It is not the rotation round the Sun that causes the seasons.It is the tilting of the World on its axis that creates the seasons. For instance, when the northern hemisphere tilts towards the Sun, the Sun's rays have less distance to travel to Earth through the atmosphere and loses less heat and is warm. At the same time, because the Southern Hemisphere is then tilted away from the Sun, the Sun's ray lose a lot of heat as the rays have further to travel through the atmosphere and is therefore cooler, bringing on Winter in the southern hemisphere.So while Britain is in Winter in December, Australia is enjoying their Summer.