THE LEADING EDGE by Phillip E. Johnson
Out from the Ether
Sometime in the 1990s, I read Einstein's Cosmos by theoretical physicist Michio Kaku, which described Einstein's science in the context of events in his life. Particularly fascinating was Kaku's account of the state of physics in the decade prior to 1905, when Einstein's Special Theory of Relativity set the discipline in a new direction.
When nineteenth-century physicists learned that light traveled through space in waves, they assumed that the waves must travel in a medium, just as ocean waves travel in water. Physicists called this hypothetical medium "ether," and, according to Kaku, attributed bizarre properties to it. The ether became an almost mystical substance. It was supposed to be absolutely stationary, weightless, invisible, with zero viscosity, yet stronger than steel. Then, in 1887, physicists Albert Michelson and Edward Morley performed a brilliantly designed experiment to determine the properties of ether by observing its effect on a beam of light.
Scientists believed that, as the earth moved through the ether in its orbit around the sun, it generated an "ether wind." It seemed to follow that a light beam that traveled in the direction of the earth's motion would travel faster than a beam moving at a right angle to the earth's direction of motion.
To test this hypothesis, Michelson and Morley designed an experiment in which an apparatus split a light beam into two parts, one moving in the same direction as the earth and the other moving across that path. When mirrors reflected the two beams back to the starting point, they should have been out of sync, with a resulting interference pattern. To the scientists' astonishment, they found that, no matter in which direction they pointed the apparatus, there was no interference, indicating that the two beams always moved at the same speed.
Kaku explained what this meant:
This [result] left physicists with two equally unpleasant choices. One was that the earth might be perfectly stationary with respect to the ether. That seemed to violate everything known about astronomy since the original work of Copernicus, who found that there was nothing special about the location of the earth. . . . Second, one might abandon the ether theory and Newtonian mechanics along with it.
A Quick Fix
This analysis of the dilemma left by the unexpected result of the Michelson-Morley experiment misrepresents Copernicus's conclusion: while the astronomer did write that the earth moves around the sun, he did not say that there is "nothing special" about the location of the earth; some scientists have simply assumed that this philosophical doctrine is implied by his conclusion that the earth is a planet that moves like other planets.
Nevertheless, I found it remarkable to read that, as late as 1887, it seemed that a stationary earth might be worth considering. No physicist actually did consider that possibility, as far as I know—possibly because it would be intolerably humiliating to science, and would imply that the hated Catholic Church might have been correct in disputing Galileo's endorsement of the heliocentric theory.
Instead, established scientists tried to explain the baffling Michelson-Morley result by giving new properties to the ether. The Dutch physicist Hendrick -Lorentz and the Irish physicist George Fitzgerald postulated that the earth, in its passage through the ether, was physically compressed by the ether wind; thus, the apparatus measuring the light beam traveling in the same direction as earth would also be slightly compressed.
Phillip E. Johnson is Professor of Law (emeritus) at the University of California at Berkeley. He is the author of Darwin on Trial, The Wedge of Truth, The Right Questions (InterVarsity Press), and other books challenging the naturalistic assumptions that dominate modern culture. He is a contributing editor of Touchstone.
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