11. Nathaniel Kleitman
Nathaniel Kleitman was a sleep researcher who in 1938 wanted to find out if humans could adapt to a longer day of 28 hours. Accompanied by his research assistant, Nathaniel trekked into Mammoth Cave, Kentucky where he stayed in a cave 120 feet underground. The test offered the perfect environment because there was no natural light and the temperature remained constant, so there were no clues for when it was day or night.
According to his research notes, the experiment was far from comfortable and on many nights Nathaniel found himself sharing his bed with a few resident rats. After a month, he emerged with his assistant, and while he himself had not adapted to the new 28 hour day, his assistant had. Their research would eventually go on to advance the knowledge on the human body’s circadian rhythms.