Daniel Holz spends his days thinking about gravity, black holes, and the birth of the Universe. Lately he has been working hard on detecting gravitational waves, which Einstein predicted 100 years ago but which we only finally detected a few months ago. We now can listen to the Universe! The first noise LIGO heard was from two giant black holes crashing into each other at close to the speed of light; but we are safe, since this happened over a trillion trillion miles away. Daniel went to school at Princeton and the University of Chicago, and has been a professor at the University of Chicago since 2011.