Martian equinox is almost upon us, which will usher in astronomical spring in the Northern Hemisphere and astronomical autumn in the Southern Hemisphere.
This year, the vernal equinox, or vernal equinox, occurs at 10:46 a.m. EDT (2:46 p.m. UTC) March 20 in the northern hemisphere, according to Time and date. Because the equinoxes are global events governed by the tilt of the Earth’s axis relative to the Sun, the March equinox occurs at the same moment across the globe.
Why are there seasons?
Earth experiences seasons because its axis is tilted by one average of 23.5 degrees relative to the planet’s orbit around the sun; this tilt means that different places on Earth receive varying amounts of sunlight during the year. On the equinox, neither hemisphere is tilted toward or away from sunso the sun shines almost directly over the equator, producing almost equal hours of day and night.
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Equinoxes occur twice each year, with approximately 12 hours of daylight and 12 hours of darkness in both the southern and northern hemispheres. The word comes from the Latin words “aequus” (equal) and “nox” (night). After the equinox, the nights will shorten in the northern hemisphere and lengthen in the southern hemisphere until the solstice on Sunday 21 June.
The equinoxes are among the most obvious features of the solar calendar, because the sun rises and sets due east from almost everywhere on Earth (except at the poles), just as it does on the September equinox.
Written in stone and stars
Equinoxes have been celebrated by cultures throughout history. On Chichén Itzáa Mayan complex on Mexico’s Yucatán Peninsula, light from the equinox sunrise making it look like a snake was moving down the Kukulcán pyramid. It is believed to mark the start of the planting season.
Numerous other temples are believed to be aligned with sunrise on the equinoxes, including The Great Sphinx of Giza in Egypt and Angkor Wat in Cambodia. Other celebrations associated with March Equinox include Nowruz (Persian New Year), which is believed to date back 3,000 years.
If you can’t witness the sunrise on the equinox in a location with known alignments, try looking just after sunset on March 20, when a 5% illuminated waxing crescent moon will shine just above Venus in the west-southwest.
There will also be signs of spring in the stars: the Big Dipper will ride high in the northeast for skywatchers in mid-northern latitudes. (You can remember its position with the mnemonic “jump up, fall down.”) Meanwhile, in the southern night sky for mid-northern latitudes three prominent stars of spring will be: Arcturus (in the constellation Boötes), Spica (in Virgo) and Denebola (in Leo), which together make the Spring Triangle asterism.
