Today is the first Carl Sagan Day, marking seventy-five years since his birth. Sagan was an American astronomer and astrochemist, perhaps best known best known for his popular science books and his support for SETI (Search for Extra-Terrestrial Intelligence).
Born in Brooklyn, Sagan attended the University of Chicago for his undergraduate and graduate degrees. From 1962 to 1968, he worked at the Smithsonian Astrophysical Observatory in Cambridge and taught at Harvard before moving to Cornell University, where he would teach for the rest of his life.

Sagan made many important contributions to astronomy and astrophysics, but it was his work on the public understanding of science that I feel most deserves being remembered. Among his most famous works are: The Demon-Haunted World, Pale Blue Dot, and Cosmos, which is the best-selling science book every published in English. In his books, Sagan made awe inspiring science accessible to the general public, often written in equally awe inspiring language.

He passed away on December 20, 1996 at the age of 62 after a long struggle with a rare bone marrow disease (myelodysplasia).
I can think of no more fitting way to remember such a great man than with his own words. The following passage from Pale Blue Dot describes the photo at the top of this post, which was taken by Voyager 1 from six billion kilometers past Pluto.

Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every kind of peasant, every young couple in love, every mother and father, hopeful child, 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.

The Earth is a very small stage in a vast cosmic arena. Think of the rivers of blood spilled by all those generals and emperors so that, in glory and triumph, they could become the momentary masters of a fraction of a dot. Think of the endless cruelties visited by the inhabitants of one corner of this pixel on the scarcely distinguishable inhabitants of some other corner, how frequent their misunderstandings, how eager they are to kill one another, how fervent their hatreds.

Our posturing, our imagined self-importance, the delusion that we have some privileged positions in the Universe, are challenged by this point of pale light. Out planet is a lonely speck in the great enveloping cosmic dark. In our obscurity, in all this vastness, there is no hint that help will come from elsewhere to save us from ourselves.

The Earth is the only world known so far to harbor life. There is nowhere else, at least in the near future, to which our species could migrate. Visit, yet. Settle, not yet. Like it or not, for the moment the Earth is where we make our stand.

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. To me, it underscores our responsibility to deal more kindly with one another, and to preserve and cherish the pale blue dot, the only home we’ve ever known.