Lecture 10: Telling Time

What time is it? This lecture is the first part of a two-part exploration of the astronomical origins of our time-keeping and calendar conventions. Today we will discuss the division of the year into seasons by the motions of the Sun, and the oft-forgotten origins of our holidays in in the solar Quarter and Cross-Quarter days, the division of the year into 12 months based approximately on the cycle of lunar phases, the traditional division of the month into weeks reflecting the seven moving celestial bodies, and the division of the day into hours, minutes, and seconds. We will also discuss the difference between the Solar and Sidereal days, and the introduction of timezones used in modern civil timekeeping. Recorded 2006 Oct 3 in 100 Stillman Hall on the Columbus campus of The Ohio State University.