Smartphones can tell when you're asleep because they use sensors like your phone's accelerometer. These little sensors work like a mini-motion detector, they feel the tiny movements of your body as you sleep or wake up, just like how a toy car detects motion on a road. If your phone notices that you’ve been still for a while, it thinks you're sleeping and knows when to wake you up gently with a soft vibration.
Examples
- It waits until you're about to wake up before vibrating gently.
- You feel the vibration instead of a loud alarm.
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See also
- Why Do Smartphones Always Know When You're Tired?
- Why Do Smartphones Use So Much Battery Just to Stay Alive?
- How Do Smartphones Know When to Wake Up?
- How Do Phones Know Where You Are?
- How Do Smartphones Know When to Vibrate?