1

Physics, Astronomy & Cosmology / The momentum operator

« on: 08/06/2008 03:26:38 »

Ah, Fourier Transforms!  I forget how those work.  I could probably go on wikipedia and find out but most of the time the math pages are not so user-friendly there.

2

Physics, Astronomy & Cosmology / The momentum operator

« on: 07/06/2008 19:08:33 »

In quantum mechanics, all observable quantities are defined by eigenvalues of Hermitian operators.  For momentum the operator is -i*(h/2π)*∂/∂x.  Why is that the operator and not simply p₀?  For position the operator is simply x...why can't it be the same way for momentum?

3

Chemistry / Practical Jokes

« on: 13/04/2008 18:12:08 »

Asking the questions is not important...trying to find an answer is.  Asking other people for the answer is actually less useful than doing some research on your own and figuring it out for yourself.  You learn something that way, as opposed to have the answer simply given to you.  It's harder that way but if you're really after learning something new and not just spouting "I'm a kid and I ask why" because you've been told that's what kids do then doing research yourself is the way to go.  If you have to ask anyone anything it should be to explain some of your research to you because you can't quite understand it...not to tell you the answer.

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Physics, Astronomy & Cosmology / What is energy?

« on: 02/01/2008 02:32:04 »

Energy is the ability to do work.  Therefore, if mass inherently has energy, this explains how the field it generates does work on other mass.  By the same token, charge has energy because it generates a field which does work on other charges.  Thoughts?

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Physics, Astronomy & Cosmology / What is energy?

« on: 26/12/2007 14:00:28 »

What is it?  We say, "this has more energy than that," and "mass is energy" but what are we talking about?  Energy is the ability to do work?  What is work...a change in energy!

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Chemistry / Hydrogen Foam

« on: 14/12/2007 12:01:46 »

Oh yeah, I forgot...usually metals only produce H2 when they react with acids but Al is so reactive that (under correct conditions) it reacts with the amphoteric acid, water.

If you try to use Al to make a H2 foam in a liquid, would it just bubble or could you get a foam which you might use in a fuel cell?  Would you be able to make it dense enough?

7

Chemistry / Hydrogen Foam

« on: 13/12/2007 02:29:24 »

I'm thinking of a way to store H2 efficiently for cars and such...store it in a solid or liquid so that it won't escape at relatively normal pressures and temperatures, but can still move around so ions can flow in a fuel cell.

That looks like a very intersting site.  The aluminum probably reacts to produce oxygen gas (that is if you use CaO...I'm not sure whether it's CaO or CaCO3 in concrete) or carbon dioxide.  Very neat.

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Physics, Astronomy & Cosmology / Time as a method of physical propulsion

« on: 13/12/2007 02:21:33 »

What you have suggested is TIME TRAVEL!  Not a new idea.  If you can figure out how to travel in time then you'll have international fame...until then it is just as practical as walking through a wall, and just as old of a concept.

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Physics, Astronomy & Cosmology / Direction of Radiation Emitted from Atoms

« on: 13/12/2007 02:13:49 »

Ok, so light is a spherical probability wave (it has no direction but outwards)...it is spread out over a spherical surface and any detector on that surface has a probability of detecting that photon inversely proportional to the size of the surface.  That is all well and good and easy to picture but what is it about light that makes it behave that way?  What mechanism decides where the light should be absorbed?  Probabilities only come into play when we don't know enough about the initial conditions to predict what outcome will prevail.  If I have two cups on a table and I put a coin under one while you are not looking, there is a 50% chance that the coin will be under the cup you choose.  However, if you peak over your shoulder you know with absolute certainty where the coin is even though there are still two cups and only one coin.  Therefore, can we really rule out light having a directionality?  The only systems we ever deal with are systems with a lot of photons emitted in all directions.  Dividing our chances of absorbing x amount of photons at position P by the number of photons there are gives a probability of absorbing an individual photon at that position...but isn't that just like the coin and the cup?-I don't know in what direction (under what cup) the photon (coin) is but I know the probability that I am going to absorb it.

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Physics, Astronomy & Cosmology / Does dipole moment affect the direction that light is emitted from an atom?

