The sky is full of stars, and since prehistoric times humans have known of five nomads – planets – wandering among them. No individual discovered those planets, for they're there for all to see. So why was the sixth one – now called Uranus – not known until 1781?

William Herschel was the first person ever to discover a planet. In 1781 he discovered the planet which was named Uranus for the ancient Greek sky god. Although Uranus has at least 27 moons, most of them weren't discovered until the Space Age.

Three days orbiting Earth strapped into a space capsule so primitive that no one could land in it. So how did the cosmonaut get home? That's part of the story of the first woman in space, on a solo flight twenty years before NASA sent Sally Ride into orbit on a Space Shuttle.

While World War I was tearing Europe apart in 1915, a German physicist presented a theory that would shake up the way we see the Universe. The physicist was Albert Einstein, his face still unknown to the world, his name not yet a synonym for genius. How did a solar eclipse in 1919 change all that?

A mile above the California desert stands Palomar Observatory. Its 200-inch mirror was officially impossible to make, but George Ellery Hale's vision inspired a nation in the grip of the Great Depression and it became the jewel in the crown of astronomy for the second half of the twentieth century.