Earth at Perihelion
The shape of the Earth's orbit around the Sun is an ellipse (although it is almost perfectly
circular); the point at which the Earth is closest to the Sun is known as
perihelion. The Earth reaches perihelion on 02 January 2002 (14h
UT). Food for thought: if the Earth is closest to the Sun, then why is
it Winter in the northern mid-latitudes? The answer lies in the annual
cycle of change in the apparent path of the Sun across the sky (see "Did
You Know..." sidebar).
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Did you know...
...that changing Earth-Sun distance does not cause the change of
seasons at the northern mid-latitudes? Because of the tilt of the Earth's
axis, there is an annual cycle of change in the number of hours of
daylight and the maximum altitude of the Sun. The least duration of
insolation and minimum altitude occur in late-December (and vice-versa in
late June), thereby causing seasons to change.
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