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๐ฌ Think about it
How can the small Moon hide the giant Sun? Hold up your thumb and it can hide a whole building far away. The same trick lets the nearby Moon cover the faraway Sun. Let us explore the solar eclipse.
The Moon between the Sun and Earth in a solar eclipse.
What is a solar eclipse?
- Sometimes the Moon comes between the Sun and the Earth.
- It blocks the Sun's light from reaching us.
- This is called a solar eclipse.
- The Moon's shadow falls on a small area of the Earth.
Example:
Where the Moon fully covers the Sun, people see a total solar eclipse; nearby areas see a partial solar eclipse.
A total solar eclipse with the Sun fully covered.
How can the small Moon cover the huge Sun?
- The size we see depends on actual size and distance.
- This seen size is called the apparent size.
- The Moon is much smaller but much closer than the Sun.
- So their apparent sizes look similar from the Earth.
Example:
Your small thumb held close can cover a friend's whole head 5 metres away, just as the close Moon covers the far Sun.
A thumb held up covering a distant friend's head.
๐งฌ Dive Deeper
Venus as a tiny dot crossing the Sun's face.
- Mercury and Venus are larger than the Moon.
- But they are much farther from the Earth.
- So they look far smaller than the Sun and cannot block it.
- When Venus crosses the Sun, it looks like a tiny black dot.
In this Activity, we will use a thumb to see how a close object can cover a far one.
A child covering a friend's head with a thumb.
Materials needed
A friend and some open space.
Procedure
1. Ask a friend to stand about 5 metres in front of you.
2. Think of the friend's head as the Sun.
3. Close one eye and hold up your thumb towards the friend.
4. Check if your thumb can cover the friend's entire head.
2. Think of the friend's head as the Sun.
3. Close one eye and hold up your thumb towards the friend.
4. Check if your thumb can cover the friend's entire head.
Observation
Your small thumb can cover the friend's whole head, even though it is much smaller.
Explanation
The close thumb and the far head have a similar apparent size. In the same way, the close Moon can cover the far Sun.
โ Summary
- Thumb held up close
- Friend stood far away
- Thumb hid the head
- Like Moon hiding Sun
โ ๏ธ Science and Society
A safe public solar eclipse viewing event.
- Even during an eclipse, the Sun can damage the eyes and cause blindness.
- So directly viewing a solar eclipse must be strictly avoided.
- Do not view it through sunglasses, binoculars, or telescopes.
- Astronomy clubs hold safe eclipse-viewing events with proper protection.
๐งฌ Dive Deeper
A ball-and-mirror stand projecting the Sun's image on a wall.
- A mirror can project the Sun's image onto a wall, like Activity 11.5.
- Holding it steady through an eclipse is hard, so make a movable stand.
- Half-fill a hollow ball with sand and fix a small embroidery mirror on it.
- Place the ball on a tape ring so it can be turned to aim the image.
- Do this only under a teacher and never aim the beam at anyone's eyes.
๐ Fascinating Facts
An old Indian text predicting eclipses in shlokas.
- An eclipse is called grahan in Sanskrit and many Indian languages.
- Ancient Indian texts give calculations to predict eclipses.
- The best known is the Surya Siddhanta.
- It is written in classical Sanskrit poetry as rhythmic shlokas.
Important Points
- A solar eclipse happens when the Moon blocks the Sun.
- The Moon covers the Sun because of similar apparent size.
- Never look at a solar eclipse directly.
โ Test Yourself
-
What is a solar eclipse?
View Answer
When the Moon comes between the Sun and the Earth and blocks the Sun. -
What is apparent size?
View Answer
The size of an object as seen by the eye, based on its size and distance. -
Why can the small Moon cover the Sun?
View Answer
It is much closer, so its apparent size matches the Sun's. -
Should we look at a solar eclipse directly?
View Answer
No, never; it can damage the eyes. -
What is the safest way to watch an eclipse?
View Answer
At an eclipse-viewing event with proper eye protection.
Important Definitions
- Solar eclipse — an event when the Moon comes between the Sun and the Earth and blocks sunlight from reaching us.
- Apparent size — the size of an object as seen by the eye, which depends on its actual size and its distance.
๐ NCERT Question 7 — Four friends used the
Four friends used different ways to see the solar eclipse. Who among them was being careless?
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๐ NCERT Question 9 — The Moon is much
The Moon is much smaller than the Sun, yet it can block the Sun completely during a total solar eclipse. Why?
View Answer →
๐ NCERT Question 11 — Why do you think
Why can lunar eclipses be seen from a large part of the Earth, but a total solar eclipse only from a small part?
View Answer →
