BEIJING, Oct. 30 (Xinhua) -- A senior Chinese cultural heritage official on Monday expressed the hope that Chinese astronauts could prove whether the Great Wall can be seen with naked eye from space during next space mission.

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

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

    But it's really difficult to answer the question because only a few astronauts have ever been to space, Tong said.

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

    During China's first manned space flight 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 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.

    Adding another twist, veteran U.S. 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," he was quoted as saying during an interview 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.

    According to a report in China Daily on April 19, 2005, Chinese-American astronaut Leroy Chiao, who had been on three space flights and was coming to the end of his six-month stint on the joint U.S.-Russian space station, provided the first photographic evidence of sections of the Great Wall using commercially available equipment.

    The photos had been authenticated by Professor Wei Chengjie of the Institute of Remote Sensing Applications at the Chinese Academy of Sciences, the newspaper said.

    However, Chiao was himself not certain: "It is hard to say whether or not I have seen it. That's because from our altitude, Ican not distinguish between the Wall and roads." He described his picture, taken on Feb. 20, 2005, as a "region northwest of Beijing."

    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.