Not your grandfather clock, even if it is ceiling height. This is NIST-F2, the world’s most accurate atomic clock. It’s lead designer, Steven Jefferts, is at right, with colleague Tom Heavner looking on.
As cesium atoms inside the atomic clock known as NIST-F2 pass through the combined focal point of six lasers, they instantly get stopped, cooled and quickly collected into a ball.
A new filter lets light pass through — but only if it's coming from just the right angle. Here, a light ray coming in at the 1-o’clock position reflects off the filter. But the other beam streaks straight on through.