Why Does The Earth Have Seasons?
What do we call the days when the earth is at its most extreme?
If The Earth was standing up right then every day would be twelve hours long and every month would be the same temperature. There would be no winter and no summer.But the Earth is not standing straight up! It is tilted slightly, about 23 and a half degrees from true north and south. It's this tilt that causes the seasons, and not the distance from the Earth to the Sun. So as the Earth travels around the Sun, in June the Northern part of the Earth is leaning closer to the Sun causing long days and warmer weather.Like wise during December the Southern part is tilted towards the Sun giving that part of the earth longer days and warmer weather.At the North and South poles this tilt causes the Sun to stay in the sky 24 hours a day during summer. It doesn't even set in the middle of the night!The opposite happens in the winter. The Sun doesn't rise at the poles meaning that they're in constant darkness.We call these days when the earth is at its most extreme, the Solstice. For the Northern hemisphere the Summer solstice occurs on June 21st and the winter solstice on December 21st.So between these two dates there must be a period when the earth is equal right across the whole planet. These days are called the Equinox and occur on March 21st and September 21st each year.We have drawn imaginary lines running around the Earth. At the centre we call it the equator. This is half way between the north and south poles. On both equinoxes the Sun will be directly overhead here. At 23.5° north we have a line called the tropic of Cancer and at 23.5° south we have another one the tropic of Capricorn. It is at these points that the Sun will be directly overhead on the solstice.The part between these two lines is known as the tropics as the Sun is always high in the sky and so they do not have noticeable seasonal differences.It is only above these lines that seasonal changes are more prevalent.Further north is a line called the Arctic Circle; it is at this line that the Sun does not rise on December 21st the Winter solstice and does not set on June 21st the summer solstice.The southern hemisphere has the Antarctic Circle where the opposite is true. But funnily enough, regardless of where you stand on the Earth, throughout the year every part of the Earth receives exactly the same amount of daylight hours. It's just a bit warmer nearer the equator. So pick your holiday dates carefully!For more facts and figures about the planets and our solar system, check out our other films on the VideoJug website.