Group items tagged

Each demonstration has been assigned three or more "key concepts." Since any one of these "key concepts" may appear in more than one demonstration, the key concepts have been used to cross-index all 50 demonstrations under some 79 different "key concepts."

This animated GIF shows images from the Hubble telescope and is useful for demonstrating the vast size of the universe, the number of stars it contains, and the possible number of planets out there.