Happy earliest sunset of the year: December 7

[mahatmakanejeeves]

I'm posting a day ahead of time, due to logistics. I've done a little editing, to clarify things.

Copied from Friday, December 7, 2018: Happy earliest sunset of the year: December 7

* In the northern hemisphere.
** Give or take.

2018 update: I'm checking for New York City. The sunset has stalled at 4:28 p.m. for every day from December 3 until December 12.

December 2018 — Sun in New York

It is worth looking at a thread from a few days ago, in which there was a discussion of the differences in sunsets according to latitudes:

I'm watching Pres Bush's casket arrive at capitol.

It's almost pitch dark here in Boston, and the sky above the capitol is light. How can that be?

tia
las

******

Previously at DU, on Monday, December 8, 2014:

We have just had the earliest sunset of the year, on December 7.

Things vary, depending on where you live.

The earliest sunset in Washington, DC, occurs on or around December 7 or 8 in 2015. DC's sunset is stalled at 4:46 for over a week. New York City has the same sunset time, 4:28 p.m., for three days.

http://www.timeanddate.com/sun/usa/new-york?month=12

http://www.timeanddate.com/sun/usa/washington-dc

If you live in the northern hemisphere, the sunsets will be occurring later each day from now until June. The day on which the earliest sunset occurs is not the day with the least amount of sunlight. It is also not the day on which the latest sunrise occurs.

But, but.... What's the reason?

Earliest sunset at 40 degrees N. latitude on December 7

The exact date for the earliest sunset or earliest sunrise varies by latitude. Toward the end of the first week of December, mid-temperate latitudes in the Northern Hemisphere have their earliest sunsets. The earliest sunset for 40 degrees N. latitude is on December 7. That would be the latitude of New York City (shown in Jerry Ferguson‘s photo, top of post); Philadelphia, Pennsylvania ; Kansas City, Missouri; Reno, Nevada; Beijing, China; Madrid, Spain; Naples, Italy. Meanwhile, the Southern Hemisphere’s mid-temperate latitudes are waking up to their earliest sunrises.
....

It seems paradoxical. At middle latitudes in the U.S. – and throughout the Northern Hemisphere – the earliest sunsets of the year come about two weeks before the solstice and the shortest day of the year.

Why isn't the earliest sunset on the year’s shortest day? It's because of the discrepancy between the clock and the sun. A clock ticks off exactly 24 hours from one noon to the next. But an actual day - as measured by the spin of the Earth, from what is called one “solar noon” to the next - rarely equals 24 hours exactly.

Solar noon is also called simply midday. It refers to that instant when the sun reaches its highest point for the day. In the month of December, the time period from one solar noon to the next is actually half a minute longer than 24 hours. On December 7, the sun reaches its noontime position at 11:52 a.m. local standard time. Two weeks later - on the winter solstice - the sun will reach its noontime position around 11:59 a.m. That's 7 minutes later than on December 7. ... The later clock time for solar noon also means a later clock time for sunrise and sunset.

Sunrise and Sunset, Washington, DC

You can check for any month you want.

Bonus link: Why doesn't the earliest sunset occur on the shortest day of the year?

Bonus bonus link: Equation of time

[mr_lebowski]

1. Pretty sure the answer to this is 'because the earth is tilted on it's axis relative to the sun'

And absolutely nothing to do with this:

"But an actual day - as measured by the spin of the Earth, from what is called one “solar noon” to the next - rarely equals 24 hours exactly."

That implies that the earth is not spinning at exactly the same rate from one day to the next. Pretty sure that's bullshit. The earth turns exactly 360 degrees exactly every 24:00:00.000 hours, it doesn't randomly change from one day to the next.

Or at least, that is poorly phrased

I would say 'due to the tilt of the earths axis, depending on your latitude, 'solar noon' can vary to either side of 'clock noon' by a few minutes, depending on time of year, which causes sunrise and sunset to move forward and back commensurately, relative to the clock time'.

