Through most of our history, we’ve assumed we occupy a privileged and unique place in the universe. In the 16th century, Copernicus paved the way for the understanding that we orbit but one star among many. Over the last two centuries, we’ve found that we’re a small part of one galaxy, and that ours is but one galaxy among billions. If we look at those numbers, it seems ridiculous to assume ours is the only planet in that whole universe to host intelligent life.
Until the 1990’s, the main counterargument was that planetary formation appeared to be limited to our sun. That changed in 1995, when radio astronomers were able to infer several extrasolar planets. The Kepler observatory was launched in 2009, and we’ve now verified the existence of nearly 2,000 exoplanets in more than 1,200 solar systems.
In 1960, Frank Drake decided to turn a radio telescope to the sky and listen for signals from possible alien civilizations. Continued...