Galileo Galilei was an influential figure who offered the world several scientific discoveries.

He was particularly interested in the stars, with his work building a foundation for future scientists and astronomers. Although the night sky was his main passion, Galileo also helped further the advancement of physics through his work. Unfortunately, due to the period in which he lived, some of his work was not viewed favorably by society – particularly the church – which led to his persecution later in life.

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Who was Galileo?

Galileo Galilei was an Italian astronomer born in Pisa, Italy, in 1564. He studied at the Camaldolese Monastery before advancing his education at the University of Pisa, where he studied medicine before changing to mathematics. His passion for mathematics – particularly geometry – led him to teach mathematics at the University level, both at the University of Pisa and the University of Padua.

Galileo as a teacher

For a good portion of his life, Galileo taught mathematics and undertook various teaching positions to earn a living. During this period, he intensely studied how objects in motion worked. His paper, ‘The Little Balance’, outlined hydrostatic principles when weighing small objects. This work garnered some academic attention, which provided him with a full-time position at the University of Pisa by 1589.

Galileo started work on some of his most famous experiments during his time as a teacher at the University of Pisa. He would experiment with objects falling from the air to produce a manuscript called ‘On Motion’, which broke away from the traditional (at the time) views surrounding motion and how objects interact with environments. He was proud of his work, arguably too proud, which drew criticism from his peers. In particular, his ideas shifted away from Aristotle’s theories, which his contemporaries didn’t appreciate.

By 1592, Galileo’s contract with the University of Pisa lapsed, and he got a new job at the University of Padua, where he taught geometry, astronomy, and mechanics. He would stay there for 18 years, offering students insightful and engrossing lectures that drew huge crowds. This helped him gain some fame in academic circles.

Galileo’s family life

Although Galileo predominantly concerned himself with academic pursuits, he eventually started a fruitful relationship with a woman named Marina Gamba from Venice. They met in 1600, and soon after, they started a family. The couple had three children before marriage – two daughters, Virginia and Livia, and a son, Vincenzo. The two never got married due to financial concerns or the social scorn of having children out of wedlock brought at the time.

Galileo worried that his two daughters would struggle to find suitable husbands, so he placed them in a convent. By 1616, Virginia had changed her name to Maria Celeste, and Livia became Sister Arcangela. They both became nuns but stayed in contact with Galileo throughout his life.

Galileo’s son, Vincenzo, eventually enjoyed a fully legitimized birth, allowing him to enter social circles quickly. This helped him become a successful musician throughout Italy.

Galileo’s contributions to science

Galileo’s passion for education and academics underpinned his contribution to the sciences, particularly physics and astronomy. His leading theory around motion and mechanics looked at how objects of different weights would fall at the same speed. He also noted that the descent would accelerate with the same consistency. So he theorized that the distance an object falls is proportional to the time it takes to fall. He also created the framework for Newton’s First Law of Motion by theorizing that if something moves along a flat plane, it will move at a constant speed unless impeded.

As Galileo was so passionate about the night sky, it’s no real surprise that he loved telescopes. In 1609, he devised an idea to create a powerful telescope. His idea worked, and throughout his life improved telescope magnification from x3 to x30. This additional magnification allowed him to discover entirely new features in the night sky, including the moons around Jupiter and the phases of Venus.

Unfortunately, although his work proved influential at the time, it drew significant ire from the church. His work on the phases of Venus challenged the standardized belief that the Earth was the center of the universe.

The persecution of Galileo

When Galileo released his findings about the Earth’s position in the solar system, the Catholic Church accused him of heresy. The Roman Inquisition put him on trial, and he was found guilty of heresy. He was sent to prison but spent most of his sentence under house arrest.

In his later years, Galileo lost his eyesight, but he kept working on his ideas. By 1638, he had written a book that outlined all of his ideas about motion and mechanics called, ‘Discourses Concerning Two New Sciences’. A few years later, Galileo passed away in 1642, aged 77.

What is Galileo best known for?

Galileo’s discoveries are what make him such a prominent historical figure. He used his skills in experimentation and scientific observation to readily challenge the established theories of his time. He became known for his ability to go against preconceived notions and seek a complete truth, ultimately leading to his arrest. Below are some of the things that he is best known for:

  • Laws of Motion: Galileo measured how objects fell and accelerated at the same rate. This built the foundation for Isaac Newton’s work later on.
  • Topography of the moon: Before Galileo observed the Moon, people believed there was nothing but a smooth surface on the satellite surrounding Earth. Galileo used shadows to calculate the heights of mountains and craters found on the Moon.
  • The phases of Venus: Galileo observed that Venus went through phases as our Moon does. This pointed him toward the notion that Venus moved around the Sun rather than the Earth.
  • The moons of Jupiter: Galileo also observed the moons of Jupiter for the first time, which is why they’re known as the Galilean moons, which include Io, Europe, Callisto, and Ganymede.
  • The Milky Way’s stars: Before Galileo, people believed the Milky Way was just light scattering in the night sky. His observations found that they were millions of stars.
  • Pendulum clocks: Galileo’s work extended beyond astronomy and physics, as he was also responsible for helping design a rudimentary pendulum clock through ‘Galileo’s escapement’.


Galileo Galilei was a notable academic, astronomer, and physicist who put scientific pursuits over social norms and accepted standards. Although he was passionate about his work, it, unfortunately, led to his persecution by the Catholic Church, where he was successfully tried for heresy. Still, his contributions to science live on to this day – from the telescopes we use to how we understand our solar system.