Revolution is the movement of the Earth in its own orbit around the sun. This means that the earth rotates on its own axis while moving in its orbit around the sun. One complete revolution takes 3651/4 days in ayear or 366 days every four years in aleap year. The revolution of the earth causes the following:
i) The four seasons: Spring, summer, autumn and Winter.
The revolution of the sun causes seasons because it changes the apparent p[ossotion of the overhead sun. the movment of the sun is tgherfore accompanied by changes inb the heat blt. When the sun is over head, high temperatures are experinced on earth’s surface. The sun is overhead at the equator twice in a year. Therfore equitorial regions are warm during most of the year, amnd do not experince very cold temperatures. They tend to experince on long warm season interrupted by periods of drought and rainfall each year. Regions far away from the equator, in middle and high latitudes, have for seasons-spring, summer, autumn and winter. Summer and winter are usually the longest. Autumn and spring are shorter seasons which occur between winter and summers.
(Fig 1.1)
ii) Varying lenths of day and night at different times of the year
The Earths axis is inclined at an angle of 661/2o . this eliptic plane is the path which the Earth revolves around the sun. its this inclination that causes differences in the lenth of days and nights in the nothern and southern hemisphere. When it is summer in the nothern hemisphere, longer daylight is experinces than night time. On 21 june, all areas in the northen hemisphere experince the longest day and shortest night. Similarly, during the southern Summer, days become longer than nights, reaching aclimax where areas south of the Antarctic Circle experince 24 hours of daylight.
iii) Changes in the altitude of the midday day sun.
The movement of the Earth in its orbit around the sun creates apparent