The literal translation of the word atmosphere is "sphere of vapors." The Earth's atmosphere is a protective sphere of vapors or air that surrounds the Earth and provides it with a layer of insulation from the harmful rays of the sun. It is a vital part of the Earth and has changed dramatically since the beginning of time. The earth's atmosphere had gradually changed since the Earth's birth approximately 4.6 million years ago.
             In the beginning, Earth's composition was very different than how it exists today. A long time ago the Earth's atmosphere was very similar to today's Venus and Mar's atmosphere. It had about 95% carbon dioxide, 2-3% nitrogen, and very little, less than 1% oxygen. Today the Earth contains 79% nitrogen, 21% oxygen, and 3% water vapor. It is evident that many events happened over billions of years that have contributed to this change in the Earth's atmosphere. Earth had developed so drastically because of the large amounts of dust and gas cloud within the Milky Way galaxy. The Earth grew larger as huge meteorites hit it, and the surface was covered with dust. Volcanoes began to form and emitted lava, ash, and most importantly gases. Carbon dioxide, water vapor, and nitrogen were released into the atmosphere from the volcanoes. This process is called outgassing and took place within the first million years or so of the Earth's formation. Then, about 4 billion years ago, the planet cooled, and the outgassed water vapors condensed into clouds. It rained and produced the oceans, and even enough to cover 95% of the Earth. Also, because it rained, there was less carbon dioxide in the atmosphere. The carbon dioxide was lost over billions of years, as the ocean formed there was a chemical reaction in which carbon dioxide and water formed carbonic acid. It is shown in the equation CO2 + H2O = H2CO3. The carbonic acid dissolved oceanic rock into sand, silt, and mud. It is evident because of this geochemical process occurre...