Links: Solstice astronomy
Dec. 22nd, 2018 04:43 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
soniaSunlight and night over a Mercator projection map at solstice.
viacapri0mni, in comments. The post also has an image with sunlight and night at equinox for comparison.
Why the sunrise is still later after the winter solstice shortest day by Tanya Hill. This post is based in Australia, so it talks about winter solstice in June, but it has great figures to explain why dawn still gets later for a few days after solstice. A friend of mine mentioned this disappointing fact, and I had to look it up to make sense of it.
The essence of the explanation is that most of a day's length, 23 hours and 56 minutes of it, are explained by the earth's rotation, but a variable amount we round to 4 minutes is determined by the earth moving along its orbit around the sun and needing a little extra time for rotation to catch up to that. At winter solstice, the "solar days" are slightly longer than 24 hours, so dawn moves later even while the days are very slightly longer.
via
capri0mni, in comments. The post also has an image with sunlight and night at equinox for comparison.Why the sunrise is still later after the winter solstice shortest day by Tanya Hill. This post is based in Australia, so it talks about winter solstice in June, but it has great figures to explain why dawn still gets later for a few days after solstice. A friend of mine mentioned this disappointing fact, and I had to look it up to make sense of it.
The essence of the explanation is that most of a day's length, 23 hours and 56 minutes of it, are explained by the earth's rotation, but a variable amount we round to 4 minutes is determined by the earth moving along its orbit around the sun and needing a little extra time for rotation to catch up to that. At winter solstice, the "solar days" are slightly longer than 24 hours, so dawn moves later even while the days are very slightly longer.
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Date: 2018-12-23 04:11 pm (UTC)(Also, hearing it all explained in southern-hemisphere terms was good visualization exercise!)
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Date: 2018-12-23 05:55 pm (UTC)I was up before dawn this morning (7am!) for a bike ride at 8, and it was raining, but there was this amazing near-full moon to the west. Which means, luckily, the clearing in the clouds moved over us and we didn't get rained on during the ride.
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Date: 2018-12-23 06:12 pm (UTC)We're at the Washington coast right now; not a lot of sun and a whole lot of rain.
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Date: 2018-12-23 07:21 pm (UTC)no subject
Date: 2018-12-23 08:02 pm (UTC)no subject
Date: 2018-12-23 08:06 pm (UTC)