the discovery series is called "into the universe." he said the concept of alien existence is rational. he described what his conceptions were of what life on other channels might look like, from jupiter's moon to aliens living in the atmosphere of the gas giant saturn millions and billions of miles -- sorry, i had a class with professor sagan. and then the fact that human light forms could doom our own existence. to quote, if aliens visit us, the outcome would be like when columbus visited americans, which didn't turn out well for the native americans. it's because of that threat that hawkings calls contact with aliens a little too risky. >> it might sound unlikely, if you think about it logically, alien technology should be as extraordinary to us as a rocketship to a caveman.