Childhood and Education (1564–1585)

Galileo Galilei was born in Pisa on February 15, 1564, the eldest son of Vincenzo Galilei, a musician and music theorist, and Giulia Ammannati. His family, part of the lesser nobility, provided him with a basic humanistic and mathematical education, influenced by his father, who instilled in him a critical attitude toward authority.

In 1581, he enrolled at the University of Pisa to study medicine, as his father wished, but soon developed a passion for mathematics and natural philosophy, abandoning his medical studies.

Early Studies and Academic Career (1585–1592)

After leaving university without a degree, Galileo began giving private lessons in mathematics. He wrote an early treatise on the center of gravity of solids, which attracted the attention of scholars.

In 1589, he obtained the chair of mathematics at the University of Pisa, where he began to question Aristotelian physics. It is said that during this period he conducted the famous experiment from the Tower of Pisa, dropping objects of different masses to demonstrate that falling speed does not depend on mass (a likely legendary tale, but illustrative of his experimental approach).

In 1592, he moved to Padua, at the University of Padua, where he taught for 18 years. This was the most productive period of his career.

Discoveries and Inventions (1592–1610)

During his stay in Padua, Galileo made numerous discoveries in mechanics, hydraulics, optics, and astronomy. Among his major contributions:

• In 1609, he improved the telescope, increasing its magnification from 3x to 30x.

• With this instrument, in 1609–1610, he made revolutionary astronomical observations:

  • He discovered Jupiter’s satellites (now called the “Medicean” or “Galilean” moons).

  • He observed the phases of Venus, which confirmed the heliocentric system.

  • He noted that the Moon does not have a smooth surface, but is mountainous.

  • He discovered that the Milky Way is composed of a multitude of stars.

In 1610, he published Sidereus Nuncius (The Starry Messenger), which earned him European fame and the favor of the Medici family, under whom he became court mathematician and philosopher in Florence.

Conflict with the Church (1610–1633)

His observations supported the Copernican system, according to which the Earth revolves around the Sun, in contrast to the Aristotelian-Ptolemaic geocentric view upheld by the Church.

In 1616, the Catholic Church formally condemned heliocentrism as “heretical.” Galileo received an official warning not to advocate it publicly.

In 1632, he published Dialogue Concerning the Two Chief World Systems, a brilliant work in dialogue form in which he defended Copernicanism, while formally maintaining neutrality. The work provoked strong reactions.

In 1633, he was tried by the Inquisition in Rome and forced to recant his views. According to legend, after his abjuration, he muttered, “And yet it moves,” but there is no historical evidence for this statement.

He was sentenced to lifelong house arrest.

Final Years and Death (1633–1642)

Galileo spent his final years at the villa in Arcetri, near Florence, assisted by his daughter Maria Celeste (a Poor Clare nun). He continued to write and study, despite increasingly poor health and eventual blindness.

In 1638, he published Discourses and Mathematical Demonstrations Relating to Two New Sciences in the Netherlands (beyond the reach of Church censorship), considered the foundation of classical mechanics.

He died on January 8, 1642, at the age of 77.

Scientific Legacy

Galileo is regarded as the father of modern science for several reasons:

• Scientific Method: He was among the first to combine observation, experimentation, and mathematics.

• Physics: He laid the groundwork for dynamics and classical mechanics.

• Astronomy: His observations challenged dogma and expanded knowledge of the universe.

• Technology: He improved instruments such as the telescope, geometric compass, and other scientific devices.

Posthumous Rehabilitation

Galileo remained a controversial figure for centuries. Only in 1992, under Pope John Paul II, did the Catholic Church officially acknowledge the errors made during his trial.

Major Works

• Sidereus Nuncius (The Starry Messenger, 1610)

• Dialogue Concerning the Two Chief World Systems (1632)

• Discourses and Mathematical Demonstrations Relating to Two New Sciences (1638)

• Treatises on mechanics, motion, hydrostatics, and geometry

Conclusion

Galileo Galilei was much more than a great scientist: he was a revolutionary thinker who challenged authority in the pursuit of truth through reason and experience. His legacy lives on today in modern science and critical thought.