The earth is round- if someone always goes in the same direction, undoubtedly he could return to the starting point. All around the outside of the earth is a thick layer of air that covers everything on it. Sufficient air is indispensable for humans and the other creatures to live. Apart from feeding the jet motors, the air also provides flotation and propeller resistance for airplanes.

Beneath the air, the surface of the earth is covered with mountains. The higher the mountains, the thinner the air on the tops. How did mountains come from? It could date back to millions of years ago the beginning of the earth - a huge burning ball of fire. With the cooling progress, the ocean formed. Then the continents and mountains arose out of the ocean with wrinkles and crinkles. The earth is still shivering and shaking in the form of the earthquake, whereas its power is much smaller than the first boom of the continents. Evidences showed that mountains came from under the sea due to the fact that seashells were found on tops of some mountains. But until now, we could not prove whether the beginning was a boom or a long gradual process.