Eclipses
Eclipses occur when Sun, Moon and Earth align.
About this topic
A solar eclipse occurs when the Moon passes between the Sun and Earth, casting a shadow on part of Earth: total, annular or partial. A lunar eclipse occurs when Earth is between the Sun and Moon, and the Moon enters Earth's shadow, turning reddish.
They don't happen every month because the Moon's orbit is tilted about 5° to Earth's orbital plane. Totality is possible because the Sun is about 400 times bigger than the Moon and 400 times farther. Never look at the Sun without proper eye protection.
Eclipses are a great test of geometry. During totality, the Moon's umbra (the darkest shadow) is only about 100 to 270 km wide on Earth, so total solar eclipses are visible from a small path while a much wider region sees a partial eclipse. Totality lasts at most about seven and a half minutes, and in that time the sky darkens, temperatures drop, and the Sun's corona becomes visible. An annular eclipse happens when the Moon is farther away and looks too small to cover the Sun, leaving a ring of fire.
Eclipses have been important in history and science: in 1919, observations of starlight bending near the eclipsed Sun supported Einstein's general relativity, and ancient cultures used eclipse records to refine calendars. A total lunar eclipse is safe to watch with the naked eye and visible from the whole night side of Earth; the red colour comes from sunlight refracted through Earth's atmosphere, as if every sunrise and sunset were projected on the Moon. Remember that solar eclipse viewing requires certified eclipse glasses.
Key ideas
- Solar: Moon blocks the Sun
- Lunar: Earth's shadow on the Moon
- Rare because orbits are tilted
Quick check
Use cases: where Eclipses helps
- Homework: review the key idea behind Eclipses before you start a problem set.
- Exam revision: use the quick check to test whether you can recall Eclipses without notes.
- Visual learning: play with the interactive lab to see how Eclipses changes when you adjust its inputs.
- Teaching a friend: explain Eclipses in your own words, then compare your version with the key ideas.
Earth science helps with weather forecasts, natural hazards, energy and climate planning.
Frequently asked questions
What is Eclipses?
Eclipses occur when Sun, Moon and Earth align.
What will I learn in Eclipses?
Solar: Moon blocks the Sun. Lunar: Earth's shadow on the Moon. Rare because orbits are tilted.
Is Eclipses part of Earth & Space?
Yes. It is one of 60 Earth & Space topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the Eclipses lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study Eclipses?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.