"When we originally went to the moon, our total focus was on the moon. We weren't thinking about looking back at the Earth. But now that we've done it, that may well have been the most important reason we went."

The Blue Marble, taken on December 7, 2012 (NASA)

Forty years ago today, astronauts on board the Apollo 17 spacecraft snapped a picture of a brightly lit planet -- our planet. Cast against the black backdrop of space, Earth's vibrancy leapt out from the emptiness that surrounded it. In the decades since, that photograph has reshaped how we think of our place in the universe. "We have been evolving from the beginning of civilization to a larger and larger perspective of life on the Earth," David Beaver, co-founder of the Overview Institute, says in the short film below. "But the next natural evolution is understanding the life in space -- that is the fact that the Earth, as Buckminster Fuller used to famously say, is a spaceship, Spaceship Earth. We are in space already."

Overview, a Planetary Collective movie, makes that realization fresh again, showing us just how awesome a place our planet is, and how much depends on the health of the thin sleeve of gases -- our atmosphere -- that surrounds it. "When we originally went to the moon, our total focus was on the moon," Beaver says. "We weren't thinking about looking back at the Earth. But now that we've done it, that may well have been the most important reason we went."

H/t @andersen.