powers of four

The intriguing remark was made by Lord Martin Rees, a leading cosmologist and astrophysicist who is the president of Britain’s Royal Society and astronomer to the Queen of England. Rees, who last month hosted the National Science Academy’s first conference on the possibility of alien life, said he believes the existence of extra terrestrial life may be beyond human understanding.

There's an interesting breakdown of the "Why Don't We See Anyone?" possibilites. On a somewhat related note (particularly to point C in the article), yesterday I listened to the Starship Sofa reading of David Brin's Crystal Spheres, which I highly recommend. I'd read the story about six years ago, but the reading was pretty high quality.