Jo Ellen Barnett takes us a step further in our perpetual quest to comprehend time. She bridges the gap between the mechanical clocks which record the fleeting moment as it passes, and the powerful radioactive "clocks" which have opened up to us the eons of the earth's history, by showing that both are based upon the counting of identical time segments.

Beginning with a historical look at clocks to tell the time of day, she discusses the impact of such inventions as the church bell, the pendulum, and the wristwatch on human culture, and explains how they've gradually transformed our perception not only of the world, but of time itself.