TAMPA (CBS Tampa) – While we are scanning the heavens looking for signs of intelligent life in the universe, is it possible that alien life already visited Earth…and decided we weren’t smart enough to be contacted? That’s a big worry for Neil DeGrasse Tyson, director of the Hayden Planetarium and host of ‘Cosmos.’ “My great fear is that we’ve in fact been visited by intelligent aliens, but they chose not to make contact, on the conclusion that there’s no sign of intelligent life on Earth” he told MSNBC’s Chris Hayes. DeGrasse Tyson says one obstacle to contact may be human arrogance. “The audacity of us to even claim we can define intelligence.” But another problem may be the means to communicate. “It takes more than just intelligence,” said DeGrasse Tyson. The radio signals we send into the universe and listen for would have been unimaginable just 200 years ago, because human beings had yet to discover that radio waves even existed. So while we assume aliens would use radio to communicate, they may have moved on to some other technology we have yet to discover. via CBS Tampa.