https://www.scientificamerican.com/article/tiny-gravitational-wave-detector-could-search-anywhere-in-the-sky/

The smallest, most precise measurement ever made required one of the largest scientific instruments ever constructed. Five years ago the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected a ripple in spacetime that was just one ten-thousandth the width of a proton—a technical tour de force tantamount to pinpointing the distance to the nearest star to three one-thousandths of a centimeter. The Lilliputian ripple was a gravitational wave, a distortion in the fabric of the cosmos generated by the collision of two black holes more than a billion light-years from Earth.

According to Albert Einstein’s general theory of relativity, the acceleration of any massive object creates waves in spacetime, much as a ship churns out waves in water. Einstein himself, however, thought gravitational waves would be too weak to detect. He was not unduly pessimistic. It took LIGO’s four-kilometer-long interferometers—which were completed in 1999 and began searching for the waves in 2001—13 years to finally spot one. The discovery marked the beginning of a new field of astronomy and netted a Nobel Prize for three of the observatory’s physicists. The experiment has since detected nearly a dozen more gravitational-wave events. Now, just as LIGO is hitting its stride, a team of physicists has outlined a way to build a portable gravitational detector that is only one meter long—4,000 times smaller than LIGO.