So why are there Dark Days Before Christmas in the northern latitudes? Had my wife’s grandmother been born in New Zealand what would she say about the days before Christmas?
There is a neat website I found that gives sunrise and sunset times for various cities in the world.
So let’s have a look at the relative sunrise and sunset times, for of course the Paris of Appalachia, and some of the Dunedins scattered about the world on the darkest day before Christmas (for the northern hemisphere)…the winter solstice which will occur on December 21, 2010 at 23:38 (11:38 PM) Greenwich Mean Time or 18:38 (6:38 PM) Eastern Standard Time.
Click on the image to zoom in on the chart.
For the Paris of Appalachia, (Pittsburgh, Pennsylvania) which sits about 40.5º north latitude, we enjoy 9 hours and 17 minutes of daylight and at high noon the sun will be 26.2º off the southern horizon.
For the original Dùn Èideann (Edinburgh, Scotland) which sits about 56º north latitude, you only will see roughly 7 hours of sunlight, and at high noon the Sun will only climb 10.7º off the southern horizon. For those of us further south, you can visualize this by going outside, face south, hold your closed fist at arms length away from you. Align the bottom of your fist with the southern horizon, the Sun at high noon in Edinburgh will only rise to the top of your fist. Dark Days indeed!
Now for those of you who live in sunny Dunedin, Florida which sits about 28° north latitude, the Sun will bless you with 10 hours and 22 minutes of glorious light and it will reach 38.6º off the southern horizon.
Now lets consider Dunedin, in Otago District, New Zealand. You are sitting at roughly 46° southern latitude and you are going to get a whopping 15 hours and 45 minutes of sunlight on our shortest day of the year. The Sun at high noon will be a high in the sky 67.6º off the northern horizon. It is your longest day…the first day of summer in the southern hemisphere.
Oh oh, what about poor Murmansk, Russia. The Sun will not shine for you at all on this shortest day of the year. At almost 69º northern latitude, you are above the Arctic Circle and at high noon the Sun will still be 1.4º below your southern horizon. Well cheer up, 6 months from now the Sun won’t set so you will make up your light deficit.
So what about the north and south poles? Well the December solstice is exactly midnight for the north pole and high noon for the south pole. Days and nights last 6 months at the poles.
So what the hell is going on? Why does Edinburgh Scotland gets less than half the amount of sunlight as Dunedin, New Zealand on the very same day?
Click on image to view full size.
Take a look at this diagram from Wikipedia. It shows the Earth at four locations in its orbit around the Sun. Notice the purple line extending from both pole regions. This is the axis of the Earth and it is canted relative to the plane of orbit by about 23.4 degrees. Notice that the axis points in the same direction no matter where in the orbit that the Earth is located. Currently the axis in the northern hemisphere always points to the North Star, Polaris. However due to a phenomenon known as precession, the Earth being a giant gyroscope, the axis will slowly drift away from Polaris and then drift back in a 13,000 year cycle. Because the Earth’s axis is tilted and the axis remains in a stable position during the orbit around the Sun, the sunlight distribution changes from northern hemisphere to the southern and back as each year and the Earth’s orbit about the Sun progresses. This is why we have seasons, and my suspicion is that if it were not for the tilted axis of the Earth, life, or at least life as we know it, may not be possible here.
Again looking at our diagram, the Earth is now in the far most right position in the diagram. The December solstice, which occurs around December 21, is the winter solstice for the northern hemisphere and summer solstice for the southern hemisphere. Note that the north pole is completely dark and will not be exposed to any sunlight at all during the daily revolution of the Earth. The south pole will have 24 hours of sunlight. The days are short in the northern hemisphere and long in the southern.
Following counter clockwise along the orbit the Earth, at the top of the diagram is at the March equinox which occurs around March 21. This is the vernal or spring equinox for the northern hemisphere. Although not readily apparent in the diagram, the Sun is directly over the equator and both hemispheres will have 12 hours of daylight and 12 hours of night.
Continuing along the orbit to the left side of the diagram, we see the June solstice which occurs around June 21. This is the summer solstice for the northern hemisphere and winter solstice for the southern. Now the days will be long in the northern hemisphere and short in the southern.
The last position at the bottom of the diagram is the September equinox which is the autumnal or fall equinox for the northern hemisphere. Again both hemispheres have an equal 12 hours of daylight and night.
The second diagram shows the effect of increased light density in the southern hemisphere and the reduction in the northern during the winter months.
