How to Sleep Better: How Circadian Rhythm Affects Sleep

A woman sits on a sofa with alarm clock in hand. In this short clip, she defines circadian rhythms and how they affect sleep.

She also explains why going to bed at a decent hour helps our processes of rejuvenation. What are circadian rhythms? Is there any truth to the adage early to bed and early to rise makes a man healthy, wealthy, and wise? Why does the speaker suggest going to bed between 9pm to 10pm?