In fact, c stands for the speed of causality. But it is easy to say that it is the speed of light. It really is the speed of light. So why is the speed of light the speed of causality? Galileo stated in the principle of relativity that all experiments must have the same results under constant velocity. However, this principle of relativity does not determine the speed of light.
Suppose an electrician was following a ship carrying lightning. From Maxwell’s equations, the field strength of an electric field can be calculated from the total velocity of that electric person. So what is total velocity? According to Galileo, total velocity is the velocity of the electrician onboard + the velocity of the ship. Field strength is not a field. force electromagnetic force. This force is called the unregulated Lorentz force.