The winter solstice has a deep psychological importance to human beings. The continual loss of daylight being halted and the days becoming longer has been the cause for celebration among many social groups in history. It is no accident that the birth of Christ, which is historically unknown, is considered December 25. Pagan Rome celebrated Brumalia a month long festival to Roman god of wine and intoxication Bacchus that reached its peak on December 24 and 25 When Rome officially adopted Christianity in the 4th century AD, a celebration of the birth of Christ replaced Brumalia.
I have a theory, very much unproven, that people retain an ancestral predisposition for a location within their genes. Why are the northern central states so appealing to people of Scandinavian descent? Being of Irish and Scotch ancestry, I believe I have the gloom of the Atlantic Isles' winters embedded in my bones. When the days get shorter in September and October, I do find that I miss the longer hours of daylight. However, when the solstice is bearing down on us, I find that I have a deep and abiding longing for the Dark Days Before Christmas. In the movie, The Christmas Carol with George C. Scott, I love the scenes where Scrooge is walking through the dark foggy and snowy Victorian streets, especially the scene where the horse drawn white hearse mystically disappears into the fog. For reasons that I do not fully understand I find a deep comfort leaving work in the late afternoon to a darkened world often blowing with a fine frozen mist of lake effect snow. Walking to the car through the cold, wintry, gloom has a mystical Soul pervading loneliness, quite Dickens like in character. I love the sight of it, the feeling of it, the loneliness of it…like Scrooge walking home by himself. You can almost sense Marley near by. And yet how lovely to walk through the door into my warm home, beautifully decorated for Christmas, to a loving wife and a hot dinner. It makes me feel like Bob Cratchet. Cold. lonely, wintry gloom is a wonderful thing in small and temporary doses! God bless us, every one!
1. Screen Print of Sunrise & Sunset Spreadsheet, Me, using data from:
2. Solstices & Equinoxes from:
Wikipedia, Winter Solstice
3. Winter Solstice
Wikipedia, The Seasons
Edit 12-23-10: It occurs to me that I have several items in the chart above that are not defined. So let me provide definitions for all of the data columns in the above chart.
Sunrise: is the local time that the Sun will rise in the morning, that is appear above the horizon.
Sunset: is the local time in which the Sun will set in the evening, that is drop below the horizon.
Hours of Daylight: How much elapsed time in hours, minutes and seconds between sunrise and sunset.
Solar Noon: The local time when the Sun reaches the highest point in the sky for the day. This is a function of where the Earth is in its elliptical orbit around the Sun, and where the location is positioned within the time zone. Each time zone is one hour wide and covers ideally the circumference of the Earth divided by 24 at the equator. The actual width at any particular location will be a function of the latitude of the location and at times the political or economic shifts applied to the time zone borders. The closer to the poles that a particular location lies, the more narrow will be the time zone in miles. Boston, Pittsburgh and Indianapolis are all in the Eastern Time Zone but their solar noons will be different. For today the solar noon will occur at 11:43 for Boston, 12:19 for Pittsburgh, and 12:44 for Indianapolis. Yet all three are in the Eastern Time Zone.
Altitude of Sun: This is the maximum elevation off the horizon measured in degrees that the Sun will attain at solar noon for the day in question. The higher the Sun at solar noon the longer daylight will last.
Latitude: The position of the location measured in degrees, minutes, and seconds North or South from the equator as indicated on a GPS or sextant.
Longitude: The position of the location measured in degrees, minutes, and seconds East or West of the 0 Meridian at Greenwich England as measured by a GPS or sextant. Longitude is not a factor in the amount of daylight for any given day but is a factor in when the solar noon will occur.
EDIT 5-14-2011: Falling under the category of "There is so much cool stuff on the Internet", I found this web page in response to a search indicated on StatCounter. It gives a better albeit more complicated explanation of the Dark Days of Winter. Lot of cool stuff on this site.
Naval Oceanography Portal, Dark Days of Winter
EDIT 5-13-2012: I found these handy diagrams showing the approximate angles between stars. The measurement is conducted by extending your arm full length. To measure the approximate angle of height of the sun above the horizon, orient your fist vertically so that your thumb is pointing toward the sun and your little finger is touching the horizon.
|For the elevation of the sun, the bottom object is the horizon.|
Image Copyright ©2010-2011 by Daniel V. Schroeder
|Angle estimates using fist and fingers with arm outstretched.|
For elevations from horizon turn fist vertical.
Copyright ©2010-2011 by Daniel V. Schroeder
Image Credits: Daniel V. Schroeder, Understanding Astronomy, Motion of The Stars
For more information, Schroeder has and excellent explanation of the seasons at:
Daniel V. Schroeder, Understanding Astronomy, The Sun and Seasons