Knowra Autumn Autumn Autumn is the temperate season between summer and winter in one hemisphere, marked by shortening days and cooling temperatures. In common usage, it is also called fall.
Axial tilt : The angle between a body's rotational axis and the axis of its orbit. As a hemisphere tilts away from the Sun, autumn brings less direct sunlight and shorter days.
Photoperiodism : The biological response of organisms to the relative lengths of day and night. Changing day length cues many autumn events, including dormancy and migration.
Harvest festival : A celebration marking the gathering of crops and the close of the agricultural growing season. Many communities hold harvest celebrations in autumn, when major crops are gathered.
Thanksgiving : A holiday observed in the United States and Canada, centered on gratitude and communal meals. Its North American dates fall during the autumn harvest season.
Solar declination : The angular position of the Sun north or south of Earth's equator. Its seasonal shift changes the Sun’s height and the energy received at the surface.
Leaf senescence : The final stage of leaf development, involving cellular breakdown and nutrient recovery before leaf death. It leads deciduous trees to withdraw nutrients and shed leaves in autumn.
Harvest : The gathering of mature crops from fields or other growing sites. Autumn is the harvest period for many temperate crops, including apples and squash.
Halloween : A holiday observed on October 31, associated with costumes, trick-or-treating, and supernatural themes. Its timing and imagery are closely linked to autumn in the Northern Hemisphere.
Equinox : An astronomical event when the Sun crosses the celestial equator, making day and night nearly equal in length. The autumnal equinox marks autumn’s astronomical beginning in each hemisphere.
Anthocyanin : A class of plant pigments that produce red, purple, and blue colors. These pigments create many of autumn’s red and purple leaf colors.
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