Einstein: right again

Black Hole Blues.jpgEinstein predicted gravitational waves in 1916, but it took us a century to find them. Astrophysicist Janna Levin’s new book explains how.

What are gravitational waves?

Gravitational waves are motions in the shape of spacetime. Just as mallets create waves in the shape of a drum, black hole collisions create waves in the shape of spacetime. By recording the ringing of spacetime, we can reconstruct the motion and size and shape of the mallets.

How was LIGO able to detect them?

LIGO suspends mirrors so that they’re free to bob on the passing gravitational wave. By measuring the distance between mirrors, the machine records changes in the shape of spacetime of less than one ten-thousandth of the width of a proton over 4 km’s.

What was the atmosphere like at LIGO when they were found?

People were incredulous – then ecstatic.

What are the implications of Einstein being proved right?

Not exactly a surprise. More important are the astronomical discoveries this new era will make possible. We have already heard the first gravitational wave sounds, observed the first black hole pair, and discovered black holes a few times bigger than expected. Who knows what’s next.

Published in Shortlist, 17 March 2016.