There was that photograph from one of the Apollo trips to the moon, where an astronaut turned and shot a photo of Earth rising at the moon. Thousands saw a new way at looking at our planet, large and brimming with life, off the horizon of its dead moon. But, perhaps a more significant photograph was that that Carl Saga had an unmanned probe take of Earth from much further way in our solar system, which made Earth look like a “Pale Blue Dot.”
This vision of a small, delicate planet in a bad (lots of asteroids) part of our solar system in a distant part of our galaxy, among billions of galaxies, made our planet look tiny and vulnerable. As far as we know, there’s nothing else like Earth. And, there’s nothing else like Earth at this moment in history when conditions are ripe for mankind, which given its four billion-year history, hasn’t been so hospitable.
Granted a vision is just a glimpse, not a comprehensive argument that, for example, our planet is in great environmental trouble. Nevertheless, a small vibrant planet out there all by itself amidst countless suns and dead worlds has compelled some of us to think we ought not to take chance with our environment—which is only a narrow band of all possible environments in which our species can thrive.
So anyway, you can request a transcript of this discussion with the late Dr. Sagan from Science Friday, but you can also listen to the program as a podcast from Science Friday. Or you can order the "Pale Blue Dot : A Vision of the Human Future in Space." Ballantine Books, 1997. –from Amaon.com.