January 6, 2012
Although the days are getting longer here in the northern hemisphere, we’re having the latest sunrises of the year now. While the shortest day (total hours of daylight) was winter solstice on December 22nd what I call the “solstice season” doesn’t happen all at once. The cycle is earliest sunset, shortest day, latest sunrise. The earliest sunsets occured in early December followed by the “shortest” day. It all seems to happen at solstice because most people see, or are more aware of, the sunsets.
Of course the opposite is true for people in the southern hemisphere where the December solstice marks the longest day and the sequence reverses at summer solstice.
By way of example I compared the sunrise/sunset tables for Louisville, central Wyoming and southern California. I live near the former and have family at the latter locations. It’s all about latitude. Louisville latitude is 38 north. I plotted locations in Wyoming at 42 north and southern California 34 degrees north. Earliest sunrise in Louisville was 5:23 pm EST November 30-December 13. In Wyoming it was 4:41 pm MST December 3-13 and 4:47 pm PST December 1-10 out in southern California. As I write this on January 6th sunrise is 15 minutes later here near Louisville (5:38 pm), and 17 minutes later in Wyoming and California.
By January 31st sunset will come at 6:05 pm here or about 45 minutes later than in early December at the places I’ve listed.
On the morning side, the latest sunrise in Louisville, 8:00 am EST, happens December 30-January 7. Its 7:46 am MST at 42 N and 7:04 am PST on the west coast at 34 N. By month’s end sunrise will be 11 minutes earlier here. 14 minutes earlier in Wyoming and 6 minutes earlier in Ventura.
You might also find it interesting to learn that we (planet Earth) are closest in our annual circle about the Sun right now. Perihelion, Earth’s nearest point to our star, occurred January 4th. Because our orbit is slightly oblong we’re about 2% closer to the Sun. This may seem counter intuitive because its winter but remember we have seasons due to the tilt of Earth’s axis. The northern hemisphere is “leaning away” from the Sun now.
Also, I suggest you watch and make note of where the Sun and Moon rise and set. This exercise will help with our next observing exercise.
For your local sunrise/sunset tables visit the US Naval Observatory Portal Click USNO, then Sun/Moon rise/set table for one year