Why winter is the shortest season

Thursday, January 13, 2011

I was involved in a rather interesting conversation at the grocery store last week. One person was overheard to say, "I am so tired of winter, it is so long."

Well, not being one to let some astronomical error pass without comment I replied that winter is, in fact, the shortest of the four seasons, whereupon I was surrounded with a crowd of people who were convinced I had gone off the deep end.

At this point Astronomy Class 101 will be called into session.

OK, first point for the defense: According to Johannes Kepler (the guy who postulated the laws of planetary motion) Earth's orbit is not a circle, but an ellipse, a sort of squashed circle. Another word for it might be "oval."

Point 2: The sun is not located at the center of this ellipse, it is slightly off to one side which makes Earth travel closer on one end of the orbit than the other. So far, so good.

Point three: The closer Earth comes to the Sun during its year-long orbit along the ellipse, the faster it will travel.

OK, now. Let's start at as neutral a point as possible, the first day of spring. From the first day of spring to the first day of summer is generally 93 days. From the first day of summer to the first day of autumn is about 94 days.

From the first day of autumn to the first day of winter is about 90 days, and lastly, from the first day of winter to the first day of spring is about 89 days.

Thus winter, at 89 days is the shortest season and summer, at 94 days, is the longest. Spring is next longest at 93 days and autumn is third at 90 days.

Now, since we have established that a planet travels fastest when it is closest to the sun -- and on Jan. 3, Earth was at its closest-to-the-sun-point for the year -- and thus traveling at its fastest, therefore winter is the shortest season.

I rest my case.

SKY WATCH: First-quarter moon tonight Jan. 12. Jupiter is still shining in the southwest these evenings. For the next week or so use your binoculars to find another of the outer gas giant planets, Uranus. It will be down and below giant Jupiter. By the first of March Uranus will be lost in the glare of sunset. On Jan. 14, look for a growing moon near the Pleiades star cluster. The next evening the moon will be on the other side of the cluster just above bright, reddish, Aldebaran, the brightest star in Taurus, the Bull. Take some time to examine the Hyades star cluster located behind Aldebaran while you are in the area.

The morning sky is also showing some activity and if you are an early riser now would be a good time to examine it. Venus is the bright object in the southeast and way up above and right along the ecliptic, try to find Saturn.

Saturn is rising earlier each day and will soon be in our evening sky. And, if you a wishing for winter to be over, the stars of summer, the Summer Triangle of Vega, Altair, and Deneb are showing nicely in the east about an hour before sunrise and the stars of spring, Cancer, Leo, and Virgo are in the southwest. All a good sign of what is to come.

NEXT WEEK: More astronomical blathering.

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  • Oh, sure, ruin a perfectly good belly ache, with logic and truthful facts, why don'tcha?? (^8

    You might have noted that if the proximity factor were reversed, nothing could grow in the heat of summer, and very few plants, and possibly people could live through winter. I forget what the prof's said, but I believe summer would be about 145 deg/F, and winter would be something like -75 deg/F. No matter the real number, Awesome couldn't describe it. Of course there is the tilt factor to consider.

    See what you did, ruined my 'stay warm' fantasy.

    Ironic, people find it difficult to believe we are closer to the sun in the winter, and farther in the summer, and the axis tilt is about the only thing that keeps our weather within human tolerance levels.

    You need aughta splain all the technicalities, now that you knocked Humpty Dumpty off the wall. Ha.

    Good report. An eye opener.

    -- Posted by Navyblue on Thu, Jan 13, 2011, at 8:03 PM
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    Gosh Vernon, I thought maybe you were going to explain the analemma to us! :) :)

    We enjoy your interesting columns!

    -- Posted by ksfarmer on Mon, Jan 17, 2011, at 9:10 PM
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