COVER STORY

摘要

Back in the 1860s, James Clerk Maxwell was melding electricity and magnetism into one unified theory. But however he sliced the equations, they only made sense if light travelled through space at the same constant speed, regardless of the speed of its source. This is odd. If someone fires a bullet from a moving car, to a bystander the bullet travels at the sum of its speed and the car's speed. Yet when 20 years later US physicists Albert Michelson and Edward Morley were looking for the luminiferous ether, a medium supposed to carry light, they reached the same conclusion: however you look at it, the speed of light is a constant.