Ancient Astronomical Observations and the Study of the Moon's Motion (1691-1757)

Two changes in the collective mindset of humanity had to take place before astronomy could make the major advances that it has. First, the belief that Earth was the center of the universe had to be overturned by the strength of the evidence that it was not. This dramatic shift in mindset meant that physical evidence would forever be stronger than simple belief based on superficial observation. The second was that the belief that the astronomical bodies were perfect in form and movement, repeating the same paths over and over had to be eliminated. By using evidence compiled over time, this second belief was overturned and science could then proceed unfettered by these two notions.

The idea that the paths of heavenly bodies changed over time was a difficult one to verify, for the changes take place very slowly, in most cases centuries must pass before the differences are apparent. The best candidates for verifying such changes are the moon and the sun, the two easiest to follow and measure. Furthermore, the sun and moon together create eclipses of two types and these events were nearly always precisely recorded by the observers. Accounts of eclipses go back thousands of years; these records are even used to accurately date past events.

This book is a tale of how centuries of data about the movement of the moon were examined, criticized and then used to discover and then quantify the secular acceleration of the moon. Since the earlier observations were not as accurate, due to limitations of the observational techniques of the time, the people analyzing the data were reasoning under conditions of uncertainty.

The stories in this book are almost exclusively about the personalities of the investigators, what they did, how they interacted, the accuracy of the observations and some of the disagreements they had over the data and conclusions. It is easy to be impressed by what the astronomical investigators of this period accomplished in reaching their conclusions about the motion of the moon. While they sometimes disputed the accuracy of the data, they never questioned the scientific method and went where the data took them. This is a story of scientific inquiry and advancement at its best.

Charles Ashbacher splits his time between consulting with industry in projects involving math and computers, teaching college classes and co-editing The Journal of Recreational Mathematics. In his spare time, he reads about these things and helps his daughter in her lawn care business.