Astronaut Yang Liwei was not myopic. He and Gene Cernan were probably both right ('US astronaut says the Wall is visible from space', March 15).
Assuming that Yang's plane of orbit, inclined by about 65 degrees to the equator, did not spin around with the earth's rotation eastwards, each successive orbit would have receded to the west by about 20 degrees meridian.
In other words, Yang would have passed close to the Great Wall only three times in his day-long mission: first, during the launch, with its great G forces; halfway through, when the Great Wall was in darkness; and coming around from the east on the fiery re-entry orbit.
So, even if there was no cloud cover, Yang would not have had much of a chance to see the Great Wall.
PETER LOK, Heng Fa Chuen