Quantum Mechanics after the detection of Gravitational Waves

  • Of course everyone knows by now of the detection of Gravitational waves



    But, since General Relativity and Quantum Mechanics don't get along, can we say now that this detection proves that Quantum Mechanics doesn't actually apply and that General Relativity did prevail?



    Another question: how can we identify the ripple's origin (let's say whether it's a result of the big bang or another big event)?



    EDIT 16-2-2016



    I was reading an article today and I thought I'd share it here; It's basically saying that without a third detector we can't triangulate the signal.
    Some scientists tried ways to observe the light of the event directly after the observations of the wave but they couldn't detect the merger simply because it's too far away or too faint to be observed with our current technology.


    It was a black hole merger, not from the big bang. Primordial gravitational waves have an even longer wavelength, probably too long for LIGO,

    Quantum physics and Relativity are NOT competing theories. They are complimentary theories , with relativity about what happens at massive scales, and quantum talking about really tiny scales. The controversy is nobody really knows how to unify these two fiels. What physicists want is a theory that in one comlete swoop describes how everything works. Maybe an elegant equasion or a set of simple rules. We're not even sure such a thing actually exists, but it'd sure be nice if it did, because that theory would be the pinacle of human scientific achievement. Problem is, nobody really knows how.

  • James K

    James K Correct answer

    6 years ago

    No more than the observation of light waves disproves quantum mechanics.



    Light has properties of both a particle and a wave. At low energies, the particle nature of light is hard to detect: radio waves are made of photons, but individual radio wave photons are pretty hard to detect. I'm not sure that we have directly detected individual photons with energies below the infrared band.



    Gravitational waves (probably) also have both a wave and a particle nature. The gravitational field is probably quantised. But at the frequencies and sensitivity at which LIGO operates, individual quanta cannot be measured. So this detection does not prove the ascendency of GR over QM.



    If anything, understanding extreme events like black hole mergers might lead to a theoretical understanding of the quantum nature of gravity.


    Thank you for your answer it really helped me understand the idea.. I'll mark it as the answer in a couple of hours to give a little more time for other answers as well

    @Odin: waiting a couple (or rather something like 5, or 7) days seems better than just a couple hours, as experts are not always behind their screen...

    There are probably no reasonable experiments that can detect an individual graviton. Here reasonable means things like "is not large enough to collapse to a black hole", and "detects at least one graviton per age of the universe". http://arxiv.org/abs/gr-qc/0601043 And this event really isn't close to where you would expect quantum gravitation. For black holes of 30 solar masses, the Schwarzschild radius is something like $10^5$ m, but the Planck length is something like $10^{-35}$ m.

    Of course compared to something like the solar system, this is extreme: a distance of $1$ AU from the sun (i.e., here on earth), the curvature radius is on the order of $10^{12}$ m, at the surface of the sun some $5\cdot 10^8$ m. But gravitation is *seriously* weak so you are still many many orders of magnitude from quantum gravitation. (Note that large curvature *radius* = small curvature. A large sphere is less curved than a small one.)

    By the way, if anyone knows the energies of the lowest energy photons that have been directly or indirectly observed, I'd be interested.

    "Probably": certainly. The uncertainty principle is contagious and once introduced must apply to everything. You will find that the object's momentum in response to a gravitational force will be an all-or-nothing lump of some minimal size. How that comes about might be more or less convoluted, but the principle must hold. After all, the time and energy (in general) are already showing quantum effects due to the existance of a smallest scale and the conjugate pairing of thise two.

    How does the observation of light *disprove* quantum mechanics? The existence of "particles" doesn't disprove QM any more than that GR could.

    @rubenvb You have misread my answer. The observation of gravitational waves doesn't "disprove" QM. Nor does the observation of light waves.

    Right. I see it now. Never mind me then :)

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