Galileo vs Newton: Revolutionaries of Science

“If I have seen further, it is by standing on the shoulders of giants.” This famous phrase by Isaac Newton perfectly summarizes the relationship between him and Galileo. One opened the way, the other turned it into a highway. Together, they created what we now call modern science.

Galileo Galilei (1564-1642) and Isaac Newton (1642-1727) are the fathers of the scientific revolution. The first pointed his telescope at the sky and saw what no one had seen before. The second watched an apple fall and understood why planets orbit the Sun. Two simple gestures, two immense revolutions.

But these two men were also profoundly different. One was an Italian showman, provocative, who loved debates and controversies. The other was a solitary Englishman, paranoid, who kept his discoveries secret for years. Together, they tell us the story of the birth of science - and what it takes to change the world.

Two Lives, Two Eras

Galileo: The Flamboyant Italian

Galileo Galilei was born in 1564 in Pisa, the same year as Shakespeare. His father, Vincenzo, was a musician and mathematician - a combination that profoundly influenced young Galileo. Music taught him the mathematical harmony of the world; mathematics gave him the language to describe it.

He first studied medicine at the University of Pisa - his father’s wish. But the courses bored him. One day, during a sermon in the cathedral, he observed a chandelier swinging. Regardless of the amplitude of the oscillation, the time for one round trip seemed constant. He had just discovered the isochronism of the pendulum. Medicine could wait.

Galileo became a professor of mathematics, first in Pisa, then in Padua. He was a popular teacher, a brilliant lecturer, a man who loved life - wine, women, animated debates. He never married but had three children with his mistress Marina Gamba.

In 1609, everything changed. He heard about a Dutch invention - a tube with lenses that brought distant objects closer. Within weeks, he built his own telescope, far better than the original. And he did what no one had thought to do: he pointed it at the sky.

What he saw turned the world upside down.

Newton: The Solitary Englishman

Isaac Newton was born in 1642, the very year Galileo died - as if the torch was passed from one hand to another. He was born premature, so small that they said he could fit in a quart pot. No one thought he would survive.

His father had died three months before his birth. His mother remarried when he was three and left him with his grandmother. This abandonment marked Newton for life. He became suspicious, resentful, incapable of normal relationships. At 19, he made a list of his sins: among them, “threatening my father and mother Smith to burn them and the house over them.”

At Cambridge, he was a mediocre student - until he discovered mathematics. There, something awakened. Within a few years, he mastered everything that was known, then went far beyond. During the Great Plague of 1665-1666, the university closed and Newton returned home. Those two years were the most productive in the history of science.

Alone, at the family farm in Woolsthorpe, Newton invented calculus, discovered that white light is composed of all colors, and formulated the first ideas about gravitation. “The miraculous year,” as it’s called. He was 23.

But Newton kept his discoveries secret for decades. It took Edmund Halley, the astronomer of the comet, to convince him to publish the Principia Mathematica in 1687. This book changed the world - but Newton almost never wrote it.

Their Discoveries: Two Revolutions

Galileo: The Eye That Sees

Galileo’s telescope wasn’t very powerful - about 20x magnification. But what it revealed was stunning.

The Moon wasn’t perfect. Aristotle taught that celestial bodies were perfect spheres. Galileo saw mountains, craters, valleys. The Moon looked like Earth. If the Moon wasn’t perfect, maybe the heavens weren’t so different from the terrestrial world.

Jupiter had moons. Four small points of light orbiting Jupiter. Galileo called them the “Medicean stars” (in honor of his patrons). It was proof that not everything revolved around Earth. If Jupiter could have satellites, why not the Sun?

Venus had phases. Like our Moon, Venus went through phases - full, crescent, waning. This was impossible in the Ptolemaic system where Venus orbited Earth. But perfectly explainable if Venus orbited the Sun.

The Milky Way was made of stars. That milky cloud in the sky wasn’t celestial mist, but millions of stars, too faint to be seen with the naked eye.

These observations didn’t prove that Earth orbited the Sun. But they made the old system increasingly hard to defend. Galileo published his discoveries in Sidereus Nuncius (The Starry Messenger) in 1610. The book caused a sensation throughout Europe.

Newton: The Mind That Understands

Where Galileo had observed, Newton understood. He didn’t just describe the world - he explained it.

