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When the first person set the very first clock, how did they know what time to set it to? This question, from listener Chris in the UK, sends CrowdScience off on a quest into the history of timekeeping.

From sundials to water clocks, from uneven hours to precision seconds determined by the vibration of an atom, we examine how we came to measure time. We visit possibly the oldest working mechanical clock in the world to discover how its time was originally set; and hear how the time we go by today is not quite the same as it was in the past.

Will all this be enough to solve Chris' question, or has he stumped the team?

Featuring:

Ian Westworth, Clock Mechanic
Dr. Chad Orzel, Associate Professor of Physics and Astronomy at Union College
Anna Rolls, Curator of Clocks, Clockmakers’ Museum
Peter, Guide, Salisbury Cathedral
Dr. Jun Ye, Physicist at NIST (National Institutes of Standards and Technology) and The University of Colorado, Boulder.

Presenter: Caroline Steel
Producer: Margaret Sessa-Hawkins
Editor: Cathy Edwards
Production Co-ordinator: Jonathan Harris
Studio Manager: Jackie Margerum

(Photo:Stopwatch on red background. Credit: Martin Poole / Getty Images).