SF-0003Photographs That Need Explaining
The astronaut who took the first confirmed photograph of the Great Wall from orbit could not see the wall
Leroy Chiao shot it with a 180 mm telephoto in 2004. He said afterwards that he never saw the Great Wall, and wasn’t sure his picture showed it.
Frame ISS010-E-8497, photographed by Expedition 10 commander Leroy Chiao from the International Space Station on 24 November 2004 at 06:08:06 GMT, from 348 km up, using a 180 mm telephoto lens. NASA describes this as apparently the first verifiable photograph of the Great Wall of China made from low Earth orbit. This is the unannotated frame; NASA's own feature article publishes a version with arrows added to mark where the Wall runs.
This picture, apparently the first verifiable photo of the Great Wall of China made from low Earth orbit, was taken by International Space Station Commander Leroy Chiao on Nov. 24, 2004.
- Image
- NASA / Leroy Chiao (ISS Expedition 10)
- Taken
- 2004-11-24
- Location
- Northern China, Laoha River drainage — photographed from 348 km altitude
- Archive ref.
- NASA JSC ISS010-E-8497 (Kodak DCS760c, 180 mm)
- The image itself
- Authentic, unaltered
Image ISS010-E-8497, NASA Johnson Space Center, Gateway to Astronaut Photography of Earth. Public domain.
Verdict
"The Great Wall of China is the only man-made object you can see from space with the naked eye — astronauts say it’s the only sign of humanity from up there."
The claim is demonstrably untrue, and the evidence against it is clear.
The claim is stated as fact about visibility and fails on direct evidence from the agency best placed to judge. NASA states the Wall "generally isn't" visible to the unaided eye in low Earth orbit and "certainly isn't visible from the Moon", and gives the physical reason: the Wall is built from local material, so it matches the colour and texture of the ground either side of it. The "only structure" half fails independently — NASA notes cities, major roadways, bridges, airports, dams and reservoirs are more visible, and publishes a Station photograph in which the pyramids at Giza are clearly visible. The strongest single piece of evidence is testimonial: the astronaut who took the first confirmed photograph of the Wall from orbit said he did not see it and was unsure his own picture showed it.
In short
The Great Wall of China is routinely described as the only human structure visible from space, and sometimes as visible from the Moon. NASA has addressed this directly and the claim fails twice: it is not the only such structure, and the Wall is among the harder ones to pick out because it is built from the ground it crosses. The first confirmed orbital photograph of it was taken in 2004 with a 180 mm telephoto lens — by an astronaut who did not see the Wall with his own eyes and was unsure the frame contained it.
The photograph is the argument
There is no annotation on the image above. No red circle, no arrow, no “ZOOM IN”. That is deliberate, and it is most of the file.
This is frame ISS010-E-8497, taken by Expedition 10 commander Leroy Chiao on 24 November 2004, at eight minutes past six in the morning GMT, from 348 kilometres up, with a Kodak DCS760c and a 180 millimetre telephoto lens. NASA describes it as apparently the first verifiable photograph of the Great Wall of China made from low Earth orbit.
Now find the Wall.
Most people cannot, and that is not a failure of attention. NASA’s own catalogue record for this frame lists what it depicts as “Mountains, snow, and Laoha River drainage system.” The Great Wall does not appear in the feature list of the photograph taken to show the Great Wall.
One disclosure, before anything else. NASA’s feature article publishes an arrow-annotated version of this image, marking where the Wall runs. We are showing you the unmarked frame because the unmarked frame is what an astronaut actually sees — but you should know the marked one exists rather than conclude that NASA could not find the Wall either. It could. It had to draw on it.
The man who took it did not see it
This is the detail that ends the argument, and it comes from NASA’s own account:
Chiao himself said he didn’t see the wall, and wasn’t sure if the picture showed it.
He was in orbit, above the right part of China, with a telephoto lens, on the day the definitive photograph was taken. He looked. He did not see it. That is the strongest possible testimony about naked-eye visibility from the strongest possible witness, and it is a far better answer than any amount of optics.
