The main goal today is the first direct detection of gravitational waves. In the aftermath, physicists hope for the birth of a new type of astronomy: With the information carried by gravitational waves, one could test whether the properties of black holes are really those predicted by Einstein's theory (left: a simulation of merging black holes and the associated gravitational waves), certain waves might hold clues as to the properties of neutron star matter, others could test cosmological theories about the early universe. And last, but not least, in the past, every new window into the universe - from radio to x-ray astronomy - has brought about surprising new insights into the workings of the universe. Physicists are hopeful that gravitational wave astronomy will prove no exception.