Do Gravitons Exist?

[Alex K]

The fact is that nobody knows. We know that gravitational waves exist, but there is no real experimental test which could tell us that these waves have quanta the same way electromagnetism has photons. It seems overwhelmingly likely though, for the simple fact that matter causes gravitation, but matter is fundamentally made of particles subject to quantum uncertainty, and it is difficult to imagine how this quantum uncertainty would not get transferred to the gravity. For example, if an electron is in a quantum superposition of being in place A and in place B, what is its gravity? Half here half there? Does the superposition vanish when you measure the gravity? It should! So, in order not to mess up the logic of quantum mechanics, the gravitational force needs to play by the same quantum rules, and that would usually entail the existence gravitons.

Would there be a spectrum of energy analog in regards to gravitons as there is with photons ?

I guess I was assuming the LIGO device was measuring gravitational waves 'composed' of gravitons of identical energy equivalence.  If individual gravitons can have varying levels of energy, well, there outta be some really biguns leftover from the big bang flying around still and scattered sufficiently they are no longer organized into detectable waves but are more like the 'sea of neutrinos' we are saturated in.

And if there is enough of 'em is that the dark matter, or dark energy or quintessence, or ylem they are looking for and not finding ?

In the simplest case, I'd even say in the most likely case by far, gravitons behave like massless particles, and grav. waves are a collective effect of a superposition of many gravitons just as a coherent light wave or radio wave is a superposition of many photons. The energy of an individual graviton would also be given by planck's constant h times the frequency, like with photons.

When you measure the electric field of an em wave, you measure the collective effect of many photon particles, and likewise, when you measure the displacement of LIGO, of gravitons.

Since gravity does not get exponentially suppressed at the distance, gravitons need to be massless to very high precision. This would mean that they get diluted in cosmic expansion with the expansion factor to the fourth power like radiation, and would not form structure. Thus, normal individual gravitons are not a candidate for dark matter. Balls of tightly bound gravitons, i.e. black holes, could serve as DM. Before you cross this threshold of black hole formation, the gravitons would move at light speed.