You will have heard of the detection of gravitational waves, just announced this past week. For once the mass media haven’t over-hyped a scientific discovery: this really is an important find. We’re not going to try to explain the science behind it (there are lots of articles on line and offline that do that). It’s the fact of the 100-year gap between the theoretical prediction and the actual observation that tells us something about the nature of science.

Our astronomer writes:

The LIGO consortium announced the detection of gravitational radiation recently, a very important observation. The announcement was this past week, but the detection occurred back in September; they spent the intervening months checking to make sure they hadn’t made a mistake, and that what they’d seen was real. That’s responsible science.

(I’ve seen two paradoxers at work already. One says that Einstein’s equations are right but his physics is wrong, whatever that means; characteristically of paradoxers, he bases this on a single introductory course in the subject. The other claims that there was no detection, because atomic clocks can be reset. I didn’t go into his explanation of why this matters.)

Many of the articles mentioned that this detection came almost exactly a century after Einstein first predicted gravitational radiation. It’s not the first confirmation of a prediction of General Relativity. The theory came together in 1915, and measurements made during a solar eclipse in 1919 convinced many physicists that Einstein had gotten it right. Since then, many increasingly powerful and refined tests have always supported GR. My point is that the tests came after the theory. There was only one observation known beforehand in which GR gives a measurably better answer than Newtonian gravity, the “anomalous precession of Mercury;” it’s a tiny effect, and in 1915 astronomers had by no means given up on explaining it within existing science.

So there was no great mass of inexplicable observations begging for an explanation. Contrast this with the contemporary development of quantum mechanics (on which Einstein also worked), where many things just could not be reconciled with Newtonian mechanics. Straightforward calculations showed that atoms could not exist, a box of radiation would hold an infinite amount of energy, and there was no explanation at all for atomic spectra.

The point is that science can progress in very different ways. Quantum mechanics fits the script of Thomas Kuhn’s “paradigm shift,” in which an accumulation of discrepancies forces a revolution in a science. In this sense General Relativity was unnecessary; it was only decades later that scientists began to need it to explain their observations.

This makes it even more of an intellectual achievement, of course: Einstein had few clues to go on when he set out to construct a new theory of gravity. And to predict things that are only found a century later is truly wonderful; it means he discovered something very deep about nature. It’s the dream of every scientist to do just that.