⏳ Pendulum & g on Planets

📖 The Physics

A simple pendulum keeps almost perfect time, and that is more useful than it sounds. Its period depends only on its length and the local gravity — not on the mass, and (for small swings) not on how far it swings.

Turn that around and the pendulum becomes an instrument: just time the swings and you can measure g at your location.

Tap Moon and the same pendulum swings lazily (small g, long period); tap Jupiter and it whips back and forth. Making the string longer also slows it — but four times the length only doubles the period.