Solar and Lunar Eclipses
Lesson notes
Overview
Eclipses occur when the Sun, Earth and Moon line up and cast shadows. This topic is rated intermediate and is number 28 of 98 in Earth & Space. Builds on the basics with relationships, methods and trade-offs.
What you are seeing
The panel above shows the steps of a process, laid out in order. Click a step to see what happens next. 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
A solar eclipse occurs when the Moon passes between the Sun and Earth, casting a shadow on a part of the Earth, and a lunar eclipse when the Earth is between the Sun and the Moon, and the Moon enters the Earth’s shadow. They need the three bodies in line, syzygy, at a new or full moon, and because the Moon’s orbit is tilted by 5° to the ecliptic, they do not happen every month. Total solar eclipses are possible because the Moon and Sun appear nearly the same size.
Reading the relationship
The expression "syzygy" is a compact summary of the idea. It uses the symbols s, y, z, g; name what each one stands for before you start. Then use the sliders to see how changing one quantity changes the others.
A guided exploration
1. Run the animation once with the default settings and describe in words what happens. 2. Change one slider at a time and note which quantity responds most. 3. Push each slider to its extreme and decide whether the result still makes sense.
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 “Why We Have Seasons”, the topic before it in Earth & Space. Once you are comfortable, continue with “Ocean Tides”.
Why it matters
Earth and space science helps us understand our planet, its climate and the wider universe.
Where you might use it
- Revising “Solar and Lunar Eclipses” 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 Solar and Lunar Eclipses?
Eclipses occur when the Sun, Earth and Moon line up and cast shadows. It is an intermediate topic in Earth & Space.
How do I use the Solar and Lunar Eclipses simulation?
The panel at the top shows the steps of a process, laid out in order. Click a step to see what happens next. Move the sliders one at a time, then press Space to pause the animation and look closer.
What does the formula mean?
The expression syzygy 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 “Why We Have Seasons”, 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
More in Earth & Space
See all →Ocean Tides
The Moon and Sun produce two daily tidal bulges; spring tides occur when they line up.
Distances of the Planets from the Sun
Planetary distances grow roughly geometrically, so a log scale is needed.
Surface Gravity of the Planets
Weight depends on a planet’s mass and radius; Jupiter’s gravity is 2.5 times Earth’s.