How Are Pendulums Used Today?

A plumb bob is a pendulum commonly used by construction workers and surveyors to accurately locate the levels over a specific spot on the Earth?s surface. Inertial guidance systems on some aircraft instrumentation, missile guidance systems and seismographic instruments all use a modification of the pendulum. The Foucault pendulum is a special pendulum used to demonstrate the Earth?s rotation.

According to Science Clarified, the first seismoscope was developed by a Chinese mathematician and astronomer named Zhang Heng, and it used a pendulum. The seismoscope consisted of a cylinder surrounded by bronze dragons with bronze frogs beneath. When the Earth shook, a ball would drop from the dragon?s mouth into the frog?s mouth. The number of released balls and the direction in which they fell indicated the location and magnitude of the seismic disruption.

In A.D. 718, a Buddhist monk named I-Hsing and a military engineer named Liang Ling-Tsan built an astronomical clock using a pendulum. This was the earliest precursor to the grandfather clock developed by Dutch physicist and astronomer Christian Huygens.

In the early modern era, physicists started using pendulums for purposes that included calculations to determine the magnitude of the gravitational force. The first fax machine was developed by a Scottish inventor, Alexander Bain, which used matching pendulum receivers and transmitters that sent and received electrical impulses.