The city of Chang'an in the twelfth year of Zhenguan was a mechanical fantasy that spanned a thousand years. Li Yan, a modern mechanical engineer, fell into the body of a craftsman in the prosperous Tang Dynasty with a green dragon jade pendant engraved with a quantum star map. When he measured Zhuque Street with a vernier caliper and recast the Taiye Pond with concrete, he did not know that he was slowly turning a giant mechanism that enveloped China—from the bearings of the plow to the gears of the armillary sphere, from the codes of the Dunhuang beacons to the steam core of the Luoyang Underground Palace, the entire Tang Dynasty was becoming a sophisticated historical correction machine.
