The Physics Laboratory of the National Institute of Standards and Technology (NIST) provides A Walk Through Time, a site devoted to examining the question of how humans have measured time throughout history. In one...

In this lecture, a physics professor describes wormholes in space and other ideas that might allow travel into the past or future, based on special and general relativity and quantum physics. The physicist explains how...

The University of California Los Angeles Division of Astronomy and Astrophysics professor Edward Wright maintains the Relativity Tutorial Web site. The site explains the history and general concepts behind relativity....