<div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>A French scientist emerged from a cave after 63 days living in total isolation away from natural light on September 14, 1962.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>Michel Siffre had nothing more than a four-volt lamp for illumination in his two months underground.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>Though a trained geologist, his time underground had nothing to do with rocks.</span></div></div><div><div id="adspot-mobile-medium"></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>Instead, he was conducting an experiment on how the body clock operates without sunlight.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>And quickly, he stopped operating on the same sleep cycle as everyone on the surface.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>His waking hours began to extend to 25 hours.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>Consequently, his two months underground felt to him more like one.</span></div></div><div><div class="OUTBRAIN" data-reactroot="" data-src="//www.9news.com.au/world/today-in-history-september-14-what-happened-on-this-day-michel-siffre-cave/75d3bfe7-3350-4a60-906c-468bbb887b38" data-widget-id="AR_5"></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>"After one or two days, you don't remember what you have done a day or two before," he told Cabinet magazine.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>"The only things that change are when you wake up and when you go to bed. </span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>"Besides that, it's entirely black. It's like one long day."</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>His research was funded in part by the French Army, who wanted to know if they could keep soldiers awake longer.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>NASA also contributed funding, because they wanted to know if removing people from the Earth's solar cycle would harm their sleep patterns.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>When he came out, Siffre had to wear special sunglasses to cope with what felt like blinding sunlight to him.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>He also had to be helped to move around as he was so unused to walking.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>He later supervised other cave experiments. </span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>In 1964, Siffre planned a rescue mission after hearing silence on another cave-man's microphone for an alarming amount of time.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>But his health was revealed by a snore. The subject had been asleep for 34 hours.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>Siffre would return to a cave for three months in 1999, spending the turn of the millennium underground.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>To mark the New Year's, he brought champagne and foie gras to celebrate by himself.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><span>But by then, he had lost track of the days, actually celebrating on what turned out to be January 4.</span></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><a href="https://www.9news.com.au/today-in-history" target="" title="For more from our Today in History archive, click here."><strong><span>For more from our Today in History archive, click here</span></strong></a></div></div><div class="block-content"><div class="styles__Container-sc-1ylecsg-0 goULFa"><a href="https://www.9news.com.au/national/how-to-follow-9news-digital/29855bb1-ad3d-4c38-bc25-3cb52af1216f" target="_blank" title=""><strong><em><span>DOWNLOAD THE 9NEWS APP</span></em></strong></a><strong><em><span>: Stay across all the latest in breaking news, sport, politics and the weather via our news app and get notifications sent straight to your smartphone. 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