A Supermassive Test for Einstein’s Famous Theory

Editor’s note: Following the publication of this article, Chiara and colleagues have published research in the Astrophysical Journal Letters showing that, for the first time, there is evidence for a low-frequency gravitational wave background, and that general relativity has indeed passed another test.

You’re oscillating. Well, technically, not just you. We are all being stretched and squeezed by an event we can’t see—at least not with the naked eye. Imagine that throughout the day we have imperceivable fluctuations in our height, starting taller in the day, shorter at night, constantly stretching and squeezing like a spring. Our entire universe experiences something of the same, just rather than fluctuations repeating every 24 hours or so, it’s every decade.

Somewhere, far, far away and long, long ago, two supermassive black holes came together, forming a binary system. These black holes have gargantuan masses, at least 100 million times the mass of our sun. They were bound to each other in a seemingly perpetual orbital dance, spending tens of millions of years orbiting each other, creating