Galileo Galilei – The Father of Science

Interesting Facts About Galileo Galilei

Here’s everything you need to know about the great Italian astronomer and physicist, Galileo Galilei.

• Because of his many contributions, Galileo Galilei is considered the father of several different areas in the fields of science. Aside from being called the “Father of Science,” he is also referred to as the “Father of Observational Astronomy” for his effective use of telescopes in making astronomical discoveries. 

• Galileo was able to prove Nicolaus Copernicus’s heliocentric theory through his observations of Venus and Jupiter’s moons. Using his telescope, Galileo found out that Venus had phases much like Earth’s Moon. Also, what he thought of as stars before were actually moons that orbited the gas giant Jupiter. 

• Galileo did not invent the telescope. The telescope was invented by the Dutch lensmaker Hans Lippershey, though it only magnified objects up to three times. Galileo immediately made significant improvements to the design. He was the first one to point it to the sky and used it for astronomical observations. 

• Galileo Galilei was a college dropout. At 16 years old, he attended the University of Pisa to study medicine, as his father wanted. However, he became fascinated with mathematics so he left without finishing his degree to pursue this subject.

• Galileo Galilei and William Shakespeare were both born in the same year, in 1564. Interestingly, in one of the plays of “The Bard of Avon” titled Cymbeline, there are four ghosts dancing around the god Jupiter. This could be a reference to the four newly discovered moons (previously Medicean Stars) of the gas giant at the time.

• The Roman Inquisition sentenced Galileo to life in prison. During his time, it was widely believed that the Earth was the center of the solar system. However, Galileo championed Copernicus’s theory of heliocentrism (Sun-centered model) which challenged the widely accepted view. The Catholic Church considered his views heresy and he was forced to publicly repent.

• Galileo Galilei became blind in the last few years of his life—but it was not caused by his telescopic solar observations. He was 72 when he lost his sight, more than 20 years after his observations of the Sun. His blindness was caused by glaucoma and cataracts. 

• Despite the fact that he was not on good terms with the Catholic Church, Galileo’s daughters were actually nuns. His daughters, Virginia and Livia, were born out of wedlock. He placed them in a convent as he thought they would be unsuitable for marriage. This is where they spent the rest of their lives. 

• Through his telescopic observations, Galileo revealed that the Milky Way is composed of individual stars. Before that, it was thought that our Milky Way was just a band of clouds that we can see in the sky. 

• Galileo Galilei’s right middle finger has been displayed in different museums. Many years after his death, as Galileo’s remains were transferred to a different place, some parts of the corpse were removed. One of such is his middle finger which has been in different museums in Italy. 

Galileo Galilei (February 15, 1564 – January 8, 1642)

Galileo Galilei was born on February 15, 1564, in Pisa, Tuscany. He was a polymath who was known for his great knowledge in the field of astronomy, physics, engineering, and even art. 

Galileo played a major role in the Scientific Revolution. He improved on the telescope and his effective use of this tool opened up the way to study the heavens better. Through his observations, he discovered the phases of Venus and the four biggest moons of Jupiter. He also revealed that the Moon’s surface is not smooth, as it has different features such as craters and mountains. 

It is not a coincidence that Galileo Galilei’s first and last names sounded similar. In Tuscany, it was a tradition that the first born son should be given a Christian name according to the family name. Since the family name is Galilei, his parents gave him the name “Galileo” based on the biblical region of Galilee. 

Unlike other known figures who were often referred to by their last names, the Italian scientist is often called simply by his first name, Galileo.

Galileo is one of the reasons why we now know that the Sun is the center of the solar system. Like Nicolaus Copernicus who presented this idea years earlier, his books were banned as they contradicted the established belief of the Aristotelian cosmology at the time. The Church held such great authority that anyone who would contradict it was prosecuted. 

Galileo’s conflict with the church ended with him being sentenced to life in prison. In the later years of his life, it was changed to house arrest where he spent his last days until his death on January 8, 1642. He was 77 years old. 

Personal Life

Galileo’s parents were Vincenzo Galilei and Giulia Ammannati. He was the eldest of six children. The family moved to Florence in the early 1570s where they lived for generations. His father, who was a musician, wanted him to study medicine. Because of that, he enrolled in the University of Pisa to grant and honor his father’s wishes.

While studying medicine, Galileo became fascinated by mathematics. As a result, he ended up leaving without finishing his degree in medicine, and the rest is history. In 1589, he was appointed to the Chair of Mathematics at the University of Pisa. 

