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Spring Equinox

March 20, 2014

The Sun is one of those things we tend to take for granted. We might long for it during a blizzard, or curse it during a heat wave, but otherwise we pretty much ignore it. For much of human history, though, that was not the case — the Sun’s position played a key role in everything from agriculture to politics to religion.

The early Christian church, for example, needed a precise determination of the spring equinox to help set the date for Easter — a need that continued for centuries. During the 16th century, one astronomer tried to incorporate a solar marker in the design for Basilica Santa Maria in Florence. Known as a meridian line, it projected the Sun’s image onto the church floor. Seeing where the path overlapped in March and September would reveal the dates of the equinoxes.

The astronomer’s patron died before the project could be finished. But the spirit of his work is recalled in a meridian line at Austin College in Sherman, Texas. A solar viewing port in the wall of the college’s new science building projects an image of the Sun on the ground floor. A stripe along the floor marks where the image will appear at the solstices and equinoxes.

Since today is the spring equinox, the Sun’s image will shine on a Chinese Sun symbol at precisely local noon — the time the Sun is highest in the sky. This and other symbols commemorate the contributions to science made by different cultures over the ages — all of which kept a careful eye on the Sun.


Script by Damond Benningfield, Copyright 2014

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