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How do we determine the time? Believe it or not, there is an official clock. In this episode of The Atlas Obscura Podcast, we visit that clock, the NIST-F1 Cesium Fountain Atomic Clock, at the National Institute of Standards and Technology in Boulder, Colorado.

Our podcast is an audio guide to the world’s wondrous, awe-inspiring, strange places. In under 15 minutes, we’ll take you to an incredible site, and along the way you’ll meet some fascinating people and hear their stories. Join us daily, Monday through Thursday, to explore a new wonder with cofounder Dylan Thuras and a neighborhood of Atlas Obscura reporters.

NIST physicists Steve Jefferts (foreground) and Tom Heavner with the NIST-F2 cesium fountain atomic clock
NIST physicists Steve Jefferts (foreground) and Tom Heavner with the NIST-F2 cesium fountain atomic clock National Institute of Standards and Technology (Public Domain)