Galileo Galilei
Timed a swinging chandelier against his pulse and found the pendulum's secret.
Biography
Galileo Galilei was born in Pisa in 1564 and spent most of his working life as a professor of mathematics at Padua and a court philosopher in Florence. In 1583, still a medical student, he sat in Pisa cathedral watching a bronze chandelier sway overhead and timed its swings against his own pulse. Every cycle took the same amount of time, no matter how wide the arc. That observation — isochronism — became the seed of the pendulum clock and of modern mechanics.
In 1609 he heard that a Dutch spectacle maker had built a device for making distant things look closer. Within months he had ground his own lenses and built a telescope several times better than anything in Europe. He pointed it at the night sky and saw craters on the Moon, four moons orbiting Jupiter, and the phases of Venus. None of it fit the Earth-centered universe he had been taught. He published the observations in Sidereus Nuncius in 1610 and became the most public champion of Copernicus's heliocentric model.
For that stance the Roman Inquisition tried him in 1633 and sentenced him to house arrest, where he remained until his death in 1642. In those last years, blind and confined, he wrote Two New Sciences — the book that founded the study of motion and materials as quantitative, mathematical subjects.
Contributions
- 01discovered isochronism of the pendulum (1583)
- 02improved the telescope and observed Jupiter's moons (1610)
- 03documented the phases of Venus, confirming heliocentrism
- 04established the law of falling bodies
- 05founded the modern science of motion in Two New Sciences
Major works
First published account of observations made through a telescope. Described lunar craters, the Milky Way as individual stars, and four moons orbiting Jupiter.
A polemic on the nature of comets that became a manifesto for the scientific method. Contains Galileo's famous declaration that the book of nature is written in mathematics.
A conversation among three characters comparing the Ptolemaic and Copernican models. Its persuasive case for heliocentrism led directly to Galileo's trial by the Inquisition.
Galileo's final and most important book. Founded the sciences of materials strength and kinematics, deriving the parabolic trajectory of projectiles and the law of falling bodies.