Stephen P. Eckel

A laser beam passes through a glass cell containing rubidium vapor, and by how the atoms absorb light, you can determine their temperature. This is like measuring the speed of cars by the blur in a photograph: the faster the atoms move, the wider the absorption line becomes.

A thermometer that doesn't lie for years. Ordinary resistance thermometers, even very accurate ones, start to err over time: the material ages, contacts oxidize, and readings drift. The new quantum thermometer works differently: it uses the rubidium atoms themselves as a reference.