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BIG ENCYCLOPEDIA FOR CHILDREN AND ADULTS
What is bacteria? Detailed answer
Directory / Big encyclopedia. Questions for quiz and self-education Did you know? What is bacteria? Man has a very peculiar attitude towards bacteria. We all know that many bacteria are harmful. Diseases such as typhoid, cholera, diphtheria, pneumonia and all infections in open wounds are caused by certain types of bacteria. Therefore, people are fighting these bacteria. And yet, without other bacteria, life on Earth would be impossible! Man propagates certain types of bacteria because he needs and uses them. Bacteria are generally considered to be the lowest rung in the plant kingdom. Each bacterium is a separate particle of living matter without a nucleus. On average, their size is about 0,001 mm in diameter. Some of them are so small that they cannot even be seen with a normal microscope. Bacteria usually occur in three forms: round cocci, rod-shaped bacilli, and spiral-shaped spirilli. They reproduce by simple division into two parts. Under favorable conditions, they reproduce very quickly. Fortunately, nature has several ways to control this reproduction. Otherwise, bacteria would occupy the entire surface of the globe. Bacteria that cause decay of dead plants and animals are very beneficial to humans. Not only because they decompose dead tissues into the simple compounds of which they are composed, but also because without the bacteria of putrefaction the earth would be covered with useless dead matter and there would be no room for the living. Some other bacteria are beneficial in that they induce fermentation. The best known types of fermentation are the souring of milk and the fermentation of sweet fruit juices. Many industrial processes owe their existence to the fermenting action of bacteria. The ripening of the cream, from which excellent butter is obtained, is also based on fermentation. Many cheeses get their exquisite taste from the products of bacterial processes. And as we know, plants cannot live without bacteria, which combine nitrogen with other elements to make nitrates used by plants. Author: Likum A.
Who Invented the Compass? The simplest form of a compass is a magnetic needle mounted on a rod so that it can rotate freely in all directions. The arrow of such a so-called compass points to "north", which refers to the North magnetic pole of the Earth. Since its location is known, all points on land, on land and water, are plotted on the map in accordance with it. Thus, the compass can be a guide for the traveler everywhere on Earth. No one knows how and when it was first discovered that a magnetized iron needle, freely rotating in a circle, always points north. At one time it was believed that the Chinese made this discovery about 4500 years ago, but now this version is being questioned. In any case, the Chinese were among the earliest people to know the principle of the compass. Arab merchants learned about the compass from them and introduced Europe to it. It is known for sure that during the XII century the compass became already well known in Europe. Probably the earliest type of compass consisted of a magnetized needle threaded into a piece of wood and floating in a bowl of water. The next step was to use a needle, put on an axle protruding from the bottom of the bowl. The purpose of the first compasses was to determine only the north-south direction, and the bowl was turned so that the north end of the arrow was above the north designation printed on the bowl. In later devices, a card was attached to the arrow itself with all the applied parts of the world. As you know, the North Magnetic Pole and the North Pole are not the same. The North Magnetic Pole is located at the northernmost point of the Arctic coast of North America, on the Butia Peninsula. All compass needles in the Northern Hemisphere point to this point. The ancient peoples did not know the difference between the North magnetic and geographic North Poles. They were far from both and it seemed to them that the compass needle always points to the north. Sailors of later times, who ventured far from home, noticed this difference and were greatly puzzled. You can imagine the bewilderment of the ancient Scandinavians, traveling the arctic seas around Greenland, when they discovered that at some points the compass needle points almost to the west!
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