The Ballet of the Planets by Donald C. Benson

Rating: 8/10

Humans have been observing the sky for thousands of years, and the most noticeable objects there are the ones that seem to move, if observed throughout a year. The Moon, the Sun and the five planets visible to the naked-eye can be seen moving on the background of the so-called fixed stars. There have been theories trying to explain these movements since before the Common Era, and they've been modified throughout the ages.

The Ballet of the Planets tells the story of the movements of the planets and the historical theories that sought to explain them.

The motions of the planets are a topic that is introduced in astronomy and science to students quite early, however usually they don't find out about the mathematics that goes with it, nor about all the other theories and improvements to the theories that were used before for predicting the locations of the planets.

This book makes for excellent reading if you want to know more about the history of theories in celestial mechanics and also if you want to find out about the mathematics and geometry that is involved there.

For example you can find out how Hipparcus improved on Aristotle's model of the Solar system in which of-course the Earth was in the centre, but there were problems with the accuracy of the models predictions and Hipparcus moved the Earth a little bit away from the centre to make the observations agree better with the calculations.

Hipparcus was of course just one of the earlier scientists to think about the planetary movements, and so starting from him you can go all the way through Ptolemy, Tycho Brahe, Copernicus and to Kepler's laws and Newton's Universal Law of Gravity.

In the mean time you'll also get acquainted with the relevant geometry and mathematics involved - for example you can find out how some closed two-circle and three-circle epicyclic curves look like and what exactly are cycloidal curves and who were the scientists who devoted a lot of time on them, and find proofs for some theorems- Pascal's theorem for example.

So over-all I think this book would make for great additional reading if you're learning about the planetary motions at a higher level, as the mathematics and history are not usually touched upon for example in undergraduate astronomy courses.

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