![]() ![]() ![]() Today, we celebrate the equinox as an astronomical event caused by Earth’s tilt on its axis and its motion in orbit around the Sun. Additionally, earlier civilizations built the first observatories, like Stonehenge in Wiltshire, England, and the Intihuatana stone in Machu Picchu, Peru, to follow the Sun’s annual progress. They knew that the Sun’s path across the sky, length of daylight, and location of sunrise and sunset all shifted in a regular way throughout the year. The people of ancient cultures used the sky as a clock and calendar. We will also feel cooler days with chillier winds, and dry, falling leaves. In the Northern hemisphere, the September equinox marks the start of a period bringing us later sunrises and earlier sunsets. The September equinox occurs sometime between September 21 and 24. But on these special days – the spring and fall equinoxes – the Sun shines almost equally on the Northern and Southern hemispheres. The March equinox happens sometime between March 19 and 21. That’s because Earth’s axis is tilted with respect to the Sun-Earth plane. The rest of the year, the Sun shines unevenly over the Northern and Southern Hemispheres. This only happens twice in Earth’s year-long trip around the Sun. Spring twilight at the North Pole begins a few weeks before the vernal, or spring, equinox in March, when the Sun rises above the horizon again. Credit: NASA/JPL-CaltechĪlong with marking the beginning of astronomical fall, the Sun will be exactly above Earth’s equator, moving from north to south, making day and night nearly equal in length – about 12 hours – throughout the world.Īt the North Pole, over the upcoming days, the Sun will sink below the horizon for a kind of twilight from now until sometime in October when it will be completely dark, according to NASA solar scientist Mitzi Adams. During the equinoxes, both hemispheres receive equal amounts of daylight. An illustration of the March (spring) and September (fall or autumn) equinoxes. The Seasons, the Equinox, and the Solstices - National Weather Here are 5 things to know about the autumnal. 1, however, the September (or fall) equinox gives us the green light to welcome the astronomical fall season in the Northern Hemisphere (and astronomical spring season in the Southern Hemisphere). In meteorology, the fall season begins on Sept. Why Does the Spring Equinox Fall on Different Dates If you thought that the Spring Equinox only ever occurred on March 21, you may be dating yourself.
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