The Speed of Light is NOT About Light

Caption notes

PBS Space Time starts with transformations between inertial frames to explain the constant c in special relativity. The episode connects two ideas. Lorentz transformations preserve the same speed scale between inertial frames, and electromagnetic waves described by Maxwell’s equations travel at c in vacuum. The episode calls c the speed of causality because, in special relativity, it bounds which events a signal can reach from a given event. It also points out that the symmetry and relativity arguments it presents by themselves leave open the Galilean case with an infinite speed limit.