My friend asked me,''which is more basic or fundamental? constancy of speed of light which makes space-time behave dynamically OR dynamical behavior of space-time that makes light to travel with constant speed? I think 1st one because space-time is just a human-created model...''?
I answered ,''space-time is more fundamental ,because speed of light is constant only locally,where space-time can be taken as flat ,so constancy of speed of light is a property of space-time ,so space-time is more fundamental(?).''
he replied,''speed of light is always constant ,its only different in different coordinate system''.
So what should be the correct ans?