: a FTL signal could potentially cause a communication to be received "before" it was sent. -- mattb @ 2007-02-10T21:20Z

Well, it depends. If the FTL communication can be done in a frame-independent way, then you can send a signal backwards in your own time frame. You do it by sending a message faster than light (in your frame) to a collaborator moving fast (but slower than light) relative to you. It gets there before you sent it, in his time coordinate. No problem yet. But then he can run the same trick and get a message to you before he sent it in your time coordinate. Now the message gets to you before you sent it, in your own time coordinate. So you could send yourself a message not to send it, and then we've got a problem.

Of course if it's not frame-independent -- that is, if there really is a preferred coordinate system, and we just can't discover it using slower-than-light stuff -- then we're OK. --Trovatore 21:23, 10 February 2007 (UTC)[reply]

I don't think your example is quite right - suppose you have a pair of glasses that allow to percieve all things that move, even things moving faster than light - if that were possible..

So even at faster than light it takes time for the message to be sent, (if the message was in a bottle you could watch it going to your friend with 'faster than light' glasses), then you could watch the message being sent back (again using the 'faster than light glasses') this takes time too. So the returned message arrives after you sent it - albeit sooner than you could have expected with a limited speed of light. It doesn't arrive before.87.102.9.117 21:30, 10 February 2007 (UTC)[reply]

In your coordinates, the return signal goes backwards in time. Melchoir 21:54, 10 February 2007 (UTC)[reply]

In a standard euclidean 3d geometry with time constantly moving forward - it takes time for the thing to travel. I understand that relativity uses a different form of geometry - but if I ignore that - I find that at any speed it will be later on in my measure of time that the thing arrives. (I don't know if trying to look at it from the point of view of an observer who has a method of observation that is instantaneous (ie infinite speed) would help)87.102.9.117 22:12, 10 February 2007 (UTC)[reply]

Sure, there are no violations of causality in Galilean spacetime. There's also no finite speed of light to move "faster than", so it's not relevant to the question at hand. Melchoir 23:51, 10 February 2007 (UTC)[reply]

Lets say you send a message to me 2 times the speed of light. Because things going faster then the speed of light go 'back' in time, a conversation could run backwards. I send you 'Hi' and you get it 2 seconds before I type, so you send me back a message 'sup', and I get it 1 second before I originally sent 'hi', so I may not send it if you are already talking to me, violating causality--Honeymane_{Heghlu meH QaQ jajvam} 09:30, 11 February 2007 (UTC)[reply]

If "things going faster then the speed of light go 'back' in time" then it's crystal clear why the violation occurs. But why does it happen in the first place? I've read a lot about relativity, but this seems to be a question I'm totally clueless in. Who said anything about traveling backwards in time? Are you talking about tachyons? As I understand, their behavior is caused by the mass being an imaginary number. But what about things without mass (or just with real mass) as information carrier? A part of deep space where the speed of light is larger than in vacuum? Wormholes? I know they are not proven to exist, but if they did, why would FTL information (not necessarily matter, and no tachyons please) travel backwards in time? --V. Szabolcs 14:37, 11 February 2007 (UTC)[reply]

It has to do with the way coordinate changes work in relativity; events that are simltaneous in any particular reference frame are non-simltaneous in others, and in fact there's a reference frame where A occurs before B and vice versa. This is no problem as long as the two events aren't causally-connected (that is, information isn't sent from A to B). But if a signal is going from A to B (two points in spacetime) faster than the speed of light, then there exists a reference frame in which B occured before A, so the information is travelling back in time. To demonstrate this explicitly requires some math; it's explained, in probably over-technical language, in Special relativity#Causality and prohibition of motion faster than light. -- SCZenz 14:50, 11 February 2007 (UTC)[reply]

SCZenz's answer is fine (though not quite complete; there's no immediate causality problem caused by a signal ending at a smaller time coordinate than the one it started -- it's just a coordinate, after all. You have to get the signal back to the originator before he sent it, to get the paradox.)

