How Does the Entrainment Effect Synchronize Your Sleep?

Your body has an internal clock that tells you when to wake up and go to sleep. This clock is set by the sun! Every day, sunlight acts like a reset button for your brain.

When it is bright outside, your eyes send a signal to your brain saying 'It is daytime!'. This stops you from feeling sleepy. When the sun goes down and it gets dark, the signal changes. Your brain starts making a sleep chemical called melatonin. This makes you feel tired.

Sometimes our clocks get confused. Maybe you stayed up late looking at a bright tablet screen. The screen looked like sunlight to your eyes! So your brain thought it was still daytime and did not make enough melatonin. Now, try to imagine your body is a team. The sun is the coach blowing the whistle to start practice (waking up) and stop play (going to sleep). Light entrainment is just your body learning to dance to the music of the day.