Dark Winter Days

After I have a cup of coffee and read the morning paper, I do my morning exercises and yoga. I do the routine using a Wii balance board and my personal routine selected from the Wii software. I bought the Wii setup about eleven years ago and have used it off and on since. For the past seven months I've been doing it faithfully almost every morning. 

The routine consists of ten yoga poses and eight exercises followed by a dozen pushups. The routine is committed to memory so instead of watching the TV screen, I observe the morning scene from the living room windows. 

From these north-facing windows I see what real estate agents call a territorial view. There are two partially vacant lots in the foreground with apartment and condominium buildings beyond. There are several trees and in the middle distance stands a telephone pole that a seagull uses as a lookout and resting spot. I can tell which way the wind blows by watching the seagull land into the wind. If there is little or no wind, it seems to land facing the sun.

This time of year it's usually dark when I do my exercises. A week ago I finished the paper and coffee early and started exercising a little after six. Noticed that we had a clear sky and watched as the day arrived. It was interesting to see the transition from dark to light so thought I'd take photos during the next clear day so I could share the brightening sky with you. 

The next day reverted to our normal winter weather.  I've been hoping for a clear morning but it's been clouds and rain since. This morning, a few hours after the winter equinox, I decided to take photos despite the low clouds and rain.

This was taken at 0659. To the naked eye it was dark with some ambient light from security lights and streetlights, but the camera optimizes what light there is to get the best photo possible without specialized lenses, etc. The branches in the foreground are lighted by the living room lights behind me.

Now we move to 0714. The sky is a little lighter but the trees are still in silhouette and the ground is dark. 

At 0725 the clouds are brighter, the trees are still in silhouette and the fields are still mostly hidden. Above the low apartment building with the two lighted windows on the left side of the photo we see two poles. The pole on the left has crossbars and wires while the one on the right is a bare pole where the seagull likes to land to survey the scene. Those poles are only a block away even though it looks farther. About this time the hummingbirds begin their visits to my feeder. 

At 0735 the trees have shifted to three dimensions, the sky is brighter and we can make out a little color, even though the shaded windows of the apartment still shine with light. The hummingbirds have been busy and now the seagulls and crows are flying. Beginning about now I see occasional pairs of ducks and small flocks of geese flying to the east.

Now it's 0747 and the day is arriving. The lights in the apartment windows are still visible but soon will fade away in the brightening day. About now this morning I saw a rabbit running from my side of the field and scamper into the briar patch in the bottom left. In the spring and summer we watch the rabbits feeding on the green grass and playing in the longer grass to the right of the blackberry thicket. We haven't seen one since late September, so this was a special morning despite the rain. Last spring and summer, on three occasions I saw a coyote in this field so the rabbits have to be careful or they will be a quick breakfast.

Now it's five minutes after official sunrise (0759) and the glow of the apartment windows is gone. 

This photo was taken shortly after the one above, also at 0759. The rain is dripping off my storm flag and there are flood warnings for the local rivers. Typical winter weather for us.

Full daylight, such as it is, arrived around 0825. The light that shines on my flag during the night is controlled by a photocell and turns off when there is enough light to trigger the photocell. On a clear day the light would have gone off shortly before sunrise, but today it was half hour after sunrise before it got bright enough.

Watching night turn to day had me wondering about the relative speed of that change in various places on earth. When I lived in Panama, the twilight periods were quite different. Now I live in Edmonds, Washington at approximately 47.8 degrees North latitude. Today being the shortest day of the year, we have only 8 hours and 25 minutes of daylight. The other 16 hours and 35 minutes are the three kinds of twilight and night. 

Today astronomical twilight (center of sun between 18-12 degrees below horizon) when we can't yet see the horizon and most stars are still visible, lasted from 0602 until 0639. Nautical twilight (center of sun 12-6 degrees below horizon) when the horizon is visible and some stars are still visible lasted from 0639-0719. Civil twilight (center of sun 6-0 degrees below horizon) lasted from 0719-0755 when the it was sunrise. 

Some authorities describe the morning twilights as dawns and the evening twilights as dusks, but I'll keep it simple and refer to those periods as twilight. Another note, nautical twilight was very useful before GPS and other kinds of geo-positioning because it allowed mariners to locate their position by using a sextant, the horizon and astronomical bodies (astronavigation).

I said that the days and twilights were different in Panama. I noticed the same thing in Viet Nam. The twilight periods in the tropics are notable for their shortness compared to those of more temperate climes. This is caused by the speed of the earth's rotation in the particular local. 

The earth spins on its axis approximately once in 24 hours. If you measure the circumference of the earth at the equator and do the math you see that the point on which you are standing is rotating at about 1,037.5 mph. As you move toward the poles, the circumference (following the latitudes) shrinks. Once again, you can do the math (using cosign and multiplication) and find the speed. Here in Edmonds, we are moving at about 631.24 mph. Moving farther north, the distance gets shorter and shorter until at the north pole you can literally encircle the earth with your arms. There the land (water and ice) beneath you is moving not in miles per hour but in inches per hour. 

This speed combined with the angle of the suns rays, gives us the length of the twilights. Here in Edmonds, since we're traveling only about half as fast as people at the equator, the twilights are much longer. 

Interestingly, the maximum northern latitude for astronomical twilight at midnight during the summer solstice (longest day of the year) in the northern hemisphere is 48.56 degrees. At 48.75 degrees, Bellingham just falls within that range and thus is the only large city in the continental US to do so.

Well, that's probably more than you wanted to know about twilight, so I'll stop there and wish you a Merry Christmas and a peaceful and prosperous New Year.

I took this an hour or so ago. I'm sure Iko's orchids are glad they are inside that window instead of out in the deluge we are having today.