To most of the passengers on Pan American Flight 106 from Washington's Dulles International Airport, it was simply a routine trip to London. But for Physicist Joseph C. Hafele and his companion, Astronomer Richard Keating, it was the beginning of a journey into the most esoteric realms of modern science. Occupying four seats in the big 747's tourist compartment—two for themselves and two for their scientific gear—they were setting off on an extraordinary round-the-world odyssey: an expedition to test Albert Einstein's controversial "clock paradox," which, stated simply, implies that time passes more slowly for a rapidly moving object than for an object at rest.
