Kick

When two black holes finally merge the waves don't always leave evenly, and what's left takes the recoil, several million kilometres an hour, like a gun, the paper says.

Mostly it isn't enough to leave. It goes out, slows, turns, comes back through the middle it was made in at its fastest, and out the other side.

You can tell from the gas. What's close goes with it. What's farther stays behind, and the light from the two doesn't quite agree.

Ten years ago three of them said there would be a sign. This year one of their graduates went through a hundred thousand quasars and didn't look for the one strange one.

It's after six, the sun gone at three to. Somewhere a swing is still going after the child's been called in, quickest at the bottom, passing the one place it could rest without resting.