Happy “Infinity Eve”, from the bottom of the Analemma! [minor update]

When I was in grade school, a friend told me that if you photograph the sun at noon every day (disregarding Daylight Saving Time), using a stationary camera without advancing the film, after one year you’d have a picture of an “8”. This is called an analemma, and it’s been well-studied and documented.

The Analemma in winter

(Animation courtesy Starry Night Pro. Click to view the movie.  You’ll need QuickTime to watch it.)

Since that day in grade school, I harbored the idea that the symbol for infinity had its roots in early man’s subconscious awareness of the sun’s tracings. What other natural phenomenon symbolized the inexorable passage of time unending? It was an interesting observation, but unlikely when one considers that December 25 is also the birthday of the Roman Sun God Mithras, known to be celebrated as early as 1400 BC. Why unlikely? Because the (northern) civilizations of the time, enduring the hard, cold winter with food from the previous season’s hunt and harvest, were not sure the Sun would return as they watched its transit get lower in the Autumn and Winter sky. While the solstice occurs about December 21 each year (sol means “sun”, sistere means “to cause stillness”), the technology of the day was unable to detect the tiny rise in the Sun’s path for a few days, thus December 25th was a celebration of dies natalis solis invicti, or the birth of the invincible Sun. Celebration of a new year, and the Sun’s return to strength is said to go back to earliest history. So much for boyhood theories, precocious and interesting though they may be.

At this time of year, Earth is nearest the Sun and traveling at the maximum speed of its elliptical orbit, in keeping with Kepler’s Laws of Planetary Movement. The Sun, at its lowest point in our sky at solstice, is very near the bottom of the analemma. That’s why the lower loop is larger and why the Sun traverses it faster–we are closer and moving faster. For the curious, the Sun is at the top of the analemma at Summer Solstice, when we are farthest from the Sun and moving slowest. The Sun crosses the middle intersection at both equinoxes.

And all because of a 23.5° tilt of Earth’s axis relative to its orbital plane around the Sun, and its slightly elliptical orbit.

[Update:] Space.com just printed a related article.

So, as long as we’re celebrating that the Earth is at this particular Sun-relative location yet again (rather like birthdays), and the Sun is likewise in its historical spot on its analemma, I wish you a Happy Infinity Day, and many more to come.

Explore posts in the same categories: Astronomy Links

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