On Aug. 17, 2017, LIGO scientists detected gravitational waves from two colliding neutron stars for the first time. Not only did the collision produce a shockwave that rippled through the fabric of spacetime, it also created a bright flash of light seen by telescopes around the world. Daniel Holz, associate professor in physics at the University of Chicago, describes UChicago's role in the international LIGO/Virgo collaboration, which announced the discovery on Oct. 16, 2017. Among Holz's contribution to the research is a paper explaining a new measurement for the size of the universe and how quickly it is expanding.