ATMOSPHERE
| The Earth's atmosphere is mainly a mixture of gases, 78 per cent nitrogen and 21 per cent oxygen. There are five layers to the atmoshere; troposphere, stratosphere, mesosphere, thermosphere, and ionosphere at the highest level. The atmosphere is 120 miles thick. Composition of the Earth's atmosphere is the same at all altitudes, but clouds of water vapour are concentrated only in the troposphere. At any given moment, half the Earth's surface is covered with clouds. The Earth's atmosphere acts as a modulator of temperatures. Its 23.4° inclination to its axis produces the seasonal effect, summer, autumn, winter, and spring. Throughout the annual seasonal cycle, the equator receives more sunlight than any other part of the planet, while the poles receive the least. |