Solar and lunar eclipses
Solar and lunar eclipses
- Unit 1: Particles & Pressure
- Unit 2: Forces & Motion
- Unit 3: Energy & Heat
- Unit 4: Electricity
- Unit 5: Magnetism & Electromagnetism
- Unit 6: Waves: Sound & Light
- Unit 7: Scientific Investigations
In this topic you will:
- find out how solar eclipses happen
- find out how lunar eclipses happen.
Key words
- lunar eclipse
- opaque
- partial
- ray
- shadow
- solar eclipse
- total
Shadows
An opaque object is an object that will not allow light to pass through.
When an opaque object passes in front of a source of light, a shadow will form.
Look at the shadow of the aeroplane in the picture. The shadow looks dark because the light from the Sun has been blocked from reaching the ground. The aeroplane is made from metal which is opaque.
The grass around the shadow looks brighter because light from the Sun is reaching those areas.
The next picture shows how the shadow is formed.
Light travels in straight lines called rays. Light rays from the Sun cannot pass through the aeroplane, so light rays that reach the aeroplane cannot reach the ground.
Imagine you were standing on the grass. When the shadow of the aeroplane passes you, it will seem to go dark. When the shadow has gone, it will get brighter again.
Important concept
Shadows are formed when an object blocks light from reaching a surface. The shape and sharpness of the shadow depend on the light source and object’s size and distance.
Solar eclipse
A solar eclipse happens when the Moon comes between the Sun and the Earth.
The Moon is made from rock, so is an opaque object. The Moon blocks the rays of light coming from the Sun. The shadow of the Moon forms on the Earth.
The diagram shows how the shadow of the Moon is formed on the Earth. In the middle of the shadow, all the light rays from the Sun are blocked. People in the middle of the shadow observe a total solar eclipse.
The left picture shows what a total solar eclipse looks like.
A partial solar eclipse is seen away from the middle of the shadow of the Moon. (left)
Away from the middle of the shadow of the Moon, some of the light rays from the Sun can reach the Earth. Away from the middle of the shadow there is a partial solar eclipse.
The picture below shows a series of photographs taken as the Moon passes between the Earth and the Sun.
The picture on the next page shows what a solar eclipse looks like from space. The dark part of the Earth is in the shadow of the Moon. At the centre of the shadow, there is a total solar eclipse. Away from the centre, there is a partial solar eclipse.
You must never look directly at the Sun, even when there is an eclipse. The light from the Sun is very bright and can cause permanent damage to your eyes.
Lunar eclipse
A lunar eclipse happens when the Earth comes between the Sun and the Moon.
The Earth is also an opaque object, so the Earth blocks the light from the Sun. The shadow of the Earth is formed on the Moon.
The diagram shows how the shadow of the Earth forms on the Moon.
The picture shows a series of three photographs of the shadow of the Earth passing across the Moon.
You might think that solar and lunar eclipses should happen every month. The Moon takes 28 days to orbit the Earth, but the orbit of the Moon is tilted slightly. The orbit of the Moon is not exactly in the same plane as the orbit of the Earth around the Sun.
It is only when the Sun, Earth and Moon are in the same straight line that eclipses can happen.
Questions
Write the letter.
B. The Earth comes between the Moon and the Sun.
C. The Moon comes between the Earth and the Sun.
Show Answer
C The Moon comes between the Earth and the Sun.
Write the letter.
B. The Earth comes between the Moon and the Sun.
C. The Moon comes between the Earth and the Sun.
Show Answer
B The Earth comes between the Moon and the Sun.
Show Answer
A solar eclipse happens when the Moon blocks sunlight from reaching the Earth, which can only happen during the day when the Sun is visible.
A total lunar eclipse can only ever be seen in the daytime.
Explain your answer.
Show Answer
False. A lunar eclipse occurs when the Earth blocks sunlight from reaching the Moon, which is only visible at night when the Moon is above the horizon.
Think Like a Scientist
Making predictions about eclipses
In this task, you will think about making observations and using them to make predictions.
Astronomers in the Middle East made the earliest known predictions of when eclipses would happen. The astronomers were working about 3000 years ago.
Questions
Show Answer
Date, time, location on Earth, and type of eclipse (solar or lunar).
Calculate the number of days in 223 lunar months.
Show Answer
223 × 29.5 = 6588.5 days
Show Answer
They return to nearly the same relative positions, allowing similar eclipses to occur.
Show Answer
If a pattern repeats consistently over time, it can be extended to predict future events.
Show Answer
Compare predictions with actual observed eclipses and note time/location differences.
Show Answer
Small errors accumulate over time due to gravitational effects and orbital changes.
Show Answer
By matching historical descriptions of eclipses to modern eclipse calculations, scientists can date events accurately.
Explain your answer.
Show Answer
A total solar eclipse — the Sun is completely blocked by the Moon, visible as a dark circle with a bright corona.