Question: Do you know of someone who sleeps in the day and wakes up in the night? Is it common? Does someone do it?

Mike Ambler answered on 5 Nov 2018:

Well lots of people do this from time to time for working night shifts for example, and it can be really hard on your body and brain – they say that trying to drive a car after a night shift is as difficult as it would be after drinking alcohol.

But I suspect you mean do any people naturally sleep in the day and wake at night?

I’ve never heard of this happening, because we all have an internal clock that works in our brains telling us when to sleep and when to eat etc. Light and dark periods in the day help to keep this clock set correctly, and that is how you can adapt if you fly to the other side of the world – the clock gets reset by the new pattern of light and dark.

If you put somebody in a room with no windows so they can never see whether it is light or dark outside, their clock will slowly lose track of the correct time and they will end up sleeping at the wrong time.