10 Biggest Unsolved Mysteries In Science
6. Why Do We Sleep?
For all of our scientific progress, the best answer most scientists can give to the question, "Why do we sleep?" is "Because we get tired."
Quite why we evolved the need to completely switch off all consciousness for hours at a time is a mystery. It's thought that sleep has something to do with memory consolidation, brain plasticity, and it's an opportunity for you body to get a bit of repair work done, but as far as we know, there's no good reason why a good night's sleep should restore your energy and make you feel so refreshed.
As far as we know we convert our food into energy, but no matter how much you eat, you wouldn't be able to stay awake indefinitely.
We know that it's definitely something we need to do, as those who don't sleep will eventually grind to a halt and, if kept awake for long enough, you simply die.