V.

Galileo Galilei

Contemporary scientists regard Galileo as the model of the new scientist. He made major advances in physics, helped popularize physics, and became even more famous when he was arrested and tried by papal authorities. For his discoveries, which directly defied the teachings of the Catholic Church, Galileo was convicted and sentenced to house arrest. This sentence turned out to be a lot better than being jailed or burned at the stake, fates met by many other early scientists who defied church authority.

The story of Galileo starts with his telescope. Galileo reportedly constructed many telescopes after hearing about one built by a Dutch optician. Lenses were quite common in Galileo’s time, and it did not cost him great effort to calculate the separation of lenses that would produce proper magnification. Technology has advanced enormously, of course, and Galileo’s best telescope would not rival a pair of good binoculars today. Nevertheless, the telescope enabled Galileo to make profound discoveries.

First, he determined that the Moon’s surface had mountains and craters and that, like Earth, it was craggy and corrugated. He discovered that, like the Moon, Earth also shines. He then looked at Jupiter, and in one glorious week of careful observations, discovered Jupiter’s moons in orbit around the planet. This finding contradicted the prevailing Aristotelian belief that everything orbited Earth. Galileo opened the heavens to observation. Anyone could look through Galileo’s telescope and conclude, as Copernicus had, that Earth was just another planet. Some prominent philosophers who were critics of Galileo refused to look through the telescope, afraid that their safe conclusions about the way the world worked would be jeopardized.

Galileo’s discoveries of the laws of motion were also revolutionary. By experiment and mathematical analysis, he demonstrated a style of science that has been the model for physicists ever since. Galileo made two major contributions to physics: He advanced the use of mathematics to understand “how nature is,” and he pioneered difficult experiments to test the consequences. Galileo wrote, “Philosophy [science] is written in this grand book, the universe, which stands continually open to our gaze … but this book cannot be understood unless one learns to comprehend the language and read the letters in which it is composed. It is written in the language of mathematics and its characters are triangles, circles and other geometric figures without which it is humanly impossible to understand nature.”