Dec. 20, 2010 at 10:12 PM ET
On Feb. 14, 1990, NASA controllers instructed the Voyager 1 spacecraft to turn around and take one last look at its home planet as it pushed on to the fringe of our solar system. Look closely at the resulting image. That tiny pinpoint of light in the center-right is us – you, me, and everyone else that calls Earth home.
The request came from the late, great astronomer Carl Sagan, one of the world's greatest advocates for advancing the general public's appreciation and understanding of science. He passed away 14 years ago today after a two-year battle with bone-marrow disease.
The image, called "A Pale Blue Dot," was made when Voyager 1 was about 4 billion miles away. It inspired Sagan's 1994 book "Pale Blue Dot: A Vision of the Human Future in Space." An excerpt puts the image's significance into context:
"It has been said that astronomy is a humbling and character-building experience. There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. It underscores our responsibility to deal more kindly with one another, and to preserve and cherish the only home we've ever known, the pale blue dot."
We leave you to reflect on Sagan's thoughts as we head into the final days of our Cosmic Log Space Advent Calendar. For more views of Earth from space, check out these past offerings. We've also included links to other online Advent calendars that have been serving up space images daily since the beginning of the month: