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Can someone give me a good plausible answer

  1. Sep 19, 2007 #1

    Ian

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    1/. I have calculated the ratio between gravitational and electric forces in atoms and it is ~ 2x10^39.

    2/. I have calculated the value "velocity of light squared / permitivity of vacuum squared" and it is exactly half the value of 1 above.

    Why the similarity?
     
  2. jcsd
  3. Sep 19, 2007 #2

    ZapperZ

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    1. I'm skeptical. How exactly did you find this? You have to make SOME assumptions somewhere (as in at what distance did you calculate each of them, and that an electron actually is in a particular location, which would not work with QM). And in making such assumptions, you are already making an approximation.

    2. Unlike #1, this ratio is NOT dimensionless. So how can you compare the two?

    Without you showing what you have done, there's no way to know why you accidentally got such a thing.

    Zz.
     
  4. Sep 19, 2007 #3

    russ_watters

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    3. "Exactly"? You have only one significant figure there!

    Look at enough numbers and you will find coincidences much more interesting than this.
     
  5. Sep 20, 2007 #4
    Although "Big Number" comparisons are not known for their precision so much as their accuracy, they must be of similar dimensions to establish any correlation. One could hypothetically (and erroneously) create arbitrary systems of measurement to make correlations between numbers with any combination of units.

    Here are results you may wish to digest: http://www.google.com/search?hl=en&q=%22big+numbers%22+Dirac&btnG=Search
     
    Last edited: Sep 20, 2007
  6. Sep 20, 2007 #5
    I think that Mr. Watters is correct about the coincidence. When I used to work with radar in the Navy the number 1.414 microseconds would be a constant in determining range. I always thought it was odd that 1.414 is the square root of two but that was only a coincidence.
     
  7. Sep 20, 2007 #6

    rbj

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    does it really matter what the distance is? they're both inverse-square. the ratio of forces are the same at different distances.

    that 10-39 is a common figure we see all the time. it's why they commonly say that gravity is by far the weakest of the fundamental interactions. but being a Planckian Unitarian, i would say that the ratio of forces is so disparate because, while the Elementary Charge is in the same ballpark as the Planck Charge, the mass of any of those particles is far, far less than the Planck Mass. that's why gravitational forces are so much smaller than the EM forces.
     
  8. Sep 20, 2007 #7

    ZapperZ

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    Ah, but it does!

    Depending on what atom you are using, there's something called SCREENING. This is where the outer shell electrons are screened from the nucleus by the inner shell electrons. So yes, it DOES make a difference. That is why I also asked what kind of ASSUMPTIONS that were made in deriving such numbers. If you ignore QM completely, then wouldn't that in itself ring a very loud bell in your head?

    Zz.
     
    Last edited: Sep 20, 2007
  9. Sep 20, 2007 #8

    rbj

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    assuming both particles are charged ( +/-e ), does it make so much a difference that the EM forces (or the effect of the EM potential energies in the QM solution) do not completely overwelm the gravitational forces (or the effect of the gravitational potential energies in the QM solution) by a factor of somewhere around 1039?

    it's not an exact ratio, ignoring QM, but that ratio of around 1039 is commonly cited in the lit as the ratio of EM over gravity for a pair of charged elementary particles. doesn't that ballpark figure come from just the two inverse-square relations using the known charge and known masses of the particles?
     
  10. Sep 20, 2007 #9

    ZapperZ

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    Er.. we're not arguing about the forces between 2 charged particles. If we are, I wouldn't have asked about the assumptions about the atom. Please read the OP. He claimed that he "... calculated the ratio between gravitational and electric forces in atoms.."

    Zz.
     
  11. Sep 20, 2007 #10

    rbj

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    i guess i was thinking that the gravitational and electric forces in atoms were the gravitational and electric forces between the constituent particles inside the atoms.

    dunno what else it would be.
     
  12. Sep 20, 2007 #11

    Shooting Star

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    I think he has calculated the ratio of the electrical to the gravitational forces between a proton and an electron, which is about 4.4*10^40. (A Hydrogen atom!)

    (As a matter of scientific history, the existence of such a high dimensionless number was interpreted by many early scientists, like Eddington and Jeans, to be equal to the number of particles in the Universe.)
     
