Le Operazioni del Compasso Geometrico e Militare (review)

Galileo is best known for his scientific discoveries and his trial by the Catholic Church. In physics, he discovered the laws of falling bodies and formulated approximations to the laws of inertia and conservation of momentum. In astronomy, he discovered lunar mountains, Jupiter's satellites, Venus's phases, and sunspots, and correctly interpreted them to strengthen the Copernican theory. In instrumentation, he invented or improved the telescope, microscope, and thermometer. In methodology, he pioneered the art of experiment (as distinct from passive observation); developed the quantitative approach through the application of mathematics to motion; and advocated the irrelevance of Scripture in natural science. Culturally speaking, he was persecuted, tried, and condemned as a suspected heretic by the Inquisition for holding that the Earth moves and the Bible is not a scientific authority; but this tragedy made him an icon in the struggle for freedom of thought and for understanding the interaction between science and religion.

Less well known is the fact that in 1606 Galileo published a booklet of instructions on using an instrument ("compass") to make rapid calculations to solve engineering and military problems such as the following: extraction of square and cube roots; currency conversions; compound interest; construct a plane or solid figure similar and equal to several others; given two unequal similar figures, find a third similar to these and equal to their difference; find the mean proportional; how every parallelepiped can be reduced to a cube; given two sides for two similar solids made of different materials, find the ratio of their weights; make any desired regular figure that equals any given irregular but rectilinear figure; arrange armies with unequal fronts and flanks; calibrate guns for all cannonballs of any material and weight.

This aspect of Galileo's work is more than a biographical aberration. There are two reasons for its significance. This book was his first publication, and so it suggests that in his early career he was involved in practical mathematics and military engineering; and this in turn suggests a very particular source for Galileo's work, and more generally for modern science. Second, this publication was part of a money-making enterprise Galileo engaged in during his university career; for he supplemented his meager salary by using his own home as a boarding house for students, by giving private lessons, and by his compass business. The latter included manufacturing and selling compasses and teaching how to use them, although not how to build them, which he regarded as a trade secret.

This CD contains Stillman Drake's 1978 English translation of the original Italian; a useful introduction by Filippo Camerota describing the instrument and placing it in its historical context; and images of every page of the original book, from a copy held in the Library of Congress.

It is awe-inspiring that a field to which Galileo contributed has progressed so much that it becomes possible to own such material for a small sum. The editors are to be commended. However, I did not find the electronics user-friendly: for example, although I could view all pages and print most, I could not print some; and a list of keyboard shortcuts was partly unclear and partly nonworking.