A 13,000 mile dragon of earth and stone winds its way through the countryside of China with a history almost as long and serpentine as the structure. The Great Wall began as multiple walls of rammed earth built by individual feudal states during the Chunqiu period to protect against nomadic raiders north of China and each other. When Emperor Qin Shi Huang unified the states in 221 BCE, the Tibetan Plateau and Pacific Ocean became natural barriers, but the mountains in the north remained vulnerable to Mongol, Turkish, and Xiongnu invasions. To defend against them, the Emperor expanded the small walls built by his predecessors, connecting some and fortifying others. As the structures grew from Lintao in the west to Liaodong in the east, they collectively became known as The Long Wall. To accomplish this task, the Emperor enlisted soldiers and commoners, not always voluntarily. Of the hundreds of thousands of builders recorded during the Qin Dynasty, many were forcibly conscripted peasants and others were criminals serving out sentences. Under the Han Dynasty, the wall grew longer still, reaching 3700 miles, and spanning from Dunhuang to the Bohai Sea. Forced labor continued under the Han Emperor Han-Wudi , and the walls reputation grew into a notorious place of suffering. Poems and legends of the time told of laborers buried in nearby mass graves, or even within the wall itself. And while no human remains have been found inside, grave pits do indicate that many workers died from accidents, hunger and exhaustion. The wall was formidable but not invincible. Both Genghis and his son Khublai Khan managed to surmount the wall during the Mongol invasion of the 13th Century. After the Ming dynasty gained control in 1368, they began to refortify and further consolidate the wall using bricks and stones from local kilns. Averaging 23 feet high and 21 feet wide, the walls 5500 miles were punctuated by watchtowers. When raiders were sighted, fire and smoke signals traveled between towers until reinforcements arrived. Small openings along the wall let archers fire on invaders, while larger ones were used to drop stones and more. But even this new and improved wall was not enough. In 1644, northern Manchu clans overthrew the Ming to establish the Qing dynasty, incorporating Mongolia as well, Thus, for the second time, China was ruled by the very people the wall had tried to keep out. With the empire's borders now extending beyond the Great Wall, the fortifications lost their purpose. And without regular reinforcement, the wall fell into disrepair, rammed earth eroded, while brick and stone were plundered for building materials. But its job wasn't finished. During World War II, China used sections for defense against Japanese invasion, and some parts are still rumored to be used for military training. But the Wall's main purpose today is cultural. As one of the largest man-made structures on Earth, it was granted UNESCO World Heritage Status in 1987. Originally built to keep people out of China, the Great Wall now welcomes millions of visitors each year. In fact, the influx of tourists has caused the wall to deteriorate, leading the Chinese government to launch preservation initiatives. It's also often acclaimed as the only man-made structure visible from space. Unfortunately, that's not at all true. In low Earth orbit, all sorts of structures, like bridges, highways and airports are visible, and the Great Wall is only barely discernible. From the moon, it doesn't stand a chance. But regardless, it's the Earth we should be studying it from because new sections are still discovered every few years, branching off from the main body and expanding this remarkable monument to human achievement.
Un dragón de terra e pedra de case 21.000 km serpentea polo campo da China cunha historia case tan longa e serpentina como a estrutura. A Gran Muralla comezou coma múltiples muros de terra batida construídos por distintos estados feudais no periodo Chunqiu para protexerse dos asaltantes nómades do norte da China e entre si. Cando o emperador Qin Shi Huang unificou os estados no 221 a.C. a meseta tibetana e o océano Pacífico convertéronse en barreiras naturais, pero as montañas do norte seguiron sendo vulnerables ás invasións mongolas, turcas, e dos xiongnu. Para defenderse deles, o emperador ampliou as pequenas murallas feitas polos seus predecesores, conectando algunhas e fortalecendo outras. Mentres as estruturas crecían desde Lintao no oeste ata Liaodong no leste, no seu conxunto se lles coñecía coma a Longa Muralla. Para realizar esta obra, o emperador alistou soldados e plebeos, non sempre voluntariamente. Dos centos de miles de construtores rexistrados na dinastía Qin, moitos eran campesiños reclutados á forza e outros eran delincuentes cumprindo condenas. Baixo a dinastía Han a muralla medrou máis aínda, chegando case aos 6.000 km, estendéndose desde Dunhuang ata o mar de Bohai. O traballo forzado seguiu baixo o emperador Wu de Han, e as murallas colleron a reputación dun lugar de sufrimento. Poemas e lendas da época falaban de obreiros enterrados en fosas comúns próximas, ou mesmo dentro da propia muralla. E aínda que non se atoparon restos humanos no seu interior, hai fosas que indican que moitos obreros morreron de accidentes, fame e esgotamento. A muralla era formidable pero non invencible. Gengis e o seu fillo Kublai Kan conseguiron superar a muralla durante a invasión mongol do século XIII. Despois de que a dinastía Ming tomase o control no 1368, comezaron a refortalecer a muralla e a consolidala aínda máis utilizando ladrillos e pedras de fornos locais. Cunha media de 7 m de alto e 6,4 de ancho, as murallas duns 9000 km estaban marcadas por torres vixía. Cando se vían asaltantes, os sinais de lume e fume viaxaban entre as torres ata que chegaban os reforzos. Pequenas aberturas na muralla permitían aos arqueiros disparar aos invasores, mentres que as grandes usábanse para tirar pedras, e máis cousas. Pero nin sequera esta muralla nova e mellorada bastou. No 1644, os clans manchúes do norte derrocaron aos Ming para establecer a dinastía Qing, incorporando tamén Mongolia. Así, por segunda vez, China foi gobernada pola mesma xente que a muralla intentara manter fóra. Agora que as fronteiras do imperio chegaban máis aló da Gran Muralla, as fortificacións perderon o seu propósito. E sen reformas regulares, a muralla comezou estar en mal estado, a terra batida erosionada, e se saqueaban ladrillos e pedras para usar de materiais de construción. Pero o seu traballo non rematara. Na Segunda Guerra Mundial, China usou partes dela coma defensa contra a invasión xaponesa, e aínda se rumorea que algunhas partes se usan para adestramento militar. Pero hoxe, o obxectivo principal da muralla é cultural. Como unha das maiores estruturas da Terra feitas polo ser humano, foi declarada Patrimonio Mundial da UNESCO no 1987. Orixinalmente construída para manter á xente fóra de China, a Gran Muralla recibe agora millóns de visitantes ao ano. De feito, a afluencia de turistas fixo que a muralla se deteriorase, o que levou ao goberno chinés a lanzar iniciativas para preservala. Tamén é a miúdo aclamada como a única estrutura feita polo ser humano visible desde o espazo. Desafortunadamente, iso non é certo. Na órbita terrestre baixa, todo tipo de estruturas son visibles, como pontes, autoestradas e aeroportos, e a Gran Muralla apenas pode percibirse. Desde a Lúa, non ten ningunha posibilidade. Pero é desde a Terra desde onde debemos estudala porque aínda se descobren novas seccións cada poucos anos, ramificándose do corpo principal e ampliando este notable monumento ao logro humano.