Everyone knows that no information can escape a black hole.But a gravitational wave rippling outward from a massive collision between two hefty black holes may have brought us right to the brink – carrying the very first signature ever received of an event horizon.Scientists had theorized that a gravitational wave known as a direct wave could carry information about the event horizon's properties. Now they've finally identified such a wave.If it sounds like something out of science fiction to you, you are not alone. "The event horizon is not something we can see directly with light, because by definition nothing escapes from inside it. But gravitational waves give us a different pathway," theoretical physicist Sizheng Ma of the Perimeter Institute in Canada told ScienceAlert."When two black holes orbit each other and merge, this violent process disturbs spacetime itself in the region very close to the final black hole's horizon. Some of those spacetime vibrations can travel outward as gravitational waves and eventually reach our detectors."We often find it thrilling that something which once felt almost like science fiction, namely using observations to learn about black-hole horizons, has become something we can actually do."