Galileo was known as a devout Christian, though he was never married, he had three children. He had a relationship with a Venetian woman named Marina Gamba. They had three children, one son (Vincenzo) and two daughters (Virginia and Livia). 

When his father died, Galileo was entrusted with his brother, Michelagnolo Galilei. He was also responsible for providing a dowry for his sister Virginia Galilei Landucci. Though he was teaching mathematics at the University of Padua, Galileo was not doing well financially. In fact, he started designing and selling mathematical instruments to supplement his income. 

Galileo never considered starting a family of his own because of financial constraints, among other reasons. He thought that he had to pay large amounts of dowries if his daughters were to marry. Because of that, he brought his daughters to a convent in Arcetri and they became nuns. 

The two later changed their names as they took the veil. Virginia later became Maria Celeste and Livia’s name became Arcangela. Maria Celeste maintained a close relationship with his father even from inside the convent. 

Career as an Astronomer, Physicist, and Engineer

Galileo’s contribution encompassed a wide range of disciplines. As an astronomer, he discovered many celestial objects and helped us understand the universe better. 

He studied the natural laws that govern us and has contributed significantly to the development of the scientific method. He published his early works on dynamics (titled On Motion) around the 1590s. 

Galileo devised useful inventions using his scientific knowledge. With his empirical and systematic approach to understanding things, he greatly helped in paving the way for modern science. 

Galileo and His Telescope 

The first person to patent the telescope was the Dutch spectacle maker Hans Lippershey. This object was able to magnify objects by about three times, so it was more of a spyglass than a telescope at the time.

When Galileo heard about this, he immediately designed his own version of it, with much more magnification. In 1609, he designed a refracting telescope which became known as the Galilean telescope. The design incorporated a plano-convex convergent lens as the objective and a concave divergent lens as the eyepiece. 

Galileo used his self-improved telescope for sky observations and he discovered four moons going in circle around Jupiter. He also observed the phases of Venus, the rings of Saturn, the sunspots on the Sun, and the lunar surface. These observations strengthened Galileo’s beliefs about Copernicus’ theories that the Earth and other planets revolve around the Sun.

In 1620, Galileo published his findings in Sidereus Nuncius (The Starry Messenger) and it was an instant success. His telescope became a valuable object that navigators found very useful at sea. His invention of an improved telescope became a lucrative sideline. 

The Law of Falling Bodies

There is a famous story that Galileo dropped two balls from the Leaning Tower of Pisa to demonstrate that falling bodies have the same acceleration, as anything that is subjected to gravity. These objects were made of the same material but are of different masses. This contradicted Aristotle’s earlier ideas that heavier objects tend to fall faster than lighter ones.

While this famous story has made it easier to understand the concept of falling bodies, there have not been many accounts saying that this experiment really took place. 

In 1971, the lunar mission Apollo 15 did a similar experiment to prove Galileo’s law of falling bodies. On the Moon, NASA astronaut David Scott used a hammer and a feather and dropped them at the same time. Amazingly, even though the hammer is much heavier than the feather, in the absence of friction both objects reached the lunar ground at the same time. Thus, proving that Galileo was right. 

Galileo’s work on physics had inspired many other scientists, including Sir Isaac Newton who later formulated the laws of motion. 

Inventions

His extensive knowledge in math and science proved useful as Galileo was also a great engineer. He devised many inventions which have been useful even today. Aside from his works on telescopes, Galileo also improved a compass for military and land surveyors’ use. 

The Astronomical Discoveries of Galileo Galilei 

The discoveries of Galileo caused a paradigm shift in how we view the world. Though he was greatly objected to during his time, the truths of his discoveries prevailed and changed the way we view the world. 

The Heliocentric View of the Solar System

One of Galileo Galilei’s greatest contributions to science is that he proved a Sun-centered solar system. His claims which were backed by observations created a factual and more accurate way of understanding the heavens. It gave birth to what became known as modern astronomy.  

His observations of our Moon, Venus, Jupiter, and the Sun proved that Copernicus’s heliocentric model was right. He not only helped us understand the solar system better, but he also opened doors to the bigger Milky Way galaxy. It was believed that the Milky Way was a nebulosity, but he revealed that it is actually made up of so many individual stars. They are so many that they seem like bands of clouds as seen by the naked eye. 

The Phases of Venus

Venus is the second-brightest object in the night sky after the Moon. With that said, it was one of the easiest objects to observe in the night sky. Using his telescope, Galileo pointed his telescope toward this planet and made a great discovery. 

