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๐ฌ Think about it
Why is June hot in India but cold in Australia at the same time? Many people think it is because the Earth gets closer to the Sun in summer — but that is wrong! The real reason is a tilt. Let us uncover how seasons happen.
The tilted Earth at four positions causing seasons.
What causes the seasons on the Earth?
- The Earth's axis is not upright; it is tilted.
- The Earth keeps this same tilt as it orbits the Sun.
- The tilt and the Earth's round shape cause the seasons.
- A hemisphere tilted towards the Sun has summer.
Example:
In June the Northern Hemisphere tilts towards the Sun, so India has summer, while the Southern Hemisphere has winter.
How the Tilt Causes Summer
A hemisphere tilts towards the Sun
↓
Sunlight is more intense
The same sunrays fall on a smaller area, so it heats more.
↓
Days are longer
That hemisphere gets sunlight for more than 12 hours.
↓
That hemisphere has summer
How do seasons differ between the hemispheres?
- The seasons are reversed in the two hemispheres.
- In June it is summer in the North and winter in the South.
- In December it is the opposite.
- Near the equator, seasons are not very strong.
Example:
The southern states of India lie near the equator, so the effect of seasons there is not very strong.
June (Northern Hemisphere)
December (Northern Hemisphere)
Tilted towards the Sun
Tilted away from the Sun
Intense sunlight, longer days
Weaker sunlight, shorter days
Summer season
Winter season
๐งฌ Dive Deeper
A note correcting two wrong reasons for the seasons.
- Two wrong reasons are often given for the seasons.
- One: a hemisphere tilted to the Sun is closer to it.
- Two: the Earth's oval orbit changes its distance.
- These distance changes are too small to cause seasons.
- In fact, the Earth is closest to the Sun in January.
๐งฌ Dive Deeper
A year diagram of solstices and equinoxes.
- The longest day in the North is around 21 June, the summer solstice.
- The shortest day is around 22 December, the winter solstice.
- Around 21 March and 23 September, day and night are each 12 hours.
- These are the spring and autumn equinoxes.
โ๏ธ Fascinating Facts
The North Pole with six months of continuous sunshine.
- At the North Pole, the Sun rises on 21 March.
- It stays in the sky continuously for six months.
- The Sun sets on 22 September.
- The polar regions get six months of light then six of darkness.
Important Points
- The Earth's axis is tilted, not upright.
- The tilt and round shape cause the seasons.
- Seasons are reversed in the two hemispheres.
โ Test Yourself
-
What causes seasons on the Earth?
View Answer
The tilt of the Earth's axis and its spherical shape. -
When is it summer in the Northern Hemisphere?
View Answer
In June, when it tilts towards the Sun. -
Is the Earth closer to the Sun in summer?
View Answer
No, the Earth is actually closest to the Sun in January. -
What is the summer solstice?
View Answer
The longest day, around 21 June in the North. -
Why are seasons weak near the equator?
View Answer
Sunlight intensity changes little there through the year.
Important Definitions
- Summer solstice — the longest day in a hemisphere, around 21 June in the Northern Hemisphere.
- Winter solstice — the shortest day in a hemisphere, around 22 December in the Northern Hemisphere.
- Equinox — a day when daytime and night are each 12 hours, around 21 March and 23 September.
๐ NCERT Question 10 — The Indian cricket team
The Indian cricket team matches in Australia are often held in December. Should they pack winter or summer clothes?
View Answer →
๐ NCERT Question 12 — If the Earth's axis
If the Earth's axis were not tilted with respect to the axis of revolution, explain what would be the effect on seasons.
View Answer →
