For many ancient civilizations these solar changes not only dictated the beginning of seasons but also when to plant and harvest crops. People have been tracking the sun's movements for thousands of years, often incorporating equinoxes into cultural and religious traditions. (Image credit: © Egypt Ministry of Antiquities) Who discovered the equinoxes? The sun set over the right shoulder of the Sphinx during the spring equinox in 2020. In fact, every planet in the solar system has them when the planet's orbit and tilt with respect to the sun result in both hemispheres receiving roughly equal amounts of light. The converse is true in September, when the northern half of the planet descends into the colder months of autumn and the southern half enters spring.Įarth is not alone in experiencing equinoxes. At the same time, the Southern Hemisphere shifts into autumn. In the Northern Hemisphere, the March equinox heralds the beginning of spring, and is referred to as the spring or vernal equinox (vernal comes from the Latin term "ver" for spring). However, the meteorological beginning of these seasons is March 1 and Sept. The equinoxes mark the astronomical beginning of spring or autumn, depending on the hemisphere. The planet's orientation toward the sun is also constantly shifting, tweaking the timing of the equinox.
These shifting dates are because an Earth year is not exactly 365 days: There is an extra quarter of a day (6 hours) that accumulates each year, causing the date of the equinox to shift. They happen around or on March 20 and Sept. And, because of how sunrise and sunset are defined, the equilux occurs a few days before the spring equinox and a few days after the autumn equinox, according to the U.K.'s Met Office.Įquinoxes don't necessarily occur on exactly the same day each year. National Weather Service.Įquilux ("equal light"), on the other hand, is the term for when day and night are exactly equal. "On the equinox and for several days before and after the equinox, the length of day will range from about 12 hours and 6 and one-half minutes at the equator, to 12 hours and 8 minutes at 30 degrees latitude, to 12 hours and 16 minutes at 60 degrees latitude," according to the U.S. Also, the atmosphere refracts the sun's light and it continues to travel to "nighttime" Earth for a short period, even after the sun has dipped below the horizon. And because the sun is a disk rather than a point-source of light, Earth sees just a few more minutes of extra light (rather than darkness) during an equinox. This is because sunrise occurs when the tip of the sun edges over the horizon, and sunset is defined as the moment when the other edge of the sun disappears under the skyline. However, day and night are still not exactly equal during an equinox, according to EarthSky, although it is very close.ĭuring an equinox, Earth gets a few more minutes of light than darkness. Day and night are perfectly balanced in this spring equinox photo snapped from space Why the autumn equinox doesn't fall on the same day every year How do flat-Earthers explain the equinox?
0 kommentar(er)
