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Uncertainty and energy

  1. Aug 26, 2004 #1
    An orbiting electron that is further from a proton has a higher energy .
    And is attracted to the proton by a weaker electric force.
    If space is filled with fast-moving particles they could push the electron closer to the proton and back to the groundstate so a photon would be emitted.For a large number of proton-electron systems the electron would
    emit a photon (after initial excitation to the same excited energy state each time) over a range of times corresponding to the different distances of an electron from a proton before and after excitation.Could such a mechanism of de-excitation lead us to conclude that the flow of fast moving particles
    causes the equation: E x t = hbar.In other words, the uncertainty principle?
    And could the flow of particles be dark energy?
     
    Last edited: Aug 26, 2004
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  3. Aug 27, 2004 #2

    Tom Mattson

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    The language is a little loose for my taste, but I guess I'll say "ok", if you talk about mean radius instead of distance.

    In truth, the wavefunction is defined out to infinity.

    As to this:

    And this:

    I'd say:

    The thing is that the uncertainty principle is derived from a well-tested, well-defined theory (quantum mechanics) and no undetectable field of fast-moving particles is required. It's possible that little invisible elves push the electron around, but why would I want to hypothesize that?
     
  4. Aug 27, 2004 #3
    Tom Mattson:
    It's possible that little invisible elves push the electron around, but why would I want to hypothesize that?

    Kurious:

    Just in case the elves are dark energy and we can learn something about it.
    Also the uncertainty principle is a mathematical derivation lacking a physical mechanism and mathematical descriptions of reality often have an underlying physical mechanism.
     
    Last edited: Aug 27, 2004
  5. Aug 27, 2004 #4

    Tom Mattson

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    But what's the point in hypothesizing an arbitrary, superfluous entity (or field of entities) that are not necessary to account for what we observe?

    Who says there is no physics behind it? The uncertainty principle can be attributed to the fact that quantum particles are to be regarded as waves. There is an analogous relationship for EM waves, derivable from that wave equation. It's not nearly so arbitrary if you abandon the conception of an atom that regards it as a tiny solar system.
     
  6. Aug 27, 2004 #5
    I would not dispute that the mathematical description of particles as waves
    leads to experimentally accurate predictions for the behaviour of particles.
    But why is the wave description right? What makes it right? I'm a fan of
    David Bohm's version of quantum mechanics because it has a go at trying to explain this and says that particles are guided by a wave that physically moves them around instead of a probability wave determining where they are at any moment in time.
    Max Born said that the amplitude squared of a wavefunction was proprotional to the probability of finding a particle at a particular point in space.Nobody has ever proved why this gives the right predictions of particle behaviour.It was an inspired guess.
    Nothing wrong with that - it has proved to be a very fruitful guess indeed!
    But scientists are usually unhappy with something if they can't understand why it works.There is no harm in trying to see if it is possible to find out if there is a reason why Born was right.And why the idea of a wavefunction
    is valid.I gather that Born compared the amplitude squared of a photon - which gives its intensity - to the wavefunction amplitude squared.
    So he must have had in mind that the wavefunction was a real physical entity like the photon.This is not dissimilar from Bohm's idea of a pilot wave.
     
    Last edited: Aug 27, 2004
  7. Aug 27, 2004 #6
    Interpretation Vs. Theory

    Kurious,
    First of all, I applaud your curiosity. I think if more scientists listened to you, there might be some more inspiration out there.

    What I think is happening is mistaking interpretation for theory. Although colloquially we use the term "theory" interchangeably with "idea", this isn't the case in math or science. True, sometimes ideas lead to "dualities", which shine a little more light on a subject. True, history says that Einstein came up with relativity by imagining what it would be like to ride a wave of light. But just as I like to imagine the speed of light as a wave propegating through curved spacetime, it doesn't do a wole lot of good for me unless I can formulate it mathematically and then make sure it is consistent with everything already out there.

    My point is, physics-shaking theories may come about by wonderful ideas, but the most efficient way to improve upon an existing theory is to ride out the mathematics and see where it takes you.

    I agree, and always will agree, that QM interpretations, at a gut level and a philiosophical level, are unsatisfying. The problem is that this isn't necessarily a problem with the *theory*; I think it's a problem with the interpretation. The theory points out very well that psi-squared is, in fact, a measure of probability that the observable will have a certain value.

