20140706_wesun_keeping_time_by_rubidium_at_the_naval_observatory.mp3?orgId=1&topicId=1091&d=397&p=10&story=329154831&t=progseg&e=329154696&seg=21&ft=nprml&f=329154831

Copyright 2016 NPR. To see more, visit http://www.npr.org/.