The book consists of six chapters， highlighting the main line of historical development in chronological order， and telling the history from the ancient period to the Qing Dynasty with the help of real and vivid stories. By connecting the past with the present， this book enables young people to base themselves on the present and look at the world， which helps them to form values and international perspectives.

Can Ships Really Sail Thousands of Miles Without Losing Direction?

Interesting History: Ancient China

Editor-in-chief: Liu Jianxin

Tsinghua University Press

December 2022

59.80 (CNY)

Liu Jianxin

Liu Jianxin is a Beijing special grade teacher， and off-campus practice tutor of the School of History， Capital Normal University.

How to Clearly Describe Directions

Imagine you arrive in an unfamiliar city and want to go to the local theme park， but you don’t know where the park is， so you pick up the “old-fashioned” mobile phone that can only make calls and call a friend in the area for help. Although your friend is very enthusiastic and tells you that the park is on your left， don’t you feel confused? Do you know where the problem lies?

In fact， the directions we talk about in daily life can be divided into relative and absolute directions. Relative direction refers to judging direction based on a certain object as a reference， that is， the commonly used front， back， left， and right， such as the theme park being on the left side of Xiao Ming. When using relative direction to describe the position of an object， if the reference object chosen is different， the description of the position will change， such as the left side of Xiao Ming may be the right side of Xiao Hong. In addition， when your facing direction is different， your “l(fā)eft side” corresponds to a different direction. Therefore， without a clear reference object， just saying “the park is on your left” naturally makes people feel at a loss.

In order to more conveniently describe the position of an object and to make up for the shortcomings of relative position， the ancients decided to find an object whose position would not change as a reference for describing direction， that is， to use absolute direction. After a long period of exploration， people found that at noon， the position of the sun does not change year-round; at night， there is a bright star in the sky that always shines in a fixed position. Therefore， the sun shadow method and the polar star method became two common methods for the ancients to determine direction. During the Qin and Han dynasties， people used a sundial to measure the sun’s shadow during the day and observed the angle formed between the North Star and the ground at night. Ancient books described this method as: “During the day， refer to the shadow at noon， and at night， examine the North Star to correct the morning and evening.” However， these two methods also have obvious limitations—if it is cloudy and rainy， then the sun cannot be seen during the day， and the stars cannot be seen at night. Imagine， if people encounter such bad weather during navigation and lose their course， it will at best delay the journey for several days， and at worst face the danger of running out of food and fresh water. Therefore， finding a more reliable absolute position reference than the sun and stars had become what the ancients were working towards.

Fortune favors the persistent， and by the Warring States Period， people discovered a magical magnetite. This stone， after being polished into a long strip， if suspended， will always point in a fixed direction， and this characteristic is not affected by weather conditions or space limitations. Therefore， in the following long period of time， people gradually adjusted the shape of the magnetite， changed the placement of the magnetite， and fully utilized the “magnetite pointing south” characteristic.

The Evolution of the Magnetic Stone

As mentioned earlier， as early as the Warring States Period， the ancients discovered the phenomenon of magnetic induction. In the ninth volume of The “Lüshi Chunqiu” (Master Lü’s Spring and Autumn Annals)，" chapter “Jing Tong” states: “Ci attracts iron， or draws it in.” At that time， people called magnetic “Ci，” and they regarded the attraction of iron by a magnet as the attraction of a mother to her children， thinking: “The stone is the mother of iron， but there are two kinds of stones， kind and unkind. The kind stone can attract its children， while the unkind one cannot.” Based on this characteristic， people made natural magnets into the shape of a soup spoon and placed one in a square dish， with the dish’s circumference inscribed with 24 directions. By twirling the magnetic spoon with a finger， when the spoon stops rotating on the base， the handle points to true south， and the mouth of the spoon points to true north. This is the world’s earliest directional instrument， known as the “Si Nan.”

