GREAT WALL OF CHINA History of the Great Wall of China: The Great Wall of China is the national military defense project in the cold weapon war era with the longest time and the largest amount of construction in the world. It condenses the sweat and wisdom of our ancestors and is the symbol and pride of the Chinese nation. According to historical records, since the Warring States period, more than 20 vassals and feudal dynasties have built the Great Wall. The earliest was the Chu Kingdom. To defend the nomadic or enemy countries in the north, they began to build the Great Wall. Subsequently, Qi, Yan, Wei, Zhao, Qin, and other countries also began to build their own Great Wall for the same purpose. After Qin unified the six countries, the famous emperor Qin Shihuang sent Meng Tian northward to the Xiongnu, connecting the Great Walls of various countries. From Linyao in the west to Liaodong in the east, it stretched for more than 10,...
Archimedes
Greek physicist
Archimedes' Biography
Archimedes (287–212 BC) was a Greek physicist, mathematician, and inventor. The "Arquimedes Spiral" and the "Lever" are some of his inventions. He developed the idea of "specific gravity", called "Archimedes' Principle".
Archimedes was born in the Greek colony of Siracusa, in Sicily, around 287 BC. C., Son of Phidias, a Greek astronomer, who used to gather in his home the elite of philosophers and men of science, to exchange ideas about their works. At that time, Híeron II reigned, who was somewhat related to the family of Archimedes.
Formation
Archimedes studied at the School of Mathematics in Alexandria, which at the time was the intellectual center of the Greek world. He had contact with what was most advanced in the science of his time, living with great mathematicians and astronomers, including Eratosthenes of Cyrene, the mathematician who made the first calculation of the circumference of the earth.
Discoveries and Inventions
Upon returning to his city, Arquimedes decided to put into practice a series of projects. He came to the idea of "specific gravity", called "Principle of Archimedes", in which he stated, "Anybody denser than a fluid when dipped in it, will lose weight corresponding to the volume of fluid displaced". After the discovery, he ran down the street shouting: Eureka! Eureka!
His statement, which from then on became known as the “Archimedes Principle”, came to allow a much better understanding of the behavior of liquids and is one of the main foundations of hydrostatics.
Archimedes invented a spiral device to raise water, "Archimedes' Screw", which consists of a kind of spiral spring, fitted inside a cylinder, that when rotating, the water goes up in the cylinder.
Archimedes was particularly proud of his work on the sphere and the cylinder. He developed the formulas for the surface area and the volume of the sphere, as well as the formulas for the cylinders in which the sphere could fit. Archimedes showed that the sphere is the most efficient of solid figures.
Geometry seems to have been the subject that most appealed to him, so much so that, when asked what they should have engraved on his grave, the sage determined it to be a sphere and a cylinder.
He returned his creations to war machines, developed the “lever”, which allowed heavy loads to be moved. His knowledge of levers was used in "catapults". Archimedes declared: "Give me support and a lever and I will move the earth".
He created huge mirrors to direct the sun's rays over the sails of enemy ships, setting them on fire and huge cranes to grab and turn over enemy vessels.
Death
After King Híeron died in 216 BC, Syracuse was besieged by Roman troops, but resisted for three years, thanks to Archimedes' warlike devices, including powerful catapults.
In 212 BC, after bloody struggles, Siracusa surrendered to Roman troops led by Roman general Marcellus Claudius. During the massacre, contrary to Marcellus' orders to save Archimedes and not destroy his home, a Roman soldier approached Archimedes and killed him.
The Romans buried him with honor and marked his tomb with their favorite figures, the sphere, and the cylinder.
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