Chinese astronaut Yang Liwei said the same after his 2003 flight — he could not see the structure. NASA notes this prompted talk in China of rewriting the textbooks that teach the claim, which it drily calls “a formidable task in the Earth’s most populous nation”.
The claim is older than the thing it claims
NASA records the theory that the Wall could be seen from the Moon as dating back to at least 1938, and notes it “was repeated and grew until astronauts landed on the lunar surface”.
That is more than two decades before Yuri Gagarin. For a generation this was a boast nobody was in a position to test, repeated until it acquired the texture of common knowledge. By the time anyone could look, everyone already knew the answer.
You will find older origins online — a 1754 line attributed to the antiquary William Stukeley, a 1932 Ripley’s Believe It or Not! cartoon. They may well be right. We have not read either primary text, so we are not going to state them as fact, and we have led with the date NASA actually gives.
Why it is so hard to see
The explanation is better than the correction.
The Wall was built from the land it crosses. Local stone, rammed local earth. Kamlesh P. Lulla, NASA’s chief scientist for Earth observation at Johnson Space Center:
it is very, very difficult to distinguish the Great Wall of China in astronaut photography, because the materials that were used in the wall are similar in colour and texture to the materials of the land surrounding the wall — the dirt.
So it is a very long, very narrow object with almost no contrast against its own background. Length is not what makes something visible from orbit. Width and contrast are.
The “only” half fails on its own
Even if the Wall were easy to see, it would not be the only thing. NASA notes that cities at night are perhaps the most visible human works from low Earth orbit, along with major roadways, bridges, airports, dams and reservoirs.
And in the same article NASA publishes a photograph taken from the Station with a plain caption: the ancient pyramids at Giza are clearly visible.
Three ways we could be wrong in the other direction
The correction has itself become overstated, and we would rather name that than benefit from it.
It is not invisible. Lulla judged the interpretation of this photograph “seems to be good”, and identified why it worked: “the right set of conditions must have occurred” — a sunny day, and a recent snowfall that helped pick the Wall out. A second Chiao photograph, taken on 20 February with a 400 mm lens, may also show it.
It is readily visible in radar. Lulla again: “you can see the wall in radar images taken from space.” Radar is not the naked eye, but a flat “you cannot see the Wall from space” is wrong.
“Visible from space” hides an enormous ambiguity. Low Earth orbit is 350–400 kilometres up. The Moon is roughly a thousand times further. A claim already wrong at 350 kilometres is physically absurd at lunar distance, and letting the two blur lets the claim retreat to the easier ground whenever it is challenged.
Alan Bean, who walked on the Moon with Apollo 12, settled that half himself:
The only thing you can see from the Moon is a beautiful sphere, mostly white, some blue and patches of yellow, and every once in a while some green vegetation. No man-made object is visible at this scale.
The evidence
NASA states plainly: "The Great Wall of China, frequently billed as the only man-made object visible from space, generally isn't, at least to the unaided eye in low Earth orbit. It certainly isn't visible from the Moon."
Cited sources:S1
Leroy Chiao, who took the photograph, "himself said he didn't see the wall, and wasn't sure if the picture showed it". The person best placed to confirm naked-eye visibility, on the mission that produced the definitive image, did not confirm it.
Cited sources:S1
Kamlesh P. Lulla, NASA's chief scientist for Earth observation at Johnson Space Center, on the physical reason: "it is very, very difficult to distinguish the Great Wall of China in astronaut photography, because the materials that were used in the wall are similar in colour and texture to the materials of the land surrounding the wall — the dirt."
Cited sources:S1
Apollo 12 astronaut Alan Bean, on the view from lunar distance: "The only thing you can see from the Moon is a beautiful sphere, mostly white, some blue and patches of yellow, and every once in a while some green vegetation. No man-made object is visible at this scale."
Cited sources:S1
The "only structure" half of the claim fails independently. NASA notes that cities at night are perhaps the most visible human works from low Earth orbit, along with major roadways, bridges, airports, dams and reservoirs — and publishes a Station photograph in which the ancient pyramids at Giza are clearly visible.
