Stephen Hawking recently mentioned that he believed it might be wiser for Earthlings to not draw attention from aliens in outer space. This is because he suggested that intelligent beings from elsewhere in the universe might be far more advanced than humans technologically, and may destroy our civilization if they find us.
I was therefore thinking about the possibility of making the entire Earth invisible. I don't how that would be done. I recently listened to the commentary on DVD of the animated film "G-force" by director Hoyt Yeatman, who noted that people are already developing stealth suits to try to make people invisible. Sounds quite interesting.
I'm not sure how feasible it would be, though, to do it on a large scale, such as making the entire Earth invisible from extraterrestrial beings. I guess that there's still a possibility that intelligent beings elsewhere may be so much more advanced that even if we made the Earth invisible, they could still detect it somehow at a certain frequency of the electromagnetic spectrum.