The claim is one of the most persistent myths in popular science. The core problem is the Great Wall's width — only about 6 meters — not its length. At orbital altitudes, human visual acuity simply cannot resolve an object that narrow. A peer-reviewed study published in PMC concluded that "not even the best of human eyes at a simple glance could see the Great Wall of China from Space," attributing the impossibility to the optical limits of the human eye when resolving thin, diffusing objects at extreme distances.
Multiple astronauts have weighed in directly. China's Yang Liwei, who returned from orbit in October 2003, told host Bai Yansong he could not see the Wall. American astronaut William Pogue similarly stated in his 1991 book How to Bathe in Space that the Wall is invisible to the naked eye even with a telescope at such altitudes. NASA has published the same conclusion on its official channels, noting the myth persists despite clear evidence to the contrary.
Regarding the Chris Hadfield quotes that drive much of the search interest: Hadfield has discussed the Wall's visibility in interviews, but his statements are consistent with the scientific consensus — extraordinary conditions (ideal lighting, atmospheric clarity, optical aids) would be required, and casual naked-eye observation is not possible. Isolated or misattributed astronaut anecdotes do not overturn the quantified optical limits confirmed by NASA, the Chinese Academy of Sciences, and peer-reviewed research.