During the Tang Dynasty， people found that if an iron needle was continuously rubbed on a natural magnet in one direction， it could also be magnetized. At this time， if the magnetized needle was made to float on the surface of water， the needle could point to the south. Inspired by this， people suspended the magnetic needle in the middle of a water basin on a scale plate， inventing the floating needle， also known as the water compass. Compared to the “Si Nan，” the floating needle was smaller in size and could be artificially made， thus gaining widespread application. By the time of the Northern Song Dynasty， people improved the water compass. They made a thin iron sheet into the shape of a fish， with both the head and tail pointed， then heated it to a high temperature. After taking it out， they placed it according to the Earth’s north and south magnetic poles， with the fish head pointing south and the tail pointing north， and then immediately put it into cold water， so that the iron sheet was magnetized into a magnet. Finally， placing this magnetic fish in a bowl-shaped container would allow it to indicate direction.

However， the structure of the water compass was relatively complex， requiring water to be added， and the position of the floating needle in the water was not easy to fix， making it inconvenient to use. Therefore， by the time of the Southern Song Dynasty， people further improved the water compass by directly fixing the iron needle in the middle of the scale plate， inventing the dry needle， that is， the dry compass. This type of compass was convenient to carry and especially suitable for swaying and bumpy situations such as navigation， making it an essential item for travel and thus creating convenient conditions for the advancement of navigational technology.

The Small Compass and the Great Age of Navigation

Have you heard the story of Dias discovering the Cape of Good Hope? If we carefully examine his route， we will notice a peculiar phenomenon: Early navigators mostly chose to sail along the coast close to the mainland. This was because early navigation technology was not advanced; navigators had to cautiously follow the contours of the continent to avoid losing their way. Otherwise， once the ships entered the open ocean， without reference points and unable to discern direction， they could only drift helplessly at the mercy of the vast sea.

During the Yuan Dynasty， the compass was introduced to Europe， greatly promoting the advancement of European navigation technology， allowing navigators to discern direction at any time during ocean voyages. European navigators placed great importance on the compass， often setting up a special room on the ship called the “compass room” to house the compass and assigning dedicated personnel to watch over it. With the divine assistance of the compass， European navigators， like tigers with wings， boldly ventured into the open ocean， ushering in the great age of navigation—Columbus discovered the American continent under the guidance of the compass， Vasco da Gama sailed eastward through the Cape of Good Hope to the long-desired India in the East， and Magellan and his crew even completed the feat of circumnavigation. Since then， the footsteps of Western navigators have spread all over the world. They transported wealth plundered from Asia， Africa， and Latin America back to Europe， completing the early accumulation of capital. The gap between the East and the West also began to widen， with the East falling behind the West， and the world’s pattern underwent a revolutionary change. As a historian of science Pan Jixing said， “The small magnetic needle， with a turn， brought tremendous changes to human society on Earth.” However， China， which first invented the compass， implemented a maritime prohibition policy in the late Ming Dynasty， and even pursued a policy of seclusion in the Qing Dynasty; the mighty fleet of Zheng He has long since disappeared into the vast mist.

The Origin of the Name of China’s Navigation System ---- “Beidou”

With the continuous development of science and technology， the way humans discern direction has also taken a leap forward. Today， there are four major satellite navigation systems in the world，" the American Global Positioning System (GPS)， Russia’s GLONASS， the European Union’s Galileo Satellite Navigation System， and China’s Beidou Satellite Navigation System (BDS).

As early as the 1970s， the world only had the American GPS navigation system， which was unparalleled and provided high-precision positioning services for military and civilian equipment.

Over time， our country recognized the importance of developing satellite positioning technology and decided to build its own satellite navigation system. Our ancients had a tradition of using the Polaris method for positioning， and our country’s satellite navigation system has a similar charm to the “Polaris，” hence it was named the Beidou Navigation System. Since 1994， the Beidou system has gone through three iterations and updates， completing significant breakthroughs from non-existence to existence， from active navigation to passive navigation， and from regional service to global networking.

On June 23， 2020， the Long March 3B rocket soared into the sky from the Xichang Satellite Launch Center， and the last global networking satellite of the Chinese Beidou-3 navigation system was sent into orbit. This launch marked the completion of the Chinese independently owned global satellite navigation system， which took more than 20 years to build， and the Chinese Beidou Navigation System became the brightest star in the night sky， profoundly affecting people’s lives in various fields. The mobile phones we use， shared bicycles that can be found everywhere on the street， delivery carts for couriers， and driverless cars all use Beidou navigation technology. China， which once led the world’s technological trend with the compass， is once again at the forefront of the world’s navigation technology.