We Have No Idea: A Guide to the Unknown Universe

by Jorge Cham

These events don’t happen on schedule and are not repeatable, but every so often, black holes get close enough to each other that they try to suck each other in. This is exactly what scientists are looking for. There are places in the cosmos where black holes are engaged in a death spiral and the collision might be generating gravitons shooting out in every direction. All we need to do is see them! It turns out that is not so easy. Even the gravitons produced by a black hole collider will be very hard to spot. The weakness of gravity means that even if a graviton passed through you, you would hardly feel it. Remember neutrinos, the ghostlike particles that can pass through light-years of lead? Gravitons make neutrinos seem like social butterflies that like to talk to everyone at the party. In fact, one calculation suggests that a detector the size of Jupiter would see one graviton every ten years even if it was near an intense graviton source.