March/April 2005 Table of Contents
courtesy of the author.
always have been fascinated by the movement of objects in the sky.
The ability to accurately locate the heavenly bodies and to predict
celestial events had practical applications for many early cultures.
For the ancient Egyptians, the heliacal rising of the star Sirius
predicted the flooding of the Nile, signaling the optimal time for
planting. For the classical Greeks, accurately locating a heavenly
body in the sky using their skill with spherical geometry satisfied
their urge to understand the structure of the Cosmos. For the Medieval
Christians, knowing the time of the full Moon after the Vernal Equinox
for a given year helped them calculate the date of Easter Sunday
every year. For Islamic peoples, understanding the location of objects
in the heavens helped them determine the direction of Mecca, which
they needed to face several times a day during prayer. Thus, events
in the sky were important for the day-to-day life of many early
measure and calculate the location and movement of heavenly bodies
in the sky, as well as to tell time and determine one’s location
in latitude on Earth, a number of instruments were developed, such
as the astrolabe and the armillary sphere. However, such instruments
were made of metal or wood, were expensive to produce, and were
used mainly by scholars who had the incentive to purchase them.
But with the advent of moveable type and the development of printing
in Europe in the 1450s, an opportunity arose to incorporate principles
of these instruments into books, which could be produced more cheaply
and could reach more people. This led to the popularization of moveable
devices on the printed page that were called volvelles.
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