Where is the circle of illumination during the solstices

At any one moment in time, one half of the Earth is in sunlight, while the other half is in darkness. The edge dividing the daylight from night is called the circle of illumination.

The orbit of the Earth around the Sun is called an Earth revolution. This celestial motion takes Further, the Earth's orbit around the Sun is not circular, but oval or elliptical see Figure 6h An elliptical orbit causes the Earth's distance from the Sun to vary over a year. On January 3, perihelion , the Earth is closest to the Sun The Earth is farthest from the Sun on July 4, or aphelion The average distance of the Earth from the Sun over a one-year period is about The ecliptic plane can be defined as a two-dimensional flat surface that geometrically intersects the Earth's orbital path around the Sun.

On this plane, the Earth's axis is not at right angles to this surface, but inclined at an angle of about Figure 6h-3 shows a side view of the Earth in its orbit about the Sun on four important dates: June solstice , September equinox , December solstice , and March equinox. Note that the angle of the Earth's axis in relation to the ecliptic plane and the North Star on these four dates remains unchanged.

Yet, the relative position of the Earth's axis to the Sun does change during this cycle. This circumstance is responsible for the annual changes in the height of the Sun above the horizon. It also causes the seasons , by controlling the intensity and duration of sunlight received by locations on the Earth. Figure 6h-4 shows an overhead view of this same phenomenon. During the two equinoxes, the circle of illumination cuts through the North Pole and the South Pole.

On the June solstice, the circle of illumination is tangent to the Arctic Circle The Arctic Circle is in 24 hours of darkness during the December solstice. On June 21 or 22 the Earth is positioned in its orbit so that the North Pole is leaning During the June solstice also called the summer solstice in the Northern Hemisphere , all locations north of the equator have day lengths greater than twelve hours, while all locations south of the equator have day lengths less than twelve hours see Table 6h On December 21 or 22 the Earth is positioned so that the South Pole is leaning During the December solstice also called the winter solstice in the Northern Hemisphere , all locations north of the equator have day lengths less than twelve hours, while all locations south of the equator have day lengths exceeding twelve hours see Table 6h On September 22 or 23, also called the autumnal equinox in the Northern Hemisphere, neither pole is tilted toward or away from the Sun Figures 6h-3 , 6h-4 , 6h-6 and see animation - Figure 6h At equinox, both polar regions receive the same illumination.

At the Equator, the Sun is directly overhead at local noon at both the vernal and autumnal equinox. The Tropic of Cancer and the Tropic of Capricorn denote latitudes where the Sun is directly overhead at local noon at a solstice. Along the Tropic of Cancer, the Sun is directly overhead at local noon at the June 21 solstice the Northern Hemisphere's summer solstice and the Southern Hemisphere's winter solstice.

Along the Tropic of Capricorn, the Sun is directly overhead at local noon at the December 21 solstice. Although the most dramatic changes in illumination occurs within the polar regions, the differences in daylight hours—affecting the amount of solar energy or solar insolation received—cause the greatest climatic variations in the middle latitude temperate regions.

The polar and equatorial regions exhibit seasonal patterns, but these are much more uniform i. Differences in illumination are a more powerful factor in determining climatic seasonal variations than Earth's distance from the Sun. Because the majority of tropospheric heating occurs via conduction of heat from the surface, differing amounts of sunlight differential levels of solar insolation result in differential temperatures in Earth's troposphere that then drive convective currents and establish low and high pressure areas of convergence and divergence.

See also Atmosphere observation ; Atmosphere, composition and structure ; Atmospheric circulation ; Atmospheric optical phenomena ; Latitude and longitude ; Meteorology ; Precession of the equinoxes ; Seasons.

Hancock, P. Skinner, eds. On the contrary, the portion which is away from the sunlight experiences night. The orbit of the earth is elliptical. Because of the oval machine setup of its orbit, the range between the sun and the world carries on altering throughout the year. Occasionally, the planet is hassle-free to the sun and, at various other times, it is too far from the sun.

When the size of night and day is equal in all parts of the planet, such a day is called equinox. This happens on March 21st as well as September 23rd. On March 21st, the South Pole of the planet is in the direction of the sunlight.

Because of this, this is the springtime season in the northern hemisphere and also autumn in the southern hemisphere. On September 23rd, the North Post is towards the sun.

Consequently, this is the springtime season in the southerly hemisphere and also fall in the northern hemisphere. Therefore, it is the lengthiest day and also the fastest night in the northern hemisphere. On the other hand, it is the quickest day and longest night in the southern hemisphere. It is the summertime period in the northern hemisphere and the winter months in the southern hemisphere. Between March 21st to September 23rd, the North Pole obtains sunshine constantly for around six months.

On December 22nd, the South Pole inclinations towards the sunlight and the Tropic of Capricorn obtain straight sunlight. Consequently, it is the longest day as well as the quickest evening in the southerly hemisphere. However, it is the fastest day as well as the most extended evening in the northern hemisphere.

It is the summer season in the southern hemisphere and wintertime in the northern hemisphere. Between September 23rd to March 21st, the South Pole receives sunshine continuously for around six months.

Half would have been frequently in daylight if there had been no circumvolution of the Earth, and the other half would have been frequently in the dark. The portion under sunlight would have been as well heated. On the other hand, the section in the night would have been cooling chilly.

Such unwanted temperature can have made it impossible forever to prosper on our Earth. Current Hazards. Rivers and Lakes. Climate and Past Weather. The Seasons We all know that the Earth makes a complete revolution around the sun once every days, following an orbit that is elliptical in shape. The Relationship Between Length of Day and Temperature There is a lag between the longest day of the year and the warmest average temperatures for most mid and high latitude locations.

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