How Do Our Bodies Know When to Sleep and When to Wake Up?

Your body has a special clock called the circadian rhythm, which tells you when to be awake and when to sleep. It’s like an invisible timer inside your brain that uses light, from the sun or your phone screen, to decide whether it's time for bed or time to get up. When it gets dark, the body starts making a sleepy chemical called melatonin.

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Examples

  1. A child goes to bed at night because it’s dark outside.
  2. An adult feels drowsy in the evening after a long day at work.
  3. Someone wakes up early on weekends but struggles during the week.

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