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Lunar Tide: Bulge Lag & Orbital Recession (2D)

Interactive 2D tidal-locking simulator: friction drags Earth's tidal bulge ahead of the Moon, and the resulting torque simultaneously slows Earth's spin and pushes the Moon into a wider orbit — watch the day lengthen and the Earth-Moon distance grow toward eventual mutual lock.

Physics & Mechanics2DModerate60 FPS📱 Mobile-adapted💧 Water 🌍 Earth ⇄ 3D version

Earth spins faster than the Moon orbits, so friction drags Earth's tidal bulge a few degrees ahead of the Earth-Moon line instead of letting it point straight at the Moon. That misaligned bulge exerts a torque: it pulls the Moon forward, gradually widening its orbit, while the equal and opposite reaction drags on Earth's rotation, gradually lengthening the day — angular momentum simply moves from Earth's spin into the Moon's orbit. The lag angle self-limits as Earth's spin rate approaches the Moon's orbital rate, so the system settles toward mutual tidal lock, the same end-state that long ago fixed the Moon's rotation to always face Earth. Time is accelerated by billions of times so a billion-year process is watchable in real time.

⚙ Under the hood

Interactive 2D tidal-locking simulator: friction drags Earth's tidal bulge ahead of the Moon, and the resulting torque simultaneously slows Earth's spin and pushes the Moon into a wider orbit, both governed by torque ∝ sin(2·lag)/distance⁶ and conservation of angular momentum between Earth's spin and the Moon's orbit — watch the day lengthen and the distance grow toward mutual lock.

tidal lockingtidal torqueangular momentumearth-moon systemmoon2d

2D · HTML5 Canvas 2D · 60 FPS target · runs fully client-side, no install