    A particle has a particle-wave duality (literally meaning just that it acts like one or the other, and either stance will give you new information about it), simply because we thought that it was *either* a particle or a wave, and developed the mathematics for each one. For a long time our interpretation hurt our theory.

    No matter what interpretation one favors, it will always boil down to this: at a quantum level, our analogies for the systems in question fail. It's not that the theory fails, but our ability to picture the system with macroscopic ingredients fails.
     
  8. Aug 27, 2004 #7

    ZapperZ

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    I disagree. We'd be doing nothing but wasting time correcting misinterpretation, outright bastardization of physics principles, and really curious mixup of physics ideas.

    I assert that the majority (not all) of "physics-shaking" ideas are NOT initiated by theories - they come from quirky and new experimental discoveries. Harry Lipkin (who himself is a theorist) wrote a rather provocative letter in Physics Today a few years ago titled "Who Ordered Theoriests?".[1] He highlighted the fact that most of the so-called "new" physics and advances really started by experimental discoveries, not via theoretical impetus. Phenomena such as the CP violation, superconductivity, fractional quantum hall effect, etc., were NEVER predicted by theory till they were discovered. In fact, if one looks carefully, Quantum Mechanics was born due to the failure of classical physics to explain several experimental observations!

    Note that I am NOT saying that there is nothing that was first predicted by theory. Antiparticle is a clear example of something predicted first out of Dirac's QM formulation. Nor am I saying that theories have no use in understanding anything. Without theories, experimentalists like me would be doing nothing but stamp-collecting (to paraphase Ernest Rutherford's infamous quote). However, I suggest that we all look at what we know of today, and chances are, the impetus of that branch of knowledge came from an experimental observation and not from theoretical gymnastics (even if you change the start value).

    Zz.

    [1] http://www.aip.org/pt/vol-53/iss-7/p15.html
     
  9. Aug 27, 2004 #8
    If Michelson and Morley hadn't measured the speed of light relative to the Earth Einstein would not have created special relativity or general relativity.So I agree with you.However, Paul Dirac said (in the 1970s) that we are in a situation now where
    Heisneberg was in the 1920s.Lots of experimental data that needs a theory to explain it properly.He also said that he thought totally different ideas would be needed.
    He said Einstein produced new theories without new data.Feynman said that he found it worrying that there was not a fundamental theory that could predict the masses of
    all particles and he even said half-jokingly " a layman guessing the mass of the next particle to be found in accelerators would be just as likely to get it right as anyone else." Stephen Weinberg has called Dark Energy "the bone in the throat for cosmologists and particle physicists". He does not sound very optimistic about the prospects of reconciling dark energy with the rest of physics, and he said in
    "dreams of a final theory" that nobody knows if a unified field theory will be found in a few years or a few hundred years.Why is a theorist of his stature so unconfident.
    Would it be because deep down he doesn't believe the standard model is correct-
    it leaves out gravity without proving that this is okay.And nobody even knows if gravity in principle has a force-mediating particle.Looking for symmetry in physics is undoubtedly a useful thing to do but why the universe is so symmetrical is not understood.There are deep questions like this which have not been answered or perhaps can't be answered.But physicists should at least try and see if they can in
    case the answers lead to new knowledge that can benefit society as a whole.

    As regards my question at the start of this thread:because dark energy particles striking an electron would carry so little momentum (10^-27 kg in one m^3 : 10^-63 kg could strike an electron from one side at most in
    10^-8 seconds, if the dark energy particles move at the speed of light and if the electron had a radius of some sort of the order of 10^-18 metres.This amounts to an acceleration of 10^-16 m/s^2 at most, and it would take
    an electron at least one million seconds to move 10^-10 metres and change orbitals), they would not be able to push an electron with many many orders of magnitude more mass around to any significant extent - certainly not in the sort of timespan over which a typical electronic transition occurs - about 10^-8 seconds.From this point of view my proposition is flawed.But if dark energy particles that collide with an electron and become fermions (let's suppose that dark energy particles can be bosons that yield fermions), and add to a space that is already saturated by dark energy fermions,since fermions obey Fermi-Dirac statistics, the new dark energy fermions might cause the space around the side of the electron where the collision occurs to expand to accommodate them, and this expansion of space could push the electron toward the proton.
    How much new space could be created by a single fermion obeying fermi-dirac statistics in space already saturated with fermions -does this idea have a reasonable chance of being right?
     
