🌕 Tidal Forces
About this simulation
Tidal forces arise because gravity weakens with distance, so a moon
is pulled harder on its near side than its far side — stretching it
along the line to the planet. This visualisation lets a moon orbit a
planet, deform under that stress, and shatter into a debris ring once
it crosses the Roche limit. The same physics shaped
Saturn's rings, drives volcanism on Jupiter's moon Io, and explains
why comet Shoemaker–Levy 9 broke apart before hitting Jupiter.
How it works
- The moon orbits the planet at a distance you set, measured in multiples of the Roche limit.
- Differential gravity stretches the moon into an ellipse; arrows show the pull on each side.
- The Roche limit (red dashed circle) depends on the densities of both bodies.
- Cross inside the Roche limit and the moon is torn apart into an orbiting debris ring.
Key equations
d = 2.44 R (rho_p / rho_s)^(1/3) — the rigid Roche
limit, where d is the breakup distance, R
the planet's radius, and rho_p, rho_s the
densities of planet and satellite. Tidal force scales as
F_tidal ∝ 1 / r^3.
Controls
- Satellite type — rocky, icy, or loose rubble pile (sets density).
- Distance — orbital radius in multiples of the Roche limit.
- Mass ratio — how much heavier the planet is than the moon.
- Speed — animation playback rate.
- Pause / Reset — freeze or restore the default scenario.
Did you know?
Mars's moon Phobos is spiralling inward and will likely be torn into
a ring of rubble within about 50 million years — Mars may one day
have rings of its own.