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Global Skywatch

March 20th is Spring Equinox

Let’s celebrate … let’s make today somehow memorable.

Your wall calendars and media might call today “first day of spring” or some other trivializing phrase, as if it is a meaningless Hallmark holiday. Do not confuse it with other fabricated events on your pre-printed calendar. Mankind has paid attention to solstices and equinoxes throughout our history.

The days have been getting longer since the winter solstice, and will continue growing until the summer solstice June 21st. Wednesday is exactly half-way in between. It defines the shift from snow-cold-snow-cold to robins, flowers, butterflies and shedding jackets during the day.

Pessimists say The Bitterroot has three seasons: snow, flood and smoke.
I suppose we had better broadcast it like that lest we end up like so many places where the snowflakes are a political force rather than a natural one.

The equinoxes are the only times when the solar terminator (the “edge” between night and day) is perpendicular to the equator. As a result, the northern and southern hemispheres are equally illuminated. The word comes from Latin equi or “equal” and nox meaning “night”.

In other words, the equinoxes are the only times when the subsolar point is on the equator, meaning that the Sun is exactly overhead at a point on the equatorial line. The subsolar point crosses the equator moving northward at the March equinox and southward at the September equinox.

The equinoxes, along with solstices, are directly related to the seasons of the year. In the northern hemisphere, the vernal equinox (March) conventionally marks the beginning of spring in most cultures and is considered the New Year in the Persian calendar or Iranian calendars as Nowruz (means new day), while the autumnal equinox (September) marks the beginning of autumn.

The Old Farmer’s Almanac on Vernal Equinox