There are only 6 Foucault pendulums in Texas. Why is one at a San Antonio middle school?

Pendulum shows rotation of Earth in real time

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San Antonio – There are only six Foucault pendulums in Texas and one is at a middle school in San Antonio.

Usually reserved for museums and universities, David “Tex” Hill Middle School has a Foucault pendulum right in the middle of the campus.

These incredible pendulums demonstrate the rotation of the Earth by swinging back and forth in an elliptical pattern.

They require very specific care to set up. For instance, the pendulum bob (the spherical weight at the end) needs to be extremely heavy, while the wire holding it needs to be long.

The precision required to set up and design of these pendulums makes them rare. If the design of a Foucault pendulum is anything less than perfect, they won’t work as intended.

Even the cord used to suspend the bob must be perfectly polished and symmetrical.


It was the Northeast Independent School District’s idea to put a Foucault pendulum at Tex Hill.

NEISD’s curriculum correlates to the pendulum’s applications in many ways, according to Executive Director of Construction Management Gary Sullivan.

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Students learn related topics in force, motion and energy throughout their middle school years, including information about space science, the Earth’s rotation, the lunar cycle, the seasons, atmosphere and climate, he said.

The 8th-grade standards for the Texas Essential Knowledge and Skills test require students to show an understanding of how the tilted Earth rotates on its axis, a direct parallel behind the science of the Foucault pendulum.

Facts about the Foucault Pendulum

Foucault is pronounced FOO-koh.

The pendulum is named after Leon Foucault, the French physicist who originally devised it in 1851.

The largest Foucault pendulum in the world is located at the Oregon Convention Center and is called “Principia.” It’s bob weigh’s 900 pounds and the cable is 70 feet long.

The initial launch of the pendulum is so critical to the design that the pendulums were originally launched by lighting a string on fire to release the bob. This ensured no sideways friction could disturb the pendulum's motion.

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