I'm an astronomer and I think aliens may be out there – but UFO sightings aren't persuasive
- Written by Chris Impey, University Distinguished Professor of Astronomy, University of Arizona
Many people who say they have seen UFOs are either dog walkers or smokersAaron Foster/THeImage Bank/Getty ImagesIf intelligent aliens visit the Earth, it would be one of the most profound events in human history.
Surveys show that nearly half of Americans believe that aliens have visited the Earth, either in the ancient past or recently. That...

