Today, almost everyone has seen the Blue Marble, a photograph of Earth from space that was taken 40 years ago today. But only a handful of people have actually viewed our world firsthand from the outside, and the idea of being able to see the planet as a single, fragile whole was unprecedented when the first Blue Marble shot was taken. For the Blue Marble's anniversary, filmmaking group Planetary Collective has put together "Overview," a short documentary featuring five astronauts whose perspective on the world changed when they went into space. It's a moving look at how leaving Earth has given everyone, perhaps most of all the astronauts themselves, a new way to appreciate our place in the universe.