Have you ever wondered why most people start feeling sleepy towards the end of the day when the sun is setting or why they wake up after sunrise? Have you ever been able to estimate the time of day without having to look at a watch or check whether it’s still bright outside? Well, you can thank your internal body clock for that.

Our circadian rhythm is an internal biological process which is very closely related to the Earth’s rotation period, i.e. the 24 hours that make up a day, and it is responsible for regulating our sleep-wake cycle.

Although it is an internal and self-sustained process, our circadian rhythm adjusts to the local environment using information from outside our body (zeitgebers), primarily whether it is light or dark. Nonetheless, if our body doesn’t receive any information from the outside, it will still follow an approximate 24 hour cycle.

But why do we need to follow this 24 hour cycle? As you have probably realised by bumping your small toe into a piece of furniture during the night, we’re not very good at seeing in the dark, we wouldn’t be very good at getting most things done in the dark, such as searching for food or hunting. What better time than during the night to allow our body and mind to rest and restore themselves?

Circadian rhythms are thought to allow organisms to make better use of their time putting them at a selective advantage compared to those that don’t follow such cycles. But what happens now that us humans don’t need to search for food, or are able to create light with the flip of a switch? Do we still need to follow this 24 hour cycle? This is something which we can talk about in an another article.

Sweet dreams.