Obessions with Light and Dark

5 January 2012
6:45 PM

Sunrise at	10:49 AM	in direction	151°	South-southeast
Sunset at	3:04 PM	in direction	209°	South-southwest

Duration of day: 4 hours, 15 minutes (4 minutes, 9 seconds longer than yesterday)

Alaska is a region of extremes in many ways.  One of those extremes is the balance between daylight and night.  You might say, based on reading this over the last several days, that I am obsessed with light and dark.  You would be right - at least with respect to light.  I was not raised at this latitude and it is a source of constant fascination for me to see the variations in daylight through out the planet.  One surprise was that as one's latitude gets closer to the pole, the more dramatic the difference from north to south.

I have some facts to back my statement.  You can see the duration of the day for Fairbanks above.  Yes, this is sun above the horizon and not usable light as I wrote about before, but let's leave it to just that for comparison.

Anchorage, by Google map is 358.7 miles south by the most direct route via the Parks Highway. Today's daylight hours ... 5 hours, 48 minutes (2 minutes, 42 seconds longer than yesterday).


Two things should jump out at you:  First the number of minutes Fairbanks is gaining is nearly double that of Anchorage.  Don't forget that at the Spring and Autumn Equinox, most of the planet has 12 hours of daylight and night.    Secondly, you should notice that currently, in this time near solstice, Anchorage has an hour and 30 minutes more daylight (above the horizon - remember).


Now let's compare the difference between Stockton, California near where my Dad lives and Palm Springs, his favorite winter retreat.   Google maps indicates Stockton and Palm Springs, CA are @ 441.5 miles apart along the nearest route.


Stockton:  9 hours, 38 minutes (49 seconds longer than yesterday)
Palm Springs:  9 hours, 59 minutes (42 seconds longer than yesterday)

That is a difference of 21 minutes of sunlight a day and only 7 seconds difference for the change interval.

I wanted to toss in how quickly daylight is changing at Prudhoe Bay.  Prudhoe Bay is 499.8 miles from Fairbanks and is the most direct destination north that approximates the other comparisons, but the sun isn't technically rising there yet.  The site I used for the other comparisons provides Twilight differences.  And the one I found that does an on the fly calculation doesn't provide that type of information.  However, I can post what is expected for January 18 & 19, the first two days the sun is above the horizon ( http://aa.usno.navy.mil/cgi-bin/aa_rstablew.pl ).

January 18, 2012
Sunrise 12:44 PM, Sunset 1:24 PM  :  40 minutes of daylight


January 19, 2012
Sunrise 12:25 pm, Sunset 1:45 pm  :  1 hour, 20 minutes of daylight

Prudhoe Bay will gain 40 minutes of sunlight in one day.  Is that Crazy or what?