The history-altering medical mystery of an astronaut who fell in the bathroom

What really caused the debilitating illnesses?
a man looks into the ear of a man with thick glasses on

John Glenn's balance mechanism is tested by running cool water into his ear and measuring effect on eye motions (1962). NASA

On February 26, 1964, a 40-year-old man slipped in a hotel bathroom and clocked his head on the tub. The painful tumble would end up altering how the entire world approached space exploration. Why? Because that man was John Glenn, the first American to orbit the Earth, and that fall triggered a medical mystery that pushed to the forefront research into what spaceflight might do to the human body.

In the latest Popular Science video, we dig into the intriguing backstory of Glenn’s bathroom spill.

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