# How is the electromagnetic/gravitational force transmitted? [duplicate]

So I was thinking about how a positive and a negative charge (or positive/positive, negative/negative) interact. I have read previously about how photons carry the electromagnetic force. However, how does this occur exactly?

How does a photon compel a particle to move towards/away from another? At the very least, if we say that a positive charge emits photons and a negative one absorbs them (seems wrong, but I guess that's what happens?), then wouldn't the negative one be repelled away instead?

Similarly, for gravitation, I understand that it's the curvature of spacetime that results in the "force". However, what compels a particle to move down the curvature of spacetime and not just stay where it is? In a regular rubber sheet situation, it is gravity that pulls an object down a curve. However, in spacetime there's no such equivalent.

Any help would be greatly appreciated!

• chat.stackexchange.com/transcript/message/50969499#50969499 refer this from beginning.I hope this helps you a bit. – P-S-S Jul 21 '19 at 3:36
• Possible duplicate of How are fundamental forces transmitted? – BioPhysicist Jul 21 '19 at 4:28
• The idea that particles move “down” the curvature of spacetime is wrong. Freely-falling particles (i.e., those with no non-gravitational forces acting on them) simply move “straight ahead” through curved spacetime. It’s like “Newton’s First Law” but in curved spacetime. – G. Smith Jul 21 '19 at 5:33
• The idea that photons are only emitted by positive charges and only absorbed by negative ones is wrong. Repulsion of like-sign charges is also mediated by photons. Both positive and negative charges can emit and absorb photons. – G. Smith Jul 21 '19 at 5:34
• How does a photon compel a particle to move towards/away from another? By transporting four-momentum between the two charged particles. – G. Smith Jul 21 '19 at 5:39