Science: Clocking Einstein

None of Einstein's ideas have so fascinated the public and provoked such controversy among physicists as the so-called "clock paradox." One of the major predictions of the great physicist's Special Theory of Relativity, the paradox is based on the assumption that time passes more slowly for an object in motion than one at rest. Thus, if Einstein was correct, an astronaut traveling at extremely high speeds—say to a distant star and back—would age less during his trip than a twin brother who had remained on earth. Depending on the length of his mission,...

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