An Etymological Dictionary of Astronomy and Astrophysics

A gaseous ball of atoms, usually → cesium (¹³³Cs), created by the → laser cooling technique and used in an → atomic fountain clock. The ball, typically a few millimeters in diameter and containing some 10⁷ atoms,
can be launched upward against gravity using a → laser beam. The launch velocity is chosen such that the atoms reach a height of about one meter before they turn back and fall down the same path they came up. The motion of the ball resembles that of the water in a pulsed fountain.

Etymology (EN): → atomic; fountain, from M.E. fontayne
from O.Fr. fontaine, from L.L. fontana, noun use of feminine of L. fontanus “of a spring,” from fons “spring of water.”

Etymology (PE): Favvâré, Pers. construction from Ar. faur “boiling, bubbling.”