ARCHIVE.

The push that drives a rocket happens between the rocket and its own exhaust. Outside air isn't what it pushes against, which is why empty space doesn't stop it.

Give randomly jiggling atoms long enough and, very rarely, they could fall into the shape of a single working brain, complete with memories of a life it never lived. Some models of the universe seem to predict far more of these lonely minds than ordinary people. Physicists don't take that as news about reality. They take it as a sign that a theory has gone wrong.

A gravitational-wave detector rests on glass mirrors hung at the far ends of long laser arms. Its real trick isn't sensing motion. It's stopping almost every other kind of motion first.

A lump of corroded gears from an ancient shipwreck turned out to be a calculator for the sky. What survives shows how it flagged eclipse months; how much more it once did is partly a modern rebuild.

A comet's tail isn't exhaust trailing behind it. It points away from the Sun, wherever the comet happens to be going. And look closely, and there are two of them, because the Sun is pushing on the comet in two quite different ways.