Yang Liwei has exploded the widely held belief that the Great Wall is the only man-made object visible with the naked eye from outer space.

"The scenery was very beautiful," Yang said in an interview on China Central Television about his 21-hour space voyage. "But I didn't see the Great Wall."

Yang gave the interview 15 hours after he landed in Inner Mongolia early on Thursday on board the Shenzhou V space craft, having completed 14 orbits around the world.

Yang told the interviewer he had only had time to sleep for about 30 minutes.

He said he had been too busy to be particularly worried about anything, but had started feeling a bit homesick as he reentered the atmosphere.

Shrunken landmark

It may come as a disappointment to patriotic Chinese that their most famous landmark does not uniquely bestride the world as once was thought.

In fact, NASA's returning space travellers say a great many man-made objects are visible from a low orbit of the earth, including roads, cities, and ships at sea. But at roughly six metres wide, the Great Wall is hard to make out.

"We spent several passes looking for the Great Wall of China with no luck," Jay Apt, Michael Helfert and Justin Wilkinson wrote in ORBIT (NASA Astronauts Photograph the Earth). 

"Although we could see things as small as airport runways, the Great Wall seems to be made largely of materials that have the same color as the surrounding soil. Despite persistent stories that it can be seen from the Moon, the Great Wall is almost (sic) invisible from 180 miles up."

Weather conditions were good over China on Wednesday, so it is possible that, with a little imagination and consideration for his countrymen, Yang could have managed a glimpse.