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Rotation And Revolution Of The Earth
Rotation Of The Earth
Rotation :Rotation is when planetary bodies rotates on its own axis about a fixed point.
Revolution Of The Earth
Revolution : is when planetary bodies revolves round the sun or the moon in an elliptical orbit.
For example, the earth
Earth : the earth revolves round the sun in an elliptical orbit.
During the earth revolution, the earth is inclined at an angle of 66½ to the plane of elliptical.top↑
It takes the earth 365¼ days , that is, a year for one complete revolution, the ¼ or 6 hours is added up in every four years to make a leap year.
Difference Between The Earth Rotation And The Earth Revolution
Note : rotates is to rotation while revolves is to revolution.
a] The earth rotates on its axis while it revolves round the sun along its orbit.
b] The earth rotates through an angle 360° in 24 hours, that is, one day while it revolves round the sun in 365¼ days ( a year).
c] The rotating earth is inclined at an angle of 23½ along its axis while the revolving earth is inclined at an angle of 66½ to the plane of elliptical.top↑
4] The earth rotation causes day and night while the earth revolution causes season .
5] Rotation of the earth is 1 hour between two meridians with 15° apart while the revolution of the earth cause change in the altitude of the midday sun.
Effect Of Revolution Of The Earth
1] Varying length of day and night : due to the inclination of the earth axis on the plane of elliptical,
Plane of elliptical is the plane which the earth orbits round the sun.
The earth is inclined at angle which varies the length of day and night.top↑
In the northern hemisphere, winter (December), as we progress northward the hours of darkness gradually increases, at the arctic circle 66½N the sun never rises which causes the total darkness for the whole day. Whereas in the southern hemisphere, the period of daylight increases towards the south pole in December 22nd but the region experience summer.
In the summer (june), daylight increases in the northern hemisphere as we move towards the north pole, at the arctic circle, the sun never sets at mid summer (june) and there is a complete 24hours period of continuous daylight,top↑
During summer, the region of arctic circle is popularly referred to as land of midnight sun.
In the southern hemisphere, the period of darkness increases towards the south pole in June 21st but the region experience winter.
2] It causes season : In tropical areas like west Africa, there are two seasons, the rainy and the dry season, for example in Nigeria, the is only two seasons, it is either raining or dry season
But in temperature countries, like USA, the revolution of the earth causes four seasons, winter, spring, autumn and summer.
3] it determines a year : it is the time taken by the earth to move round the sun, that is, to complete it orbit that determines a year, it could take the earth 365 days or 365¼ or plus 6 hours to complete its orbit.top↑
4] Changes the altitude midday of the sun : due to the revolution of the earth round the sun with its axis inclined at 66½ to the plane of elliptical changes the apparent altitude of the midday sun.
The sun is vertically overhead at the equator on two days each year, these two days are 21st on march ( spring equinox) and 23rd of September ( autumn equinox), equinox means equal nights because on these two days all part of the world have equal day and night.top↑
After march 21, the sun appears to move towards north and is vertically overhead in the tropical cancer at an inclination angle of 23½°N on about june 21, this is known as the june or summer solstice when the northern hemisphere have longest day and shortest night.
Later in december 22nd the sun appears to move southward and vertically overhead at the tropical capricorn at an inclination angle of 23½°S, this is known as december or winter solstice when the southern hemisphere have its longest day and shortest night.top↑
The tropic thus mark the limit of overhead, for beyond these, the sun is never overhead at anytime of the year, such regions are marked by distinct season changes, which are spring, winter, autumn and summer.
5] Effect on temperature : seasonal changes thus have effect on temperature, summer is usually associated with much heat and daylight and winter with cold and darkness.
This happens because the sun is higher in the sky than in winter.
When the sun is overhead, its rays is almost vertically on the earth, concentrating its heat on small area, therefore temperature rises and summer are always walm.top↑
During winter, the oblique(slant) rays of the sun coming through the atmosphere lies directly and have much of the heat been absorbed by the atmosphere impurities and water vapour,
The sun's ray fall faintly and spread over a great area.
Hence, days are longer than night during Sumner while night are longer than days during Winter
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