Shadow square
From Wikipedia, the free encyclopedia
The shadow square, also known as an altitude scale,[1] was an instrument used to determine the linear height of an object, in conjunction with the alidade, for angular observations. It is an early example of an analog computer.[2] It was invented by Muhammad ibn Mūsā al-Khwārizmī in 9th-century Baghdad.[3] Shadow squares are often found on the backs of astrolabes.
References
- ↑ "Shadow Square". Retrieved 2009-07-18.
- ↑ "Astrolabe detail within shadow square". National Maritime Museum. Retrieved 2009-07-18.
- ↑ King, David A. (2002). "A Vetustissimus Arabic Text on the Quadrans Vetus". Journal for the History of Astronomy 33: 237–255. Bibcode:2002JHA....33..237K.
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