What is the theory of relativity?
A theory that explains
“1. The principle of relativity
The laws of physics are the same in all inertial frames of reference in constant motion
- The constancy of speed of light in a vacuum
The speed of light in a vacuum has the same value c in all frames of reference”
Einstein’s first postulate means that if you are standing still relative to the earth, you’re in an inertial frame of reference, and everything you view that’s not accelerating will have the same laws of physics. His second postulate states that no matter if you’re in an inertial frame of reference or not, the speed of light remains constant.