Ocean Tides
Lesson notes
Overview
The Moon and Sun produce two daily tidal bulges; spring tides occur when they line up. This topic is rated intermediate and is number 29 of 98 in Earth & Space. Builds on the basics with relationships, methods and trade-offs.
What you are seeing
The panel above shows a graph of the function. Each slider changes one parameter, so you can see exactly how the curve bends, shifts or stretches. The animation is drawn live from the model, so everything you see responds to the sliders. Press Space to pause, use Restart to replay from the start, and change the speed to slow down quick events.
In depth
Tides are caused by the difference in the gravitational pull of the Moon and Sun on different parts of the Earth, which creates two bulges of water, one facing the Moon and one on the opposite side, so most coasts have two high tides a day. When the Sun and Moon line up, at new and full moon, their effects add up to produce spring tides, and at the quarters they partially cancel, giving neap tides. Local shapes of coasts make tidal ranges vary greatly, up to 16 m in the Bay of Fundy.
Reading the relationship
The expression "h = A₁cos(ω₁t) + A₂cos(ω₂t)" is a compact summary of the idea. It uses the symbols h, A₁, ω₁t, A₂, ω₂t; name what each one stands for before you start. Notice that it contains a trigonometric function, so the result repeats as the angle goes round. Then use the sliders to see how changing one quantity changes the others.
A guided exploration
1. Set every slider to its middle value and note the shape of the curve. 2. Move one slider at a time and describe whether the curve shifts, stretches or turns. 3. Find the value where the behaviour changes sharply, then connect it to the formula.
Try this
Predict the outcome first, then test extreme slider values to find where the pattern changes or breaks.
Common pitfalls
Earth and space systems work on very different scales of time and distance. Check which scale a number refers to before comparing it with another.
How it connects
It builds on “Solar and Lunar Eclipses”, the topic before it in Earth & Space. Once you are comfortable, continue with “Distances of the Planets from the Sun”.
Why it matters
Earth and space science helps us understand our planet, its climate and the wider universe.
Where you might use it
- Revising “Ocean Tides” before a class, exam or certification
- Forecasting weather and understanding climate records and their uncertainty
- Planning for earthquakes, floods and other natural hazards in cities
- Interpreting satellite images, space missions and the age of rocks and stars
Frequently asked questions
What is Ocean Tides?
The Moon and Sun produce two daily tidal bulges; spring tides occur when they line up. It is an intermediate topic in Earth & Space.
How do I use the Ocean Tides simulation?
The panel at the top shows a graph of the function. Each slider changes one parameter, so you can see exactly how the curve bends, shifts or stretches. Move the sliders one at a time, then press Space to pause the animation and look closer.
What does the formula mean?
The expression h = A₁cos(ω₁t) + A₂cos(ω₂t) packs the idea into symbols. Name each symbol first, then change one quantity with the sliders and see which others respond.
Who is this topic for?
Builds on the basics with relationships, methods and trade-offs. If the quiz feels hard, reread the lesson notes and try the previous topic first.
What should I learn before this?
Start with “Solar and Lunar Eclipses”, the previous topic in Earth & Space. Each topic in a subject builds on the ones before it.
How do I track my progress?
Press “Mark as learned” on this page. Progress is stored only in this browser and is never sent anywhere. The Browse page can show topics you have learned or still need to learn.
Quick quiz
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Kepler’s Third Law
The square of a planet’s orbital period is proportional to the cube of its distance.