« on: 11/12/2007 22:29:59 »

Consider one atom in a closed and isolated system.  It is in an excited state.  Then it emits a photon of light and it settles into its ground state.  The photon has to be emitted in a direction.  How is that direction decided?  If you think of the electron as a standing wave about the nucleus (which explains the quantization thing because standing waves have modes of discrete energy levels) then it is everywhere around the nucleus at once (as QM postulates).  The only vector associated with this atom (which I can think of) is its dipole moment (related to orbital angular momentum of the electron).  Would this somehow affect the radiation direction of the photon?

If you take the equation E² = (mc²)²+(pc)² you can see that p (momentum) is directly proportional to E (total energy).  If an electron loses energy when it emits a photon, its momentum goes down.  That means that by conservation of momentum (assuming the electron's momentum vector stays oriented in the same direction through the whole process) that the photon's momentum vector would have to point in the same direction as the electron's (to make up for the lost momentum of the electron).  The question is, where does p point.  Is it along the dipole moment?  Can you align a group of atoms' p vectors and create a directional light emitter?

11

Physics, Astronomy & Cosmology / Direction of Radiation Emitted from Atoms

« on: 11/12/2007 22:09:19 »

Here's my problem with the spherical wave model:  when a wave (which has a photon of energy) is detected it loses energy.  Since it can only have integer multiples of hf in energy, it loses all of its energy.  Therefore, if I put a detector one meter from a light source, none of that light would ever reach me if I stand on the other side of the light source but 1.1 m away.  However, two people can see the same light bulb from different distances...how does that work?

-I know you can model light like a spherical waves but are they really like that or are they directional and it is only when there are many of them that you can treat light like a spherical wave?

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Chemistry / Hydrogen Foam

« on: 11/12/2007 02:32:15 »

What, no one up on their foam chemistry?!?  I thought we had some good chemists on this forum! [] []

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Physics, Astronomy & Cosmology / Does dipole moment affect the direction that light is emitted from an atom?

« on: 11/12/2007 02:29:48 »

If you magnetized the wire enough, could you show that if a significant percentage of the light emitted was in a specific direction that, dipole moment affected emission direction?...or can you show this with Quantum Theory without running tests?

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Physics, Astronomy & Cosmology / Does dipole moment affect the direction that light is emitted from an atom?

« on: 10/12/2007 21:34:40 »

As far as I can tell, using various resources, the best modern theories can do to predict the direction that light has when it is emitted from an atom is to say that on average, with a large sample, it is emitted omnidirectionally.  But, probability is only useful for describing what you don't yet know...for example, in a coin toss, the probability of a heads is 1/2 because you don't know what will happen yet.  Why it happens when it does is dependent on intitial and environmental conditions; if you knew all of those, you would be able to predict absolutely whether the coin would come up heads or tails.  What causes light to move in this direction instead of that when it leaves the atom?  Could it be the magnetic dipole moment of the atom (or some other vector singular to that atom)?  If I were to take a magnetized monofilament and apply a voltage to it would it emit most of its light in one direction (most of the magnetic dipole moments of the wire would be aligned in the same direction)?

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Physics, Astronomy & Cosmology / Direction of Radiation Emitted from Atoms

« on: 10/12/2007 16:38:32 »

Light is a directional wave...it is a linear wave which propagates in a specific direction.  What in the atom determines which direction it emits radiation in?  Is it dipole moment or something to do with the nucleus?  I can't seem to find anything on the internet.  Anyone have an idea?

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Physics, Astronomy & Cosmology / Photons and why they're so hard to explain

« on: 08/12/2007 17:41:59 »

The solution to a problem is much easier to see once the question becomes clear.  In this thread, I think that McQueen is deeply troubled by the lack of a sound metaphyisical interpretation of modern physical theory.  That is to say, we have math to describe what happens and it is very accurate, but we don't really know what those equations mean for reality.  Metaphysics is the study of what is.  Is a photon, the common term for a quanta of light, a particle or a wave, both or neither?  What does it mean that light is quantized?  What makes it quantized?  Modern theory offers no attempt to answer these questions, although their answers could provide much future insight into physics and bear fruit to new mathematical models and physical theories.  While I applaud any attempt, including McQueen's, to provide answers to these questions (thus showing an understanding of the principle that physical theories must not only be mathematically sound but must abide by the same logic as the rest of the universe), I do think that nothing I have read anywhere insofar has even scratched the surface of the problem.

