On April 1, 1976, English astronomer Patrick Moore announced a unique opportunity on BBC Radio 2. At 9:47 a.m., he said, Pluto would pass behind Jupiter, and the combined gravitational forces of the two bodies would noticeably reduce gravity on Earth. If listeners jumped in the air during the conjunction, they’d feel a floating sensation.

Shortly after the appointed moment, the BBC began to receive hundreds of phone calls from listeners who’d confirmed the effect, including “a woman who said that she and 11 friends had been wafted from their chairs and orbited gently around the room.”

None of them had noted the date.