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Children's Museum celebrates return of pendulum

| Tuesday, Feb. 22, 2005

Time might stand still for some people, but the Earth doesn't -- the Foucault Pendulum is proof. From 1939 to 1994, the pendulum was a mesmerizing curiosity that drew people to the brass railing that encircled the attraction in the grand hallway of the old Buhl Planetarium and Institute of Popular Science on the North Side. The pendulum was reinstalled last November, at the Children's Museum of Pittsburgh.

The museum will celebrate the return of the pendulum on Wednesday. "Bringing the bob back was a little bit of a science project," says Jane Werner, museum director. An extra structure had to be added to the roof of the building during the restoration to support the 150-pound pendulum. GlaxoSmithKline Consumer Healthcare helped to pay for the restoration and reinstallation as part of a $50,000 gift to the Children's Museum's capital campaign, Werner says. The museum piece remains in its original spot in the Buhl building.

As part of the celebration, 100 fourth- and fifth-graders from Pittsburgh Public Schools will visit the museum Wednesday for a performance by actor and storyteller Tim Hartman of Ben Avon. His presentation will tell the tale of how Jean Bernard Foucault, a French physicist, used a pendulum in 1851 to demonstrate that the Earth spins.

The pendulum was one of the original exhibits on display in the planetarium in 1939.

The pendulum with its original bob was relocated to the Carnegie Science Center in the mid-1990s when the planetarium was closed. It remained on display there until October 2002, when it was returned to the Great Hall of Buhl Planetarium -- now the Children's Museum -- where the original marble-floored pendulum pit had remained.

Not all of the children who watched the bob swinging from the wire realized the magnitude of the scientific principle it demonstrated -- that although it appeared that the pendulum's path was changing, in reality it was the floor beneath it that changed because of the Earth's daily rotation.

But today, as adults, they have fond memories of it. "I remember going there on a field trip in third or fourth grade and seeing it hanging from the ceiling," says Scott O'Mara, 54, of Robinson, who attended the former Vernridge Elementary School in Castle Shannon. "But no one was listening to the teacher explaining what it did. There were so many other things around you to see."

Hartman, who grew up on the North Side, hopes his presentation will help a new generation of children to understand the concept that the pendulum demonstrates.

"I don't think I ever got it when I was young," he says. "If you can wrap your head around the fact that the pendulum is not moving, but the whole floor below you is moving, hopefully it will make a good impression."

Werner says the pendulum appeals to people of all ages. "There's something mesmerizing about it," she says. "It's a simple yet elegant example of an everyday phenomenon that draws people in. I think there's some kind of comfort in knowing the world's still revolving."

How it works

The Foucault Pendulum consists of a 150-pound bob, affixed to a 35-foot wire that hangs from the Grand Hall of the Children's Museum of Pittsburgh. The pendulum includes a circle of 108 silver pegs that sit on the floor of the pit beneath it. Each day, the pendulum is set swinging directly on the north-south line of the pit. Although the swinging pendulum appears to rotate about 10 degrees an hour, it does not move. In fact, the pendulum "remembers" the direction in which it was started and tries to maintain that direction. The Earth however, turning counterclockwise from west to east, moves the building under the pendulum. The silver pegs circling the pendulum pit are set up to 2.5 degrees apart, and as they enter into the path of the swinging pendulum they are knocked over. One peg is knocked over about every 20 minutes.

This direction change of the pendulum, illustrated by the falling pegs, shows that the Earth is turning.

SOURCE: CHILDREN'S MUSEUM OF PITTSBURGH

Additional Information:

Details

What: Celebration of the reinstallation of the Foucault Pendulum

When: 10:30 a.m. Wednesday

Admission: Free with museum admission: $8; $7 for ages 2 to 18 and senior citizens; free for children younger than 2. Admission is discounted to $6 for all ages on Thursdays.

Where: The Grand Hall, Children¹s Museum of Pittsburgh, 10 Children's Way, North Side

Details: (412) 322-5058 or www.pittsburghkids.org

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