Henri's Tide Lab

Watch the Moon orbit Earth, Earth rotate beneath the tidal bulges, and Henri's lighthouse move through high tide and low tide.

SCIENCE SIMULATION

Space view — Earth, Moon and tides

Henri's coastHIGH TIDE

Relative level+1.00

Next high tide—

Moon orbit day1.0 / 27.3

Henri's lighthouse — one lunar day

high tidelow tideHenri now

What Henri sees at the shore

What is happening now?

Real-world note: this is an equilibrium-tide learning model. Coastlines, bays, seafloor shape, wind, air pressure and the Sun can strongly change real tide times and heights.

1. Near-side bulge

The Moon pulls the ocean on Earth's Moon-facing side a little more strongly than Earth's center.

2. Far-side bulge

The Moon pulls Earth's center more strongly than the far-side ocean. Relative to Earth, a second bulge appears opposite the Moon.

3. Two highs each lunar day

Because Earth spins while the Moon moves, the same coast faces the Moon again after about 24 h 50 min, giving roughly 12 h 25 min between highs.

Henri challenge

If the lighthouse is about 90° away from the Earth–Moon line, what tide should it be closest to?