The winter solstice, the longest night of the year in the Earth’s northern hemisphere, will take place on Sunday night, Dec. 21. At that point, the sun will have reached its lowest point in the sky and will rapidly “reverse” direction – as shown in the photographic composite above.
The image above shows an analemma, a graceful figure-8 curve that results from marking the position of the sun at the same time each day throughout the Earth’s year. In the image above, photographer Thomas G. Matheson superimposed 26 separate exposures, all taken at 8 am in the morning in northern New Jersey, on a single foreground image.
The sun was not moving, of course: The figure-eight curve of the analemma results from the tilt of Earth’s axis and the variation in its speed as it moves around its orbit. The summer and winter solstices correspond to the top and bottom of the figure-8, respectively, the northern and southernmost excursions of the sun in the sky. Analemmas created from different latitudes appear slightly differently, as do those created at different times of the day. Those in the southern hemisphere see the figure reversed, with the larger loop facing “upwards.” From the Earth’s poles, only half of the loop is visible.
Analemmas can be created with other heavenly bodies as well. A lunar analemma captures the view of the Moon from Earth over the course of a lunar month, while a Martian analemma captures the view of the sun from Mars. Mars’ analemma is shaped like a pear rather than a figure-8, because Mars has a more elliptical orbit. The pointy side of the pear occurs when Mars is farther from the sun, and the sun progresses slowly in the sky. The rounded bottom occurs when the sun is closer and appears to be moving more quickly.
Photograph reproduced courtesy of Thomas G. Matheson, www.guidescope.net. All rights reserved.