A former CIA-linked physicist's comments about 'four alien species' have reignited UFO conspiracy theories online.

New Unidentified Anomalous Phenomena (UAP) files have ignited a global conversation about the nature of our reality, as the Pentagon releases its third major tranche of declassified material. Interest ...

WASHINGTON (AP) — A polarizing Harvard astronomer known for splashy theories about alien visits has been tapped by the Trump administration to lead a team of outside scientists to study the national ...

The Great Filter theory suggests advanced civilisations may self-destruct before contacting others, explaining the universe's silence.

"Hearst Magazines and AOL may earn commission or revenue on some items through these links." This story is a collaboration with Popular Mechanics. Do you think the U.S. government is hiding, and ...