What is the difference between hot weather and cold weather? Why is it cold and why is it hot?

There is no difference in the composition of the air. The components are nitrogen (about 78%), oxygen (about 2 1%), rare gas (about 0.94%), carbon dioxide (about 0.03%) and other gases and impurities (about 0.03%). Cold and hot are caused by sun irradiation, and light energy itself is a kind of energy. On March 2 1 every year, the sun points directly at the equator, which is the vernal equinox, so it is spring in the northern hemisphere; Around June 22, the sun points directly at the Tropic of Cancer, which is the summer solstice; Around September 23, the sun pointed directly at the equator, which was the autumnal equinox; Around February 22, 65438, the sun pointed directly at the Tropic of Cancer.