WHAT MAKES ATOMS TICK

摘要

Physicists send strontium atoms into a vacuum chamber and fire two different lasers at them in succession. The lasers gather the atoms into a group, herding them like sheepdogs. This restricts the atoms' physical motion, cooling them to just a few millionths of a degree above absolute zero.rnAfter cooling the atoms, physicists must prevent them from running into each other, which can change the atoms' oscillation frequency and thus limit the accuracy of the clock. To do so, the scientists organize some 2,000 of the atoms into groups of about 30 using a lattice of light from a third laser.