Winter Solstice arrives Saturday Dec. 21st. at 12:11 P.M.

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Sarasota - The autumnal equinox or fall comes to an end this Saturday for the Northern Hemisphere. The fall of 2013 has been bitterly cold for most of the United States, with the exception of Florida.

Earths orbit around sun

At exactly 11 minutes after noon on Saturday Dec. 21st. winter will commence for the Northern Hemisphere 2013-2014. How is the time determined? The winter solstice begins when the suns direct rays (90 degrees) appear at noon at its lowest altitude above the horizon. That 90 degree angle will be over the Tropic of Capricorn shortly after noon on Saturday. This will occur near our Longitude in the southern hemisphere. That will be the point that the suns direct rays (90 degrees) will be occurring for only a short period of time, before the earth slowly continues its elliptical orbit around the sun. Solstice means "stand still" And that's just what the sun appears to be doing at that time.

NASA image of Sun

Since the earth is tilted at 23 1/2 degrees on its axis, the sun's angle of incidence is the highest at the Tropic of Capricorn, near December 21st. - 22nd. So in the Southern Hemisphere it's the start of summer, while here it is the beginning of the coldest months.

The sun is not centered directly in the middle of earth’s elliptical orbit. In fact, while the earth is rotating around the sun, earth will be at its closest point during December (perigee). The sun is at the greatest distance from the earth during September, or our summer (apogee). The earths average distance from the sun is 93 million miles. One would think that when we are closer the sun, which occurs during winter, we would be the warmest. That is not true. The temperature is directly related to the angle of the suns rays, not the proximity to the sun.

So there you have it, winter is at hand and I hope it's a mild one. Stay warm.