The air we breathe, is a part of the atmosphere, the gas mixture that covers the globe. This mixture of gases ensure life on earth and protects us from harmful rays of the sun. The atmosphere is maintained by gravity, so can not disperse in cosmic space .In every day millions of people go through the atmosphere with different aircraft, from balloons to airplanes. You can go by foot, bicycle, car, train, metro, plane, by boat.
Atmosphere, compound word of Greek origin (athomos = air and spherein = sphere), is designated as air envelope of the Earth.
The atmosphere of our planet is virtually 100% gasous, but also containing traces of solid substances .Compozition of atmosphere has changed over the approximately 2.5 - 2.8 billion years ago, from a primitive atmosphere at the current , passing through several intermediate stages, during which the atmosphere has changed not only the chemical composition, but also other characteristics such as density, thickness, transparency and others.
The atmosphere is named in normal speech air.
At 4.56 billion years ago, when earth globe appeared, hydrogen (H2) and helium (He) were already present.
Subsequently, due to the low density of these 2 gases, they will not be attracted by the planet, spreading progressive in cosmic space.
Thanks to the slow cooling of the Earth, volcanic activity, were brought to the surface various gases, which were the result of chemical reactions of the internal layers of the globe. These processes arose an atmosphere with a composition of about 80% water vapor (H2O), 10% carbon dioxide (CO2) and 5 to 7% hydrogen sulfide. This combination of gases can be seen today in the emanations and volcanic eruptions.
The climatology depends not only the shape of the atmosphere , but also its size.
For an atmosphere 35 times thicker than today, would see the sun until the afternoon as a red spot and Heatstroke should be almost null. "Silver Clouds" that we see at night show heights of almost 80 km, and other facts allow us to say this atmosphere even beyond 250 km.
In terms of utility, more interesting than the shape and dimensions of the atmosphere is it's temperature.
Immediately after the air temperature is relative air density and it's weight of each region. Aristotle knew that the air is heavy - even had made some attempts to weight it, but only in modern times found a reliable means of measuring the weight of the atmosphere, when it was discovered barometer (1644).
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