Theoretical physicist Stephen Hawking has once again opened up about his fears and warned the world to be hesitant about making contact with alien life. He said planet Gliese 832c potentially had alien life but said humans needed to be wary. "One day, we might receive a signal from a planet like this, but we should be wary of answering back," he in the documentary, "Stephen Hawking's Favourite Places." "Meeting an advanced civilization could be like Native Americans encountering Columbus. That didn't turn out so well." He claimed alien life could be "rapacious marauders roaming the cosmos in search of resources to plunder, and planets to conquer and colonize." His fears have not changed since he first spoke out about it on the Discovery Channel in 2010. He said as he grew older he became more convinced humans were not alone. "After a lifetime of wondering, I am helping to lead a new global effort to find out," he said. Planet Gliese 832c has five times the mass of earth and a similar