| Book Review | The American Historical Review, 106.1

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| Book Review | The American Historical Review, 106.1 | The History Cooperative

Book Review

Europe: Early Modern and Modern

J. L. Heilbron. The Sun in the Church: Cathedrals as Solar Observatories. Cambridge: Harvard University Press. 1999. Pp. ix, 366. $35.00.

The problem of placing Easter correctly in the calendar was the main reason why scholars from the Renaissance onward punched small holes in dark churches to direct a beam of light toward a calibrated line on the floor. This same problem, which involves reconciling lunar and solar calendars, "kept mathematics alive in the Latin West during the Dark Ages and also conveyed a little exact information about the physical world" (p. 35), according to J. L. Heilbron. In the early modern period, he argues that it created niches for science within the Roman Catholic Church, despite censorship, the Index, and the Inquisition. 1

When a late Renaissance scholar pierced the fabric of an Italian church and transformed it into an immense gnomon, the process took a lot of expensive engineering. Only a scientific entrepreneur with the combined skills of mathematician, courtier, and engineer could accomplish it. Heilbron explains every detail in the process. If it was done right, a small solar image would move along the meridian line on the floor and show the exact moment of the spring equinox. Easter was the Sunday after the first full moon following the equinox. . . .

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