Explorer

Fifty-two years ago today, the United States answered the Soviet Union's Sputnik triumph with the launch of its first satellite, Explorer 1.

The launch of Explorer may or may not be seen as the initiation of the Space Race, but it did help begin the modern revolution in our understanding of the universe-- a revolution that is still going full speed ahead-- with its discovery of the radiation belts around Earth, named the Van Allen Belts after American physicist James Van Allen.