How we know gravity is not electromagnetic (split from electricity explains everything)

[robinpike]

Anyway, all personal attacks aside, EllyDlight now has the chance to rethink based on the replies here. In short, there is no way we can properly explain gravitational phenomena using electromagnetic theory. It was a nice thought, but discounted a lot time ago.

 

ajb, separate to EllyDlights thoughts, I would be interested to know, did you have a particular example in mind with your above comment?

[ajb]

ajb, separate to EllyDlights thoughts, I would be interested to know, did you have a particular example in mind with your above comment?

Gravitational lensing would be a good example. Photon-photon scattering is very suppressed and does not happen very often. I read that the Large Hadron Collider (LHC) at CERN could detect 20 photon-photon events or so per year. So there is no way you would see any light bending due to photon-photon interactions.

 

I am not even sure how one could attempt to describe gravitational phenomena using just EM theory. Planet are just about electrically neutral.

 

One core concept of gravitational physics that does not work in EM is the equivalence principal. The motion of test particles does depend on the intrinsic properties of the test particle, in particular the charge-mass ratio. I posted on my blog more details of this, but in short using Newton's second law and Coulomb's law you see we don't have an equivalence principal.

[robinpike]

ajb, thanks for putting up the detailed explanation on your blog.

 

So theories that attempt to explain gravity through an electromagnetic theory can always be discounted - that is, unless they happen to include an explanation for the following observations (which no electromagnetic theory so far has been able to do)...

• Light is affected by gravity (as demonstrated by gravitational lensing), but light is not affected by electric fields - for example photon-photon interaction.
• Acceleration of an object due to gravity is not related to the mass-charge ratio of the object, whereas acceleration due to an electric field is related to the mass-charge ratio of the object.
• Neutral objects are influenced by gravity (for example the orbits of the planets), whereas neutral objects are not influenced by electric fields.

However, the current absence of an electromagnetic solution to the above is not proof that one does not exist, although obviously as time goes by, it would seem to be more and more likely that such explanation is not possible.