Autumn
Channel: all the knowledge of the universe PRINCIPIA
Date: 2021-12-05

Autumn, by Wikipedia https://en.wikipedia.org/wiki?curid=3049 / CC BY SA 3.0

#Autumn
#Etymologies
The variety of colours between the trees and the forest floor is like a giant mural in autumn, particularly out of cityscapes Autumn, also known as fall in North American English, is one of the four temperate seasons.
Outside the tropics, autumn marks the transition from summer to winter, in September （Northern Hemisphere） or March （Southern Hemisphere）.
Autumn is the season when the duration of daylight becomes noticeably shorter and the temperature cools considerably.
Day length decreases and night length increases as the season progresses until the Winter Solstice in December （Northern Hemisphere） and June （Southern Hemisphere）.
One of its main features in temperate climates is the striking change in colour for the leaves of deciduous trees as they prepare to shed.
Some cultures regard the autumnal equinox as "mid-autumn", while others with a longer temperature lag treat the equinox as the start of autumn.
In the English-speaking world, autumn traditionally began with Lammas Day and ended around Hallowe'en, the approximate mid-points between midsummer, the autumnal equinox, and midwinter.
Meteorologists （and Australia and most of the temperate countries in the southern hemisphere） use a definition based on Gregorian calendar months,
with autumn being September, October, and November in the northern hemisphere, and March, April, and May in the southern hemisphere.
In North America, autumn traditionally starts with the September equinox （21 to 24 September） and ends with the winter solstice （21 or 22 December）.
Popular culture in the United States associates Labor Day, the first Monday in September, as the end of summer and the start of autumn; certain summer traditions, such as wearing white, are discouraged after that date.
As daytime and nighttime temperatures decrease, trees change colour and then shed their leaves.
In traditional East Asian solar term, autumn sta...