But I think Szabolcs and the anon have a good point. Information sent faster than light would not, for that reason, go backwards in time, in the frame of the sender. This is something a lot of science fiction gets very wrong. The fast-moving spaceship runs into some unexpected condition, it goes just a little faster, and all of a sudden all the clocks start running backwards. That's nonsense on so many levels. The paradox about what would happpen if you could send information faster than light (in a frame-independent way) is a serious one, but the garbled version that gets transmitted to the public is garbage. --Trovatore 08:30, 12 February 2007 (UTC)[reply]

But if I send information back in time in some other frame, the information is received, and they send it in the other direction by the same method (so it's now going back in time with respect to my frame), then the information can get back to me before I send it. It's only a matter of repeating what I described twice. -- SCZenz 12:18, 14 February 2007 (UTC)[reply]

This is an impossible question. It's like asking: "If one plus two was six, what would that do to my bank balance" - the fact is that it's not six...so how can you answer? The equations relating to relativity produce results that math can't solve when you plug in a velocity that's faster than light. Look at something like the Lorentz transformation - it says that the amount of time/distance/mass distortion when things fly fast is: $\gamma ={1 \over {\sqrt {1-v^{2}/c^{2}}}},$ - OK - so let's make 'v' (the speed of our FTL thing be 1.1 times c...what happens to the math? Well, $v^{2}/c^{2}$ turns out to be 1.21 so the number inside the square root sign works out to be -0.21...soooo...the mass/length/time-distortion experienced by an object moving at 1.1c is the square root of a negative number. Would anyone like to tell me the square root of negative 0.21? Feel free to use a calculator! Yep - it's a complex number - what the heck would having a mass equal to the square root of negative 0.21 mean anyway? So this is a nonsense question - it's precisely as meaningful as "What would the world be like if 1+2=6"...it just isn't. SteveBaker 00:05, 13 February 2007 (UTC)[reply]

No, that's way too facile. You can't prove something doesn't exist merely because our equations for describing other things would blow up if applied to them. Tachyons may in fact exist, and their having imaginary rest mass, if you can't bring them to rest, is not really a problem.

But, if we can communicate with them, and if they behave in a frame-independent way, then we have a problem, and this can be demonstrated without knowing anything at all about what tachyons are like in terms of mass or in terms of how they would experience time. --Trovatore 00:16, 13 February 2007 (UTC)[reply]

Oh, to clarify: By "communicate with them", I mean "communicate, using them to transmit the message". I didn't mean "Hey there, Mr. Tachyon!". Hope no one was misled. --Trovatore 01:07, 13 February 2007 (UTC)[reply]

The well known equations about relativity are only referring to object with mass, aren't they? What about waves? (I know it's still disputed whether light is wave, particle or both). This equation cannot give an answer for (yet undiscovered) places where the speed of light would be faster than in vacuum, or hypothetical methods transmitting information without mass involved. However, thank you all for the interesting answers :) So I must assume that ftl communication would only be possible if our understanding about the universe and our formulas based on that knowledge are either wrong or incomplete.. --V. Szabolcs 16:50, 13 February 2007 (UTC)[reply]

Actually the argument is extremely robust; it doesn't depend at all on the details of how a message might be sent faster than light. It doesn't matter if the signal stays inside the universe or goes outside it, whether the particles/waves/whatever composing the signal satisfy conservation of mass or momentum, or even whether the signal is natural or supernatural. It could be carried by gods or demons or little green faeries and the argument would still apply.

The only thing you need to know is that you can send a signal to your collaborator, moving with respect to you, so that it arrives there (in your inertial coordinate system) faster than a photon would, and that he can send a message back so that it arrives to you (in his coordinate system) faster than a photon would. Well, let's make it "arbitrarily fast" rather than "faster than a photon", just to avoid some computations and inequalities. If you've got that, and if the unknown agency doesn't also alter the relationships between y'all's two coordinate systems, then you've got the paradox. --Trovatore 18:19, 13 February 2007 (UTC)[reply]

Ok, then I will not even mention the Infinite Improbability Drive :) --V. Szabolcs 22:37, 13 February 2007 (UTC)[reply]

Carving in a live tree?

If an artist carves a large design deep into the trunk of a living tree, does it harm the tree's health in any way? Is it harmless? Is it bad for the tree? Clearly this is fine to a dead tree, but I am concerned if it's bad for a living healthy tree.

For images of the specific type of carving I am asking about, please Google "colin partridge", and it's the first hit.

--Sonjaaa 23:06, 10 February 2007 (UTC)[reply]

Yes I can affect the health of a tree - in the worst case (carving all the way round) in can sometimes cause the death of a tree (see girdling).

In many trees (not sure if all) growth takes place round the perimeter of the tree (trunk) just below the bark. - if this is removed then the tree will be damaged (stunted) on that side. I don't know the extent to which trees can recover from this.87.102.9.117 23:13, 10 February 2007 (UTC)[reply]

Carving in the tree also makes the tree much more susceptible to all sorts of infections (insects, fungi, etc.) But it's likely that a tree would survive a small carving in the same way it usually survives branches breaking in storms and the like.

