Earth Revolution and Sun Angle

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This animation shows the changing orientation of the earth's axis as the earth revolves around the sun through the year. Note that the angle of axial tilt remains the same for all times of the year. In addition, the earth's axis always points in the same direction as it revolves around the sun. These two factors causes variations in the angle that the sun's rays makes with respect to the earth on different days of the year. On June 22 the earth is tilted towards the sun and perpendicular rays strike at 23.5 degrees north latitude. Moving to September, the earth's axis is parallel with the sun's and perpendicular rays strike at the equator. By the time December rolls around, the axis in the southern hemisphere is inclined toward the sun and perpendicular rays strike 23.5 degrees south latitude. During March the conditions are the same as September. Finally, the earth completes its path around the sun and the northern hemisphere receives the highest sun angles.