ABOUT.

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.

Everyone learns that ice is slippery because a thin skin of water coats it. Why that skin forms is a different matter, and the argument has run for nearly two centuries without a winner.

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.

Cool helium far enough and it slips through gaps no ordinary liquid can pass, and creeps up and over the rim of its container. Here's what was actually measured, and the model that makes sense of it.

Nothing with mass can outrun light in empty space. But put light in water or glass and it slows down, and a charged particle that moves faster than that slower light gives off a blue glow. It's called Cherenkov light.

Over a couple of centuries, the long vowels of English (vowel sounds held for longer than their short partners) moved, and the letters that spelled them mostly stayed put. For the most part the spelling didn't change to follow the sounds, so English spelling that looks wrong is often a record of older speech.

An inclusionary housing quota doesn't build anything by itself. It's a condition attached to new projects, a share of homes at capped prices or a fee instead, and what it produces depends on what gets built under it.

A micromort is a one-in-a-million chance of dying, packaged as a unit. Giving tiny risks a shared scale lets them be compared and, within limits, added up. And the limits turn out to be the interesting part.

A century ago, a quiet electric car was a perfectly normal way to get around town. Then the job it was good at stopped being the job most drivers wanted done, and a better battery, much later, helped bring it back.

Print the word BLUE in red ink, ask someone to name the ink, and watch the answer stall. The word and the colour are both shouting, and the word is louder.

Swap a ship's planks one at a time and every repair looks harmless. Then someone builds a second ship from the old planks, and "the same ship" stops being an easy phrase.

One grain of sand is not a heap, and one more grain never seems to make the difference. Follow that thought all the way and you end up somewhere absurd.

Things can get better and people can still feel worse off. It depends on who they're comparing themselves with.

Two spoons sit in the same drawer for a week and end up at exactly the same temperature, yet the metal one feels colder in your hand. Your skin isn't measuring the spoon. It's reporting the temperature of the handshake between you.