Focus on Arts and Ecology

Purpose of the articles posted in the blog is to share knowledge and occurring events for ecology and biodiversity conservation and protection whereas biology will be human’s security. Remember, these are meant to be conversation starters, not mere broadcasts :) so I kindly request and would vastly prefer that you share your comments and thoughts on the blog-version of this Focus on Arts and Ecology (all its past + present + future).

Premium Blogger Themes - Starting From $10
#Post Title #Post Title #Post Title

Why the equinox ushers in the arrival of fall

Posted by Focus on Arts and Ecology on - -
0 nhận xét

Every six months, the equinox splits Earth's day almost in half. Here's how it happens—and why people have celebrated it since ancient times. 

SEPTEMBER 21, 2023

A flock of swans fly at sunrise on the first day of fall in London's Richmond Park. The autumnal and vernal equinoxes signal the beginning of fall and spring, respectively. They're caused by a combination of Earth's orbit and its axial tilt.
PHOTOGRAPH BY PETER MACDIARMID, EYEVINE/REDUX

Every six months, once in March and again in September, an equinox splits Earth’s day almost in half, giving us about 12 hours of daylight and 12 of night.

On September 23, 2023, the autumnal equinox will signal the coming of fall for the Northern Hemisphere. Then, in March, nature will once again bring us the vernal equinox, the time of year that ushers in spring in the North. Those dates are swapped for the vernal and autumnal equinoxes in the Southern Hemisphere. (Here's why each season begins twice.)

What are equinoxes? What causes these astronomical events? Find out how they influence the seasons and hours of daylight on each planet.

Why do equinoxes happen?

Our planet normally orbits the sun on an axis that’s tilted 23.5 degrees, meaning that the hemispheres trade off getting more warmth from the sun. Two times a year, Earth’s orbit and its axial tilt combine so that the sun sits right above Earth’s Equator, casting the dividing line between the light and dark parts of the planet—the so-called terminator, or twilight zone—through the North and South Poles.

The terminator doesn’t perfectly divide the planet into dark and light; Earth’s atmosphere bends sunlight by 37 miles (60 kilometers), which equals half a degree. That means one half of the planet is still a little more lit than the other, even on an equinox.

Earth isn’t the only planet that experiences equinoxes: Every planet in our solar system has them. In 2009, the Cassini probe in orbit around Saturn captured an equinox on the ringed planet. As on Earth, equinoxes occur every half-year on Saturn, but that equals 15 years on Earth, making Cassini's photo session a unique event.

Left: Afghan horsemen compete for a goat carcass during a game of Buzkashi in Mazar-i Sharif. Each spring, hundreds of thousands of people flock to this city in northern Afghanistan to celebrate Nowruz, a spring festival that coincides with the vernal equinox.
PHOTOGRAPH BY MASSOUD HOSSAINI / AFP, GETTY IMAGES
Right: View of the sun behind the Temple of the Seven Dolls in the Mayan archaeological site of Dzibilchaltun, in Merida, Yucatan state, Mexico, on March 21, 2021, during the spring equinox.
PHOTOGRAPH BY HUGO BORGES, AFP/GETTY IMAGES

Marking the equinox

Ancient cultures have tracked the equinoxes in different ways over the millennia. From constructed monuments, like pyramids, to stone engravings that acted as calendars, to churches that incorporated the sun into their architecture, civilizations marked the passing of the sun and the seasons with great accuracy.

Some cultures continue to celebrate the equinox today, like the Lakota Tribe of the U.S. Midwest. The Lakota connect the earth with the sky by making tobacco from the red willow tree, which matches the Dried Willow constellation, where the sun rises on the spring equinox. They smoke this sacred tobacco in a ceremony marking the return of longer days.

And at Stonehenge's equinox celebrations in England, druids, pagans, and anyone else who wants to join in gather to witness the sunrise over the ancient stones.

(Sources: National Geographic)

Posted in
    Powered By Blogger