>>11300180In reality, if you go deep into the philosophy of science, what’s really going on here is einstein saying if you define your ways of measuring space and time, define the rate of flow of time in a manner that it makes the laws of physics look simple so for example that time is ticked at a regular way by atomic clocks, atoms vibrate in a molecule, and if you define space in such a way that the laws of physics looks simple so that if you measure the distances between atoms in a lattice those distances are always the same, if you define length and time in a way that makes laws of physics look simple then the speed of light will always be the same for everybody.
It’s the one constant that results from asking that the space and time be defined so that laws look simple