The seasons are the result of the tilt of the Earth's axis as it rotates around the sun. For example, when the northern hemisphere is tilted towards the sun, it will receive a greater amount of sun than the southern hemisphere: it will therefore be summer time in the northern hemisphere and winter time in the southern hemisphere. The phenomenon will be reversed in the next six months. This rotation of the Earth around the sun lasts one year. Photo credit: Luca Bravo