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][not in citation given] It was invented by Muhammad ibn Mūsā al-Khwārizmī in 9th-century Baghdad.[3][not in citation given] Shadow squares are often found on the backs of astrolabes.
References [edit]
- ^ "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.
