Scientists use lasers to cool atoms to nearly absolute zero

Intuition says a laser is a heat source — something that burns, cuts, or scorches. In atomic physics, it works exactly backwards.

In a technique called laser cooling, a precisely tuned beam of light slows down the motion of atoms by striking them from just the right direction and at just the right frequency — and temperature, at bottom, is simply a measure of how fast particles are moving.

The method can chill clouds of atoms to within a few billionths of a degree of absolute zero (-273.15°C) — among the coldest spots that have ever existed in the universe, colder than any naturally occurring corner of space.

The stakes: these techniques are far from an academic curiosity with no application — they underpin today's most precise atomic clocks and experiments with Bose-Einstein condensates, a state of matter predicted theoretically long before anyone managed to actually create it in a lab.