Nuclear physicist Stanton Friedman said extraterrestrials have repeatedly visited our planet but have no intention of revealing themselves just yet.
The Canada-based expert said there "was not a shadow of a doubt" aliens had come to Earth but that it is being covered-up my governments and security services around the world.
The 82-year-old is a leading figure in the Ufologist community and has previously worked on numerous highly classified projects for American aerospace corporation McDonnell Douglas.
He told Daily Star Online: "We have enough to prove without a shadow of a doubt that Planet Earth is being visited [by aliens].
"This is kept from people because who would want the world in upheaval? There would be mass panic and distress.
"If they (the aliens) want to make themselves known, it's easy - they will."
He believes there is a wealth of evidence that aliens exist, citing examples where the CIA has released redacted documents of UFO sightings.
But Mr Friedman thinks the reason they have remained hidden is to eventually quarantine humans on Earth and stop them from attempting to colonise space...read more>>>...
