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WonderHistory fact

Contrary to a popular legend, the Great Wall of China cannot normally be seen from space with the naked eye. It is thousands of kilometres long but only a few metres wide, and it is built from local stone and earth that blend into the land around it.

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History

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The idea is older than spaceflight. In 1754 the English antiquarian William Stukeley wrote that the Chinese wall might be made out from the Moon, and the claim spread from there. From the Moon, about 384,000 kilometres away, seeing the wall would be like spotting a human hair from 3 kilometres. From low Earth orbit, a few hundred kilometres up, NASA says it is barely visible, and only in near-perfect conditions; it stands out no more than many other human-made structures. Yang Liwei, China's first astronaut, said after his flight in 2003 that he had looked for it and could not see it. A survey completed in 2012 by China's cultural heritage authority put the length of all the wall's sections, trenches and natural barriers at 21,196 kilometres.

Türkçe oku
Çin Seddi, yaygın inanışın aksine, olağan koşullarda uzaydan çıplak gözle görülmez. Binlerce kilometre uzunluğundadır ama genişliği yalnızca birkaç metredir; üstelik yapıldığı yerel taş ve toprak, çevresindeki araziden pek ayırt edilmez.

Bu inanış uzay yolculuklarından çok daha eskidir. İngiliz tarihçi ve eski eser araştırmacısı William Stukeley 1754'te, Çin Seddi'nin Ay'dan bile seçilebileceğini yazmıştı; iddia oradan yayıldı. Oysa yaklaşık 384.000 kilometre uzaktaki Ay'dan Çin Seddi'ni görmek, 3 kilometre öteden bir saç telini görmeye benzer. NASA'ya göre birkaç yüz kilometre yükseklikteki alçak yörüngeden bile ancak kusursuza yakın koşullarda, güçlükle seçilebilir; insan yapımı pek çok başka yapıdan daha belirgin değildir. Çin'in ilk astronotu Yang Liwei de 2003'teki uçuşundan sonra Çin Seddi'ni aradığını ama göremediğini söyledi. Çin'in kültürel miras kurumunun 2012'de tamamladığı araştırma, Çin Seddi'ne ait bütün duvar bölümlerini, hendekleri ve doğal engelleri toplam 21.196 kilometre olarak ölçtü.

Sources and further reading

Background reading: Great Wall of China
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