Why we have seasons

Why is it hot in June in Delhi but cold in Sydney?

Earth travels around the Sun once every year, and it spins like a top that is leaning over.

Many students think seasons happen because Earth gets closer to the Sun. That is not the reason.

• Not about distance!

The real reason is the tilt. Earth's axis leans by about twenty three and a half degrees.

• Tilt = 23.5 degrees

The tilt always points the same way in space, even as Earth moves around the Sun. When the north half leans toward the Sun, sunlight hits it straight on and strongly.

Direct sunlight means more heat and longer days, so that half of Earth has summer.

At the same time, the other half leans away. Sunlight is slanted and weak, and days are short.

So in June, Delhi is tilted toward the Sun and hot, while Sydney is tilted away and cold.

Six months later, Earth is on the opposite side of the Sun, and the seasons swap.

Near the equator, the tilt matters less, so places like Kerala stay warm all year round.

Let us recap the big ideas on one map of thoughts. Now a quick question to test yourself. In short, Earth's tilt as it orbits the Sun gives us seasons.