Humans spend approximately one-third of each day sleeping. In addition to the usual 8 hours, we frequently nap during the day. However, the sleep/wake cycle varies from person to person. Some people go through periods where they get little sleep or take naps throughout the day. Others maintain a consistent schedule with no interruptions. Despite these differences, our bodies have a “circadian rhythm” that controls how much we sleep and when.
In 1962, French caving expedition member Michel Siffre spent 2 months underground without any contact with the outside world. He found that he naturally fell into an almost 24-hour cycle. It is clear that humans need to sleep regularly to maintain their health, and disturbing this daily rhythm can be detrimental both physically and mentally – jet lag or constant illness among shift worker is proof enough for this fact. However, psychologists disagree over the purpose of sleep; whether it is physically or mentally restorative, or serves another evolutionary function.
