University of Texas at Austin

Tuesday, February 17, 2009

Austin swings like a pendulum do

Most Foucault Pendulums are in places where they can be seen: in science museums or the lobbies of the buildings of university physics departments.

A view of the pendulum from above

Where the pendulum swings/Photo by Shae Small

The one at The University of Texas at Austin is a bit off the beaten path. It’s on the far east side of campus in the Development building, which houses the university’s development offices, the Charles Dana Center and a health clinic.

But it still gets traffic.
Video of the pendulum

Some comes from Austin area schools that send groups of students to study the pendulum for science projects. Recently fifth graders from a Leander elementary school observed the pendulum, said Shae Small, an administrative associate in the Dana Center.

She’s made keeping an eye on the pendulum one of her duties.

“We’re very proud of it and very protective of it,” Small said.

And the Austin Chronicle made the pendulum a critics pick as “Best Moment of Zen That’s Not On the “Daily Show” in its 2007 Best of Austin awards.

A Foucault Pendulum demonstrates the rotation of the Earth on its axis. The pendulum swings back and forth and appears to move. But, it’s not the pendulum that’s moving. It’s the Earth.

Here’s the nutshell explanation from John Markert, the chairman of the university’s physics department:

“A Foucault pendulum is simply a pendulum that swings back and forth freely, suspended from one point (that is, not confined to one plane the way a pendulum in a grandfather clock is confined),” he said. “Because the Earth rotates every 24 hours, and the pendulum’s inertia keeps it swinging in one plane, then in the reference frame of the Earth, the apparent plane of the pendulum’s swing precesses slowly, shifting 15 degrees per hour, that is, once per day.”

Leon Foucault, a French physicist, developed the pendulum in 1851. Since then, scores of Foucault pendulums have been installed around the world. The one in Austin is said to be the first successful installation of one in Texas.

So why is the pendulum, the first successfully installed in Texas, not in the heart of 40 Acres?

What happened is that the university bought the building and the pendulum was included. It’s sort of like buying a car that has an option you really don’t need, but is nice to have.

A company called Engineering Services Inc., installed the pendulum when it built the building for its headquarters in 1983. When Engineering Services moved out, Pharmaco Dynamics, a drug-testing company moved in. The university leased space in the buildfing in 1988 and bought it in 1995.

The pendulum hangs in a four-story tower at the front of the building. Workers with offices in the building walk from floor to floor via the spiral staircase that surrounds the pendulum.

When the pendulum stops, David Dedear, a fire/life/safety systems technician in the facilities department, is called.

In December 2007, he and other workers fixed sensors and a magnet that keep the pendulum swinging. A sturdy scaffold was built so they could work at the top of the tower.

“If we kill the power to it, it would probably run 15 minutes and then it would just stop,” he said.

Every once in a while it stops and Dedear comes over, makes some adjustments to the control panel and off the pendulum goes again.

The Development building is open to the public so swing by and check out the Foucault Pendulum.

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» Austin swings like a pendulum do



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