Science
What is an eclipse?
Quick answer
An eclipse happens when the Sun, Earth and Moon line up. In a solar eclipse the Moon blocks the Sun; in a lunar eclipse Earth's shadow falls on the Moon.
In one sentence
An eclipse is when one object in space moves into the shadow of another: the Moon blocks the Sun in a solar eclipse, and Earth's shadow darkens the Moon in a lunar eclipse.
Explained
The Sun, Earth and Moon are always moving. Sometimes they line up in a straight line, and that is when we see an eclipse.
Solar eclipse. The Moon passes between the Sun and Earth, at new moon. Its shadow falls on a small part of Earth. People in the darkest part, the umbra, see a total eclipse: the sky goes dim, birds go quiet and the Sun's glowing outer layer, the corona, appears. This is possible because the Sun is about 400 times wider than the Moon, but also about 400 times further away, so they look almost the same size in the sky. Totality lasts only a few minutes. Nearby, people see a partial eclipse.
sun
moon
star
Lunar eclipse. Earth passes between the Sun and Moon, at full moon, and its shadow falls on the Moon. During a total lunar eclipse the Moon often looks dull red or orange. That is sunlight bending through Earth's atmosphere onto the Moon. Everyone on the night side of Earth can see it.
We do not get eclipses every month because the Moon's orbit is tilted. Most months it passes above or below the line between the Sun and Earth. Eclipses happen only when the lineup is just right. To understand the cycle, see phases of the Moon and how shadows form.
Examples
| Solar eclipse | Lunar eclipse | |
|---|---|---|
| Moon phase | new moon | full moon |
| In the middle | the Moon | Earth |
| Who sees it | people in a narrow path | anyone on the night side |
| Safe to watch? | only with eclipse glasses | yes, with your eyes |
Common mistakes
- Looking at the Sun. Never look directly at a solar eclipse without proper eclipse glasses or a pinhole projector. Normal sunglasses do not protect your eyes.
- "Eclipses happen every month." Only when the lineup is exact.
- Mixing them up. Solar is about the Sun being covered, lunar is about the Moon being darkened.
Quick quiz
Solar and lunar eclipses
Check what you know with 4 quick questions.
Question 1 of 4
What passes between the Sun and Earth in a solar eclipse?
Practise it
Try it
Space practice
Practise it step by step in a full course: Grade 6 Science
For grown-ups
Related topics
The Moon
The Moon is Earth's natural satellite, a rocky ball about a quarter of Earth's width that orbits us roughly once a month. It shines by reflecting sunlight.
Phases of the Moon
The Moon does not really change shape. As it orbits Earth, we see more or less of its sunlit half, which gives the phases from new moon to full moon and back in about 29.5 days.
Shadows
A shadow is a dark area made when an opaque object blocks light. Because light travels in straight lines, it cannot bend round the object, leaving a dark shape behind it.
Day and night
We have day and night because Earth spins once around every 24 hours. The side facing the Sun has daylight, and the side facing away is in darkness.
The solar system
The solar system is the Sun and everything that orbits it, including eight planets, their moons, dwarf planets such as Pluto, asteroids and comets.
Space exploration
Space exploration began in 1957 with the first satellite, Sputnik 1. Since then people have orbited Earth, walked on the Moon and sent robots to planets, moons and beyond.