Chapter S3 Spacetime and Gravity
The laws of nature are the same for all reference frames.
The effects of gravity are exactly equivalent to the effects of acceleration.
Equivalence principle 1 2
3 space and 1 time = 4
a worldline 1 2 more imaginative worldlines 1 2 3 4
But what if it is curved?
Shortest distance on a sphere is a great circle 1 2
Three geometries 1 2 3
Inertial frames are in straight worldlines. Non-inertial [with gravity/acceleration] are curved.
What we perceive as gravity is the curvature of spacetime.
Mass causes spacetime to curve and the curvature of spacetime determines the paths of freely moving objects.
Rubber sheet views. 1 2 black holes and event horizons.
Detection by LIGO