The Accuracy of Time Keeping

Chapter 18 traces the evolution of timekeeping accuracy from pendulum clocks to modern atomic and optical clocks. Early pendulum clocks in the 17th century achieved accuracies of about 10 s per day, while the Harrison marine chronometer in 1761 improved this to 1 s per day. Quartz clocks introduced in the 1920s marked a major leap, reducing error to 0.01 s per day. The first atomic clock, based on an ammonia maser, appeared in 1949 with an accuracy of 1 s every 300 years, followed by cesium atomic clocks in 1955, achieving 1 s every 30 million years. In 1967, the second was officially defined using cesium vibrations. Cesium fountain clocks in 1994 improved accuracy to 1 s every 100 million years. Optical lattice clocks, introduced in the early 2000s, reached 1 s every 30 billion years. Future nuclear clocks may add five more orders of magnitude, revolutionizing precision in science and technology.