In many parts of eastern US, winter has arrived with a blanket of snow and bone chilling cold temperatures just in time for the holidays. It’s always good to have snow for Christmas. There is so much to enjoy at this time of year in the natural world. For example we are approaching the winter solstice on December 22nd. This is the official first day of winter despite what it looks like outside.
So what does the solstice mean? The solstice is either of two times of the year when the sun has no apparent northward or southward motion. It’s the day when the sun’s setting position along the horizon stops changing. Solstice means “sun stop”.
I think everyone knows the earth rotates or spins on an axis which gives us night and day. One complete spin takes 24 hours. However, I am not sure everyone understands the earth also tilts as it spins. It is the tilt towards or away from the sun that gives us our seasons, not the distance to the sun. So at the winter solstice we have tilted the furthest away from the sun and marks the shortest amount of daylight all year. It also gives us the longest shadows at noon. So if you go outside at noon on December 22nd the length of your shadow will never be longer. It also means the longest night. The good news is, after the solstice the days will start to get longer.
Another interesting fact, at this time of year we are actually closer to the sun in our obit than we are during the summer months. You might think we should be warmer due to the closer proximity of the sun but since we are tilted away from the sun we only get a glancing blow of the suns energy, not a direct hit. During winter we are about 91 million miles from the sun as compared to about 94 million miles during the summer. Since we are in an oblong orbit around the sun it is said that we average about 93 million miles from the sun.
During the winter solstice we have slightly less than 9 hours of sunlight which means we have about 15 hours of night. At the equinox, which is when the earth is not tilted and the sun lines up above the equator we have 12 hours of light and 12 hours of night and during the summer solstice we have about 15 hours of daylight and only 9 hours of dark.
The earths tilt is also why at this time of year the southern hemisphere has summer while we have winter. The sun lines up at 23 degree south latitude giving the earth south of the equator more direct sunlight and the results are summer. The opposite happens during June 22nd when the sun lines up over 23 degree north latitude. So, if you live anywhere north of 23 degree north latitude you never get direct sunlight overhead. Since 23 degrees north latitude runs just above Cuba and runs directly through the middle of Mexico no one in the US ever gets the sun directly overhead. The southern tip of Florida and Texas would be about the closest you can get while still being in the US.
Degrees latitude are numbered from 0 to 90 north and south. Zero degrees is the equator, the imaginary line which divides our planet into the northern and southern hemispheres. 90 degrees north is the North Pole and 90 degrees south is the South Pole.
So I hope I have given you something to think about during these long cold dark nights this winter. Until next time…