Closer than we think: a supposed UFO sighting in the 1950s
MARTIN REES © BETTMANN / GETTY IMAGES
We are used to thinking of extraterrestrial life and intelligence as topics on the speculative fringe. But recent advances on several fronts are rendering them almost mainstream. The transition from complex chemistry to the first entities that could be described as “living” poses one of the most crucial problems in science. Now this problem is being taken seriously. And as it is grappled with, we can begin to think rigorously about whether some of the hundreds of billions of Earthlike planets in our galaxy might also have a biosphere.