Universal gravitation. The apple story is probably true, or at least partially. Newton understood that the force that makes an apple fall is the same one that keeps the Moon orbiting Earth, and Earth orbiting the Sun. A single law, universal, mathematical: F = G(m₁m₂)/r².

This equation is perhaps the most important ever written. It explains why planets have elliptical orbits (as Kepler had discovered), why tides rise and fall, why comets return. It allowed predicting Neptune’s existence before it was observed.

The three laws of motion. Every body perseveres in its state of rest or uniform motion unless a force acts upon it. Acceleration is proportional to force and inversely proportional to mass (F = ma). To every action there is an equal and opposite reaction.

These three laws, simple in appearance, are the foundation of all classical mechanics. They explain how objects move, from tennis balls to rockets. They remain valid today, except at atomic scales or near the speed of light.

Optics. Newton decomposed white light into its constituent colors with a prism. He understood that colors are not “added” by the prism, but “separated.” He invented the reflecting telescope to avoid the chromatic aberrations of lenses.

Calculus. Newton invented a new type of mathematics to solve his physics problems. Differential and integral calculus - derivatives and integrals - are the basic tools of all modern physics and engineering.

Their Methods: Observing vs Calculating

Galileo: The Experimenter

Galileo is often called the “father of the modern scientific method.” That’s not quite accurate - others before him had done experiments - but he systematized the experimental approach like no one before.

His genius was asking simple questions and testing them. Do heavy bodies fall faster than light ones? Aristotle said yes. Galileo rolled balls of different masses down inclined planes and measured. No, they fall at the same speed (in a vacuum).

He combined observation with mathematics. He didn’t just describe - he measured, calculated, predicted. “Nature is written in mathematical language,” he wrote. Triangles, circles, geometric figures are the letters of that language.

His telescope was a scientific instrument, not a toy. He calibrated it carefully, noted his observations precisely, published his methods so others could verify. This is the essence of modern science: reproducibility.

Newton: The Theorist

Newton was a pure theorist. He did experiments - his work on light shows that - but his genius was in mathematical abstraction. He saw the hidden laws behind phenomena.

His method was deductive. He started from general principles (the three laws of motion, the law of gravitation) and deduced particular consequences. Why are orbits elliptical? Because that’s what the law of gravitation predicts. Why tides? Same reason.

The Principia Mathematica is written in Euclidean style: definitions, axioms, theorems, proofs. Newton wanted physics to be as rigorous as geometry. He succeeded.

But Newton had a flaw: he didn’t share. He kept his discoveries to himself, sometimes for years. When Leibniz published his own version of calculus, Newton accused him of plagiarism and triggered a quarrel that poisoned relations between English and continental mathematicians for a century.

Their Conflicts: The Church and Rivals

Galileo: Facing the Inquisition

Galileo’s conflict with the Catholic Church is one of the most famous in the history of science. But it’s often misunderstood.

The Church wasn’t systematically anti-science. Popes had encouraged astronomy, Jesuits made observations. The problem wasn’t really scientific - it was political and personal.

Galileo was provocative. His Dialogue Concerning the Two Chief World Systems (1632) featured three characters: a Copernican supporter (intelligent), a Ptolemaic supporter (an idiot named Simplicio), and a moderator. Pope Urban VIII, Galileo’s former friend, recognized himself in Simplicio. He never forgave.

The 1633 trial condemned Galileo for “vehement suspicion of heresy.” He had to abjure his “errors” and was placed under house arrest for the rest of his life. Legend says he muttered “And yet it moves” - but that’s probably a later invention.

Galileo wasn’t tortured, not imprisoned in a dungeon. He lived comfortably in his villa near Florence, continued his research on mechanics, and published his most important work, the Discorsi, in 1638. But the message was clear: science had to submit to theology.

Newton: Facing His Rivals

Newton had no problems with the Church - Anglican England was more tolerant than Catholic Italy. His conflicts were with his peers.

The quarrel with Leibniz over calculus lasted decades. Newton had invented calculus first (around 1666), but Leibniz had published it first (1684). Who had stolen from whom? In reality, they had probably invented independently - but Newton couldn’t accept that.

