Why it’s night in Australia when it’s day here, and why Christmas is in summer there.
🌍 Play this lesson on the globe
The Sun can only light up the half of the Earth that faces it. The other half has night. The Earth spins round once a day, so every place gets its turn. Push the slider to spin through one day.
This is the Earth right now, worked out from your device’s clock. Everywhere in the dark is having night. Spin the globe and find where you live!
The Earth spins around an imaginary line called its axis. But the axis doesn’t stand up straight. It leans over by about 23.4°, and it keeps leaning the same way all the way round the Sun.
The half of the Earth that leans toward the Sun gets long days, and the sunlight hits it more directly. That’s summer! The other half has winter. Slide through the year.
What if the Earth didn’t lean at all? Try it.
In June, the far north leans so far toward the Sun that it never turns into the dark. The sun just goes round the sky, even at midnight! Everywhere north of the Arctic Circle (the dotted line) gets at least one day like this.
Lots of people think it’s summer when the Earth is closest to the Sun. But the Earth is closest in early January, in the middle of the northern winter! The distance only changes a little. It’s the lean that makes the seasons.
It’s Christmas Day, 25 December. Look at the far north: it’s in the dark all day.
🌍 Play this lesson on the globe
The globe pictures are simplified to show the idea. Earth images: NASA Blue Marble (public domain).