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Winter Solstice

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origin

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This is probably a dumb question but I just can't seem to figure it out.

Dec. 21 is the shortest day so after that starting on Dec. 22 the sun starts setting later and later. Fine makes sense, but the sun continues to rise later until Jan 10 then it starts rising earlier. Why exactly does that happen?

Edited: Changed the incorrect date of Feb 10 to the correct date of Jan 10.
 
M

MeteorWayne

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The answer is that it is due to the eccentricity of the earth's orbit and the difference between the solstice and perihelion (and aphelion for the summer one). Remember, the solstice occurs a few weeks before perihelion. For example this year's solstice is Dec 21 at 17:46 UT, perihelion is Jan 3, 00:09.
Now, trying to put into words why that causes the sunrise/sunset shift is quite difficult, but that is the answer. Perhaps I'll give it a try after my morning coffee. A cup or three :)

Wayne
 
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origin

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MeteorWayne":1dinpg92 said:
The answer is that it is due to the eccentricity of the earth's orbit and the difference between the solstice and perihelion (and aphelion for the summer one). Remember, the solstice occurs a few weeks before perihelion. For example this year's solstice is Dec 21 at 17:46 UT, perihelion is Jan 3, 00:09.
Now, trying to put into words why that causes the sunrise/sunset shift is quite difficult, but that is the answer. Perhaps I'll give it a try after my morning coffee. A cup or three :)

Wayne
Well, at least it doesn't seem like a dumb question if you need coffee to answer it!
 
M

MeteorWayne

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Well, I answered it; explaining it coherently is harder. Halfway through my first cup :) Plus I'm recovering from being up half the night watching the Yankee game (with appropriate lubrication).

It certainly wasn't a dumb question, in fact it was a darn good one.
 
O

origin

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MeteorWayne":39736p2l said:
Well, I answered it; explaining it coherently is harder. Halfway through my first cup :) Plus I'm recovering from being up half the night watching the Yankee game (with appropriate lubrication).

It certainly wasn't a dumb question, in fact it was a darn good one.
I will have to noodle on this one...
 
O

origin

Guest
This site explains it pretty well. I accidently learned a few things that I didn't know!
 
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MeteorWayne

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Glad you found it. That's one of the clearer explanations I've read. You have to ignore the solstice times in the first paragraph since it was written in 2006, but the sunrise/sunset explanation is superb.
 
L

LeaveEarth

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Length of Day

I live in the PST time zone, near -118 degrees longitude and +34 degrees latitude. Although December 21 is the shortest day, the earliest sunset is December 14 (4:43 PM local time) and the latest sunrise is January 7 (6:56 AM local time. Today (January 16), 26 days after the shortest day (Solstice, December 21), sunset occurs nearly 30 minutes later than the ewarliest time (4:43 PM) but sunrise is only about 2 minutes earlier than the latest time.

Why/how does this occur? The day is noticeably lighter in the evening while the morning is unchanged basically. I know the morning catches up at we approach the vernal equinox (spring).

I know the Earth is closer to the sun in the winter, the Earth's orbit is not circular, the axis is tilted 23 degrees, and there are sun setting and rising refractions that have an effect. Lopcation in a tiome zone, and latitude may also play a part. But I can't seem to tie all this together.

Thanks.
 
M

MeteorWayne

Guest
Re: Length of Day

Welcome to Space.com.

You've got it exactly right, the two factors that cause the effect are the eccentricity of the earth's orbit (perihelion ~ Jan 3) and the obliquity (tilt) of the earth's axis. I had a link to a great explanation, it's in another thread here. If I can find it, I'll probably merge the two topics together, which should make it easier to find the link.

Wayne
 
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3488

Guest
I'll have a look Wayne & I will merge them.

BTW where I live in Ashford, Kent, UK, (51 deg 8' North, 0 deg 53' East) we have our earliest Sunset on 12th December (3:48 PM), nine days before the Solstice, latest sunrise not until 2nd January (8:02 AM), twelve days after the Solstice.

Andrew Brown.
 
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