# Can anyone explain to a novice physicist whether there is a gravitational-electromagnetic symmetry?

I am trying to understand how the four fundamental forces relate to one another and to a theory of everything. As I understand it the unified force that is thought to exist at very high energies gets broken via symmetry breaking into the four forces observed at our energy. I don't fully understand how this happens and in particular if there is a gravitational- electromagnetic symmetry and if, when and how this breaks.

Anyhow, there is some evidence that the electromagnetic, weak and strong forces converge to similar strengths at an energy scale of around $10^{16}$ GeV, and this has lead to speculation about a symmetry breaking similar to the electroweak symmetry breaking, but happening at much higher energies and splitting the strong and electroweak forces. The best known models for this are probably the Georgi–Glashow SU(5) theory and the SO(10) theory. However there is no experimental suppoprt for these theories so at the moment they are entirely speculative. Actually I think proton lifetime measurements have ruled out the simplest SU(5) theory, though I confess I'm not up to speed with this area.