Autumn has officially begun! In the Northern Hemisphere, the autumnal equinox falls on September 23 this year, marking the beginning of autumn and the Earth and Sun"s unique positions. Today is one of the two moments in the year when day and night are equal in length, thanks to the Sun"s location exactly above the Equator. The same celestial phenomenon applies to the Southern Hemisphere, but it is their vernal equinox as they head into spring.
Autumnal equinox
Today in History
More Desktop Wallpapers:
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Sunset on the Valley of the Moon
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One rare streak
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Happy Pi Day!
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Wind River, Arctic National Wildlife Refuge, Alaska, USA
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Independence Day of the Argentine Republic
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Why is this cliffside ablaze?
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Ludlow aglow
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More of a moustache than a beard?
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Blending in nicely
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Naxos, Cyclades, Greece
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Cades Cove, Great Smoky Mountains National Park, Tennessee, USA
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A breathtaking cave when it’s cold
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World Bee Day
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Stones on the solstice
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A wave of remembrance
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Castell Coch, Wales
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Shell-ebrating sea turtles
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Pumpkin field, Victoria, British Columbia, Canada
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Misty mountain hop
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Yi Peng lantern festival, Chiang Mai, Thailand
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International Archaeology Day
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Gespensterwald, Nienhagen, Germany
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World Rivers Day
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Bohemian waxwings
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Icon of the Highlands
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Two hungry baby beavers
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Staghorn coral in shallow ocean
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All is calm
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Delicate Arch, Arches National Park, Utah, United States
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Lago Pehoé, Torres del Paine National Park, Chile