McQueen's theory, as well as many others, try to determine whether a photon is a particle or a wave.  They fail to clarify what is meant by quanta of light however.  They assume, as many books such as "The Elegant Universe" state (in an attempt to explain something in simple terms that the author cannot explain accurately in complex terms), that light comes in material chunks.  These pieces of light, are called photons.  Therein lies the problem.  Any new interpretation of quantum theory must discard all other flawed interpretations or risk being flawed itself.  Digging past all of the mumbo-jumbo of frantic physicists and philosophers bending head-over-heels to make sense of a particle that isn't a particle, we see that photons-light quanta-arise from Planck's theory of black-body radiation.  His theory is that light is absorbed and emitted from a perfect black-body with energy that comes in discrete quantities.  This was an assumption he made to make his theory work, thinking that it had only mathematical validity, not physical truth.  However, subsequent theories have shown that by assuming that energy of light comes in discrete units it is possible to construct successful theories.  This lends some weight to the argument that light actually comes in discrete units of energy.

The name photons was coined to describe these units.  The only difference between photons and joules or ergs is that you cannot have partial photons, only whole number quantities whereas you can have 1.5 joules or 9/15 ergs.  From this interpretation, derived from the very fundamental assumption of Planck, we can see that light is not photons and photons are not light.  Light is an electromagnetic wave and photons are units of energy.  The work done to stand up can be described in photons (since they are analogous to joules).  This is the fundamental nature of a photon.

As for light being a particle or a wave we must examine only the direct results of experiment and the products of generally accepted theories such as Maxwell's theory on electromagnetism (assumed to be true because of the large amount of experimental data in support of it).  Light is a wave by Maxwell's theory, an oscillation in the EM field.  It is easy enough to see where that idea comes from.  However, light acts like a particle because it can be observed "moving" from point A to point B.  I put moving in quotes because we don't actually see the light propagate; we see a start and end point.  Particles move along paths that have start and end points and waves do not.  There in lies the dilema.

Consider a ripple on the surface of a pond.  If I drop a pebble straight down into the pond, a wave appears on the surface of the water.  I know the start point (where the pebble hit the surface).  Now, eventually I will see the reeds poking out of the pond several feet away sway.  I have an end point.  Now think of light.  I cannot see the actual wave, only the emission and detection points.  If the ripple on the pond were a light wave, I would see the pebble hit the surface of the water and then, after some time, I would see the reeds sway, without seeing the wave.  It would seem that there was some particle that made a B-line for the reeds from the origin of the ripple but in reality I would know it was a wave because I knew that dropping a pebble in a pond makes a wave on the surface of the water.

It is hopefully apparent now that a knowledge of the origins of physical theories is necessary for developing metaphysical interpretations of them and, McQueen, although attempting to answer some of the fundamental philosophical conundrums of modern science is admirable, you cannot simply take a flawed theory (that of the photon being a material thing) and build upon it in hopes of creating an unflawed theory.  You have to shove aside all the erroneous preconceived interpretations of reality and start at square one again-at the empirical facts.

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Chemistry / Hydrogen Foam

« on: 05/12/2007 22:28:00 »

That'll be the last bath I ever take!!

How dense would that be?  Not very I'd imagine.  Can you create a dense foam out of hydrogen (dense in hydrogen)?  Or, even a gel?

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Chemistry / Hydrogen Beer

« on: 04/12/2007 22:11:32 »

What is the density of H₂ in hydrogen beer?

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Chemistry / Hydrogen Foam

« on: 04/12/2007 22:06:26 »

Does anybody know of a way to suspend H₂ in a relatively common, hard-to-oxidize-in-the-presence-of-O₂ liquid to create a sort of foam? 

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Technology / Re: How does a hydrogen fuel cell-powered car work?

« on: 04/12/2007 22:04:22 »

Anybody know how they are currently making the hydrogen transportable?  I thought you had to liquefy it and hold it under extreme pressures.  This is certainly not practical for the average car.  Is there some new method that I don't know about?