One of the most common phrases to hear amongst students in school is “I’m tired.” We all know why we are tired, whether it is from staying up late to finish an assignment, study for a test, or just waste time online. Everyone knows the reasons they are tired, but no one ever stops to ask why we need to sleep in the first place.

We all know that when we sleep more, we feel more energized, alert, and can think more clearly, but the actual answer of why organisms need to sleep is as of yet unanswered. There are dozens of theories on the subject, but so far the only solid answer to the question of “why do we need to sleep” is simply, we get tired.

Scientists have landed a rocket on a comet, discovered microorganisms from billions of years ago, and completely eradicated once fatal diseases. Yet we still cannot figure out the purpose of something we have done every day since we were born.

Most theories about sleep involve its necessity for our bodies to conserve energy or recuperate, but there is no actual evidence that proves this. We do know that sleep, specifically REM sleep, where dreaming occurs, is integral to our early development and health throughout our lives.

Sleep deprivation can have extreme consequences on our health, causing hallucinations, extreme weight loss or gain, diabetes, and even death. And yet, we still do not know why. Even research into different sleep disorders such as insomnia provide us with no solid answer.

Perhaps one of the most perplexing thing about sleep is that not all people need the same amount of sleep, and some need no sleep at all. Thai Ngoc is a Vietnamese man who, for no explainable reason, never sleeps. Not only can he function perfectly fine after not having slept for over forty years, but he is physically unable to fall asleep. This phenomenon is still unexplained, and only adds to the mystery that is sleep.

So when you drift off to sleep tonight, enjoy it – but understand that no one really knows why you’re doing it.