Galileo Galilei demonstrates his first telescope to Venetian lawmakers.

Galileo Galilei (1564–1642) was an Italian astronomer, physicist, and polymath often called the “father of modern science.” He made groundbreaking contributions to mechanics, motion, and astronomy, challenging long-standing Aristotelian ideas. Using systematic observation and mathematics, Galileo helped establish the scientific method as a foundation for inquiry. His experiments with falling bodies demonstrated that objects accelerate at the same rate regardless of mass, which laid the groundwork for Newton’s laws of motion.

In astronomy, Galileo’s improvements to the telescope in 1609 opened the heavens to unprecedented study. He discovered the four largest moons of Jupiter (now called the Galilean moons), observed the phases of Venus, mapped sunspots, and studied the rugged surface of the Moon. These findings provided powerful evidence against the geocentric model of the universe and supported the Copernican heliocentric system, which placed the Sun at the center. His telescopic work fundamentally reshaped humanity’s understanding of its place in the cosmos.

However, Galileo’s defense of heliocentrism brought him into direct conflict with the Catholic Church. In 1633, he was tried by the Roman Inquisition and forced to recant his views, spending the rest of his life under house arrest. Despite this, his works—such as Dialogue Concerning the Two Chief World Systems—continued to spread across Europe and deeply influenced future scientists. Today, Galileo is remembered not only for his discoveries but also for his courage in pursuing truth against immense opposition.