We spend a third of our lives sleeping and most of us think we sleep to restore body and mind. Now that may be true, but there is no scientific proof. Crazy as it may seem, scientists don’t actually know why we sleep. If you continuously deprive rats of sleep, they die after 14 days, but autopsies fail to reveal the cause of death. The human record is held by a student who went 11 days without sleeping. He had no discernable ill effects apart from feeling sleepy, but in the end he just could not stay awake, which does not tell us much about why we sleep, only that we have a very powerful mechanism to make us sleep.