Guest: Alan Boss, Ph.D.

NASA's Kepler mission is the first space telescope designed specifically to look for planets similar to Earth outside of our solar system. In his recent book The Crowded Universe, astronomer Alan Boss argues that Earth-sized planets are plentiful in the universe. He joins the show today to talk more about the formation of Earthlike planets and the search for extraterrestrial life.

Guest: David Grinspoon.

Where do planetary science and philosophy intersect? In one fascinating field: the search for extraterrestrial life. Today on Focus, David Grinspoon speculates about the possibility of life on other planets and in other solar systems, how intelligent life may evolve both on our own planet and in the rest of the universe, and what the philosophical implications of these future discoveries may be.