The earth is surrounded by an ocean of air called the atmosphere. People dwell on the floor of that ocean. It is hundred of miles deep and becomes thinner the farther away from the earth’s surface. It consists of nearly five quadrillion tons of air. The composition of air is seventy eight percent nitrogen, twenty one percent oxygen, and almost one percent argon. Other elements which are found in earth’s atmosphere in tiny amounts are helium, krypton, hydrogen, ozone, carbon dioxide, nitrous oxide, methane, neon and xenon.
Earth’s atmosphere is divided into four layers. The troposphere is closest to the earth and stretches for about eighteen kilometers above the equator to approximately eight kilometers over the poles. It is here that most weather occurs. The stratosphere lies right above the troposphere. The ozone layer is housed in the stratosphere. The ozone is a thin layer of gas which blocks out the ultraviolet rays of the sun, which have been associated with cancer. During the 1970’s, scientists discovered that fluorocarbons, a chemical used in refrigeration and aerosol sprays, were capable of doing possible damage to the ozone layer. This resulted in much concern from both the scientific and general communities. This concern eventually led to a ban on the use of fluorocarbons in the United States and the 1985 Unsponsored Vienna Convention for the Protection of the Ozone Layer on a global scale. The ionosphere continues above the stratosphere for eighty five to five hundred kilometers while the exosphere extends to the border of space. The atmosphere wraps around the earth like a protective garment blocking out a portion of the radiant energy of the sun. This garment of air also acts like a well regulated blanket, retaining enough of the earth’s warmth to preserve life.
Gravity, like a giant hand, is a force which pulls air towards the earth, making it denser nearer the surface. The push of air towards the earth is called air pressure. People, plants and animals dwell on the floor of this ocean of air but because the pressure of the air is equally distributed around them, they do not feel its weight.
The earth itself, is constantly in rotation, causing winds to blow and thereby keeping the air circulating and fresh. This air is heated by the radiation of the sun and the heat is absorbed by the earth and water. As this heat rises from these two sources, it warms the air above. Air over the land is heated quicker than that over the oceans because the land absorbs heat and warms quicker than the oceans. When this air over the land is warmed it rises allowing the cooler air form the water to blow in. As the night settles in, the air over the land cools and flows out towards the ocean. This moving air is called wind.
The French physicist Gaspard de Coriolis noted that the earth’s rotation on its axis, caused the winds to deflect in relation to the direction of the earth’s rotation. This movement became an important factor in the attempt to determine prevailing winds and currents. It also was a factor to be considered in the launching of missiles and rockers. This effect is called the Coriolis effect. Coriolis determined mathematically, that trade winds, easterlies, and westerlies do not blow north to south but deflect from the earth’s rotation and flow in the opposite direction. In the northern hemisphere the winds deflect to the right, while in the southern hemisphere the winds deflect to the left.