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This article appeared in the fall print issue of Popular Science, but I missed that this article had also been published online.
For Popular Science:
In 2015, scientists caught evidence of a cosmic throwdown that took place 1.3 billion light-years away. They spied this binary black-hole collision by capturing gravitational waves—ripples in spacetime created when massive objects interact—for the first time. But now physicists want to see even farther. Doing so could help them accurately measure waves cast off by colliding neutron stars, impacts that might be the source of many Earthly elements, including gold. For that, they need the most sensitive gravitational-wave detectors ever.
The devices that nab waves all rely on the same mechanism. The U.S.-based Laser Interferometer Gravitational-Wave Observatory (LIGO) and its European counterpart, Virgo, fire lasers down two mile-plus-long arms with mirrors at their ends. Passing waves wiggle the mirrors less than the width of an atom, and scientists measure the ripples based on when photons in the laser light bounce off them and come back. Ordinarily, photons exit the lasers at random intervals, so the signals are fuzzy.