Meet Clyde Tombaugh, discoverer of Pluto (1930)

Because of the discovery made by this young farmer of Kansas, every dictionary in the world will have to be revised. For all time to come, students of astronomy will read that the ninth planet, Pluto, was discovered in 1930 by Clyde Tombaugh.

Moon landing video & transcript (1969)

With more than half a billion people watching on television, Neil Armstrong climbs down the ladder and proclaims, "That's one small step for a man, one giant leap for mankind."

Ham, the first chimp in space (1961)

Shepard. Glenn. Armstrong. All of them rode on the back of a little 37-pound chimp whose name sounded more like lunch meat than the first primate in space.

Unlimited size of universe inspires awe (1949)

Some of the ancient astronomers were sure these heavenly bodies were far away, but not until recent methods of measurement were applied did we know the true spatial relationship of the various members of the universe.

Challenger shuttle explodes shortly after liftoff (1986)

A confused and stunned nation searched for answers to what caused the catastrophic explosion of the space shuttle Challenger that sent schoolteacher Christa McAuliffe and six other astronauts to a fiery death 74 seconds after liftoff Tuesday.