Special Theory of Relativity
(Space, Time, and Motion)
 Principle of relativity: All
observers not acted on by forces experience the same laws (an
assumption, and we also assume that they move with constant velocity).
 Constancy of speed of light:
All observers measure the same speed for light (a fact!).
 Consequences: Time dilation and length
contraction; Increase of effective mass with speed, E = mc^{2}; Mixing of space
and time, replaced by spacetime.
 What does this have to do with black
holes? Special relativity works well as long as
gravity can be considered as a very weak force, and if we only observe
what happens in relatively small regions; But otherwise, you have to
add spacetime curvature...