Atlant 23:59, 10 February 2007 (UTC)[reply]

Can you look at the pictures on that website? Is his art "small" or maybe it's too big?--Sonjaaa 04:37, 11 February 2007 (UTC)[reply]

Carving a live tree wounds its living tissue. If the wound does not go through the bark, the tree can usually heal pretty easily, although there is a danger of infection if the cutting utensils are dirty. If the wound goes through the bark then the wood is exposed, creating a danger for fungal infections which can kill a tree. When branches are damaged there is a risk for infection. This is why you are supposed to prune branches flush with the trunk, so that the bark can grow over the cut surface, closing the wound. Since wood is dead tissue there is no way for a tree to defend itself against pathogens which have infected the wood, and no way to replace any tissues that have been lost. Guettarda 05:08, 11 February 2007 (UTC)[reply]

Unless you're a tree-rights activist, I'd say don't worry about it. Cutting a design into a person's arm is damaging, but usually they don't die from it. Cut off a tree branch, it'll be just fine. It has to deal with all sorts of damages in nature, and it deals with them quite well I'd say, I bet if you look outside your window most places in the world you can see a tree. [Mαc Δαvιs] X (How's my driving?) ❖ 16:45, 11 February 2007 (UTC)[reply]

When i sometimes make carvings to trees i use pine tar to the carved place. This protects the tree from diseases and fungus. 193.167.45.242 16:55, 13 February 2007 (UTC)[reply]

All the trees on that page (on the first page anyway, I didn't surf deeper) are dead anyway, so I suspect it's a moot point. Matt Deres 02:14, 15 February 2007 (UTC)[reply]

Per User:Mac Davis, if I carve a design in a person's arm, should I apply pine tar there as well? Edison 05:12, 15 February 2007 (UTC)[reply]

Science and the supernatural

Dear Wikipedians,

I have several questions:

(1) Why is it that science "cannot approach" the supernatural? This is what I've usually heard and it's what the supernatural article says. But the ID people insist that the supernatural can be included in science, or that the accepted definitions used for "science" and "supernatural" are flawed.

(2) Is a claim like "The Bible is the fully inspired Word of God" inherently unverifiable by scientific methods?

(3) If so, is it because of an inherent philosophical difficulty, or simply because, in practice, there is no scientific proof for such a claim?

I would like detailed answers, but any help is greatly appreciated. 69.223.156.241 23:28, 10 February 2007 (UTC)[reply]

Science is a process, a way of thought. It insists that its truths be demonstrable, repeatable, and robust under doubt. It rejects any claims to faith -- other than perhaps faith in the scientific method itself.

But this means that science cannot "prove" any statement which requires, for its "proof", faith in one book that was written centuries ago, or trust in the unverified statements of lone observers who claim to have seen some otherwise inexplicable phenomenon.

Actually, science can begin to approach these subjects, in that it can go a pretty long ways towards disproving them. But (a) it can never utterly disprove them, and (b) lots of people are more interested in believing in these phenomena than in believing in cold, rational science. Furthermore, most scientists (with the exception of, say, Richard Dawkins), aren't interested in angering people by claiming to disprove their cherished beliefs. So there ends up being a pretty deep divide between scientific thought on one side, and religious and/or supernatural thought on the other. Each rejects the other's methods (in a nutshell, scientists reject faith, while dogmatists insist on it), so the schism remains. —Steve Summit (talk) 23:39, 10 February 2007 (UTC)[reply]

The above was a pretty good answer. I could recommend reading the first couple of lines of science whithout getting involved in explaining what is objective and what is subjective - I could quickly over-simplify to say that science is the study of things that are knowable and controllable.

Thus it's easy to scientifically study inanimate things such as rocks and the like - since we have no problem having control over them.

It's more difficult to study things that we have less control over such as other human beings (the science of behavour etc has difficulty coming to consistent conclusions..), fire (chaotic - difficult to understand), the atmosphere (difficult to predict the weather).

So in attempting to apply science to things that are inherently uncontrollable - such as supernatural phenonoma and powerful superntaural beings and gods then science falls down - it's simply not the right tool to apply for their study.

Matters such as religion and faith can be considered subjective (different people have different gods - some have none etc) - science is the wrong tool for the study of subjective knowledge - because it's a tool for the study of objective knowledge.

