The earth revolves around the sun in the speed of 30 kilometers per second, around the sun takes 365 days to five forty-eight 46 seconds, there is just one year, called the tropical year on The earth revolves around the sun's orbit is an ellipse, the long diameter and short diameter difference, can be approximated as a perfect The sun was a focus of the ellipse, and the focus is not on the ellipse center, so the distance between earth and the sun is sometimes a bit closer, sometimes a little At the beginning of the January, the nearest to the earth, 147100000 kilometers, it is called Seven early Earth farthest from the sun, is 152100000 kilometers, it is called In fact, when the earth is at perihelion, the northern hemisphere winter, the southern hemisphere summer at aphelion; when, the northern hemisphere summer, the southern hemisphere This shows, the changes of the seasons and the perihelion and aphelion independent