The Space Race led to increased questions as to whether there was life on other planets. This greater curiosity resulted in people regularly seeing unidentified flying objects. One of the most famous UFO sightings during this period was by John Lennon, who claimed he saw one on Aug. 23, 1974.

"I was lying naked on my bed, when I had this urge," Lennon said in a conversation with Andy Warhol's Interview magazine. "So I went to the window, just dreaming around in my usual poetic frame of mind. ... There, as I turned my head, hovering over the next building, no more than 100 feet away was this thing with ordinary electric light bulbs flashing on and off round the bottom, one non-blinking red light on top."

This was during his "Lost Weekend," but Lennon swore that he was "very straight" at the time. He called out to May Pang, his girlfriend during the period of separation from Yoko Ono, to confirm what he was seeing.

"As I walked out onto the terrace," she said, "my eye caught this large, circular object coming towards us. It was shaped like a flattened cone, and on top was a large, brilliant red light, not pulsating as on any of the aircraft we'd see heading for a landing at Newark Airport."

Listen to John Lennon Talk About Seeing a UFO

Pang added: "When it came a little closer, we could make out a row or circle of white lights that ran around the entire rim of the craft - these were also flashing on and off. There were so many of these lights that it was dazzling to the mind."

They took pictures, both with a Polaroid and a regular camera, but they turned up nothing. They also called the police, who told the couple that they had received other calls about it.

Lennon stood firm. In the lower left-hand corner of the sleeve of Walls and Bridges, which was released a month later, he wrote, "On the 23rd Aug. 1974 at 9 o'clock I saw a U.F.O." and it bore the initials "J.L."

In the posthumously released "Nobody Told Me," Lennon also sings, "There's UFO's over New York / And I ain't too surprised."

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