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BIG ENCYCLOPEDIA FOR CHILDREN AND ADULTS
What is the Earth's atmosphere? Detailed answer
Directory / Big encyclopedia. Questions for quiz and self-education Did you know? What is the Earth's atmosphere? When we read about human exploration of the moon and planets, we often come across questions about the atmosphere. Do other planets have an atmosphere? As far as scientists know, no planet or star has an atmosphere similar to ours. What is atmosphere? We can think of it as an ocean of air that surrounds the earth and is several hundred miles high. The ocean of air has the same composition throughout the earth. Basically it consists of certain gases, which always remain in the same proportion. About 78 percent is nitrogen, 21 percent is oxygen, and the remaining one percent is made up of gases that are called rare - argon, neon, helium, krypton and xenon. The air that surrounds the Earth has the same chemical composition up to 18 miles, although this figure can go up to 44 miles. When you reach the upper atmosphere, you are at the top of what is called the troposphere. It is the layer closest to the Earth's surface. At an altitude of 18 to 31 miles from the surface of the Earth is a layer of hot air, with a temperature of about 42 degrees Celsius. The reason for the heating of this layer is the absorption of heat from the sun's rays by the ozone present here. Ozone is a special form of oxygen where the molecule is made up of three oxygen atoms instead of the usual two. The hot ozone layer serves to protect us from the sun's most active rays - ultraviolet. Without it, we would not have survived the sunlight. Even higher is a layer, or several layers, called the ionosphere, which is located at an altitude of 44 to 310 miles above the earth. The ionosphere is made up of particles electrified by the Sun. Air molecules are in constant motion. The atmosphere can only be maintained if the molecules are constantly colliding with each other and cannot escape. But the higher you go, the thinner the air becomes. It is very unlikely that a molecule from below will bounce back after colliding with a molecule from above. Therefore, the molecules go into open space, and the atmosphere is completely rarefied. There is a zone called the exosphere, where the torn off molecules move almost freely, and this zone starts at an altitude of 400 miles and extends up to 1500 miles. Author: Likum A.
Where did the navy originate from? Do you know that initially the country's navy included all ships, including military, merchant, and fishing ships? At present, the word "fleet" has come to mean warships, as well as those that help to conduct hostilities. The first fleets arose when the armed men of a tribe or city went out to sea in the largest ships they had to fight the enemy and protect their territory from the sea. These ships were usually fishing or merchant ships. Later, ships adapted specifically for naval combat appeared. In the times of the ancient Greeks and Romans, instead of round trading ships, elongated ships were built, which had a high speed of movement. When the Persians threatened to attack Athens in 483 BC, the Greeks increased their fleet from 50 to 100 elongated ships. By the end of the 5th century BC, this fleet increased to 300, and later even up to 360 and became a real navy! In times of peace, these warships stood on stocks or in shelters in bays. The most ancient warships were multi-oared galleys, and each required a large number of rowers. These huge rowing galleys were used to ram other ships or to board enemy ships. The structure of the ancient Greek and Roman fleet had much in common with modern times. The Greeks had a captain, a sail specialist, many junior officers, sailors and rowers, as well as soldiers and sailors who participated in the battle. The Romans always had a body of soldiers called "classics", and they had a special postscript for service in the navy. Today, of course, the fleet is a very complex structure, including dozens of types of ships and their support system.
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