Galileo, the Astronomical Telescope, and the Beginning of Modern Astronomy

Abstract

The works of Tycho Brahe and Johannes Kepler mark the end of the two great trends in astronomy that opened the doors to accurate observational astronomy, as exemplified by Brahe’s work on the one hand, and theoretical astronomy as exemplified by Kepler’s work on the other hand. Fortunately for observational astronomy, Galileo’s astronomical telescope entered the stage just when Brahe had brought naked-eye observing to its limits of accuracy. Fortunately for theoretical astronomy, Isaac Newton’s discovery of the laws of motion and the law of gravity entered the arena a few years after Kepler had completed his work on the motions of the planets. These two developments—the telescope and Newton’s discovery of the laws of motion and gravity—raised astronomy to unaccustomed heights. No longer was it necessary to strain one’s fallible sight to obtain and record results, and no longer, after Newton, did one have to cover hundreds of sheets of paper with the most careful and demanding computations. The orbits not only of the planets moving around the sun but also the orbits of stars around each other could be deduced in a very short time with the elegant Newtonian mathematics and his laws of motion and gravity.