The photo above was taken by Voyager 1 in 1990 as it sailed away from Earth, more than 6 billion kilometres in the distance. Having completed its primary mission, Voyager at that time was on its way out of the Solar System. Ground Control, at Sagan's suggestion, issued commands for the distant space craft to turn around and, looking back, take photos of each of the planets it had visited. From Voyager's vast distance, the Earth was captured as a infinitesimal point of light actually smaller than a single pixel of the photo. You could easily miss the pale blue dot in the photograph if there wasn't the arrow pointing to it.
This is a profound and moving photograph, to which my pedestrian prose cannot do justice, instead I will quote Sagan's beautiful descrtiption:
We succeeded in taking that picture [from deep space], and, if you look at it, you see a dot. That's here. That's home. That's us. On it, everyone you ever heard of, every human being who ever lived, lived out their lives. The aggregate of all our joys and sufferings, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilizations, every king and peasant, every young couple in love, every hopeful child, every mother and father, every inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species, lived there on a mote of dust, suspended in a sunbeam.
To my mind, there is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world. To me, it underscores our responsibility to deal more kindly and compassionately with one another and to preserve and cherish that pale blue dot, the only home we've ever known.
The soundtrack of the video below is Sagan's extended description from which the paragraphs above were taken:
Towards the end of the video you may have noticed another famous space photograph - Earthrise:
The photograph was taken during the Apollo 8 mission to the moon.
Apollo 8 was the first human spaceflight mission to leave Earth orbit; the first to be captured by and escape from the gravitational field of another celestial body; and the first crewed voyage to return to planet Earth from another celestial body – Earth's Moon.
Here is a video that starts with the Earthrise photo and includes an Earthrise video and an Earthset video:
Awareness of the fragility of our Pale Blue Dot and the damage that we are doing to it has increased dramatically since the two photographs were taken.
Twenty years after the Pale Blue Dot photo was taken, Voyager 1 is nearing the edge of the Solar System, as this link demonstrates.
For an even more humbling view of our place in the Universe go to this post on the Hubble Ultra Deep Field.
For a post on the search for extrasolar planets try this post.
For a post on the Search for Extraterrestrial Intelligence see this post.
Recently the Cassini probe has taken its own version of the Pale Blue Dot, illustrated below. The dot, which is the Earth, can be seen above the centre of the photograph, just outside the bright ring of Saturn.
Details of the photo can be found at this post.
The photograph of Earth and the Moon below was taken from Mars orbit.
Here is a post discussing the photograph.
I will finish this post with the first five minutes of Carl Sagen's classic series Cosmos which is now thirty years old. Although the series was first aired on television 14 years before the Pale Blue Dot photo, there is a prophetic image 46 seconds into the film.