Paper Computer



Volvelles are primitive paper computers and they were found in books in astronomy. Volvelles were printed as part of a book and served as interactive devices long before the world wide web and browser. The one pictured above is from Petrus Apianus' Cosmographia published in 1524. Volvelles were also called "Apian Wheels." The purpose of these devices was to compute something such as the time of sunrise or sunset at a specific latitude. This computation is a form of simulation--of the motion of the sun or moon. How can one simulate anything with paper? Think of the volvelle as a radial look up function table. Suppose you wanted to create something to determine y=sin(x). The volvelle creator will pre-compute sines for different values of x in making the device. Then as the user/reader, you rotate the disc to x and read off y. If you have ever used a circular slide rule, this works on a similar principle where the scale is logarithmic.