of is an imaginary line on which the earth rotates it's links up the two poles dunphy axis and the earth are tilted at an angle love twenty three and half degrees during a revolution the tilting have the axis results in direct sunlight falling on different places during different seasons this causes variation in the duration a days nights and seasons relationship between the location the overhead sun and the seasons similarly the revolution of the sun and the tilting up the axis results in different anger love the sun during different periods when the sun is directly overhead. We call this the overhead some at this time the earth's surface and the mid-day. Sun forms a 90 degree angle different locations have the overhead sun results in variations in the amount of solar radiation received in different areas and at different periods spring equinox on the 21 or 22 of March the overhead son is over the equator the equator receives the largest amount of solar radiation at this time the northern hemisphere is in the spring equinox while the Southern Hemisphere is in the autumn equinox the Angolans this on decrease towards the poles on this day the two hemispheres receive a similar amount of solar radiation and the length of day and night is the same at all places on the earth after this a it is spring in the northern hemisphere where the day is longer than the night in the Southern Hemispheres it's becomes autumn when the day is shorter than the night summer solstice on the 21 or 22 of June the overhead sun he's over the tropic have cancer it receives the largest amount of solar radiation at this time the northern hemisphere is in the summer solstice