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BIG ENCYCLOPEDIA FOR CHILDREN AND ADULTS
Where did the first mirror appear? Detailed answer
Directory / Big encyclopedia. Questions for quiz and self-education Did you know? Where did the first mirror appear? Have you ever looked into the water of a lake? Did you see the reflection of the trees and the sky there? Essentially you were looking in a mirror. After all, a mirror is a smooth surface that reflects light and other objects. It is very important that its surface is smooth. The smoother it is, the better the reflection. When the breeze ruffles the water, you can only see the sun's reflections - and no other objects. In ancient times, mirrors were made of polished metal. Now the mirror is made of smooth glass with a layer of metal on the back. The glass itself is not yet a mirror: the reflection gives us a narrow layer of silver, and the glass only protects it from scratches and damage. We will never know when a man came up with a mirror. Probably, he also often looked into the smooth surface of the pond and saw himself there. Perhaps, by chance, he learned that the polished metal can also reflect objects. One fine day (we know almost certainly that a woman suggested this idea) a person began to specially polish pieces of metal and give them the desired shape. So there were mirrors. And in the times of ancient Greece, Egypt and Rome, people already widely used mirrors. Even then they had small pocket mirrors that were comfortable to carry around. They were made from a circular plate of metal: copper, bronze, silver and gold. Just as a child is surprised when he sees his own reflection, ancient people were surprised in the same way. They did not know how a reflection is obtained, so they attributed magical powers to mirrors. They thought that what they see in the mirrors is their spirit. Thus arose the superstition that if you break a mirror, it can harm the Spirit. The first who guessed to make glass mirrors with a layer of mercury or tin were the Venetians. By 1300 they were producing such mirrors, and they soon replaced the metal plates. We use them to this day. Author: Likum A.
How do birds manage to fly? When man wanted to fly, he created an aircraft. If you carefully study the structure of a bird, it becomes obvious that nature has tried to create a bird as an ideal aircraft. First, the bird has wings. The main weight-bearing feathers of the wings are attached to the forearm bone by strong ligaments called tendons. The secondary wing feathers are similarly attached to the shoulder. Each wing is controlled by a separate set of muscles, so that in flight the bird can control each feather individually. When the wing moves up, the main and some auxiliary carrier feathers are turned in such a way that their ends look up and air passes freely through them. When the wing moves down, all the carrier feathers are turned with the plane down and do not allow air to pass through them. In this case, the bird seems to be repelled from the air - and, taking off, gaining height! But, among other things, the flying body should be as light, compact and strong as possible. Therefore, large bird bones are hollow inside. Many birds have air cavities in their bones. The bird's ribs are connected in such a way as to provide firm support to the body as the wing moves down. The head, tail, wings and legs of the bird are also unusually light. The cranial bones are distinguished by very thin walls. Birds have neither teeth nor jaws, which are full of bones and muscles. Instead, they have a hollow beak. Strong muscles that move the wings are attached to the chest as close to the center of gravity as possible. Even the fact that birds are warm-blooded is helpful, as cold-blooded animals become lethargic in winter. So, as you can see, everything that a bird has is created for only one purpose - to fly!
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Comments on the article: Chyngyz Complex questions and simple answers.
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