We look forward to the warmth of summer, and we’re always surprised when the first snowfall hits, but what actually causes the Earth’s changing seasons? There are a number of different forces at work to make the leaves fall and the spring flowers bloom. Here are some facts about how the seasons change.

It’s not because the Earth is closer to the sun in the summer.
While this is a common belief, it’s simply not true. The Earth’s orbit is not perfectly circular and yes, the Earth is closer to the sun at certain times of the year. In the Northern Hemisphere, however, it’s actually winter when the Earth is closest to the sun, and vice-versa.

Earth’s tilted axis causes the seasons to change.
Earth has an imaginary pole that slices down its center, and it marks where the axis hits. The planet spins around this pole, but its uneven tilt causes different parts of the Earth to feel the sun’s direct rays at different times of the year.

The seasons aren’t the same all around the world.
While most of us in America associate December with winter and July with summer, the Earth’s tilted axis means seasons differ all around the world. In December, it’s summer for everyone south of the equator because the sun shines directly on the Southern Hemisphere at that time.

What Causes the Seasons? [NASA]

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