CHICAGO (AP) - Officials at the Adler Planetarium in Chicago are breaking
out the birthday cake to mark the 100th anniversary of the facility's
historic Atwood Sphere.
The 15-foot-diameter large-scale mechanical planetarium opened in 1913 and
museum officials say it's the oldest one in the U.S.
It shows the positions of the sky's brightest stars by allowing light to
come through 692 holes on its metal surface. The sphere was first used to
help teach pilots how to navigate the nighttime sky.
To mark the sphere's anniversary, Adler officials are waiving admission on
Wednesday for Illinois residents, giving away birthday cake and holding a
series of other events.