Chinese astronauts told to locate Great Wall from space

BEIJING: A senior Chinese cultural heritage official has expressed the hope that astronauts in the future could prove whether the over 6,000-km-long Great Wall, one of the seven wonders of the world, can be seen with the naked eye from space.

"There is still no definite evidence to prove whether the Great Wall is visible from space," vice director of the State Administration of Cultural Heritage, Tong Mingkang said while answering questions of netizens online at a Chinese government website.

"Many people including foreigners are interested in this question. The curator of the national museum of Egypt asked me the question recently," Tong said.

But it's really difficult to answer the question because only a few astronauts have ever been to space, Tong was quoted as saying by Xinhua news agency.

"We hope Chinese astronauts may prove that during next space mission," Tong said.

During China's first manned spaceflight in 2003, Yang Liwei, China's first astronaut said he didn't see the Great Wall while in orbit, contradicting the popular belief that the over 6,000-km-long structure is visible from space.

It later triggered a hot debate in China over whether a school textbook teaching that the Great Wall could be seen from space should be corrected.

Veteran US astronaut Gene Cernan insisted the Great Wall of China could be seen. Cernan, the last man to walk on the moon as commander of the Apollo 17 mission, said he had seen the Great Wall from the Earth's orbit, although he could not do so while on the moon.

"In Earth's orbit at a height of 160 to 320 km, the Great Wall of China is indeed visible to the naked eye," Cernan was quoted as saying by a Singapore newspaper in March of 2004.

It is widely accepted that in the Earth's orbit, which is normally 300 to 400 km from the ground, only an object larger than 500 meters by 500 meters can be seen with the naked eye. The Great Wall, which is made up of sections of walls approximately 10 meters wide, is indeed invisible from outer space, scientists believe.

The Great Wall was first begun in the time of the Qin Dynasty (221 BC -206 BC) as a way to defend invaders from the north. It was extended and rebuilt intermittently over the centuries.

The majority of the existing Great Wall winding west-to-east from the Jiayu Gate to the Yalu River in north China, was built and rebuilt in the Ming Dynasty (1368-1644). It was included in the World Heritage List in 1987.

Chinese government departments are currently engaged in a project to re-measure the Great Wall and the result of the most advanced survey will be announced in 2008.