    Last edited: Aug 27, 2004
  10. Aug 27, 2004 #9
    That was the 1970's. In 2005 we are overwhelmed with theories that try and predict what the next experiment will be. Due to the cost of doing high energy research, there really isn't a lot of new data out there. Since you agree that experimentation is necessary, get out there and do some.

    If you insist on throwing around theory instead, try to mathematically show (using QM) that an electron in a given state, subjected to a given energy density causes it to change orbitals in such a way that exactly equals the uncertainty principle.

    Hint: It won't work.
     
  11. Aug 27, 2004 #10
    Locrian:
    If you insist on throwing around theory instead, try to mathematically show (using QM) that an electron in a given state, subjected to a given energy density causes it to change orbitals in such a way that exactly equals the uncertainty principle.

    Hint: It won't work.

    KURIOUS:
    If you read my edited post you will see that I proved what you say without QM and then go on to suggest an alternative.And if you check many of my threads on this forum and on other forums you will see I use experimental data whenever I try to predict new data.But as Dirac said "Einstein did not rely on new data to come up with a new theory." New data is not necessarily necessary.
     
    Last edited: Aug 27, 2004
  12. Aug 27, 2004 #11
    Actually, since you didn't use QM, you didn't even disprove anything, since none of it had any meaning. You can't talk about accelleration caused by interaction on that scale in an atom, it has no meaning. Why are you assuming these "dark energy particles" have mass and are moving at the speed of light? Seems you don't think as much of Einstein as you pretend. And... why is your momentum in units of mass :surprise:

    To TD with you!!!
     
  13. Aug 27, 2004 #12
    Locrian:
    Actually, since you didn't use QM, you didn't even disprove anything, since none of it had any meaning. You can't talk about accelleration caused by interaction on that scale in an atom

    KURIOUS:

    That would be surprising given that Rutherford calculated the size of an atomic nucleus using such an interaction.Dark energy particles have to move near light speed because observation suggests they are more energy like than particle like and that their pressure has to be of the same order of magnitude as their energy density.
    And as for Einstein: I've been learning GR for months now nad even bought a book
    "a first course in relativity" by Schutz.You shouldn't prejudge people with different points of view to your own - as a scientist you should look for evidence.I would be more convinced of your willingness to contribute to rational debate if you had actually commented on the last part of my post which is a new idea about dark energy founded on established physics.
     
  14. Aug 27, 2004 #13
    Rutherford most certainly did not calculate the size of the nucleus using classical mechanics. He found it experimentally. You know, those experiments you refuse to do? A little history would make these wierd Einstein/Rutherford arguments you make more applicable.

    The second part of your post required no comment since it contained no mathematical or physical information. You didn't even come up with a single numberical value for an observable. You once again fail to relate anything you say to a quantitative calculation of uncertainty. You couldn't even disprove your old statement logically because you refuse to even try and calculate the uncertainty in these situations. You've failed at every turn to produce anything useful around this theory and simply dodge the mediocrity that implies by throwing around words any way you can.
     
  15. Aug 27, 2004 #14

    Tom Mattson

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    What makes it right is the empirical fact that particles really do have wave characteristics.

    I'm not a fan of Bohm's version for precisely the same reason. Jeff puts it perfectly in the thread Is Bohmian mechanics true?..:

     
  16. Aug 27, 2004 #15

    Tom Mattson

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    It seems to be flawed from another point of view as well. You keep talking about the electron being pushed around over distances as though those distances defined the orbits. They don't. This is precisely what I meant when I said that your languages was a little loose for me.

    You are treating the atom like a miniature version of a solar system, and it is just not like that.

    I know you like to talk about these "What if?" scenarios, but they really do fall outside the scope of the Forums here. You've got dark energy particles that are bosons, but can "yield" (whatever that means) fermions via collision, which in turn expands space, and all for no apparent reason other than to construct an ad hoc "mechanism" of the uncertainty principle. But the truth is that it wouldn't explain anything, because this undetectable field of particles are subject to the uncertainty principle themselves.
     
