# Tag Info

74

Your intuition is good, but you're mixing up some quantum and classical phenomena. In classical (i.e. non-quantum) physics, a vacuum is a region of space with no matter. You can have electromagnetic fields in a vacuum, so long as the charges creating the fields are in a different region. By the same token you can have gravitational fields in a vacuum, ...

17

The graviton is the hypothetical gauge boson associated with the gravitational field. I say hypothetical because it is far from clear whether gravity can be described by a quantum field theory, so it isn't clear whether gravitons are a useful description. In any case, you should not take the notion of virtual particles like the graviton too seriously. have ...

6

You are simply confusing vacuum with "nothingness", which is a philosophical concept. You can check the definition at wiki Vacuum is space that is devoid of matter. The word stems from the Latin adjective vacuus for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure.[1] ...

5

In quantum mechanics, it's impossible to remove all the particles from a vacuum. A volume of space time that contains only photons and gravitons in thermal equilribium (or not) sounds like a perfectly good vacuum to me.

4

In principle a gravitational wave will travel slower than $c$ when passing through matter, but in practice the reduction in speed is absurdly small. Consider first a light wave passing through a dielectric. You can explain what happens using either classical or quantum approaches, but we'll use a classical description since that's all we have available for ...

3

We only have experimental evidence for one symmetry breaking i.e. the breaking of the electroweak force into seperate electromagnetic and weak forces. With the discovery of the Higgs boson the electroweak symmetry breaking is now well established. The mechanism by which symmetry breaking occurs is complex, and to be honest it's impossible to give a layman ...

3

From the analogue of simple quantum mechanics Feynman diagrams, the graviton is what is being exchanged for two particles to feel an attractive force. Analogous to the exchange of a photon for the electron to interact with another electron. first order feynman diagram electron electron interaction The analogous diagram for the gravitational ...

1

I think it is best to answer the question "What are gravitons?" to find out what they do. In quantum field theory, one constructs fields from representations of the Poincare group. The Poincare group has a rotation subgroup, so the fields have certain transformation properties under rotations, which we refer loosely to as the particle's spin. From this ...

1

Imagine you are sitting a rowing boat on a lake. Stern-to-stern is another boat with an accomplice in it. You are both sitting facing each other (and the stern of your boat). The lake is still, there is no wind. You have a brick on your lap. You take the brick and gently lob it to your accomplice who catches it. What happens? By conservation of momentum, ...

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