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Modified Newtonian Dynamics vs. Quantum Gravity

  1. Sep 26, 2015 #1
    OK. I'm sure this is probably been considered before but it is my musings coming off a recent attempt to photograph the Andromeda Galaxy. I did a few two minutes or so shots of Andromeda and stacked them for a total of about 14 minutes. Fairly nice. There is some structure to be seen but nothing like photographs in magazines. (I'm just getting started in this field). I compared it to some really nice shots of Andromeda and see to really get a good shot of it I need a total nine hour exposure. Wow! But more importantly, why? Simple, because light is not a continuous wave, it's a photon, a quantum particle. If I just look at Andromeda through my telescope, I just see a fuzzy cloud in the sky with none of the grand structure one sees in long exposures. My eye isn't integrating the photons. So many of the emitted photons from the stars in Andromeda aren't being captured by my eye. Even if I got so close to Andromeda as it filled my naked eye field of view, it would still appear as a fuzzy spot with little or no structure. You would not view it as one does in photographs of it. The photons are just too rare.

    So if Gravity is also just the result of gravitons, wouldn't that create the same phenomenon? If you are so far away from a graviton source, you are missing a large amount of gravitons, it's not merely diffuse. You just aren't interacting at all with the source. At least some of the time. But you are also moving. You are rotating around the center of the Galaxy, which is your primary source of gravitons. But you are missing a lot of them. Thus would that create the rotation problem we observe?

    So would a proper quantum view of gravity give the same results as MOND? And thus obviate the need for dark matter?

  2. jcsd
  3. Sep 26, 2015 #2


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    Or a larger and better telescope, or a better camera (lower noise, better photon efficiency).
    True, but this has nothing to do with quantum mechanics.
    You would see a structure then.
    Be careful here. At best (and even this is speculative), gravitons might be a useful concept to describe gravitational waves and perturbative effects. The classical gravitational attraction is better described by a field, in the same way you don't use photons to describe the static field around a nucleus (you can, but it is impractical).
    You are. Always.
    This does not make sense.
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