LMR-058 · Planets
Tidal Locking
One face eternal day. The other face eternal night.
§ A first look
§ Depths
Six ways into the same idea — from bedtime story to chalkboard. No order required.
L1 · Crayon
Told like a bedtime story.
For a curious 10-year-old. No jargon. Just a picture in your head.
Watch the Moon for many nights. You'll notice we always see the same face — the same pattern of dark blotches, every single time. We never see the back of the Moon from Earth. Why? Because while the Moon goes around Earth, it's also turning at exactly the right speed to keep one side always pointing at us. This 'always showing the same face' thing happens when one object orbits another for a very long time. It's called being tidally locked. Many small planets are tidally locked to their stars — one side always day, the other side always night, and nobody gets a normal sleep schedule.
§ Strange but true
- 01The Moon always shows Earth the same face. The other side wasn't seen by anyone until 1959.
- 02Tidal locking happens everywhere — moons, planets, binary stars. Big bodies eventually still each other.
- 03On a tidally locked planet, one side is eternal day, the other eternal night, and life would huddle along the twilight ring.
§ From the field journal
Tidal Locking
"One face eternal day. The other face eternal night."
— observed, sketched, not yet fully understood.
§ Nearby