  17. Aug 27, 2004 #16
    Tom Mattson:
    You are treating the atom like a miniature version of a solar system, and it is just not like that.

    Kurious:
    An electron is on average at 0.529 Angstroms from a proton in its groundstate - QM prediction of this matches Bohr's classical prediction.So it is reasonable of me to speak of average interactions regarding an electron at this distance.

    Tom Mattson:
    You've got dark energy particles that are bosons, but can "yield" (whatever that means) fermions via collision, which in turn expands space, and all for no apparent reason other than to construct an ad hoc "mechanism" of the uncertainty principle

    Kurious:
    I was hoping someone would comment on whether or not adding fermions to a space saturated with fermions would cause that space to expand and by how much it would expand.

    Tom Mattson:
    the truth is that it wouldn't explain anything, because this undetectable field of particles are subject to the uncertainty principle themselves.

    Kurious:
    My main point is just to pose the question as to whether or not pressure exerted on an electron by particles around it could account for the lifetime of an excited to ground transition.
    I agree that I make a lot of "what if " propositions but there is no point in learning physics just so you can show other people how much you know, as many people on this forum and other forums do!
    I would like your opinion on whether or not dark energy could oppose the
    collapse of a star (since DE causes expansion of space).This is where my thinking
    on the uncertainty principle really started - could DE inside a neutron star, account for neutron degeneracy pressure instead of uncertainty.And could it stop a singularity from forming in a black hole? These are probably not easy questions to answer but it would be nice even just to know why they are not easy questions to answer.
    I said I am a fan of Bohm's theory - I didn't say I thought it was right!
    The pilot wave can change instaneously along its length.I'm with Einstein on such an issue and I say no to "ghostly action at a distance."
    I'll keep looking for evidence of an FTL signal.One that is still somehow compatible with relativity theory.


    Locrian:
    Rutherford most certainly did calculate the size of the nucleus using classical mechanics and he was so excited when he did it that his handwriting became
    shakey.I agree that I could have stuck closer to the issue of uncertainty that I mentioned at the start of this thread.
     
    Last edited: Aug 27, 2004
  18. Aug 27, 2004 #17

    Tom Mattson

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    First things first.

    Before doing anything else, this needs to be addressed. You can't just say, "it is reasonable", semiclassical arguments have to be justified. It is not at all clear to me that you can use accelerations and average values of positions when examining atomic orbitals. It is simply not the case that distance from the nucleus determines the energy state of an electron.

    You've asked for some numerical results in this post, and I'm not sure it's worth taking the time to do them. At least not until I'm convinced that an approach based on how far an electron is pushed is a valid one.

    That's right, people don't learn physics just to show how much they know. They learn physics so that they can go out and do physics. But we don't do it by making needless suppositions, such as a field of undetectable fermions that makes it look as though the uncertainty principle applies.
     
  19. Aug 27, 2004 #18
    Last edited: Aug 27, 2004
  20. Aug 27, 2004 #19

    Tom Mattson

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    The link just takes me to the main page. You'll have to be more specific if you want me to find the page that you believe makes your point.

    The Lamb shift is irrelevant. That is a small correction to s-wave energy levels due to the fact that s-wavefunctions are nonzero at the nucleus. In any case, the expression for the Lamb shift is not a function of the distance of the electron from the nucleus.

    When you talk about the uncertainty principle that describes the decay from one state to another, you are necessarily talking about the eigenvalues of the atomic Hamiltonian, not second order effects such as the Lamb shift.
     
    Last edited: Aug 27, 2004
  21. Aug 27, 2004 #20
    http://hyperphysics.phy-astr.gsu.edu/hbase/hframe.html
    LOOK IN THE INDEX ON THE RIGHT HAND SIDE OF THE PAGE AND AT THE ENTRY "LAMB SHIFT"

    Anyway, if an electron could in principle interact with some other particles which pass through the space around the proton, it would take some time before interacting by a chance collision and emitting a photon.It would take a certain time before it collided and lost energy.
    This is not an unreasonable idea.
     
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