PHYSICS TEACHING / SCIENTIST BIOGRAPHY
[Scientist Biography Series] Galileo: His Life and Free Fall
I only meant to add a little context to free fall. Somehow that turned into an expedition through Galileo’s switch from medicine to mathematics, his challenges to authority, and a fact-check of the science stories we have heard since childhood.
This article treats Galileo as more than a name in a textbook. By following his childhood, education, teaching career, and later years, it reconnects free fall, pendulums, the telescope, and heliocentrism with the person who kept challenging the authorities of his time.
- Origins and a change of direction
- His family background and his father’s practical concerns
- How he moved from medicine toward mathematics and natural philosophy, guided by Ostilio Ricci
- Early research and inventions
- From the swinging-lamp story to pendulum isochronism—and the disputed attribution of the pulsilogium
- How he taught mathematics privately before securing the Pisa post with help from established mathematicians
- Free fall and scientific reasoning
- His logical challenge to Aristotle’s claim that heavier objects fall faster
- What the famous Leaning Tower story tells us—and why its historical status remains disputed
- Later years and historical influence
- Telescopic astronomy, support for heliocentrism, and conflict with Church authorities
- How Galileo’s studies of motion became part of the foundation inherited by Newton
- Teaching and personal reflections
- How stories from the history of science can reconnect formulas with human choices and historical context
- A lighter final detour through the Japanese drama Galileo
Galileo Galilei was an Italian physicist, mathematician, astronomer, and philosopher—and one of the most important figures in the Scientific Revolution.
His many achievements earned him an impressive collection of titles: the father of modern observational astronomy, the father of modern physics, the father of science, and the father of modern science. The distinguished theoretical physicist Stephen Hawking even wrote that the birth of modern science owed more to Galileo than to anyone else.
Origins
Galileo was the eldest of the six children of Vincenzo Galilei and Giulia Ammannati. He was born in Pisa, Italy, in 1564. By then, the Polish astronomer Copernicus—who had advocated heliocentrism—had been dead for 21 years, while the birth of the English physicist Isaac Newton was still 78 years away.
Galileo’s father Vincenzo was a prominent musician and lutenist with considerable knowledge of mathematics, Greek, and Latin. Unfortunately, neither mathematics nor music was an easy way to make a living in Italy at the time, so the Galilei family was not especially wealthy and had a rather difficult life. (Why does that sound a little too much like the modern education environment and the way people think about it?)
His Student Years
When Galileo was young, he considered devoting his life to the Church. His father insisted instead that he study medicine at the University of Pisa. Doctors earned better money at the time, after all, and his father was probably terrified that Galileo would follow in his footsteps and choose not one, but two careers that did not pay particularly well.
Even while studying medicine, Galileo found time to sit in on geometry lectures and read extensively about Aristotle. Those experiences laid the groundwork for his lasting interest in mathematics and the natural sciences.
Why Aristotle? Because by Galileo’s time, Aristotle’s philosophy had long been integrated with Church authority and theology. He was revered as “the Philosopher” and “the master of those who know.” If you wanted to study serious scholarship, Aristotle was more or less unavoidable.
Around the same time, Galileo met one of the most important mentors in his life: Ostilio Ricci, a mathematician and tutor at the Tuscan court. Galileo happened to hear one of Ricci’s lectures on geometry and became fascinated with mathematics. Ricci recognized his talent and shared his knowledge generously, giving Galileo a strong mathematical foundation for his later scientific research.
According to tradition, while Galileo was studying at the University of Pisa, he noticed a hanging lamp swinging back and forth inside Pisa Cathedral. Like many science stories passed down for centuries, the details of this scene cannot be treated as perfectly secure firsthand history. It works better as an entry point for understanding how Galileo became interested in pendulums.
Galileo studied the relationship among a pendulum’s bob mass, length, and amplitude. He found that the mass of the bob does not determine the period. Under the approximation of a modest swing angle, the period depends mainly on the pendulum length and local gravitational acceleration, while the effect of amplitude is small. This is the pendulum’s approximate isochronism. At large swing angles, however, the period does change—so this does not mean that every amplitude produces exactly the same period!
The pendulum also entered medical measurement during this period. More reliable historical evidence generally credits the physician Santorio Santorio with the pulsilogium, an instrument for comparing a patient’s pulse with pendulum motion. Later biographies attributed the invention to Galileo, but modern historical research finds that attribution poorly supported.