So the answer to question 2 is yes.

I realise there are numerous ways of answering this - hope this one helped.87.102.9.117 00:15, 11 February 2007 (UTC)[reply]

It is important to stress the fact that science CAN test some supernatural claims. If someone claims to have psychokinetic powers, you could just perform a controlled experiment to see if the person actually performs such a feat without tricks or other explanations. This has been attempted several times in the past, and not a single person has ever shown such abilities. The same can be said of telepathy and other extra-sensory perception claims, or even prayer. Not a single person or experiment has ever passed double-blind experiments, and if such powers or effects did exist they would be easily measured statistically. Since after extensive research there's no evidence supporting these claims, scientific community has labeled them as most probably false and wrong.

An interesting thing arises from these results. While the burden of proof lies on people who make those claims, and not on scientific community, people who support paranormal claims often challenge science to disprove them. This is not the way things should work, but it is a widely used strategy to make science look "powerless" against the paranormal, when it is the people who make the claims that should provide evidence to support them.

The magician and skeptic James Randi has even put ut the Million Dollar Challenge, encouraging people to provide evidence of the paranormal in return for 1 million dollars. Hundreds of people have been tested, and not a single one was ever able to prove their claims. — Kieff | Talk 00:26, 11 February 2007 (UTC)[reply]

You can test "supernatural powers" like psychokinesis. But you can't test the hypothesis that "X was caused by the supernatural" because there is no way to separate causality. You can always argue that X was caused by a miracle. Some people argue that you can infer supernatural causation if you can show that the probability of something happening through natural causes is so unlikely that it's more likely to have been caused by the supernatural. However, that would only work if you had some way of assigning probability to supernatural events. But there is no way to assign probability to supernatural events, and this still doesn't rule out unknown natural causes.
The statement that "The Bible is the fully inspired Word of God" is unverifiable not only scientifically, but through any other methods as well (e.g., the bible does not claim to be "the fully inspired Word of God"). But it is impossible to test that assertion scientifically. For example, unlike the bible, the Qu'ran claims to be a direct revelation - however, there is no way to make a priori predictions of what divine revelation would look like, so there is no way to say whether something is significantly different from a divine revelation. Without some independent definition of what "divine revelation" should look like, there's nothing to compare the bible to. Guettarda 05:01, 11 February 2007 (UTC)[reply]

The above post about ESP is opinion and not fact, many scientist claim that many experiments have shown evidence of psychokinesis and ESP. Robert Jahn, brian josphson, Fred Alan wolfe, and many others support the ESP hypothesis, the question has by no means been answered —Preceding unsigned comment added by 80.6.35.89 (talk • contribs) 13:13, 11 February 2007

Well, no, the question has been answered, and that's not an opinion, it's as close to a fact as one gets in science. There are a few people who claim to be using mostly scientific methods and who claim to have found significantly suggestive results, but for whatever reason, their reports are not accepted by most of the rest of the scientific community.

Now, this brings up three interesting points:

Up above, I said that science insists on demonstrability, repeatability, and robustness under doubt. It also really, really likes -- and in many cases insists on -- some notion of mechanism. You can't just observe a repeatability; it's best if you can suggest why you think it's happening. In the case of ESP, you ought to suggest what pathway you think the "extrasensory" perception is traveling along, and what organ you think is mediating it. (Disclaimer: I'm no student of ESP, so I don't know to what extent its proponents are, in fact, attempting to suggest mechanisms.)

This isn't true. There are plenty of reproducible experiments that science does not doubt - yet for which we have no adequate mechanism. Triboluminescence for example. Take a pair of pliers and a pack of 'WintOGreen Life Saver' candy into a very dark room - let your eyes adapt to the dark and then crunch the candy into pieces using the pliers. You'll see little sparks of light. This is a perfectly simple, reproducible experiment - for which science has no good explanation. Is it 'supernatural'? No - we can demonstrate it and reproduce it - we just can't fully understand it yet. Telepathy would be in the same class as triboluminescence if it were not understood - but could be reliably reproduced - but it can't be reliably reproduced. If you can reliably reproduce it - go pick up your million dollar prize from the sceptics society. So far, the money seems safe. SteveBaker 01:14, 14 February 2007 (UTC)[reply]

One might argue that the refusal by "the rest of the scientific community" to accept the various alleged positive results concerning ESP and psychokinesis is evidence of some kind of conspiracy. One might claim that science is, in some respects, just as closed-minded, knee-jerk, and faith-based as religion. And in fact, to some extent, these charges have some basis. Scientists are people, and people make mistakes, and get overly passionate -- sometimes to the extent of becoming prejudiced or dogmatic -- about their work. But I would also claim (with more than a little justification) that (a) closed-minded refusal to consider new ideas is counter to the ideal of science, (b) science is at least aware of its shortcomings and works assiduously (and with some success) to overcome them, and (c) any number of scientific revelations, now accepted as "fact", were in fact once brand-new and utterly heretical ideas.