[BumRushDaShow]

2. Huh?

That implies that the earth is not spinning at exactly the same rate from one day to the next. Pretty sure that's bullshit. The earth turns exactly 360 degrees exactly every 24:00:00.000 hours, it doesn't randomly change from one day to the next.

Unfortunately the earth ain't a perfect circle and the molten iron core isn't uniformly distributed. That's why they use atomic clocks to represent the internationally-accepted discrete time increments (a "second" ) and will adjust the "official" time every so often when the earth's rotation varies.

[yonder]

11. "The earth turns exactly 360 degrees exactly every 24:00:00.000 hours"

Close to but not quite. It doesn't amount to much and isn't important unless one is an astronomer, land surveyor, navigator, etc. You can hear the DUT1 correction as applied to UTC by tuning into one of the broadcast WWV time signal frequencies and listening for, counting and appropriately applying the double tics after the minute signal. Currently, I think the correction is -0.3 or -0.4 seconds. There are other slight movements of our big, old rock such as a precessional wobble (think of a spinning top) which will one day result in our northerly axis pointing somewhere else rather than close to, Polaris:

The time correction DUT1 (sometimes also written DUT) is the difference between Universal Time (UT1), which is defined by Earth's rotation, and Coordinated Universal Time (UTC), which is defined by a network of precision atomic clocks.

DUT1 = UT1 ? UTC

UTC is maintained via leap seconds, such that DUT1 remains within the range ?0.9 s < DUT1 < +0.9 s. The reason for this correction is partly that the rate of rotation of the Earth is not constant, due to tidal braking and the redistribution of mass within the Earth, including its oceans and atmosphere, and partly because the SI second (as now used for UTC) was already, when adopted, a little shorter than the current value of the second of mean solar time.[1]

more:
https://en.wikipedia.org/wiki/DUT1
https://www.nist.gov/pml/time-and-frequency-division/atomic-standards/leap-second-and-ut1-utc-information

[LeftInTX]

3. Our's was Dec 1

It's one of those things that takes a brain to understand and my brain ain't working too well today!

I think our latest sunrise is Jan 10th. I can't tell for sure!! Two calendars gave me different info!!!

[mahatmakanejeeves]

4. I've never seen that chart before.

You can get an earliest sunset in November in Mexico City.

Thanks.

[LeftInTX]

5. Mexico City has their latest sunrise on January 18th

Last edited Fri Dec 6, 2019, 06:10 PM - Edit history (1)

Oooppsss

(Corrected from sunset to sunrise!!)

[mahatmakanejeeves]

6. Ummmm, do you mean their earliest sunset is on November 18th? NT

[LeftInTX]

7. Latest sunrise

Tomorrow it rises at 6:58 AM

January 13 - 23 it's 7:14 AM

If using standard time, versus CDT their earliest sunrise is in early June at 5:58 AM

Because the sun sets later, the sun rises later too. The length of day has not changed considerably. In late January the length of day increases enough so that both sunrise is earlier and sunset is later.

Confusing and boggles the mind!!!

I think their latest sunset is around November 28th!!

[LeftInTX]

8. Corrected my other post...LOL

It's Friday!!!

Brain ain't working.

[gratuitous]

9. The 45th parallel makes for an interesting demarcation

I lived just south of 45° North latitude for the first third of my life, and just north of it for the last two thirds. I noticed a definite difference from almost the first year when I moved north of 45°. While the day-to-day difference wasn't much, the Monday-to-Monday difference in sun-up and sun-down was noticeable in just a 75 mile span.

[rurallib]

10. Always thought ours was Dec. 6th. I see it is the 7th

I believe a lot of December religious days are based on the old solar observations. Dec. 6 is St. Nicholas Day (IIRC). kind of a biggie. Based on the time and date chart I look at Dec. 6 is the first of a string of earliest sunsets. This string ends Dec. 13 on Sancta Lucia Day (13th).

Anyway the point being that we seem to be re-enacting the old pagan beliefs of the sun cycle as updated by churches.