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

Presenter: Caroline Steel

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