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Shortest Day

Why is the shortest day of the year at the beginning of winter (and the longest day at the beginning of summer)?

It's true, too: winter in PA is from late December through late March. Spring is April through June. July and August are summer. September through November is fall.

5 Responses to "Shortest Day"

  1. It's the compromise we in the southern hemisphere get for not being able to have a white Christmas (but we came very close this year).

  2. Because our atmosphere holds onto (and mitigates) heat, the sun does not have a direct effect on the temperature. By the time the weather has changed to adapt to the shorter periods of sunshine, the sun has started coming out longer. It's the same reason why we on earth don't experience -100 deg Celsius temperatures every night and scorching 300 deg+ temperatures every day. Also why it's (usually, barring passing storm systems) colder at sunrise than sunset.

    Sorry to be the nerd who supplies a believable answer.

  3. Here is a side question asked to me recently based on the Earth's orbit not being a perfect circle, but rather, an ellipse.

    During what season is the earth closest to the sun, and does this make a difference in how warm/cold it is/could be? Is the difference more or less than one would get via tilting of the poles?

    Come to think of it, every twenty four hours, each one of us is further or closer to the sun by the distance of one earth diameter.

    And the moon, with sunrise every 28 days, and no atmosphere-- how much colder is IT right before sunrise than after sunset?

  4. Come to think of it, every twenty four hours, each one of us is further or closer to the sun by the distance of one earth diameter.

    That's not quite true. Only if you live on a 90 degree angle with the sun. People at the poles, for example, don't move away from the sun within a 24-hour period. And in truth, it's inconsequential. The earth is, what, one billionth or so as wide as we are from the sun?

  5. Sure, it is inconsequential, (sort of my point in mentioning it) for the same reason it takes summer and winter a while to heat up or cool down from the actual dates of shortest sun exposure.

    And similarly, that would also wipe out any difference a real distance difference from earth to the sun due to an elliptical orbit. But if it did matter, how is it measurable, if at all.

    And I am still curious about moon night temperature pre dawn and sunset due to the moons lack of insulating atmosphere.

    But the reason is that those long and short days are markers for the season are, well because they are the longest and shortest days. And if it actually takes a few weeks for the temperature to catch up, that is okay.. getting ready for the climate shift takes time too, so it was just fine with everyone that the shortest day is not the coldest day, nor the longest the hottest- they knew it was coming.