Orbital Resonance

Jupiter's moons Io, Europa, and Ganymede orbit in a precise 1:2:4 ratio known as the Laplace resonance. For every orbit Ganymede completes, Europa completes exactly two and Io exactly four. This is not a coincidence but a dynamical trap: the three moons exchange energy through regular gravitational tugs that maintain the lock over billions of years.

Resonance can stabilise or destabilise, depending on the configuration. The Laplace resonance pumps energy into Io's orbit, keeping it slightly eccentric. That eccentricity drives extreme tidal heating - enough to make Io the most volcanically active body in the solar system. The same mechanism keeps Europa's subsurface ocean liquid, making it one of the most promising places to search for extraterrestrial life.

The same physics operates throughout the solar system. The Kirkwood gaps in the asteroid belt are orbits where asteroids would resonate with Jupiter at simple ratios (3:1, 5:2, 7:3) - these orbits become chaotic over millions of years, ejecting asteroids and leaving empty lanes. Pluto and Neptune share a 2:3 resonance that prevents them from ever colliding despite their crossing orbits. Resonance is the solar system's organising principle: the invisible hand that sculpts order from gravitational chaos.