It seems like just yesterday. In 1980, astronomer Carl Sagan presented Cosmos, his PBS series about the joy and beauty of scientific discovery. More than anything else (yes, I have to admit, even more than my childhood visits to COSI), Cosmos awakened in me a love and a passion for science that has never dimmed.
In one of my favorite scenes, Sagan visits his old sixth grade classroom in the Bensonhurst section of Brooklyn. Sagan talks to the students there (who, coincidentally, were just my age at the time) about what a special time this was, the first time that humans had begun to explore the universe. In particular, Sagan talks about the beginning of our search for planets beyond the solar system.
When Cosmos aired, no one knew if even a single planet existed outside our Sun's little family. Could we be the only planetary system in the galaxy, or even the universe? Or were planets common, with many other stars sporting their own planetary systems? Might any other planets even support life? No one knew.
But Sagan knew that scientists would one day find out. He said to those students – and to me, "By the time you are as old as I am now (Sagan was 45 at the time – coincidentally, just my age today), we should know for all the nearest stars whether they have planets . . . That will happen in your lifetime, and it will be the first time in the history of the world that anybody found out, really, if there are planets around other stars."
Carl Sagan died in 1996, a time when we were just uncovering the first tantalizing hints of extra-solar planets. But Sagan's prediction was right on the money. Today, we know of hundreds of other planets. Most of them (because they're the easiest to find) are gas giants like Jupiter and larger, with no solid surface. And most of these are in tight orbits around their star, with soaring temperatures and little if any chance for our kind of life.
But this week NASA announced the discovery of three planets nearly the size of Earth, in orbits nearly like our planet's orbit. It's the closest we've come yet to finding another Earth in the heavens.
How did we find these worlds?
... the ways by which men arrive at knowledge of the celestial things are hardly less wonderful than the nature of these things themselves
— Johannes Kepler
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