When two black holes spiral inward and collide, they shake the very fabric of space, producing ripples in space-time that can travel for hundreds of millions of light-years. Since 2015, scientists have been observing these so-called gravitational waves to help them study fundamental questions about the cosmos, including the origin of heavy elements such as gold and the rate at which the universe is expanding.

But detecting gravitational waves isn’t easy. By the time they reach Earth and the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO), in Louisiana and Washington state, the ripples have dissipated into near silence. LIGO’s detectors must sense motions on the scale of one ten-thousandth the width of a proton to stand a chance.

LIGO has confirmed 90 gravitational wave detections so far, but physicists want to detect more, which will require making the experiment even more sensitive. And that is a challenge. “The struggle of these detectors is that every time you try to improve them, you actually can make things worse, because they are so sensitive,” says Lisa Barsotti, a physicist at the Massachusetts Institute of Technology.

Read more