Predicting Tides

Adding up rhythms

An interactive lesson with 6 steps, about 5 minutes: you predict, drag and solve, with instant feedback on every answer. It runs in your browser and needs JavaScript.

What you’ll learn

• Tides are predicted by adding constituents with astronomically known periods.
• M2 (12.42 h) and S2 (12 h) beat every 14.8 days: the spring–neap cycle.
• Kelvin’s mechanical machines summed the waves long before computers.

Steps

1. Tides as a sum of waves
2. From tides to spring tides
3. The beat period
4. Tide-predicting machines
5. Adding constituents
6. Daily inequality