page_title: Su Song
section_title: Su Song's armillary sphere
hierarchical_section_title: Su Song / Su Song's armillary sphere
caption_attribution_description: Beijing Ancient Observatory, replica of Ming Dynasty's Armillary in the garden
context_page_description: Su Song was a Chinese polymathic scientist and statesman. Excelling in a variety of fields, he was accomplished in mathematics, astronomy, cartography, geography, horology, pharmacology, mineralogy, metallurgy, zoology, botany, mechanical engineering, hydraulic engineering, civil engineering, architecture, invention, art, poetry, philosophy, antiquities, and statesmanship during the Song Dynasty.
  Su Song was the engineer for a hydro-mechanical astronomical clock tower in medieval Kaifeng, which employed the use of an early escapement mechanism. The escapement mechanism of Su's clock tower had been invented by Buddhist monk Yi Xing and government official Liang Lingzan in 725 AD to operate a water-powered armillary sphere, although Su's armillary sphere was the first to be provided with a mechanical clock drive. Su's clock tower also featured the oldest known endless power-transmitting chain drive, called the tian ti, or "celestial ladder", as depicted in his horological treatise. The clock tower had 133 different clock jacks to indicate and sound the hours.
context_section_description: In Joseph Needham's third volume of Science and Civilization in China, the drawing for Fig. 159 displays a drawing of Su Song's armillary sphere (as depicted in his 11th century treatise), complete with three 'nests' or layers of mechanically-rotated rings. It was the earlier Chinese astronomer Li Chun-feng of the Tang Dynasty who in 633 AD created the first armillary sphere with three layers to calibrate multiple aspects of astronomical observation. Zhang's armillary sphere has often been compared to that of the 13th century monarch Alfonso X of Castile in Islamic-era Spain. The chief difference was that Alfonso's instrument featured an arrangement for making measurements of the azimuth and altitude, which was present in the Arabic tradition, while Su Song's armillary sphere was duly graduated. For the drawing of Su's armillary sphere, the listing of components are:
  The Outer Nest
  meridian circle
  horizon circle
  outer equator circle
  The Middle Nest
  solstitial colure circle
  ecliptic circle
  diurnal motion gear-ring, connecting with the power-drive
  The Inner Nest
  polar-mounted declination ring or hour-angle circle, with
  sighting tube attached to it and strengthened by a
  diametral brace
  Other Parts
  vertical column concealing the transmission shaft
  supporting columns in the form of dragons
  cross-piece of the base, incorporating water-levels
  south polar pivot
  north polar pivot
caption: A modern replica of a Ming Dynasty era armillary sphere found at the Beijing Ancient Observatory
exif: {"Image Make": "EASTMAN KODAK COMPANY", "Image Model": "KODAK DX6490 ZOOM DIGITAL CAMERA", "Image Orientation": "Horizontal (normal)", "Image XResolution": "230", "Image YResolution": "230", "Image ResolutionUnit": "Pixels/Inch", "Image YCbCrPositioning": "Centered", "Image ExifOffset": "506", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail Orientation": "Horizontal (normal)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "2708", "Thumbnail JPEGInterchangeFormatLength": "6344", "EXIF ExposureTime": "1/350", "EXIF FNumber": "14/5", "EXIF ExposureProgram": "Program Normal", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2006:05:16 15:00:45", "EXIF DateTimeDigitized": "2006:05:16 15:00:45", "EXIF ComponentsConfiguration": "YCbCr", "EXIF ShutterSpeedValue": "17/2", "EXIF ApertureValue": "3", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "3", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash did not fire, compulsory flash mode", "EXIF FocalLength": "63/10", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "2304", "EXIF ExifImageLength": "1728", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "2404", "EXIF ExposureIndex": "80", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF DigitalZoomRatio": "0", "EXIF FocalLengthIn35mmFilm": "38", "EXIF SceneCaptureType": "Standard", "EXIF GainControl": "None", "EXIF Contrast": "Normal", "EXIF Saturation": "Normal", "EXIF Sharpness": "Normal", "EXIF SubjectDistanceRange": "0"}