He found out that Venus has different phases just like the Moon. It starts in a sickle-like shape crescent and grows into a full disk. Another important discovery was that Venus appeared larger when it was in its crescent phase. These changes did not align with the widely accepted truth at the time of an Earth-centric universe.

However, if Venus was indeed orbiting around Earth, it would not have had phases and changes in size as seen from our planet. The only explanation for this is that Venus orbits the Sun, not Earth. This discovery debunked the long-held geocentric model of the universe as taught by Aristotle and Ptolemy. 

The Galilean Moons

The observations of Galileo’s work showed how important the telescope was as a tool, especially for astronomers. It helped us see objects in space that are totally invisible to the naked eye. 

When Galileo pointed his telescope at the sky on January 7, 1610, he discovered four “stars” near Jupiter. However, he noticed something different about these objects. They seemed to have regular movement but, according to the belief at the time, they are moving in the wrong direction. 

Together, he called them the “Medician Stars” after Cosimo II de Medici, the Grand Duke of Tuscany, and his family. The Medicis were a wealthy family in Florence and they influenced many aspects of the society. They were also known for their patronage of the arts. As a wealthy family, they sponsored artists and scholars financially and provided a platform for them to do their work and studies. 

The Medicis became a patron of Galileo. They supported his studies and provided protection as his discoveries stirred controversies and challenged the established belief of the Church of an Earth-centric universe.  

As he did many observations, Galileo became convinced that these objects are not stars. These are natural satellites orbiting Jupiter. These moons are Io, Europa, Ganymede, and Callisto. As time passed, they became known as the Galilean moons after their discoverer. The discovery of these moons supported the heliocentric view, disproving that everything in the solar system revolved around Earth. 

Below are the Galilean moons of Jupiter:

• Io – the fourth largest and the densest moon in the solar system
• Europa – the sixth-largest moon in the solar system
• Ganymede – the largest and most massive moon of Jupiter and the entire solar system
• Callisto – the second-largest moon of Jupiter and the third-largest in the solar system

Other Remarkable Discoveries

The Moon’s Surface

Our silvery companion at night, the Moon, was believed to be a smooth sphere. However, when Galileo used his telescope to observe it, he learned that it was anything but smooth. The lunar surface has many features including mountains and craters, among others. 

Despite the narrow field of view of his telescope, he was able to discover many things about the Moon’s surface. It was said that he was able to estimate how tall the lunar mountains are using their shadows. Also, he drew his observations of the Moon quite impressively, like other Renaissance artists. 

Rings of Saturn

About 400 years ago, Galileo discovered yet another fascinating feature of the solar system—the majestic rings of Saturn!

As he recorded his observations, Galileo wrote that Saturn seemed to have “ears” bulging on either side of the planet. The limitations of his small telescope did not allow him to completely see the nature of these rings. However, his discovery has led to more studies on the Saturnian system many years later. Now, we know that these “ears” are actually rings made up of ice and rock. 

Study on Sunspots, Neptune, and Comets

Galileo also pointed his telescope towards the Sun and discovered that it has dark features or spots. The nature of these spots was still largely unknown at the time as. Christoph Scheiner, a Jesuit mathematician who also studied the sunspots, claimed that they were satellites of the Sun. 

Based on his solar observations, Galileo argued that the spots were actually on the Sun’s surface, or at least in its atmosphere. 

Years before its discovery as a planet, Galileo spotted what would later become known as the ice giant Neptune. It was more of a dim star and was not especially remarkable. Though, he was able to take notes of its motion in the sky.

In his book The Assayer, Galileo mentioned the nature of comets. According to him, they were more of optical phenomena rather than physical bodies, just like the Aurora. This contradicted the works of Father Orazio Grassi who believed that comets were not optical illusions.

With the improvement of science, we now know that comets are indeed physical objects made up of space rocks and dust. 

Galileo Galilei – Conflicts with the Church

Galileo’s observations with his telescope are strong evidence that proved the heliocentric theory of Nicolaus Copernicus. However, his findings weren’t received well by the Church. By literally interpreting the bible, the Church claimed that the Earth was the center of the universe.

The Danish astronomer Tycho Brahe also had a different model which posited that the planets orbit the Sun. Meanwhile, it retained that the Sun and Moon revolve around Earth. Galileo’s heliocentrism was objected to by the Church as they claimed it contradicted the teachings of the scripture. He was also opposed by Brahe in a scientific sense.

In a letter that Galileo wrote to Italian mathematician Benedetto Castelli, he argued that the bible was not an authority in science. While the Church teaches about faith and morals, science is a different field. And because of that, he claimed that his scientific discoveries did not contradict the teachings of the Church at all. 

