Brief discussion of the events at the start of the 20th century

13.  Albert Einstein (1879-1955)
 the concept of relativity was not introduced by
Einstein, his major contribution was the
recognition that the speed of light in a vacuum is
constant and an absolute physical boundary for
motion.

14.  The Basics
1. essentially deals with the question of whether rest
and motion are relative or absolute, and with the
consequences of Einstein’s conjecture that they are
relative.
2. applies to particles as they accelerate, particularly
due to gravitation, and acts as a radical revision of
Newton’s theory, predicting important new results for
fast-moving and/or very massive bodies.