Cited sources:S1
The frame was taken with a 180 mm telephoto lens from 348 km, and NASA describes it as apparently the first verifiable photograph of the Wall from low Earth orbit — 43 years after the first human spaceflight.
NASA's catalogue record for that same frame lists its features as "Mountains, snow, and Laoha River drainage system". The Great Wall does not appear in the feature list of the photograph taken to show the Great Wall.
Cited sources:S2
NASA records the Moon-visibility theory as dating "back to at least 1938", noting it "was repeated and grew until astronauts landed on the lunar surface" — established as a belief more than two decades before anyone could test it.
Cited sources:S1
Chinese astronaut Yang Liwei said he could not see the structure after his 2003 flight, and NASA notes this prompted discussion in China about rewriting textbooks that teach the claim.
Cited sources:S1
Evidence that cuts the other way
Findings that complicate or argue against the verdict above. They are listed because leaving them out would make the file look stronger than it is.
The Wall is not invisible, and a file that overcorrected into "you can never see it" would be making the opposite error. NASA's Lulla judged the interpretation of this photograph "seems to be good", and identified the conditions that made it work: "It appears that the right set of conditions must have occurred for this photograph to capture the small segment of the wall" — a sunny day, and a recent snowfall that helped make the wall more visible.
Cited sources:S1
A second Chiao photograph, taken on 20 February with a 400 mm lens, may also show the Wall. And NASA notes the Wall "can be seen readily in radar imagery" — Lulla: "you can see the wall in radar images taken from space." Radar is not the naked eye, but it is a real qualification on any flat statement that the Wall cannot be seen from orbit.
Cited sources:S1
NASA's own feature article publishes an arrow-annotated version of this photograph marking where the Wall runs, and describes the estimated location as one "where the wall is visible". This file uses the unannotated frame; a reader should know the annotated one exists rather than infer that NASA could not locate the Wall either.
Cited sources:S1
"Visible from space" hides an enormous ambiguity. Low Earth orbit is roughly 350–400 km up; the Moon is about a thousand times further. A claim already wrong at 350 km is absurd at lunar distance, and collapsing the two lets the claim retreat to the nearer ground whenever it is challenged.
Cited sources:S1
What we still don’t know
- The frequently repeated earlier origins for this claim — a 1754 line by the antiquary William Stukeley, and a 1932 "Ripley's Believe It or Not!" cartoon — are **not** established by the sources read for this file. NASA dates the belief to "at least 1938". The older attributions circulate widely and may well be correct, but neither primary text was read, so this file leads with NASA's date and records the rest as unverified.
- Whether the second Chiao photograph of 20 February 2005, taken with a 400 mm lens, does in fact show the Wall. NASA says only that it "may also show" it.
- How reliably the Wall can be distinguished under favourable conditions is not quantified by any source read here. Snow cover and a low sun angle are identified as the conditions that helped in this instance; no threshold is given.
Sources
Every source below was read in full before it was cited. Archive snapshots are recorded at research time, because a file whose sources have evaporated is indistinguishable from one that never had any.
S1Tier 1Read in full
China's Wall Less Great in View from Space
NASA — News & Features · 2005-05-09
NASA's own published treatment of the question, and the source of every substantive finding in this file. Establishes that the Wall generally is not visible to the unaided eye from low Earth orbit and certainly not from the Moon; the physical reason; Chiao's own statement that he did not see it; Lulla's assessment and the snow-and-sun conditions; Alan Bean's lunar testimony; Yang Liwei's statement; the 1938 dating; and the Giza counterexample. Originally published 9 May 2005 at nasa.gov/vision/space/workinginspace/great_wall.html; page last updated 30 November 2007. Read in full from the archived PDF.
S2Tier 1Read in full
Astronaut photography catalogue record ISS010-E-8497
NASA Johnson Space Center — Gateway to Astronaut Photography of Earth · 2004-11-24
The primary record for the photograph. Establishes the photographer, date and time to the second, altitude, the 180 mm telephoto lens, NASA's caption calling it apparently the first verifiable orbital photograph of the Wall, the photo-centre coordinates that corroborate S1's location, and the feature list — which does not mention the Wall.
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