How does a quartz crystal enable watches and clocks to keep such good time?
The workings of a watch are called the “movement”. This includes traditional mechanical watches as well as modern quartz watches. The quartz movement, as used in the vast majority of all watches and clocks made in the world today, was invented in 1927 by Warren Marrison, an engineer at Bell Laboratories in New Jersey. It relies on a phenomenon know as the piezo-electric effect. If certain types of crystal, including quartz, are squeezed or stretched, their atoms respond by producing an electric field. In timepieces with quartz movements, the mirror image of this effect is used – an electric field is applied to the crystal (hence the need for a battery!) and this makes it change shape. Marrison discovered that by applying an alternating voltage to such crystals, they could be made to vibrate at rates of anything from 33,000 to more that 4 million time per second, maintaining that rate with extraordinary precision. Using electronics and mechanical gearing, Marrison was able to create a q
