Galileo Galilei was born on February 15, 1564, in Pisa, Italy.¹⁾

He was the first of six children born to Vincenzo Galilei, a musician and music theorist, and Giulia Ammannati.²⁾

Galileo initially studied medicine at the University of Pisa but later shifted his focus to mathematics and physics.³⁾

His experiments with pendulums led to his discovery of the isochronism of pendulums, meaning that the period of a pendulum's swing is constant regardless of its amplitude.⁴⁾

In 1609, Galileo heard about the invention of the telescope and built his own version, greatly improving its design.⁵⁾

With his telescope, Galileo discovered the four largest moons of Jupiter, now known as the Galilean moons: Io, Europa, Ganymede, and Callisto.⁶⁾

He observed the phases of Venus, which supported the heliocentric model proposed by Nicolaus Copernicus.⁷⁾

Galileo's observations of the Moon revealed its rough and mountainous surface, challenging the traditional belief in a perfectly smooth celestial body.⁸⁾

In 1610, he published “Sidereus Nuncius” (Starry Messenger), describing his astronomical discoveries.⁹⁾

His observations of the Milky Way challenged the idea that it was composed of a multitude of stars too faint to see individually.¹⁰⁾

Galileo's work on the pendulum and the law of falling bodies laid the groundwork for Isaac Newton's theory of universal gravitation.¹¹⁾

He formulated the principle of relativity for uniform motion, a precursor to Albert Einstein's theory of special relativity.¹²⁾

Galileo was a proponent of the Copernican heliocentric model of the solar system, which placed the Sun at the center.¹³⁾

His support for the heliocentric model put him at odds with the Catholic Church, which adhered to the geocentric model.¹⁴⁾

In 1616, the Catholic Church issued a decree prohibiting the teaching of Copernicanism, leading Galileo to be cautious about his views.¹⁵⁾

Galileo's friendship with Pope Urban VIII initially protected him from persecution.¹⁶⁾

However, in 1632, he published “Dialogo sopra i due massimi sistemi del mondo” (Dialogue Concerning the Two Chief World Systems), which defended the heliocentric model. This led to his trial by the Inquisition.¹⁷⁾

In 1633, Galileo was found guilty of heresy and placed under house arrest for the rest of his life.¹⁸⁾

While under house arrest, he continued his scientific work and wrote “Discourses and Mathematical Demonstrations Relating to Two New Sciences,” which laid the foundation for the science of mechanics.¹⁹⁾

Galileo's work with telescopes greatly expanded our understanding of the cosmos, challenging prevailing astronomical beliefs.²⁰⁾

He made precise observations of the phases of Venus, which provided strong evidence for the heliocentric model.²¹⁾

Galileo's work on the laws of motion influenced the development of classical physics.²²⁾

He made significant contributions to the study of projectile motion.²³⁾

Galileo made contributions to the field of engineering, including improvements to the telescope and the design of the military compass.²⁴⁾

He also conducted experiments on the nature of buoyancy and developed a hydrostatic balance.²⁵⁾

Galileo was not the first person to invent the telescope, but he significantly improved its design and made groundbreaking astronomical discoveries with it.²⁶⁾

He made important contributions to the understanding of sound, including the mathematical description of sound waves.²⁷⁾

Galileo's book “Two New Sciences” laid the foundation for modern physics and mechanics.²⁸⁾

He was a professor of mathematics at the University of Padua for nearly two decades.²⁹⁾

Galileo corresponded with other leading scientists and philosophers of his time, including Johannes Kepler and René Descartes.³⁰⁾

His observations of sunspots provided evidence that the Sun was not a perfect, unchanging celestial body.³¹⁾

Galileo's work on the tides helped to refine our understanding of their causes.³²⁾

He made significant contributions to the field of optics, particularly in the study of lenses and refraction.³³⁾

Galileo designed and constructed instruments such as the thermoscope, an early precursor to the thermometer.³⁴⁾

His work on falling bodies challenged Aristotle's theories on motion.³⁵⁾

Galileo's observations of the Moon's surface inspired future astronomers and explorers.³⁶⁾

He was a prolific writer, with numerous publications on a wide range of scientific topics.³⁷⁾

Galileo's legacy includes the Galilean telescope, named in his honor, which is still used in astronomy today.³⁸⁾

The Galileo spacecraft, launched by NASA in 1989, provided valuable data about Jupiter and its moons.³⁹⁾

He made contributions to the field of kinematics, the study of motion without considering its causes.⁴⁰⁾

Galileo's works were widely read and translated into many languages, spreading his ideas throughout Europe.⁴¹⁾

He was known for his wit and sharp tongue, often using humor in his writings.⁴²⁾

Galileo's discoveries played a crucial role in the Scientific Revolution and the development of modern science.⁴³⁾

Despite his conflicts with the Church, Galileo's work ultimately contributed to the acceptance of the heliocentric model and the advancement of scientific thought.⁴⁴⁾

Galileo Galilei passed away on January 8, 1642, in Arcetri, Italy, but his legacy as a pioneering scientist and thinker endures to this day.⁴⁵⁾