*v1.3.0 / TOC (2 chapters) / 01 jul 04 / greg goebel / public domain*

* In 1905, Albert Einstein published his "Special Theory of Relativity", a simple and elegant hypothesis that made a number of remarkable assertions:

- That nothing could exceed the speed of light (300,000,000 meters per
second), even in theory.
- That clocks on an object moving at a fraction of the speed of light, Cf,
will slow down by the factor:
**1 / SQRT( 1 - Cf^2 )** - That the moving object's length will shrink by the factor:
**SQRT( 1 - Cf^2 )** - That a moving object's mass will increase by the factor:
**1 / SQRT( 1 - Cf^2 )**

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
overview of General Relativity. To read this document, you will need to be
comfortable with high-school algebra and geometry. If you are not, you will
not be able to follow the discussion. You 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 on this
site, **Elementary Classical Physics**.

- [1.1] THE ETHER WIND / DOPPLER SHIFT

- [1.2] EINSTEIN'S POSTULATE

- [1.3] TIME DILATION

- [1.4] LENGTH CONTRACTION

- [1.5] RELATIVISTIC SIMULTANEITY & SPACETIME PARADOXES

- [1.6] THE TWIN PARADOX

- [2.1] THE TWIN PARADOX REVISITED

- [2.2] THE THREE-WAY PARADOX

- [2.3] RELATIVISTIC MASS INCREASE / MASS-ENERGY EQUIVALENCE

- [2.4] A FEW SUBTLETIES

- [2.5] RELATIVITY IN PRACTICE

- [2.6] SPECIAL RELATIVITY: A SUMMARY

- [2.7] GENERAL RELATIVITY

- [2.8] COMMENTS, SOURCES, & REVISION HISTORY