Our Distant Cousin.

“‘We know of just one planet where life exists — Earth. When we search for life outside our solar system we focus on finding planets with characteristics that mimic that of Earth,’ said Elisa Quintana, research scientist at the SETI Institute…’Finding a habitable zone planet comparable to Earth in size is a major step forward.'”

New planets have been discovered at a pretty decent clip of late. But, in a milestone, NASA’s Kepler Telescope finds in Kepler 186f, 500 light years away, “the first Earth-size planet orbiting a star in the ‘habitable zone’ — the range of distance from a star where liquid water might pool on the surface of an orbiting planet.” (“Earth-size” being the key word here — Kepler has previously found larger planets in the habitable zone.) To put it all down and start again, from the top to the bottom and then…

Update: Interesting speculation: Does Kepler 186f bode ill for our future? “This apparent absence of thriving extraterrestrial civilizations suggests that at least one of the steps from humble planet to interstellar civilization is exceedingly unlikely. The absence could be caused because either intelligent life is extremely rare or intelligent life has a tendency to go extinct.”