* In 1905, Albert Einstein published his "Special Theory of Relativity", a simple and elegant hypothesis that made a number of remarkable assertions:
These assertions have been confirmed by observations and experiment, and are now generally accepted. Einstein used his theory of Special Relativity as a springboard for a much more comprehensive "Theory of General Relativity", which is also generally accepted. This document explains how Special Relativity works and provides a short survey of General Relativity.
To understand this document, a reader will need to be comfortable with high-school algebra and geometry. Readers will also need to be familiar with fundamental concepts of classical mechanics. A review of these fundamental concepts is available in the first chapters of a companion document, Elementary Classical Physics. Those preferring a less detailed treatment of relativistic physics may be interested in the brief companion document A Relativity Primer.