And Galileo was only about twenty years old at the time! When the author was twenty, I was still just a silly second-year university student. Orz.
Galileo became increasingly absorbed in mathematics and physics, spending his days studying Euclid and Archimedes while neglecting his medical coursework. His father eventually became so angry that he refused to pay any more tuition. With little choice left, Galileo abandoned his studies and left the University of Pisa without a degree.
No Degree, but He Still Came Back to Teach—OK der
After leaving university, Galileo worked as a private mathematics teacher while building connections with prominent mathematicians. He applied unsuccessfully for a position at the University of Bologna; in 1589, with assistance from Christoph Clavius and Guidobaldo del Monte, he obtained a mathematics post at the University of Pisa.
While teaching at Pisa, Galileo set out to challenge Aristotle’s view of falling bodies: heavy objects fall quickly, while light objects fall slowly.
Galileo exposed the problem through logic. Under Aristotle’s account, if a heavy object and a light object were connected, the combined object should fall at a speed somewhere between the two because the lighter object would slow the heavier one down. Yet the combined object would also be heavier than the heavy object alone, which should make it fall even faster. The assumptions contradict one another.
Then there is the famous story everyone knows: Galileo supposedly carried a heavy object and a light one to the top of the Leaning Tower of Pisa and let his opponents watch them land almost simultaneously. The story mainly comes from a biography written years later by his student Vincenzo Viviani. Galileo’s own writings contain no matching account, so historians still disagree about whether the demonstration happened in the form described by the legend. Whether or not the tower story is literally true, Galileo’s more important contribution was using logical reasoning and systematic studies of motion to challenge ideas that had been treated as unquestionable authority.
In ordinary air, a feather and a metal ball still fall very differently because they experience very different amounts of air resistance. By the mid-seventeenth century, the English scientist Robert Boyle was conducting low-pressure experiments with an air pump built with the assistance of Robert Hooke. These included observations of light objects falling after much of the air had been removed. Later vacuum-drop experiments became increasingly refined and demonstrated more clearly that, when air resistance is removed, objects of different masses undergo the same gravitational acceleration. Scientific knowledge is rarely proven all at once by a single experiment going “Ta-da!” More often, many people gradually improve the theory, the instruments, and the experimental precision.
Beyond falling bodies, Galileo continued to challenge Aristotle’s account of motion and gradually developed important ideas and principles related to inertia—but let’s save the details for another article XD. (Definitely not because I’m being lazy!)
Later Years
In 1609, Galileo heard about telescopes developed in the Netherlands that could magnify distant objects. Working from the underlying principle, he built and repeatedly improved his own instruments, greatly increasing their magnification. Then he pointed them toward the sky and used them to study the Moon, Jupiter’s satellites, the phases of Venus, sunspots, and other celestial phenomena.
Galileo had already become an important scholar. Observations such as Jupiter’s satellites and the phases of Venus created serious problems for the traditional claim that every celestial body revolved around Earth, and they offered powerful support for the Copernican system. That does not mean one observation instantly settled every competing astronomical model. The conflict that followed also involved Galileo’s public defense of heliocentrism, debates over the interpretation of Scripture, and the complicated religious and political environment of the time. In 1616, Church authorities ordered Galileo not to hold or defend heliocentrism. In 1633, he faced the Inquisition over his Dialogue Concerning the Two Chief World Systems.
Galileo was convicted at the 1633 trial and spent the rest of his life primarily under house arrest rather than in an ordinary prison. Even under those restrictions, he did not abandon science. He completed Discourses and Mathematical Demonstrations Relating to Two New Sciences, an important synthesis of his work on motion and the strength of materials, leaving a remarkable body of knowledge to later generations.
Galileo died on January 8, 1642.
A “Giant” for Later Generations
By a curious coincidence, 1642—the year Galileo died—is also often given as the year Isaac Newton was born. England and Italy were using different calendars at the time, however. Converted to the Gregorian calendar used today, Newton’s birth date was January 4, 1643. The image of one scientific giant dying just as another is born is more of a romantic story told by later generations. Even so, Newton’s achievements in classical mechanics genuinely inherited and extended Galileo’s studies of motion.
