the seasons

In the left part of the applet you can drag the earth on its orbit. On the right you can see how the axial tilt marks the seasons.

On the 21th of june the northern hemishpere is tilted towards the sun. It's summer. The sun is perpendicular to the tropic of cancer.
On the 21th of december the southern hemishpere is tilted towards the sun. It's winter on the northern hemisphere. The sun is perpendicular to the tropic of capricorn.
On the 21th of march and the 21th of september the sun is perpendicular to the equator. Everywhere on earth the length of day and night are equal. This point is called the equinox.

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