Tuesday, December 18, 2012

Anchorage Nearing Solstice

People frequently ask about the winter darkness in Anchorage.  The shortest (darkest) day of the year in the northern hemisphere is this Friday, December 21. We're actually more than a 500 mile drive south of the Arctic Circle.  And we have a fair amount of light, even on the shortest day. 

Yesterday the Anchorage Daily News said our official sunrise was 10:11am and the official sunset was at 3:40pm, but at this latitude we have very long twilights (if it's clear.)  The sun at noon is very low on the southern horizon at noon. 

Here's my shadow at 1pm today.   Time and Date says the solar noon yesterday was at 12:56 pm and the altitude of the sun was 5.6˚.
See table below for more details.

Here's the southern horizon at 4:45pm, over an hour after the official sunset time.

I remember being in Hawaii with our kids watching the sunset over the ocean and  warning them it would be dark in ten or 15 minutes and they were really amazed at that.

So, even though the official "total daylight" was listed in the paper yesterday as 5 hours and 26 minutes, we had more than an hour of twilight before sunrise and after sunset giving us seven hours and a half.  Of course, that's not true if it's cloudy in which case it gets dark very fast.

I love the soft velvety blue of the winter evening sky.  And even though it was around 0˚F yesterday, walking around in the clean, crisp air was totally invigorating.  (I didn't play with the colors of the photo, it's really that color. The trees a little off white due to the street light tint.) It is helpful to be properly dressed though. 

Here it is as background to this icy birch with the crescent moon caught in the branches.  It's about 5pm here.

Here's a post-sunset view of the Chugach mountains from Rasmuson Hall on the University of Alaska Anchorage campus.  Looking east here through the glass which caused the darker shadow on the upper left. 

The paper also says we lost 50 seconds of daylight Monday from Sunday.  For a while we were losing over 5 minutes a day, but we're slowing down as we get to the end of the earth's tilt and then we'll start to tilt back.  Soon we will be gaining time quickly again.

From Time And Date:

The December solstice occurs when the sun reaches its most southerly declination of -23.5 degrees. In other words, it is when the North Pole is tilted 23.5 degrees away from the sun. Depending on the Gregorian calendar, the December solstice occurs annually on a day between December 20 and December 23. On this date, all places above a latitude of 66.5 degrees north (Arctic Polar Circle) are now in darkness, while locations below a latitude of 66.5 degrees south (Antarctic Polar Circle) receive 24 hours of daylight.

Time and Date also calculates our sunrise and sunset schedule for this week a little bit differently from what the Anchorage Daily News has:

Length of day
Solar noon

Date Sunrise Sunset This day Difference Time Altitude Distance
(106 km)
Dec 17, 2012 10:12 AM 3:41 PM 5h 28m57s − 49s 12:56 PM 5.6° 147.204
Dec 18, 10:12 AM 3:41 PM 5h 28m19s -37s 12:57PM 5.5˚ 147.191
Dec. 19 10:13 AM 3:41PM 5h 27m54s -25s 12:57 PM
5.5˚ 147.179
Dec. 20 10:14AM 3:41PM 5h27m41s -12s 12:58 PM 5.5˚ 147.167
Dec. 21 10:14AM 3:42PM 5h27m40s <1s 12:58 PM 5.5˚ 147.157
Dec. 22 10:15AM 3:43PM 5h27m53s +12s 12:59 PM 5.5˚ 147.147
Dec. 23 10:15AM 3:43PM 5h28m17s +24s 12:59 PM 5.5˚ 147.137

Data from Time and Date.


  1. Good photos of your part of the earth. We in Ottawa have a little more light but winter seems to take a whole day away from a day. But in summer one day feels like two!

    We'll be glad to see the back of December 21 and begin to see the light creeping into the bedroom earlier and earlier every morning to gently wake us up. :)

    Have a wonderful Christmas or Whatever, a timeforyou to rest and enjoy the company of friends and family. (We don't expect a blog entry on Christmas!)

  2. The actual solstice (time at which the tilt starts the other way) is at 2:12 a.m. Alaska time.

    Source: US Naval Observatory at http://www.usno.navy.mil/USNO/astronomical-applications/data-services/earth-seasons


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