As president of the Royal Society, Newton appointed a committee to judge the quarrel. The committee (led by Newton himself) concluded that Leibniz was a plagiarist. Yet Leibniz’s notation was better - it’s the one we still use today.

Robert Hooke was another enemy. Hooke claimed to have had the idea of gravitation before Newton. This was partially true - Hooke had proposed an attractive force inversely proportional to the square of distance. But he hadn’t done the calculations. Newton had. The quarrel only subsided at Hooke’s death in 1703.

Newton was resentful, paranoid, petty. He had Hooke’s portrait removed from the Royal Society. He pursued counterfeiters with personal ferocity when he became Warden of the Royal Mint. Genius, yes. Pleasant human being, certainly not.

Their Legacies: The Foundations of Science

Galileo: The Scientific Spirit

Galileo’s legacy isn’t a particular theory - most of his ideas have been superseded. It’s something more fundamental: the scientific spirit.

Galileo showed that you could understand the world through observation and reasoning, without submitting to authorities. Aristotle says X? Let’s check. The Church says Y? Let’s look. This attitude - methodical skepticism, the primacy of experience - is the essence of modern science.

He also showed that mathematics is the language of nature. Before him, mathematics was a practical tool (for commerce, surveying) or an abstract discipline (Euclidean geometry). After him, mathematics becomes the way to understand the physical world.

His trial became a symbol. Every time science is censored, every time dogma opposes free inquiry, we think of Galileo. “And yet it moves” - even if invented, this phrase captures something true: truth always triumphs in the end.

Newton: The System of the World

Newton’s legacy is more concrete: a complete system for understanding the physical universe. Newtonian mechanics dominated physics for more than two centuries. It remains the basis of engineering, aeronautics, space exploration.

His laws are extraordinarily powerful. With three simple equations and the law of gravitation, you can predict the motion of any macroscopic object: a ball, an airplane, a planet, a galaxy. This is what Newton called the “System of the World.”

This system also had an immense philosophical impact. If the universe obeys mathematical laws, then it’s deterministic - every effect has a cause, every motion can be predicted. This “mechanistic” vision of the world dominated Western thought until the 20th century.

Einstein surpassed Newton - relativity and quantum mechanics showed the limits of classical physics. But Newton wasn’t refuted: his physics remains perfectly valid in its domain of application. That’s the fate of great theories: not to be destroyed, but to be encompassed in broader theories.

What They Teach Us

Science as Revolution

Galileo and Newton remind us that science is revolutionary. It doesn’t just accumulate facts - it overturns worldviews. Before Galileo, Earth was the center of the universe. After Newton, it was just one planet among others, obeying the same laws as everything else.

This revolution is never finished. Each generation of scientists questions the certainties of the previous one. Einstein surpassed Newton, and someone will surpass Einstein. This is how science progresses: not by accumulation, but by successive revolutions.

Genius and Character

These two men also show us that genius doesn’t guarantee good character. Galileo was arrogant, provocative, sometimes dishonest. Newton was paranoid, resentful, cruel. Their flaws don’t diminish their discoveries - but they remind us that scientists are human beings, with their weaknesses.

Perhaps certain flaws even favor genius. Galileo’s arrogance allowed him to defy authorities. Newton’s paranoia drove him to verify and re-verify his calculations. Genius is not a moral virtue - it’s a cognitive capacity that can coexist with all sorts of characters.

Conclusion: The Shoulders of Giants

Galileo opened a door. Newton built an edifice. Together, they created modern science - this collective, cumulative enterprise that has given us technology, medicine, understanding of the universe.

“If I have seen further, it is by standing on the shoulders of giants.” Newton spoke of Galileo, but also of Kepler, Copernicus, all those who had prepared the ground. Science is not the work of isolated individuals - it’s a conversation between generations.

This conversation continues. We stand on Newton’s shoulders, as he stood on Galileo’s. Each discovery opens new questions, each answer raises new mysteries. The scientific revolution they launched isn’t over - it never will be.

And perhaps that’s their greatest legacy: not definitive answers, but a method for seeking. A way of looking at the world with curiosity, asking questions, testing hypotheses, correcting mistakes. This method - the scientific method - is their true gift to humanity.

Galileo looked at the sky with a telescope. Newton watched an apple fall. Two glances, two revolutions. And the world has never been the same.