I noticed this especially this year. Once the shortest day has been you do slowly notice the day light staying a little bit longer each day in the afternoons. However daybreak seemed to get slightly later in the mornings for about a week before it started to get lighter in the mornings as well. Any ideas? I live in Aberdeenshire by the way.
The shortest day of the year (in the Northern Hemisphere) was our winter solstice, December 21st in the Western Hemisphere (December 22nd from Berlin eastward because of the effect of time zones).
The 21st (or 22nd) is not the earliest sunset, however. In my latitude, about 40 North, the earliest sunset happened December 8th (at 4:28 p.m.). Since then, we’ve gained over 20 minutes of sun in the afternoon, and we’d already picked up 3 minutes before the 21st.
Not only that, but despite the fact that the (Northern) winter solstice happened on the 21st of December, we did not have our latest sunrise until January 5th, at 7:20 a.m. On December 21st, the sun rose at 7:16 a.m. (4 minutes earlier). In fact, it will not be until tomorrow, January 10, that we pick up our first 1 minute in the mornings.
The cause of these is a phenomenon called the Equation of time.
The earth revolves around the sun at changing speeds, caused by the fact that it has an elliptical orbit. This motion is fastest in December and January, when the earth is closest to the sun.
The speed of rotation (the 24-hour day) cannot change but since, in its course around the sun, the earth moves further than average in December and January, this has the effect of making sunrise and sunset both happen about 1/3 of a minute later each day, cumulatively.
By early December, the north-south movement of the sun, caused by the seasons, is gradually starting to bottom out in a pattern known in trigonometry as a "sine curve." In November, this motion is still making the sunset happen earlier and earlier each day. By early December, however, it flattens out to the point where the seasonal change in the day’s length becomes less than one-third of a minute per day.
Meanwhile, the Equation of time is still making everything happen later and later each day. In early December, the point is reached where that 1/3 of a minute per day starts to exceed the fading seasonal change and the sunset seems to start happening later each day.
The reverse happens in the morning. In the first half of December, both the seasonal change and the Equation of time are pulling in the same direction, making the sun rise later each morning. The seasonal movement fades completely by the solstice and even starts to reverse, but the 1/3 of a minute later each day continues to make its presence felt until about January 5th here in New York, when the northward movement of the sun finally wins out and the sunrise starts getting earlier.
Is this not more to do with your staying in bed? You see the later sunsets, but don’t get up in time to see the later dawns? Or am I being silly?
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global warming
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I’m in London – & I don’t think it really got light AT ALL today. How depressing!!!
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It only seems that way because it has been overcast for the last few weeks, delaying the effect of the sun.
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I agree. When the days start to draw out again it seems to be evenings first. It has something to do with the North Pole leaning towards the Sun during our wintertime. I think you get lighter evenings up there than we do (Cornwall) anyway – especially as the summer comes along. Take Finland for example – land of the midnight sun – it doesn’t set at all for about three months. I suppose you would only get an even amount of daylight either side of noon at the Equator?
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The shortest day of the year (in the Northern Hemisphere) was our winter solstice, December 21st in the Western Hemisphere (December 22nd from Berlin eastward because of the effect of time zones).
The 21st (or 22nd) is not the earliest sunset, however. In my latitude, about 40 North, the earliest sunset happened December 8th (at 4:28 p.m.). Since then, we’ve gained over 20 minutes of sun in the afternoon, and we’d already picked up 3 minutes before the 21st.
Not only that, but despite the fact that the (Northern) winter solstice happened on the 21st of December, we did not have our latest sunrise until January 5th, at 7:20 a.m. On December 21st, the sun rose at 7:16 a.m. (4 minutes earlier). In fact, it will not be until tomorrow, January 10, that we pick up our first 1 minute in the mornings.
The cause of these is a phenomenon called the Equation of time.
The earth revolves around the sun at changing speeds, caused by the fact that it has an elliptical orbit. This motion is fastest in December and January, when the earth is closest to the sun.
The speed of rotation (the 24-hour day) cannot change but since, in its course around the sun, the earth moves further than average in December and January, this has the effect of making sunrise and sunset both happen about 1/3 of a minute later each day, cumulatively.
By early December, the north-south movement of the sun, caused by the seasons, is gradually starting to bottom out in a pattern known in trigonometry as a "sine curve." In November, this motion is still making the sunset happen earlier and earlier each day. By early December, however, it flattens out to the point where the seasonal change in the day’s length becomes less than one-third of a minute per day.
Meanwhile, the Equation of time is still making everything happen later and later each day. In early December, the point is reached where that 1/3 of a minute per day starts to exceed the fading seasonal change and the sunset seems to start happening later each day.
The reverse happens in the morning. In the first half of December, both the seasonal change and the Equation of time are pulling in the same direction, making the sun rise later each morning. The seasonal movement fades completely by the solstice and even starts to reverse, but the 1/3 of a minute later each day continues to make its presence felt until about January 5th here in New York, when the northward movement of the sun finally wins out and the sunrise starts getting earlier.
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DAYLIGHT SAVINGTIME I WOULD THINK. IT’S ALWAYS WEIRD.
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The earth is at an angle with the sun, so it tilts at different directions during the year. at summer it is towards the sun so the weather’s warmer and the days longer; Winter it is further form the sun, colder & shorter days.
It also depends on where you are on earth on how much daylight you get. below the equator it’s the opposite (longer days in December, etc.) an near the poles the days and nights could last 6 months!
One of the ways we try to make this change easier is Daylight Saving Time. That’s when the clocks are move one hour foward in the spring and back again in the fall.
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Give yourself a pat on the back for your keen eye; you are absolutely right.
After solstice, sunrise will actually occur later for about 2 weeks, up to two minutes progressively lost in the morning, before it starts getting light earlier.
Why is that?
Well, the orbit of the Earth around the Sun is not perfectly circular, so the noon to noon period (here "noon" means "when the sun is the highest", not 12:00 o’clock) will vary slightly over the course of a year, it may bve more than 24 hours at times, and 6 months later, it will be correspondingly be less to even it off. In 2007, Earth’s perihelion (closest approach to the sun) occured on January 3rd (see first link).
The second link will tell you the sunrise and sunset time for selected cities in the world.
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http://en.wikipedia.org/wiki/Apsis
http://www.sunrisesunset.com/
It’s the tilt of the earth. Aberdeenshire is far enough north for all these daylength issues to be more marked.
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