There is no evidence that what the US government calls Unidentified Anomalous Phenomena - UAPs - are extraterrestrial. That's the public, declassified assessment of the US Pentagon which has released its report into eight decades of UFO sightings.

But what the report does reveal may be even stranger, and impact how we think about publicly disclosed advances in physics. 

Guest Garrett M. Graff, journalist and historian; Contributing editor to WIRED Magazine; author 'UFO: The Inside Story of the US Government's Search for Alien Life Here—and Out There'