Einstein, Time, and Light

25 November 2015

Professor William Phillips, University of Maryland

Hosted by the Photon Factory, University of Auckland, for the International Year of Light IONS-KOALA 2015 Conference 

25 Nov 2015

It was a Wednesday evening, and the large, gathering crowd could be in no doubt they were in for a show! A busy array of thermos flasks, glassware, flowers, balloons, bins, and even cinder blocks more than hinted at the dynamic session ahead. Not every Nobel Laureate is a showman, but the co-recipient for Physics in 1997 certainly is. Prof Phillips enthralled the audience with a barnstorming presentation on the subject of super-cooling lasers and atomic clocks.

The Atom du Jour was caesium. Apparently, by using lasers, you can slow your caesium atoms down, chilling them to near absolute zero. Then you just need to probe them in a microwave-filled cavity. By doing so, you can record signals that their electrons are emitting as they change energy levels. And this is how you measure the passing of time with accuracy to within 10-9 seconds per day. Just imagine if creatures of the late Carboniferous Period had atomic clocks 300 million years ago. They’d be only one second late to a meeting held today!