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Elementary school teacher Xiao Chunlan is puzzled by a sudden jolt to her long-held belief that she thought was as rock solid as the Great Wall.

Image of Earth from space

Namely, the Great Wall is one of only two man-made structures that astronauts can see from space with their naked eyes (the other being reclamation projects in Amsterdam, the Netherlands).

Xiao, in Xishuangbanna, Yunnan Province, has long been instilling her pupils with this theory. As a matter of fact, it is inscribed in the textbook. Most Chinese learned that it came from testimonies of previous astronauts, but nobody has conducted research on its origin.

Some people had doubts, but were brushed aside by others. No Chinese citizen had ever been up there to confirm it for himself. So it became a popular myth enshrined as truth despite occasional scepticism.

That is, until Yang Liwei made the historic journey to outer space.

A reporter asked him afterwards: "Could you see the Great Wall from out there?"

Yang responded without hesitation: "No."

According to Wang Yusheng, curator of China Technology Museum, a spacecraft usually orbits 300-400 kilometres from Earth and, from that distance, only things with a circumference of at least 500 metres may register on a naked eye.

The Great Wall has an average width of 10 metres and it zigzags in mountains. There is no way one can see it from that far. By Wang's estimate, the distance it vanishes from human vision is around 36 kilometres.

Tong Qingxi, another prominent scientist, explains that astronauts can see every brick of the wall if they use advanced equipment. But without visual-enhancement aids it wouldn't even appear as a thin line.

So how about those experts who supervised the compilation of the teaching material? Shouldn't they ensure that everything is solidly backed up by science?

Some media analysts have argued that the fallacy started out of patriotism. The Great Wall is such a significant heritage that people would soon turn a belief into conviction. Any misgivings would have given way to national pride.

Some speculate that there must have been experts who had noticed the folly in the widespread myth. Yet they did not raise their concern for fear of being labelled "unpatriotic" or they did not want to prick the balloon of public illusion because they deemed it "good-intentioned and innocuous".

Would the Great Wall be any less great now that all these scientists and even China's own spaceman have come forward to refute the falsehood? Just as important, should people's good intentions come before truth?

Xiao Chunlan would love to have an insight from the education authorities.

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