  13. Sep 20, 2007 #12

    Ian

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    Shooting star is right, I did use the Hydrogen atom, but only because it is the simplest.
    What I am getting at is that the velocity of light (in vacuo) slows as gravitational potential increases (shapiro time delay).
    We can calculate the velocity of light from the permitivity and permeability of a vacuum and therefore the magnitude of permitivity in vacuo must change also if the velocity of light changes.
    This means that if we measure the velocity of light at the earth's surface and obtain the value we know, and then measure the velocity of light, say, at the neutral point between sun and earth, it must be greater than we observe here on the earth.
    This all points to the possibility that matter moves a little slower than we think (calculate) as gravitational potential decreases, and I wonder if there might be an answer here for the pioneer anomaly.
    I won't go into how I came across what you call "coincidence", I got censured for that once already and only have one life left.
     
  14. Sep 20, 2007 #13

    ZapperZ

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    See, that is why I asked what scenario you were using to get your answer. When you simply, without qualification, wave your hands and said you did this for "an atom", that is horribly too generic for you to get away with that. In doing this, what you have done is assume a classical scenario.

    Er.. hang on. This time delay is the delay in light traveling near a gravitational body when compared to when a body isn't there. It is due to how gravity affects spacetime within the vicinity of that object. In naive terms, it means that light has to travel a "longer spacetime distance". It has nothing to do with light being "slowed down".

    You may want to go back and double check this, because if this is the whole premise that you are building this on, then it might be faulty.

    Zz.
     
  15. Sep 21, 2007 #14

    Ian

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    Zapper,
    What on earth makes you think that light gets forced around a corner? If it did it would miss the target at the other end and the radar signal would never return! Sometimes you really ought to ignore what the math makes you think and listen to your common sense.
    Look, what you have said is that space-time gets "stretched" to a longer length by matter and therefore you are back in the realm of a sort of 'aether' which you also say is non-existent.
    I mean, you simply cannot change the length of something that you say is not there, and besides, you look at light and call it e-m radiation even though it appears to pass really close to the immensely strong electrical & magnetic fields of the sun and nothing happens to it.
    I just look at things in a different and more interesting manner to you that's all, like you say 'Saturns Rings' and I say 'Balmer/Paschen series lines'. But your petato ain't like my potato, is it?
     
  16. Sep 21, 2007 #15

    ZapperZ

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    That is why I said it was a naive description!

    Your insistence that this is a "time delay" that is similar to a photon slowing down isn't valid either. No where in GR is there any mention of such a thing. Would you like to point out exactly where this "time delay" has been associated with a photon slowing down? If it has, all of our measurement of the positions of various celestial bodies are wrong!

    Zz.
     
  17. Sep 21, 2007 #16
    should this thread (now) be moved to the 'relativity' area?
     
  18. Sep 21, 2007 #17

    DaveC426913

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    Go figure. A real world application of truthiness

    - something that a person claims to know intuitively or "from the gut" without regard to evidence, logic, intellectual examination, or actual facts.
     
  19. Sep 21, 2007 #18

    Ian

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    Hey ZapperZ

    You and me will never see I to I, Eye don't see photons as reality

    [personal theories deleted, and Zapper'Z's name corrected to correct spelling]
     
    Last edited by a moderator: Sep 21, 2007
  20. Sep 21, 2007 #19

    Mentz114

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    Ian said:
    It never changes for local observers. See many threads in this forum.
    Very limited I'd say. You should study GR before coming out with rubbish like
     
  21. Sep 21, 2007 #20

    pervect

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    As far as GR goes, note that the speed of light near a massive body, when measured using local clocks and rulers, is always equal to 'c'.

    See for instance the sci.physics.faq on this topic, which I'll quote in part:

    So the idea that the speed of light changes near a massive body is not necessarily totally wrong, but involves ambiguties as to "which clock" and "which ruler" to use to measure the speed of light with, ambiguities associated with the curvature of space-time. Gravitational time dilation, for instance, says (losely speaking) that clocks at different heights tick at different rates. It should therefore not be surprising that the speed of light is constant only when one picks the "correct" clock and ruler combo. Which pair is that? It is the pair of clocks and rulers associated with a local, free-falling observer at the location in question - what I call "local clocks" and "local rulers".

    Using these clocks and rulers, the speed of light will always be equal to 'c'.

    Note that this has absolutely nothing to do with the ratio of electromagnetic force to gravitational force as far as I can tell.

    Also a general reminder: we do not allow discussion of personal theories here on PF.
     
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