Happy Winter Solstice, when winter officially arrives and the shortest day of the year. It arrives at 6:12 am Friday Dec. 21, 2012 according to The Old Farmer’s Almanac. Here is an excerpt from that Almanac:
The word solstice comes from the Latin words for “sun” and “to stand still.” In the Northern Hemisphere, as summer advances to winter, the points on the horizon where the Sun rises and sets advance southward each day; the high point in the Sun’s daily path across the sky, which occurs at local noon, also moves southward each day. At the winter solstice, the Sun’s path has reached its southernmost position. The next day, the path will advance northward. However, a few days before and after the winter solstice, the change is so slight that the Sun’s path seems to stay the same, or stand still. The Sun is directly overhead at “high-noon” on Winter Solstice at the latitude called the Tropic of Capricorn. In the Northern Hemisphere, the solstice days are the days with the fewest hours of sunlight during the whole year.
From meteorology class way back when, I always thought it interesting that although it is our winter here in the northern hemisphere, the earth is actually closer to the sun at this time than in our summer. In our annual trip around the sun, we are further from it in our summer, but the angle is more direct, due to the axial tilt of 23.4 degrees. The axis of rotation points in the same direction throughout the yearly trip.
“Living on Earth may be expensive, but it includes an annual free trip around the Sun.” – Anonymous
From NASA’s website, www.nasa.gov.:
Earth has seasons because it is tilted. The season depends on whether a place is tilted toward or away from the sun. In the summer, the Northern Hemisphere is tilted toward the sun. The sun’s rays hit the Northern Hemisphere in a straight line. The days are long and hot. The opposite happens in winter. Then, the north is tilted away from the sun. The days are short and dark. When it is summer in the northern half of Earth, it is winter in the southern half. In the spring and fall, the sun shines evenly on both hemispheres.
And from Space.com:
Earth’s orbit is not a perfect circle. It is elliptical, or slightly oval-shaped. This means there is one point in the orbit where Earth is closest to the Sun, and another where Earth is farthest from the Sun. The closest point occurs in early January, and the far point happens in early July. Earth’s elliptical orbit has nothing to do with seasons. The reason for seasons has to do with the tilt of Earth’s axis.
In 2013, Earth comes closest to the sun (figure 2 above, planet at perhelion) on Wednesday, January 2 at 05:00 Universal Time (GMT). To equate that to Eastern Time, it will be exactly midnight on Jan. 1st, and for my family on the west coast, it will be 9 PM Pacific Time on January 1st, 2013.
And here is my new favorite website, from NASA, the Astronomy Picture of the Day Archive:
The following pictures are some of my favorites from this website. Credit to the wonderful photographers on this website.
The following link is to time-lapse footage of the earth as seen from the International Space Station. It is stunning.