Timekeeping

Can you imagine a world in which there is no measurement of time?

Most of us wear wristwatches or have a clock, and we organize our lives around the scheduled times that trains and planes depart and arrive, when our day at school or at work begins and ends, and when TV shows are on.

But time,- which we take for granted is divided into years, months, weeks, days, hours, minutes, seconds, even fractions of seconds - has not always been so. As we learn in this book, throughout history ingenious people have been devising ways of recording the passage of time, seeking the power to predict changes in the seasons, changes in the earth's position relative to the sun and moon, or the dates of eclipses.

The Gregorian calendar in use today is one such device, but there have been and still are many others - the Muslim and Jewish religions for example maintain their own calendars.

Alongside these attempts to invent a workable system of time, we learn about the many different timekeeping devices that have been created over the years - among them, sundials; water-clocks; sandglasses; calibrated candles; water escapements; pendulum clocks; mechanical, electrical and quartz clocks; even atomic clocks, which are accurate to within one second in 1,700,000 years.