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Sandwiched between blazing summer and chilly wintertime , autumn is the " chill off " time of year . Nighttime come earlier , temperatures start to drop and most vegetative growth decrease . fauna begin to prepare for the dearth of solid food that generally comes during the winter , gather supplies or traveling to affectionate clime .
The cycle ofseasonsis triggered by Earth ’s controversy on its axis and the satellite ’s compass around the sun . When the axis head toward the Sunday , that hemisphere experiences summer . The hemisphere tilt away from the sun live winter . After Earth travels a stern of the way of life around the sun , the axis vertebra is point along the planet ’s path , parallel to the star .
A illustration of the Earth’s position during four seasons.
From our perspective here onEarth , the sun travels along an imaginary line call the ecliptic , which marks the planing machine in which the planets orbit thesun . Another imaginary line is the heavenly equator , which is a projection of Earth ’s equator into space . For half the year , during summertime in the Northern Hemisphere , the sun come along to move along the ecliptic northward of the celestial equator . During the other half of the year , it is likely south of the heavenly equator .
The exact mo when the sunlight come along to arrive at the crossroad of the ecliptic and the celestial equator is when autumn begins . At Earth ’s equator , the Dominicus is directly overhead at noontide .
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A illustration of the Earth’s position during four seasons.
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An aerial view of a forest during its change to autumn foliage.
These moments in time are calledequinoxes , and the length of daytime and night are approximately the same , agree to theNational Maritime Museum . The word " equinox is derived from two Latin words : aequus(equal ) andnox(night ) .
24-hour interval and night are not incisively 12 hours each . Because of the way the sunshine ’s light refracts in Earth ’s atmosphere , we can in reality see the sun for a few minutes before its disk rises and for a few minute after it has truly set . Thus , daylight on any yield sidereal day lasts close to six or seven minutes longer than it ostensibly should .
The different definitions of autumn
The autumnal equinox is the start of " astronomical autumn , " which end with the start ofwinter . In the Northern Hemisphere , that is from around Sept. 23 to about Dec. 21 , though it varies from year to year , concord to theMET Office . In the Southern Hemisphere , the season runs from about March 20 to June 21 .
Weather forecastersand some countries define the time of year as " meteorologic fall " by the three calendar month in which the weather change . In the Northern Hemisphere , this is September , October and November . In the Southern Hemisphere , meteorological autumn take place in March , April and May .
Falling temperatures
fall brings a nip in the air . How much of a change is felt up calculate on the location of the area on Earth . Regions near the equator experience fairly constant temperatures throughout the yr , while those far north or south experience great variant . This is because the equator gets a consistent amount of sunlight . Far northern and southerly regions get less sun due to the curve of the sunlight , according to theAtmospheric Radiation Measurement ( ARM)program .
For the continental United States , temperatures during fall ( September through November ) average out 55.9 degrees Fahrenheit ( 13.3 . degrees Celsius ) , according to theNOAA — which is a 2.1 F ( 1.2 light speed ) increase above the 20th - century norm .
What’s in a name?
Autumn , of course , is also known as fall , primarily in the United States . Ambivalence over the name of the third time of year of the year ponder its status as arelatively new concept . Many culture only recognize two seasons , such winter and summer or winter and bounce .
The period of conversion between summer and winter came to be have intercourse as " harvest . " " Autumn , " a Romance Holy Writ , first appeared in English in the tardy fourteenth 100 , and gradually win on " harvest . " In the 17th one C , " downslope " get along into use , almost certainly as a poetical full complement to " spring , " according to the Koran " Folk Taxonomies in Early English " ( Fairleigh Dickinson University Press , 2003 ) by Earl R. Anderson
Why do leaves change color?
In response to parky temperature and the changes in day , get out stop producing green - tint chlorophyl , which allows them to fascinate sunlight and make energy . Because chlorophyl is sensitive to the cold , certain weather conditions like early frost will twist off production more apace .
Meanwhile , orange and xanthous pigments called carotenoid – also found in orangish carrots – glint through the leaves ' wash out green . The red color in some leaves comes from anthocyanins , which unlikecarotenoids , are only produced in the fall , concord to theState University of New York College of Environment . They also give color to strawberries , red apples , and plum .
But red leaves are also signal of distraint . If you see leave of a Sir Herbert Beerbohm Tree turning crimson early on , in late August , the Sir Herbert Beerbohm Tree is most likely suffering from afungusor perhaps a ding from a rash gadget driver .
Autumn in different cultures
Autumn is generally affect as the close of the growing season . Also known as the harvest season , autumn James Usher in a meter of celebration for many husbandry cultures when they pucker in their crop .
" Autumn , or capitulation , is ample with dissimilar festivals which mainly celebrate the restoration of light , harvest , and , like spring , rebirth through death,“Cristina De Rossi , an anthropologist at Barnet and Southgate College in London , told Live Science . For example , the harvest time festival in the United Kingdom is a prison term when people give thanks for the fruits of the ground and compile food for thought to donate to those in motive .
" Harvest celebrations tend to combine giving thanks with prayers for succeeding abundance , to appease the god(s ) and ensure successful crops , " said De Rossi . Another instance of this would be Thanksgiving , which is celebrated in the United States . It is a historical commemoration , but it has a spiritual proportion strongly associated with return and giving congratulations for what has been bestowed upon us , explained De Rossi .
De Rossi also points out these celebrations as further examples of gloam ’s tie with giving thanks and rebirth :
Additional resources
For more on the science of autumn check out the State University of New York College of Environmental Science and Forestry webpage on : Why Leaves Change Colorand NOAA ’s webpage on thechanging season .
Bibliography
