There's No Battery in Your Lighter

Click a push-button lighter and a spark jumps out of nowhere. Most people assume there's a tiny battery inside, or a flint. But crack one open and you won't find either, because the spark comes from the click itself.

Pressing that button doesn't close a circuit; it slowly squeezes a spring, because a thumb alone is far too gentle to make a spark. Near the bottom of the press a little latch slips, and the spring fires a metal hammer into a small block of ceramic crystal. That snap is the click you hear, and the hammer lands in about half a millisecond, hundreds of times quicker than a blink.

And the crystal is where it gets weird. Inside it, positive and negative charges sit in a lattice and cancel each other out, until something hits it hard. The blow squashes the lattice, the charges shift toward opposite faces, and for an instant that tiny block holds thousands of volts. A wire carries the pulse to a gap at the nozzle, where it jumps across as a spark, right into the gas the same press has just let out.

The trick is older than any lighter: in 1880, Pierre Curie, Marie's future husband, and his brother Jacques squeezed a crystal in a vise and watched a meter swing. It's now named after the Greek word for "press", piezoelectricity, and today the same hammer and crystal click inside the igniter buttons of many grills and camping stoves.

Send this to the friend who borrows your lighter and swears it was "always his".