The original setup of the Michelson-Morley experiment, from 1887. Image credit: Case Western Reserve Archives.

The failed experiment that changed the world

Sometimes, designing a careful experiment and measuring absolutely no effect can be the most important result of all.

“It appears, from all that precedes, reasonably certain that if there be any relative motion between the earth and the luminiferous ether, it must be small; quite small enough entirely to refute Fresnel’s explanation of aberration.” -Albert A. Michelson

In science, we don’t simply perform experiments willy-nilly. We don’t put things together at random and ask, “what happens if I do this?” We examine the phenomena that exist, the predictions our theories make, and look for ways to test them in ever-greater detail. Sometimes, they give extraordinary agreement to new precision, confirming what we had thought. Sometimes, they disagree, pointing the way to new physics. And sometimes, they fail to give any non-zero result at all. In the 1880s, an incredibly precise experiment failed in exactly this fashion, and paved the way for relativity and quantum mechanics in doing so.

The orbits of the planets and comets, among other celestial objects, are governed by the laws of universal gravitation. Image credit: Kay Gibson, Ball Aerospace & Technologies Corp.

Let’s go even farther back in history to understand why this was such a big deal…