Newton’s famous remark, “If I have seen further, it is by standing on the shoulders of giants,” appeared in a 1675 letter to Robert Hooke. It was not a reply to Edmond Halley, and the original sentence did not identify Kepler and Galileo as two specific giants. Still, within the development of classical mechanics, Galileo’s work on falling bodies, inertia, and motion unquestionably formed part of the foundation that allowed Newton to go further.
Conclusion
That was a collection of stories from Galileo’s life. I hope they have given you a basic sense of who this scientist actually was!
The author cannot help thinking that being able to spend an entire lifetime doing what you love—without letting profitability decide everything, provided you have enough financial stability—must be a genuinely happy way to live.
To finish, here is a modern-day “Galileo”: the Japanese drama Galileo. I highly recommend it! There are multiple seasons and specials, and the series offers a playful glimpse of what scientists actually do. Who knows? It might even make you like physics a little more XD.
Since Aristotle has appeared so many times in this article, the next installment should probably tell the story of his life and achievements!
References
真理的護衛者-伽利略, URL: http://www.shs.edu.tw/works/essay/2010/03/2010032616150099.pdf
Wikipedia—Galileo Galilei
科學名人堂12-伽利略, URL: http://www.bud.org.tw/museum/s_star12.htm
天文學家系列-伽利略, URL: http://web2.nmns.edu.tw/PubLib/NewsLetter/91/176/13.htm
Wikipedia—Lute
Family | Vincenzo Galilei, URL: https://galileo.library.rice.edu/fam/vincenzo.html
Galileo’s Battle for the Heavens—Fall of the Leaning Tower, URL: https://www.pbs.org/wgbh/nova/pisa/galileo.html
Science | Pendulum Clock, URL: https://galileo.library.rice.edu/sci/instruments/pendulum.html
A Phenomenology of Galileo’s Experiments with Pendulums, URL: https://www.cambridge.org/core/journals/british-journal-for-the-history-of-science/article/phenomenology-of-galileos-experiments-with-pendulums/494C00BA710DB3244C683CDE216457B9
1C20.10 Coin and Feather (Thor’s Hammer), URL: https://www.sfu.ca/physics/demos/demos-experiments/coin-feather-burnaby.html
Biography | Galileo Galilei, URL: https://galileo.library.rice.edu/bio/tov.html
Bigotti, F., & Taylor, D. (2017). The Pulsilogium of Santorio: New Light on Technology and Measurement in Early Modern Medicine. Soc Politica, 11(2), 53–113. URL: https://pmc.ncbi.nlm.nih.gov/articles/PMC6407692/
Stanford Encyclopedia of Philosophy—Galileo Galilei, URL: https://plato.stanford.edu/entries/galileo/
Chapter VI—Newton’s Correspondence with Hooke, URL: https://www.newtonproject.ox.ac.uk/view/texts/normalized/OTHE00101
FAQ
The Leaning Tower experiment is a famous story, but historians still dispute whether it happened in the form later described. The account mainly comes from a biography written years later by Galileo’s student Vincenzo Viviani; Galileo’s own writings contain no matching record. What is much better established is Galileo’s use of logic and systematic studies of motion to challenge Aristotle’s account of falling bodies.
The key condition is that air resistance and other effects are removed or made negligible. In a vacuum, objects of different masses undergo the same gravitational acceleration. In ordinary air, differences in shape, area, and drag can still produce visibly different motion.
Not under every condition. For modest swing angles, a simple pendulum’s period is approximately determined by its length and local gravitational acceleration, while the effect of amplitude is small. At larger amplitudes, the period changes by a measurable amount.
Galileo was tried by the Roman Inquisition after publicly defending heliocentrism and spent the rest of his life primarily under house arrest, rather than in an ordinary prison. The conflict also involved scriptural interpretation, publishing, and the religious and political environment of the time—not merely a single astronomical observation.
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Galileo matters not only because his name appears beside free fall, inertia, and astronomy in physics textbooks, but because his work shows how observation, reasoning, and experiment can challenge answers that once seemed unquestionable. If you want to reconnect high-school physics with that same way of understanding the world, Wakame’s High School Physics Online Course uses animation and gradually scaffolded problems to bring concepts, equations, and problem-solving logic back into one coherent framework.
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