But an American astronaut's recent reiteration about how he believes he saw China's Great Wall from outerspace is rekindling Chinese patriotic enthusiasm that was only recently watered down by their own first spaceman, Yang Liwei.

    Gene Cernan, the last man to walk on the moon as commander of the Apollo 17 mission, has been insisting of late that the Great Wall can be seen with the naked eye from outerspace, though not from the moon.

    "In Earth's orbit at a height of 160 to 320 kilometres, the Great Wall of China is indeed visible to the naked eye,'' Cernan told reporters during the Asian Aerospace Exhibit in Singapore two weeks ago.

    It was a contradiction of sorts, following China's first manned space trip of last October, when Yang, China's heroic first astronaut, told a press throng "the earth looked very beautiful in space, but I did not see our Great Wall."

    The nation, with many believing for decades that the Great Wall is the only manmade object visible to orbiting astronauts, was naturally disappointed.

    Inspired by Cernan's new reaffirmation, some Chinese are now arguing that, theoretically, it is possible to spot the ancient fortification -- with its giant expanse of thousands of kilometres over the country's northern mountains -- to be seen from above.

    "With lower-angle sunlight, the 6-metre-wide, 8-metre-tall wall could cast a shadow 200 to 2,000 metres wide on the hillsides,'' said Zhu Yinxing, a retired geological survey engineer with the Guangzhou-Shenzhen Railway Construction Co.

    "With the sunshine and perfect orbiting conditions met, the astronaut would be able to enjoy the unique wonder of the Great Wall on Earth,'' Zhu was quoted as saying by China Space News.

    Zhu suggested the government should add that proving the Great Wall's visibility as a goal for the country's space programme, adding that "all Chinese people are waiting for the good news.''

    Some proposed that the Chinese astronauts should go through specific training for spotting the wall.

    Others are calling for lighting up the wall so astronauts can easily see it at night.

    These points are similar to those made by Wei Yunhua, senior editor with the People's Education Press, when members of the public were calling for the educational authority to remove an article about the wall and space from an elementary school's textbook.

    In the text, an astronaut says that from outerspace he can see the sea embankment in the Netherlands and China's Great Wall with his naked eyes.

    People said that was misleading after China's spaceman said he did not see the Great Wall.

    But Wei said people should not be so fussy about the story, which is a fairy tale and cannot be considered a scientific article.

    "We want to help the students to be proud of their motherland and themselves as well. Our intentions are good," he said.

    But Chinese scientists believe the Great Wall, which is made up of sections of walls, is indeed invisible from outer space.

    It's widely accepted that in the Earth's orbit, which is normally 300 to 400 kilometres from the ground, only an object larger than 250,000 square metres can be seen by a person with normal vision.