Earth has seasons because its axis is tilted. Earth rotates on its axis as it orbits the sun, but the axis always points in the same direction.
December: Summer south of the equator, winter north of the equator. The sun shines directly on the southern hemisphere and indirectly on the northern hemisphere.
March: Autumn south of the equator, spring north of the equator. The sun shines equally on southern and northern hemispheres.
June: Winter south of the equator, summer north of the equator. The sun shines directly on the northern hemisphere and indirectly on the southern hemisphere.
September: Spring south of the equator, autumn north of the equator. The sun shines equally on the southern and northern hemispheres.
Fig. 5 The position of Earth at different times of the year. 396
