In 1924, the US had “Radio Silence Day” where radio broadcasts would be kept quiet for 5 minutes every hour in order to listen for radio signals from space. They didn’t hear anything.
Fermi’s Paradox proposes the theory for why we haven’t heard from or seen any aliens. One of which being that they aren’t communicating because of an impending threat they know about, that we are not aware of.
In the case of discovering aliens, we already have a representative who will handle all communication with them. Simonetta Di Pippo, is the current director of the United Nations Office for Outer Space Affairs and is the designated person to act as an ambassador to extraterrestrials.
Carbon Chauvinism is a term coined by Carl Sagan which assumes that all extraterrestrial life must be made of carbon because carbon-based humans are unable to imagine life made of radically different biochemistries.
While filming “2001: A Space Odyssey”, the director Stanley Kubrick was so worried that an alien encounter was imminent that he took out an insurance policy incase aliens were discovered before his movie was released which he believed would have ruined his storyline.
During the space race, Stanley Kubrick was so worried that humans would soon make first contact with aliens that he tried to buy an insurance policy for 2001: A Space Odyssey in case audiences found his depiction of aliens ridiculous.
The Fermi Paradox states that given how large our universe is, evidence of alien life should have been found by now, leading some scientists to believe that alien civilizations have purposely been keeping us in the dark.
Some people believe dolphins and whales are actually a race of alien beings called the Nommos.
Reagan and Gorbachev informally agreed that the US and USSR would assist each other in the event of an alien invasion.