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ptalar
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Does the discovery of gravity waves imply the existence of gravitons?
Unless the room is filled by a superfluid. Second sound.Shyan said:e.g. no one quantizes the temperature field of a room!
mfb said:No.
If gravity can be quantized - and that is the usual expectation - then gravitons should exist, but that knowledge didn't need the direct observation of gravitational waves. Under this assumption, the direct detection allows to put upper limits on the graviton mass, but those are worse than indirect upper limits from the existence of galaxy clusters.
Shyan said:So clearly the existence of some classical field doesn't mean it has to be quantized, e.g. no one quantizes the temperature field of a room!
bcrowell said:This is an apples-oranges comparison. By "field" we don't mean just any function that varies across spacetime. We mean something that carries energy and momentum. Quantization is not optional, for the reasons I described above.
Shyan said:Almost all physicists in the field think that gravitation has to be quantized.
Again, I'm not sure what you mean by quantized but temperature is certainly the result of quanta or particles. It's the speed of the particles that humans sense which gives room its temperature. So I'm not sure your inference: 'because it's possible that temperature is not quantized, it is also possible that gravity is not quantized' is correct.Shyan said:no one quantizes the temperature field of a room!
Nothing goes up and down in quantized electromagnetism, and nothing would go up and down in quantized gravity either. Assuming the direction of propagation of the signal is not called "up" or "down".gamow99 said:The only way a wave can go up and down is if it is composed of parts or particles and one part of the wave goes up while the other part goes down.
True, but we don't get those particles by quantizing the temperature fields, i.e. atoms and molecules are not quanta of temperature fields!gamow99 said:temperature is certainly the result of quanta or particles. It's the speed of the particles that humans sense which gives room its temperature.
Shyan said:True, but we don't get those particles by quantizing the temperature fields, i.e. atoms and molecules are not quanta of temperature fields!
[PLAIN]http://backreaction.blogspot.co.uk/2015/10/a-newly-proposed-table-top-experiment.html[/PLAIN]Shyan said:I can't back what I said with physical arguments because of my lack of knowledge. But there is surely some discussions going on about whether its really necessary to quantize gravity. People are even designing experiments!
Because they don't have to... Gravity waves were by themselves a prediction of classical GR (that was discovered now), and so it's not something that came to be added to searches beyond GR (into quantum gravity)...scopehead said:why gravity waves don't imply the existence of gravitons
Gravity and the rest of the known forces are still something different.scopehead said:Is it an entirely different kind of force?
That's what people believe and they suggest the particle named graviton, which we don't know from where it comes from yet [neither have seen it].scopehead said:I always had thought there was an associated particle with every force
A/4 said:Although the GW that was detected is a classical object (i.e. a prediction of a classical theory), there is some connection to the quantum nature of gravity. That is, if the graviton is massless, we expect GWs to travel at the speed of light.
That's extremely small...A/4 said:At yesterday's press conference, Kip Thorne commented the data allows a constraint on the potential mass of the graviton of mG≤10−55 mG≤10−55 m_G \leq 10^{-55}~ g.
bcrowell said:Gravitational waves have to travel at c regardless of whether they're quantized.
Yeah, yeah...But he clearly didn't have those in mind(or probably didn't know them). I just wanted to make the point that he has a wrong picture of what is quantization.ChrisVer said:I am not sure that you can define temperature everytime via the velocity of particles... Temperature can have several definitions [take for example the case when you can define negative temperatures, just by defining them from the occupation distributions alone]
Another example I can think of is the temperature of the photons, which can vary, but their velocity is always c.
A gravity wave is a disturbance in the curvature of space-time, caused by the acceleration of massive objects. It is similar to a ripple in a pond, but in this case, it is the fabric of space-time that is rippling.
Gravity waves were first predicted by Albert Einstein in his theory of general relativity. They were indirectly observed in the 1970s through observations of binary pulsars. In 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) directly detected gravity waves for the first time.
Gravitons are hypothetical particles that are thought to be the carriers of gravity. In other words, they are the particles that transmit the force of gravity between objects with mass. However, they have not yet been directly observed or confirmed by experiments.
Gravity waves and gravitons are both related to the force of gravity, but in different ways. Gravity waves are disturbances in the fabric of space-time caused by the acceleration of massive objects. Gravitons, on the other hand, are theoretical particles that are thought to transmit the force of gravity between objects. They are not exactly the same thing, but they are both important in our understanding of gravity.
The discovery of gravity waves and the confirmation of gravitons would greatly advance our understanding of gravity and the universe. It would also open up new possibilities for studying and observing the universe, as well as potentially leading to new technologies. Additionally, it could potentially help to bridge the gap between general relativity and quantum mechanics, two fundamental theories that have yet to be unified.