WEBVTT

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Why is it summer in June?

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Most people say: because the Earth is
closer to the Sun.

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It sounds right. But we are closest to the
Sun in early January,

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and farthest away in July.

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The distance changes by only about three
per cent.

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So distance is not the answer. The answer
is the tilt.

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This is the Earth in June. Its axis is
tilted,

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and the north leans towards the Sun.

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Sunlight hits the northern half more
directly, and the days are longer.

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That is summer in the north.

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Six months later, the Earth is on the
other side of the Sun.

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Watch the axis. It still points the same
way.

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Now the north leans away from the Sun.

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The light arrives at a low angle and
spreads out. That is winter in the north.

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Put the whole year together.

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The axis keeps pointing in the same
direction, all the way round.

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In June, the north leans towards the Sun.
In December, it leans away.

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So it is not about being closer. It is
about the tilt.

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Now pause the video, and draw the Earth in
June and in December.