In a speech to Congress 50 years ago today, on May 25, 1961, President John F. Kennedy challenged the nation to send a man to the moon and return him safely to Earth by the end of that decade. This video includes historical footage of the launches of Yuri Gagarin and Alan Shepard, whose flights helped prompt Kennedy’s speech, plus comments from Mercury astronauts John Glenn and Scott Carpenter, and Mercury Flight Director, Chris Kraft.  credit: NASA