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๐ฌ Think about it
Stand too close to a fire and you burn. Stand too far and you shiver. Earth sits at just the right distance from the Sun. That is why water stays liquid here. Let us find out why this matters so much.
Why does Earth's distance from the Sun matter?
- Earth is at just the right distance from the Sun.
- So the temperature lets water stay in liquid form.
- Too close, and water would evaporate; too far, and it would freeze.
- Liquid water is essential for life to develop and survive.
Distance Decides the Water
Too close
Too hot, so water evaporates.
↓
Just right
Water stays liquid, so life can thrive.
↓
Too far
Too cold, so water freezes.
What is the habitable zone?
- It is the range of distances from a star where water stays liquid.
- It is also called the 'Goldilocks zone'.
- Earth lies in this zone, so it keeps liquid water.
Example:
Like the "just right" porridge in the Goldilocks story, the habitable zone is neither too hot nor too cold.
Why is Earth called the Blue Planet?
- Most of Earth's surface is covered with water.
- So from space, the Earth looks blue.
- That is why it is called the Blue Planet.
๐ก A step further
- Mars lies at the edge of the Sun's habitable zone.
- Spacecraft and rovers have explored its surface.
- No proof of life has been found yet.
- But scientists think Mars may once have had liquid water.
- So science stays open to change as we learn more.
๐ก A step further
- Is temperature or distance from the Sun the only factor for life?
- What would happen if the size of Earth were too small or too big?
- So distance alone does not make a planet habitable.
- Size and other factors matter too, as we will see next.
Important Points
- Distance from the Sun keeps Earth's water liquid.
- The habitable zone is also called the Goldilocks zone.
- Earth is called the Blue Planet because of its water.
โ Test Yourself
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What is the habitable zone?
View Answer
The range of distances from a star where water stays liquid. -
What is another name for it?
View Answer
The Goldilocks zone. -
Why is Earth called the Blue Planet?
View Answer
Because most of its surface is covered with water, so it looks blue from space. -
What happens if a planet is too far from the Sun?
View Answer
It is too cold and water freezes. -
Where does Mars lie?
View Answer
At the edge of the Sun's habitable zone.
Important Definitions
- Habitable zone — the range of distances from a star where water can stay liquid.
- Blue Planet — the name for Earth, which looks blue from space due to its water.
๐ NCERT Question 1 — What is one major
What is one major reason Mars cannot currently support life like Earth? (MCQ)
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๐ NCERT Question 9 — You are tasked with
You must design a human settlement on Mars. Name three things to recreate from Earth and the hardest one.
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