The laws of physics are the same in all inertial frames of reference.
Relativity
Field: Relativity
Sequence of Expressions
The speed of light in a vacuum is the same for all observers, regardless of the motion of the light source or observer.
The gravitational force as experienced locally while standing on a massive body is the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.