How Was He Received at the Time?

Galileo’s writings were again interpreted as a threat to the Church. The Pope ordered him not to teach and write anything that supports heliocentrism. In short, he was asked to abandon it. He stayed away from controversy for several years until the publication of his work Dialogue Concerning the Two Chief World Systems.

While Galileo claimed that the Dialogue did not advocate for heliocentrism, it was interpreted as an attack against geocentrism. In 1633, Pope Urban VIII acted upon it and summoned him to Rome. We called to stand trial against heresy before the Roman Inquisition where he was forced to give up his beliefs about the Copernican theory. 

The Dialogue was banned, including any writings he did after the trial. He was sentenced to imprisonment by the Inquisition. It was later changed to house arrest where he stayed for the rest of his life. His daughter, Maria Celeste, helped him in any way she can. 

Galileo produced his final book, Two New Sciences, when he was under house arrest. Since his works were banned in Italy, it was published in Holland instead. Still, when this book reached Rome, it was immediately sold out which just demonstrated his influence on the subject. 

Eppur si muove! 

The famous line “Eppur si muove!” translates to “And yet it moves!” It was said that Galileo muttered this line under his breath after he was forced to deny heliocentrism under the threat of torture.

More than 300 years after Galileo was sentenced, the Church finally agreed that he was actually right. Pope John Paul II made the declaration, stating that although the Inquisition acted in good faith, they were wrong to condemn Galileo. 

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Sources:

https://www.history.com/topics/inventions/galileo-galilei#section_3

https://aty.sdsu.edu/vision/Galileo.html#:~:text=The%20truth%20is%20that%20Galileo,354%5D. New York

http://galileo.rice.edu/fam/status_women.html (The Galileo Project by Al Van Helden)

https://solarsystem.nasa.gov/news/307/galileos-observations-of-the-moon-jupiter-venus-and-the-sun/

https://www.cabinet.ox.ac.uk/phases-venus-1610-23#:~:text=As%20Galileo%20observed%20for%20the,which%20the%20cycle%20begins%20again.

http://galileo.rice.edu/sci/observations/sunspots.html

https://en.wikipedia.org/wiki/Galileo_Galilei#Controversy_over_heliocentrism

https://www.history.com/news/8-things-you-may-not-know-about-galileo#:~:text=He%20was%20a%20college%20dropout.&text=When%20he%20was%2016%2C%20Galileo,1585%20without%20earning%20a%20degree.

Image Sources: 

Galileo Galilei:

https://upload.wikimedia.org/wikipedia/commons/thumb/d/d4/Justus_Sustermans_-_Portrait_of_Galileo_Galilei%2C_1636.jpg/1200px-Justus_Sustermans_-_Portrait_of_Galileo_Galilei%2C_1636.jpg

Galileo and His Telescope: https://upload.wikimedia.org/wikipedia/commons/thumb/d/d7/Galileo_galilei%2C_telescopi_del_1609-10_ca..JPG/800px-Galileo_galilei%2C_telescopi_del_1609-10_ca..JPG

Inventions (compass): 

https://upload.wikimedia.org/wikipedia/commons/thumb/4/48/Galileo%27s_geometrical_and_military_compass_in_Putnam_Gallery%2C_2009-11-24.jpg/800px-Galileo%27s_geometrical_and_military_compass_in_Putnam_Gallery%2C_2009-11-24.jpg

Thermoscope: https://upload.wikimedia.org/wikipedia/commons/thumb/d/d5/Galileo_Thermometer_24_degrees.jpg/320px-Galileo_Thermometer_24_degrees.jpg

The Heliocentric View of the Solar System: http://misistemasolar.com/wp-content/uploads/2017/10/teor%C3%ADa-geoc%C3%A9ntrica-4-1024×512.jpg

The Phases of Venus: https://solarsystem.nasa.gov/system/resources/detail_files/482_m_GalileosPhases.jpg

The Galilean Moons: https://upload.wikimedia.org/wikipedia/commons/thumb/e/eb/Jupiter.moons1.jpg/600px-Jupiter.moons1.jpg

The Moon’s Surface: https://upload.wikimedia.org/wikipedia/commons/thumb/7/7b/Galileo%27s_sketches_of_the_moon.png/648px-Galileo%27s_sketches_of_the_moon.png?20071222034557

Conflicts with the Church: https://upload.wikimedia.org/wikipedia/commons/thumb/8/88/Galileo_facing_the_Roman_Inquisition.jpg/1024px-Galileo_facing_the_Roman_Inquisition.jpg