Ytterbium

Ytterbium is a soft, silvery rare-earth metal, named, like three other elements, after the Swedish village of Ytterby. Jean Charles Galissard de Marignac discovered it in 1878. It is mined alongside other rare earths, mostly in China.

Ytterbium has become a star of precision physics. Its atoms respond to laser light at an extraordinarily steady frequency, and ytterbium optical clocks are among the most accurate clocks ever built: the best would drift by less than a second over the age of the universe. In industry, glass fibers laced with ytterbium make efficient high-power lasers that cut and weld steel. Ytterbium is also used in other laser crystals and in some specialty alloys.