On Time: The Quest for Precision

Is time a fundamental dimension of the universe? Can it be measured in any absolute sense? Is time merely a human invention that allows us to artificially compare events in sequential order? We may be uncertain about how to define and explain time but at least one thing is certain. We sure know how to measure it.

For centuries, the instruments used to measure the sun's changing position during the day and during the year were distinctly non-mechanical. The first mechanical clocks in the thirteenth century may have been crude, imprecise, unreliable instruments. Yet by introducing a mechanical means of generating and counting a repeating beat, they marked a revolution in timekeeping. Their use of oscillating motion to divide time into countable beats was the basis for all subsequent improvements in timekeeping.

Pendulum clocks were an invention of the seventeenth century, and they brought the accuracy needed for scientific observations. With spring balances, clocks and watches became wonders of mechanical complexity and, in the case of watches, of miniaturization. Measuring the frequency of vibrating quartz crystals brought another revolution in the twentieth century. Quartz clocks, with accuracy within two thousandths of a second per day, were unmatched in their precision by any mechanical clock or watch. Today atomic clocks have rendered obsolete the definition of a second as a fraction of a solar year. Instead, a second was redefined in 1967 in terms of the vibrations in the cesium-133 atom.

The books and journals in the Linda Hall Library document these revolutions in time keeping. Major advances, interesting alternatives, and innovative applications of available methods of time keeping will tell the story of our ongoing attempts to tell the time, precisely.

The exhibition is made possible through generous support from Dr. James and Mrs. Francie Flynn, the Burns & McDonnell Foundation, the J.B. Reynolds Foundation, and the Linda Hall Library Annual Fund.

On Time lectures are made possible through generous support from the Atterbury Family Foundation; the Carter Community Memorial Trust, UMB Trustee; Mrs. Linda Nottberg; Polsinelli Shughart PC; Sandi and Jay Rozen; Bob and Sally West; and the Linda Hall Library Annual Fund.