Some old news just reached earth: about 1.3 billion years ago two black holes collided. Scientists discovered this when they detected ripples in time and space caused by the collision, called gravitational waves. Albert Einstein predicted that such waves exist a century ago, but they had never been observed. After months of checking their results, scientists have finally made the announcement. They say gravitational waves exist. Imre Bartos is one of the many scientists who worked on LIGO, the Laser Interferometer Gravitational Wave Observatory, which detected this dimension of the cosmos for the first time.
I asked him: What exactly are gravitation waves?