EXHIBITS: Instruments of Science History

Science  23 Mar 2001:
Vol. 291, Issue 5512, pp. 2281c
DOI: 10.1126/science.291.5512.2281c

Without mechanical clocks, how would you mark time in the dark? Fifteenth century scientists solved the problem by inventing the nocturnal, a device made of superimposed disks that measured time at night by following the movement of stars and the moon. Find out more at Epact, a new Web catalog of 520 medieval and Renaissance scientific instruments.

Epact was set up by the Museum of the History of Science, Oxford, and three other museums in the United Kingdom, Italy, and the Netherlands to display their collections of instruments from before 1600. The often lavish and beautiful pieces range from sundials and surveying instruments to armillary spheres, which modeled the celestial sphere with respect to the horizon of an observer (here, one from France circa 1570). Besides photos and descriptions of each piece, Epact holds a bibliography and technical articles about how the instruments were used. The site notes that nocturnals had one drawback: They didn't work too well on cloudy nights.



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