According to Kepler's law the Earth is closer to the sun in the
summer winter than in the summer. If this is true would not it be warmer in the
winter than in the summer?
The reason for summer and winter is not because of the distance
from the earth to the sun, but because of the way the earth's axis
is tilted. When it is summer in North America, it is winter in
South America and the other way around. The reason is that
the amount of energy hitting the earth's surface from the sun depends
on the angle the sun's energy is coming from - the higher in
the sky the sun is, the more that angle is close to vertical,
and the more energy we are getting. This is a much stronger
effect than the few percent change due to the distance from the
sun changing, especially when you live pretty far form the equator.
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Update: June 2012