We're not alone in the universe -- or so say half of Americans in a new HuffPost/YouGov poll. And a quarter of Americans think that alien visitors have come to Earth. According to the new survey, 50 percent of Americans think that there is some form of life on other planets, while only 17 percent think that there's not. Another 33 percent said they aren't sure. Respondents were somewhat more skeptical when asked whether there's intelligent life on other planets. Thirty-eight percent said there is, 21 percent said there's not, and the percentage saying they're not sure edged up to 42 percent. Scientists with the SETI institute have been using microwave radio to attempt to detect communication from other solar systems since the 1960s. And NASA programs, including the James Webb Space Telescope, set to launch in 2018, are currently underway to help identify other planets in the universe that may support life. In the HuffPost/YouGov poll, a quarter of Americans said that they think aliens have visited Earth, while a third said they have not -- the rest of the respondents weren't sure. Among those who said that life exists on other planets, 45 percent said that aliens have visited Earth. via Huff Post.