system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - What makes someone a morning person? And the same with night owls? Is there a scientific explanation behind being one or the other or is it simply a lifestyle choice?
gpt
The scientific concept is 'circadian rhythm' - basically you have an inner clock that gives you a sense for the time of day. Unfortunately for most people, the inner clock is not set to 24 hours exactly.

If you have a short circadian rhythm, you are likely a morning person because your subjective days are shorter and don't require that much sleep - on the other hand a long evening will feel wrong for you much quicker.

With a longer circadian rhythm you are likely an evening person. Your rhythm demands a longer night than reality can provide, so you will rise late and/or fight drowsiness. You can go much longer in the evenings though because in your rhythm barely a part of the day has passed.