We always hear about the force of gravity being the odd-one-out of the four forces. And this argument, whenever it's presented in popular science at least, always hinges on the relative strength of the forces. Or for a more in depth picture this excellent thread. But, having had a single, brief semester studying general relativity, I'm struggling to see how it is viewed as a force at all.
A force, as I understand it, involves the interaction of matter particles with each other via a field. An energy quantisation of the field is the force carrying particle of the field.
In the case of gravity though, particles don't interact with one another in this way. General relativity describes how space-time is distorted by energy. So what looked to everyone before Einstein like two orbiting celestial bodies, bound by some long distance force was actually two lumps of energy distorting space-time enough to make their paths through 3D space elliptical.
Yet theorists are still very concerned with "uniting the 4 forces". Even though that pesky 4th force has been well described by distortions in space time. Is there a reason for this that is understandable to a recent physics graduate like myself?
My main points of confusion:
- Why is gravity still viewed as a force?
- Is the interaction of particles with space time the force-like interaction?
- Is space-time the force field?
- If particles not experiencing EM/weak/strong forces merely follow straight lines in higher-dimensional space (what I understand geodesics to be) then how can there be a 4th force acting on them?
Thanks to anyone who can help shed some light on this for me!