* To my mathematical brain, the numbers alone make thinking about aliens perfectly rational… If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn’t turn out very well for the Native Americans.”
I agree that life and probably intelligent life is pretty common. I disagree that it makes much difference whether we broadcast out via SETI or not. Before aliens or we can cross interstellar space we can go to the gravitational lens of the sun (500 AU about 2 light days away) and set up large telescopes or create hypertelescopes at other locations. These observatories would be able to image planetary surfaces and take spectrographs of planets. (World Imaging telescopes)
* with a hundred billion galaxies each with potentially a hundred billion stars, Hawking considers that intelligent life is entirely possible – even, perhaps, intelligent life with technology so advanced as to be able to travel across interstellar distances. He considers it an extremely unwise move for primitive present-day humanity to attract the attention of such voyagers – by such efforts as the controversial practice of beaming out “Active SETI” signals
* Stephen Hawking’s Universe begins on the Discovery Channel on Sunday 9 May at 9pm.