Light, EM wave, gravity and electrostatic force all have the same speed, there must be serious connection.

2 electrons at r distance exists a force f=kee/rr, that force is the carrier of EM radiation. That's why light speed is equal to electrostatic force speed and decay at distance square.

Atoms are constantly vibrate, share their vibration EM force with other atoms, f=gm1m2/rr and f=kq1q2/rr connected all matters. The whole universe is ruled by the two forces.