Earth's orbit also undergoes precession, which is a slow, cyclical movement of its orbit around the sun. This precession occurs over a period of about 26,000 years and affects the timing of the seasons. Currently, the Earth is closest to the sun during the Northern Hemisphere winter, which makes winters milder and summers hotter. Much closer than people can imagine, by 2050 it will be impossible to live in the Northern Hemisphere of the Earth.