Whether the Great Wall is Visible from the Moon?
A Ripley’s Believe It or Not! cartoon from May 1932 claimed that the wall is “the mightiest work of man, the only one that would be visible to the human eye from the moon,” and Richard Halliburton’s 1938 book Second Book of Marvels makes a similar claim, but it is not true. This belief has persisted, assuming urban legend status, and sometimes even appeared in school textbooks. Arthur Waldron, author of The Great Wall of China: From History to Myth, has speculated that the belief might go back to the fascination with the “canals” once believed to exist on Mars.
The earliest known reference to this myth appears in a letter written in 1754 by the English antiquary William Stukeley. Stukeley wrote about Hadrian’s Wall that, “This mighty wall of four score miles in length is only exceeded by the Chinese wall, which makes a considerable figure upon the terrestrial globe, and may be discerned at the moon.”
The Great Wall is a maximum 9.1m (30 ft) wide and is about the same color as the soil surrounding it. Based on the optics of resolving power (distance versus the width of the iris: a few millimetres for the human eye, metres for large telescopes) an object of reasonable contrast to its surroundings some 70 miles in diameter (1 arc-minute) would be visible to the unaided eye from the moon, whose average distance from Earth is 384,393 km (238,857 miles). The Great Wall is of course not a disc but more like a thread—it can be seen from much further than would be possible if it were simply a 30 foot disc. Still, the apparent width of the Great Wall from the moon is the same as that of a human hair viewed from 2 miles away. To see the wall from the moon would require spatial resolution 17,000 times better than normal (20/20) vision. Not surprisingly, no lunar astronaut has ever claimed seeing the Great Wall from the moon.
Incidentially, if one could have seen the Great Wall from the moon, one ought to be able to see most of the roads in the world as well, given that they in total length far surpasses that of the great wall, and commonly are even wider. This is again not the case.
Who, When and Why Built the Great Wall of China?
Who built the Great Wall? There are many answers. Some say Emperor Qin Shihuang. Some say ordinary working people of ancient China, and some say that it was slaves who built the wall. This is not an easy question to answer, just like the wall was not easy to build.
Experts have given us the most credible answer. As early as the Warring States Periods (476 BC – 221 BC), the ruling powers began to build walls as a defense against the northern nomadic tribes and other potential enemies. The state of Chu (11th Century BC-223BC) was the first to build a wall, followed by the Qi, Yan, Wei, Zhao and Qin. After Emperor Qin Shihuang unified the six states, he ordered General Meng Tian to connect the existing walls and to extend them further as a front line defense against possible invasion. Thus the Great Wall of China was formed. It extended from Lintao (present Lintao County in Dingxi City in Gansu Province) in the west and ended at Liaodong (present the eastern and southern parts of Liaoning Province) in the east. It was called “Wan Li Chang Cheng” (The Long Wall of 10,000 Li).
Three groups of people built the wall. They were soldiers, common people and criminals. Many people died during its construction, due to the heavy work, short time limit and tough condition. An accurate number of those who died is unknown.
During subsequent dynasties, the wall was extended, repaired or modified. The section of wall built in Han Dynasty (206BC-220) is the longest. During the Ming Dynasty (1368-1644), the wall was substantially repaired on more than twenty occasions. Today, the best known and most visited sections of the wall are at Badaling, Mutianyu, Simatai and Jinshanling and these were built in the Ming Dynasty. They were all built to protect the people and territories south of the wall from a continued threat of invasion by the northern nomadic tribes.
The Great Wall is the longest tomb in the world?
Many people died in building the Great Wall, and it is said most people that they were simply buried in the wall. They did it mainly for the following reasons:
to save funeral expenses;
to save building materials, for bones are good, natural material friendly to environment
to deep fertilize the wall to make the roots of plants go deep so to protect the wall foundations
the wall can intimidate the avenging spirits of those who died for the building it
So,we believe the Great Wall is the longest tomb in the world
How many bricks were used to build the Great Wall of China?
The accurate number is unknown. But roughly estimated, the length of a 1 yard wide and 16 feet tall wall built from the bricks and earthworks is equal to the circumference of the earth.
How were the messages sent along the wall?
If the enemies attacked, the soldiers stationed in the towers lit fires and set off smoke to signal to the next tower. If it was a daytime attack, they lit smoky fires by burning a mixture of wolf dung and dry hay. If the attack came at night, they made bright flaming fires. In this way a signal was passed along the wall to the capital of the kingdom a lot faster than horse ride. An alarm could be relayed over 500km within just a few hours.
Based on the rules of Ming Dynasty when enemies are 100-500, then set off the smoke for one time with one shot of fire gun; if 500-1000, two times of smoke with two shots of fire gun.
When is the best time to visit the Great Wall?
A good guide or tour make a big difference!