Is a planetarium the same thing as a museum?
Not really. A planetarium may be thought of as a type of museum for astronomy. Specifically, a planetarium is a theatre built primarily for presenting educational and entertaining shows about astronomy and the night sky. It can also be used to train people in celestial navigation.
Planetariums share a large dome-shaped projection screen onto which scenes of stars, planets and other celestial objects can be made to appear and move around to simulate real planetary movement.
