Remember that light in motion is electric and magnetic fields pushing and pulling each other along. Why that speed? Because it takes time for an electric field to create a magnetic field and vice versa
Our equations for EM waves (Maxwell’s equations) predict light speed, and the same equations would predict c in any system, so long as reasonable values for the variables are known in that system
So 300 000 000 m/s isn’t going to be a reasonable approximation of the speed of light in vacuum, but any alien that one about radio would probably have Maxwell’s equations under some other name
Remember that light in motion is electric and magnetic fields pushing and pulling each other along. Why that speed? Because it takes time for an electric field to create a magnetic field and vice versa
Our equations for EM waves (Maxwell’s equations) predict light speed, and the same equations would predict c in any system, so long as reasonable values for the variables are known in that system
So 300 000 000 m/s isn’t going to be a reasonable approximation of the speed of light in vacuum, but any alien that one about radio would probably have Maxwell’s equations under some other name