As far as we know, all interactions of forces can essentially be attributed to four fundamental forces - electromagnetic force, gravity, strong nuclear force, and weak nuclear force. For example, the magnetic and contact forces (including frictional and elastic forces) that attract magnets to each other are essentially electromagnetic forces.

In theory, each fundamental force is transmitted by a fundamental particle (the graviton that transmits gravity has not yet been discovered), and in the case of electromagnetic force, its transmission depends on photons. Since electromagnetic interaction exchanges photons, why can't we see the two magnets that attract each other or the light emitted when pushing an object?

According to quantum field theory, photons carrying electromagnetic force are not ordinary photons, but virtual photons, and we cannot see these virtual particles that exist for an extremely short time. So, how do virtual photons transmit electromagnetic force?

Virtual photons are photons generated by borrowed energy and momentum, which is a result of the principle of uncertainty. According to Et ≤ h/4 π, virtual photons borrow more energy and exist for a shorter period of time. This means that high-energy virtual photons will be generated near a charged particle, and they will disappear after a short distance of propagation. The lower the energy of virtual photons, the longer they exist and the farther they propagate. It can be seen from this that virtual photons can violate the laws of energy and momentum conservation in a short period of time.