Quantum Field Nature Of Gravity

Discussion in 'Astronomy, Exobiology, & Cosmology' started by wet1, Jan 23, 2002.

  1. wet1 Wanderer Registered Senior Member

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    Neutron Bounce Quantized in Earth Gravity
    Illustration Credit: Mark Bowick (U. Syracuse) et al., NPAC
    For the first time, Earth's gravity has been used to isolate quantum energy levels of the neutron. The effect may be used in the future to test for slightly different effects of gravity on neutrally charged particles of different mass. In an experiment by Valery Nesvizhevsky and colleagues at the Laue-Langevin Institute, carefully dropped neutrons were seen to appear at only discrete heights. The effect is also of interest because it involves the intersection of two branches of physics that remain formally separate. A theory known as Quantum Mechanics tells us about how the universe works on the smallest scales, while Einstein's General Theory of Relativity tells us about how gravity and the universe works on the largest scales. The effect does not in itself, however, imply attributes of a possible quantum field nature of gravity. Pictured above is a false-color surface that might be created by the evolution of a one-dimensional string. By describing fundamental particles as tiny strings, many physicists are working toward the creation of a truly quantum theory of gravity.
     
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  3. Mr. G reality.sys Valued Senior Member

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    Is it Gravity that is quantized or its observation?
     
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  5. Crisp Gone 4ever Registered Senior Member

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    Tough one...

    Hi Mr. G,

    Tricky question. I don't think we can answer it for gravity already, but assuming that gravity behaves more or less the same as electromagnetism (you shouldn't stretch this analogy too far though), I think it is gravity that would be quantized.

    You see, the quantum of the electromagnetic field is the photon. When we measure the energy released by an electron (electromagnetically bound to a nucleus) we see that the energy indeed comes in packets - photons. Thus, a change in an electromagnetic field is only possible with quanta, so we conclude that the electromagnetic field is quantized.

    I can hear you think "but the experiment could still be quantized" but there are other effects that can only be explained when electromagnetic fields are quantized. For example: two photon absorption by an electron: an electron that would only react to blue light (high energy) can also react to red light (= low energy) when it absorbs two packets of red light (2 * low = the high energy needed for "blue" absorption). You can actually see this if you shine a red laser on a blue fluorescent medium.

    Ofcourse this involves measurement again (with the eye or photosensors or whatever) - but the effect wouldn't be possible (or explainable in a reasonable way) if light didn't come in packets as we think it does.

    It's not an exact reasoning (plenty of holes) but I think it will get the discussion started

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    Bye!

    Crisp
     
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  7. Mr. G reality.sys Valued Senior Member

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    I'm all for quantized gravity -- Gravitons, and mass -- Higgs Bosons, if they turn out to be real by consensus, but I'm still a little skeptical of your speculation that the observed discrete Neutron accelerations could be the behavioral equivalent of photons expressing themselves in whole-wavelength-multiples circumferenced atomic energy orbitals.

    What source for the gravitational destructive interference that the experimentally observed Neutrons seem to abhor?

    Gravitons of differing frequencies?
     
  8. Boris2 Valued Senior Member

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  9. Jeffery Winkler Registered Member

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    Some people are missing the point

    Some people are missing the whole point of this article. No one today could imagine that gravity is not quantized. What would be the alternative? Obviously no one ever doubted that gravity was quantized. The reason the experiment is important is becase it was amazing to actually observe it. You can actually see the energy levels of the neutrons in the Earth's gravitational field analogous to the energy levels of a hydrogen atom.

    Jeffery Winkler

    http://www.geocities.com/jefferywinkler/Aristotles_Lyceum_in_Cyberspace.html
     

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