Sina in history, through what principle to create inventions?

The earth itself is a huge magnet, and the outer core of the earth has current and convection, which is composed of molten iron and nickel, thus generating a magnetic field. Like a simple magnetic stripe, the earth's magnetic field has two poles-the North Pole and the South Pole. Put a magnetic stripe on the paper covered with iron filings, and the iron filings will be distributed along the magnetic lines radiated by the magnetic poles. A magnetized object, such as a magnet and a compass pointer, will also adjust its direction like iron filings to keep it consistent with the direction of the magnetic field lines.

In the 1 century, people in China used magnets in a device called "Sina", which was mainly used to see geomantic omen. In this device, the magnet is carved into the shape of a spoon and placed on a polished chassis, which points itself to the north-south axis. The chassis is usually engraved with azimuth (east, west, south and north), constellation distribution and symbols for divination. In 83 AD, China philosopher Wang Chong recorded this device, but did not mention its application in navigation.

In the 8th century, China people used magnetized iron needles to replace the magnets in Sina. This kind of magnetic needle is obtained by magnetizing an iron needle along the magnetic axis of a magnet with excellent magnetism. 1086, Shen Kuo, a scientist from China, explicitly mentioned a magnetic compass specially used for navigation in his Meng Qian Bi Tan. Up to117017065438, Zhou Pingke Tan written by Zhu He in the Northern Song Dynasty described the use of the compass at sea.

However, it was not until the beginning of the European exploration era that the compass was made into a complex navigation device. In view of a large number of innovations in the Far East, the compass probably spread from Arabs to the West. Before that, European travelers used the sun or Polaris to tell the north-south direction. Although they can get more accurate positioning through this astronomical method, it can only be done when the weather is clear-the bad weather that appears from time to time often seriously affects navigation activities and leads to disastrous consequences.

In 1 1 century, vikings may have used compasses to sail on the coast of northern Europe, but the first record of magnetic compasses came from Alexander, a British scholar and priest. Written by Nickmann and published in 1 180. The early European compass inserted a magnetized pointer vertically into a straw, and then let the straw float vertically in a plate filled with water.

Such equipment can indicate the accurate direction to a certain extent, but it is extremely inconvenient to carry when traveling. At 1250, the pointer is mounted on a pivot, and above it is a circular card marked with the main direction, which can rotate with the pointer. 1269, French scientist Petrus? Perigrinas first explained how magnets (and compasses) work.

He described the magnetic pole and invented the compass, so that the pointer could indicate the direction in degrees. Further improvements to the compass include putting the pointer and dial in a box. Early boxes were made of materials such as wood or ivory, which did not interfere with the magnetic force exerted on the pointer. The later use of brass was also based on this consideration. /kloc-in the 6th century, the ship's compass was installed on a self-correcting shaft or bracket to ensure that the compass could always remain horizontal on a bumpy ship.