On Elegance, Computation & Structure
"Frake's comparison of the compass rose used to compute tides to the micronesian concept of
etak is based in the abstract properties of both as organizing schemata. **I believe that the links are even stronger in that both systems achieve their computational power by superimposing several kinds of representational structure on a single framework."
On the astrolabe: a flexible, analog computer
"The astrolabe is not just a memory of the structure of the sky; it is an analog computer.
The major components of the astrolabe are the *mater, the limb, the plate, and the rete. The mater is the framework that holds the other pieces together. The limb is a circular scale around the perimeter of the mater. The limb is inscribed with a 360 degree scale and/or a 24-hour scale. In either case, the limb is a representation of the structure of sidereal time. *Each astrolabe is really a kit that can be assembled differently according to the circumstances of its use."
"An astrolabe can be made of durable materials because the regularities it captures change only very slowly. **The variables that do change, observer latitude & time of observation,are represented in the physical structure of the astrolabe* either by changeable parts (plates for each latitude) or by changeable relations among the parts (the rotation of the rete about the axis with respect to the plate and the limb). The constraints of the represented world are thus built into structure of the device.