Issue with Gravitons

[Radical Edward]

I'm really not working in this area at all, so my thoughts might be right off, and if there is good reason, I'm quite happy to abandon this line of enquiry... anyway, on to my issue with gravitons.

 

Firstly, by the equivalence principle if we imagine ourselves in a box which is being accelerated, we cannot tell whether it is being accelerated at 1g towards a planet which is below us, or accelerated at 1g by a rocket moving upwards (relative to the box) in free space - both cases in an otherwise empty universe. in my box I have a hypothetical 'graviton detector' which is good enough to detect gravitons from a planet (in reality no such thing could exist, because you'd need a detector the size of jupiter orbiting a neutron star for 10 years just to make a single measurement)

 

now if we consider gravitons being emitted from the planet towards the box, we have lots of sources - a whole planet's worth. but if we consider the empty universe with a box on a rocket, then there is no source.

 

so what is the source? when we consider other force carriers, like photons, they are emitted from a source (accelerating electron/proton or something like that), but with the graviton it is not so trivial. Both of these cases should result in an ideal detector as mentioned above detecting the same number of gravitons, but where are they coming from? First thoughts are something related to the curvature of space itself but it's not clear where to go with that.

[Mordred]

The stress energy/momentum tensor. The graviton would be a gauge vector boson. What many don't realize is the photon as a mediator (gauge vector boson) isn't precisely the same as a photon the particle. In so far as it's akin to a virtual photon. (Off shell).

 

Another common misconception is thinking of particles as little bullets.

 

Particles are excitations in a field.

Here is a good coverage.

 

http://www.google.ca/url?sa=t&source=web&cd=15&rct=j&q=particles%20as%20excitations%20of%20fields&ved=0ahUKEwjTm_va2a7LAhVW-mMKHZ3MDuYQFghWMA4&url=http%3A%2F%2Farxiv.org%2Fpdf%2F1204.4616&usg=AFQjCNGvQ8n6ZVIKYjFHcDC_yoFRbWmNkQ

https://en.m.wikipedia.org/wiki/Force_carrier

Edited March 7, 2016 by Mordred

[Radical Edward]

ok that's great, thanks. I thought it would be down to something like that.

[ajb]

Weinberg (and others) showed that if we have a Lorentz invariant theory of massless spin-2 particles the consistency of the theory leads to the equivalence principle; in the form that all particles (at low energy) couple to gravity in the same way.

 

As for 'Einstein's elevator', I am not sure, but the gravitons you are talking about are strongly off-shell and so not detectable in principle.

[MigL]

Further to Mordred's and AJB's responses, the gravitons are not 'emitted' by the planet in your equivalence scenario.

Rather they are a manifestation of a gravitational quantum field ( for which we don't have a working theory ).

And the equivalence principle states that the two elevators in your idealized scenario would experience the same space-time curvature, hence the same bosons.