Celestial Globe

The celestial globe is a device that was used in ancient China to observe the motion of celestial bodies. It is composed of two main observing devices: the armillary sphere and the celestial sphere. The armillary sphere measures the spherical coordinates of celestial bodies, while the celestial sphere demonstrates celestial phenomena. Its theoretical basis is the huntianshuo, a geocentric theory in ancient Chinese astronomy, that views the universe as a sphere, like an egg, with the Earth as the central yolk. That was a useful perspective back then.

Zhang Heng (78-139), an astronomer of the Eastern Han Dynasty (25 - 220) made significant improvements to the celestial globe based on the work of his predecessors. He created a copper celestial globe in 117. According to records, the main body of the celestial globe was a copper sphere surrounded by several layers of circles that could all rotate. The vertical circle passing through the North and South poles was called the celestial meridian, and another circle representing the horizon was called the horizon circle. On the surface of each layer were carved the South pole, the North pole, the equator, the ecliptic, the Twenty-Four Solar Terms, the twenty-eight mansions in astrology, the sun, the moon, and other celestial bodies. This ingenious design allowed the speed of the copper sphere's rotation to match that of the Earth's rotation, simulating the movement of the stars in real time.

The celestial globe is a remarkable product of ancient Chinese astronomy that had a profound impact on the world's astronomical theory and practice. Before the invention of telescopes in the 17th century, it was an essential instrument for astronomers to determine the position of celestial bodies.

渾天儀

渾天儀是中國古代觀測天體運行的儀器，主要由渾儀和渾象構成。渾儀是測量天體球面坐標的一種儀器，渾象是古代用來演示天象的儀表。其理論基礎是“渾天說”。該學說認為天是一個圓球，像雞蛋，地球就像雞蛋黃一樣，立于其中，這是當時天文學說中先進的認識。

東漢天文學家張衡（78—139）在前人的基礎上對渾天儀進行了重要改進，在117年制成一件銅鑄渾天儀。據記 載，其主體是一個由幾層均可運轉的圓圈組成的銅球，其中通過南北極的圓環叫子午圈，另一個是表示地平線的地平圈。各層分別刻著南、北極，黃、赤道，二十四節氣， 二十八列宿，日、月等天象。通過精妙的設計，銅球轉動一周的速度和地球自轉一周的速度相同，使得銅鑄渾天儀能夠實時模擬星空的運行。

渾天儀是中國古代天文學成就的杰出代表，對世界天文學理論及實踐產生了深遠的影響。在17世紀望遠鏡發明之前，渾天儀是天文學家在測定天體方位時必不可少的儀器。