Bengt Nyman from Vaxholm, Sweden · CC BY 2.0

Weiss invented the laser interferometry technique that became the basic design of LIGO, the observatory built to detect the gravitational waves Einstein had predicted decades earlier but that no instrument could yet measure. He spent much of his career pushing the experimental physics needed to make such a faint signal detectable at all, while also chairing the COBE Science Working Group. In 2017 he shared the Nobel Prize in Physics with Kip Thorne and Barry Barish for LIGO's detection of gravitational waves, a discovery that opened astronomy to an entirely new kind of signal.