But we can't go around believing in just anything that comes along. If some crackpot says that he hears alien music in his head every time the moons of Jupiter line up in a row and there is an 'R' in the month - should scientists go to all the trouble of checking his idea? Hell no - we have much better things to be getting on with. Extraordinary claims demand extraordinary evidence. Telepathy is about the most extraordinary claim there could possibly be - but so far, we don't even have a reproducable experiment. It's not that scientists are prejudiced - they simply don't have any evidence to go on - so telepathy goes onto the same pile of junk hypotheses as every other random thought that might stray into someones head. (In fact, there have been lots of serious scientific efforts to check telepathy - not one of them that has been conducted properly has produced a solid result...there comes a time when you have to say "Nope - this one isn't true" and move on to figuring out something more interesting) SteveBaker 01:14, 14 February 2007 (UTC)[reply]

There is a very interesting human phenomenon -- a subclass of our unfortunate tendency to fall into "us-versus-them" polarization -- which is the Underdog New Idea. That is, someone has a wonderful but heretical new idea, which because it's new and heretical there's a massive conspiracy by "the establishment" to ignore and suppress. Moreover, it's easy for that someone to get a certain number of ardent supporters, all of whom want very badly to believe that the conventional wisdom is wrong, and that their hero's new-and-different idea is deliciously Right. I don't know if this phenomenon has a name, but you see it all the time, and it's fascinating in its regularity. Citations welcome.

—Steve Summit (talk) 14:44, 11 February 2007 (UTC)[reply]

(1) Why is it that science "cannot approach" the supernatural? This is what I've usually heard and it's what the supernatural article says. But the ID people insist that the supernatural can be included in science, or that the accepted definitions used for "science" and "supernatural" are flawed. This is a common misconception. A true scientist would say "if something termed as 'supernatural' were real, we could test it, and we do test it many many different ways. People have claimed to have supernatural abilities, or things, or live in supernatural places, or be supernatural, but nothing has stood up to 'truth testing' yet." James Randi is a great guy, in my opinion. (2) Is a claim like "The Bible is the fully inspired Word of God" inherently unverifiable by scientific methods? No! There's plenty of ways to prove that, or disprove it, but would a believe hear you if you disproved it? If you talked about the deaths over versions of the Bible, or the Roman Congress voting on what should be in it, or various Kings? I suppose it could have been inspired but is not still. We don't know what was written by human and... written by human with God's help, for this reason, I think it is already impure, because God himself did not write it, but use a human tool. So, the question if it is asking for inspiration, can be boiled down to "does God exist?" (3) If so, is it because of an inherent philosophical difficulty, or simply because, in practice, there is no scientific proof for such a claim? There is no scientific proof, however this does not necessarily deem it wrong. Lack of evidence found does not mean no evidence ever, but simply if there is no evidence for some claim, the skeptic has no reason to believe your claim. It is not wrong, because there is no evidence, just there is no reason to say it is right if there is no evidence saying it is right. If it is a binary situation, testing is somebody has psychokinetic powers or not, then evidence that he used physically induced air currents instead of psychically induced air currents, then that's usually taken as not only a negative, but a false positive. [Mαc Δαvιs] X (How's my driving?) ❖ 16:41, 11 February 2007 (UTC)[reply]

Why is it that science "cannot approach" the supernatural? This is what I've usually heard and it's what the supernatural article says. But the ID people insist that the supernatural can be included in science, or that the accepted definitions used for "science" and "supernatural" are flawed.

The difficulty here is that the word 'supernatural' is pretty much defined as "all of the things that some people believe but scientists have effectively disproven". After all, we don't regard (say) magnitism as supernatural. It's pretty weird - this invisible force that acts at a distance that most laymen have no clue about...but it's not supernatural because science has been able to produce repeatable experiments that show it happening. With stuff like human telepathy, not one single repeatable, controlled experiment has shown it happening - so we call it 'supernatural'. This definition of the word guarantees that science can never 'approach' the supernatural since we've said that the word means "things that science cannot approach". If we could see repeatable experiments, it wouldn't be supernatural anymore...it would be 'nature'.

Is a claim like "The Bible is the fully inspired Word of God" inherently unverifiable by scientific methods?

It's not that it's unverifiable - it's unfalsifiable - there is no possible experiment that could ever prove this to be false. This book was written by humans - that much is clear. Science would say that the complex interactions of their neurons and their environment caused this to happen. But since the existance of God is unfalsifiable - then it's impossible to prove that a supposedly omnipetant being who can do literally anything "by magic" didn't tweak those neurons - then cover his tracks so perfectly that science would be unable (even in principle) to find out that he was the 'inspiration'. We must resort to 'Occams Razor' (If there is a much simpler explanation - then that's what we're likely to believe) - and to Carl Sagan's mantra: "Extraordinary claims require extraordinary proof" - since (in scientific terms) this is a pretty astounding claim, the evidence to prove that it's true would have to be gold-plated and bullet-proof...and it's not. There is zero evidence. So overall - whilst science can't say for sure that it's bullshit - that's got to be our working hypothesis until/unless some evidence shows up.

If so, is it because of an inherent philosophical difficulty, or simply because, in practice, there is no scientific proof for such a claim?

It's worse than that. There is not even a possibility that there could be a proof that this 'God' thing is false. Any entity that is capable of literally anything with no limits whatsoever could fake evidence undetectably. So whilst in theory, the 'pro-God' community could prove his existance (eg By asking him if he'd just show up and do something really impressive and difficult) - any argument that science came up with (eg We've figured out exactly how the entire universe works - and we've got it down to this really simple and easy to understand equation - and there doesn't appear to be a God anywhere in the universe) can trivially be countered with "Ah - but God is infinitely powerful - he just made the universe come out that way to test our faith."...so it's a waste of time for science to try to disprove God - it's unfalsifiable. The problem with that is that there are an infinite number of unfalsifiable hypotheses: "The Invisible Pink Unicorn made everything and is infinitely powerful"...well, guess what? We can't falsify that either. "All of mankind are just software entities running inside The Matrix" - nope, no way to falsify that one either. "All I see of the world is through my senses - so I can't prove that my senses aren't fooling me - so maybe I'm the only being in the entire universe and everything I see is false"...there are an infinite number of these propositions. If science gave them any weight - then science would be useless to us. HUMANITY: "Hey Mr Scientist, how should I shape the wing of this airplane to make it fly more efficiently?" SCIENCE: "Sorry - we don't know because God may decide at any moment that he doesn't like airplanes so our equations are useless."...you see it's not very useful to include unfalsifiables into our thinking - it renders science useless. The fact that we always assume that unfalsifiable hypotheses are false is the only way for science to be of any use - and if it's not of any use - we shouldn't bother doing it. If you doubt that unfalsifiable theories get tossed out even though they MIGHT be true - just watch what's about to happen to String Theory. It fits the facts - it's workable - but it's unfalsifiable - and serious scientists who have realised that are running away from it. SteveBaker 23:50, 12 February 2007 (UTC)[reply]

The supernatural tends to be anything that hasn't been proven by science:) There is a lot less of this now, so there is a lot less supernatural around, but still some:) And surely if god was omnipotent, he could stop scientists proving that he exists, and since they can't prove he does, does this mean he is stopping them, and therefore does exist:@Hidden secret 7 13:17, 13 February 2007 (UTC)[reply]

Cornstarch

Three Parts:

1-How is "modified cornstarch" made, including what, if any chemicals are used?

2-How is "high fructose corn syrup" made, including what, if any chemicals are used?

3-How is maltodextrin made from corn, including what, if any chemicals are used?

Neal E. Wilson Manchester, CT

View the modified starch, High fructose corn syrup, and the Dextrin articles for information. Atropos235 01:59, 11 February 2007 (UTC)[reply]

What are some examples of physical and chemical properties of Calcium Silicate?

I would like to know some examples of both the physical properties of calcium silicate and as well as some examples of the chemical properties of calcium silicate. Thank you so much.

View the Calcium silicate article. Atropos235 01:50, 11 February 2007 (UTC)[reply]

Also silicates can exist in different forms (as chains or rings) if you are looking for the properties or rock/mineral calcium silicates you should look there as well as at Wollastonite.87.102.9.15 11:25, 11 February 2007 (UTC)[reply]