Galileo Galilei

A Little Background

Before we start talking about Galileo Galilei, we need to understand a little about the era he lived in, and its view of the Universe.

Aristotle, an ancient Greek philosopher who lived in the 4th century B.C., said that the Earth was the center of the universe. Everything else--the moon, the Sun, the planets and the stars--moved around the Earth. For hundreds of years, no one questioned this idea, especially when the Roman Catholic Church said that Aristotle was right.

Finally, in 1543, someone DID question the Church's teachings. A Polish astronomer named Nicholas Copernicus said that the Sun was the center of the Universe, and that everything, including the Earth, went around the Sun. If Copernicus was right, the Church was wrong. The Church, in response, denounced the Copernican system.

And now, our story opens......

The Early Years

Galileo Galilei was born in Pisa, Italy on February 15, 1564, 21 years after the death of Copernicus and three days before the death of Michelangelo. He was the first of 7 children. Although Galileo's father was a musician and wool trader, he wanted his clearly talented son to study medicine as there was more money in medicine (some things don't change, even over 400 years!). So, at age eleven, Galileo was sent off to study in a Jesuit monastery.

After four years, Galileo had decided on his life's work: he announced to his father that he wanted to be.....a monk. This was not exactly what father had in mind for his gifted son, so Galileo was hastily withdrawn from the monastery. In 1581, at the age of 17, Galileo entered the University of Pisa to study medicine, as his father wished.

Shortly thereafter, at age 20, Galileo noticed a lamp swinging overhead while he was in a cathedral. Curious to find out how long it took the lamp to swing back and forth, he used his pulse to time large and small swings. Galileo discovered something that no one else had ever realized: the period of each swing was exactly the same. The law of the pendulum, which would eventually be used to regulate clocks, made Galileo instantly famous.

Unfortunately, except for mathematics, Galileo was bored by most of his courses and outspoken to his professors. His frequent absences from class eventually led the university to inform Galileo's family that their son was in danger of flunking out. A compromise was worked out, where Galileo would be tutored full-time in mathematics by the mathematician of the Tuscan court. Galileo's father was hardly overjoyed about this turn of events, since a mathematician's earning power was roughly around that of a musician, but it seemed that this might yet allow Galileo to successfully complete his college education. In the end, Galileo left the University of Pisa without a degree--a college dropout.

Faced with the need to somehow earn a living, Galileo started tutoring students in mathematics. He did some experimenting with floating objects, developing a balance that could tell him that a piece of, say, gold was 19.3 times heavier than the same volume of water. He also started campaigning for his life's ambition: a position on the mathematics faculty at a major university. Although Galileo was clearly brilliant, he had offended many people in the field, who would choose other candidates for vacancies. Ironically, it was a lecture on literature that would turn Galileo's fortunes. The Academy of Florence had been arguing over a 100-year-old controversy: What were the location, shape, and dimensions of Dante's Inferno?

To modern ears, this type of question sounds like asking for the location of Sherlock Holmes's 221B Baker Street, or the size of Dr. Frankenstein's castle. But the question was absolutely serious, and Galileo, asked to answer the question from the point of view of a man of science, treated it with dignity. Extrapolating from Dante's line that "[the giant Nimrod's] face was about as long/And just as wide as St. Peter's cone in Rome," Galileo deduced that Lucifer himself was 2,000 armlengths long. The audience was impressed, and Galileo was remembered with favor.

Within the year, Galileo had received a three-year appointment to the University of Pisa, the same university that never granted him a degree!

The Leaning Tower of Pisa

At the time that Galileo arrived at the University, some debate had started up on one of Aristotle's "laws" of nature--namely, that that heavier objects fell faster than lighter objects. Aristotle's word had been accepted as gospel truth, and there had been few attempts to actually test Aristotle's conclusions by actually conducting an experiment!

According to legend, Galileo decided to try. He needed to be able to drop the objects from a great height. The perfect building was right at hand--the Tower of Pisa, 54 meters tall. Galileo climbed up to the top of the building carrying a variety of balls of varying size and weight, and dumped them off of the top. They all landed at the base of the building at the same time (legend says that the demonstration was witnessed by a huge crowd of students and professors). Aristotle was wrong.

A modern-day professor who managed to successfully show that, say, Isaac Newton was in error would immediately be granted a lifetime contract. Of course, that's assuming that the professor published results, showing a theory to explain why Newton was wrong. Galileo had no such theory, and consequently didn't publish his results. He also continued to behave rudely to his colleagues, not a good move for a junior member of the faculty. "Men are like wine flasks," he once said to a group of students. "...look at....bottles with the handsome labels. When you taste them, they are full of air or perfume or rouge. These are bottles fit only to pee into!"

Not surprisingly, U. Pisa chose not to renew Galileo's contract.

Necessity is the Mother of Invention

Galileo moved on to the University of Padua. Though he enjoyed the city itself, finding good friends with whom he could party, by 1593 he found himself in desperate need of additional cash. His father had died, so Galileo was the head of his family, and personally responsible for his family. Debts were pressing down on him, most notably, the dowry for one of his sisters, which was paid in installments over decades (a dowry could be thousands of crowns, and Galileo's annual salary was 180 crowns). Debtor's prison was a real threat if Galileo returned to Florence.

What Galileo needed was to come up with some sort of device that could make him a tidy profit. A rudimentary thermometer (which, for the first time, allowed temperature variations to be measured) and an ingenious device to raise water from aquifers found no market. He found greater success in 1596 with a military compass that could be used to accurately aim cannonballs. A modified civilian version that could be used for land surveying came out in 1597, and ended up earning a fair amount of money for Galileo. It helped his profit margin that 1) the instruments were sold for three times the cost of manufacture, 2) he also offered classes on how to use the instrument, and 3) the actual toolmaker was paid dirt-poor wages.

A good thing. Galileo needed the money to support his siblings, his mistress (a 21 year old with a reputation as a woman of easy habits), and his three children (two daughters and a boy). By 1602, Galileo's name was famous enough to help bring in students to the University, where Galileo was busily experimenting with magnets.

The Telescope

In Venice on a holiday in 1609, Galileo heard rumors that a Dutch spectacle-maker had invented a device that made distant objects seem near at hand. A patent had been requested, but not yet granted, and the methods were being kept secret, since it was obviously of tremendous military value for Holland.

Such an instrument would also be valuable to Venice, and Galileo determined to attempt to construct his own spyglass. After a frantic 24 hours (according to Galileo) of experimentation, Galileo, working only on instinct and bits of rumors, never having actually *seen* the Dutch spyglass, had a 3-power telescope. After some refinement, he brought a 10-power telescope to Venice and demonstrated it to a highly impressed Senate. Galileo's salary was promptly raised, and he was honored with proclamations.

If Galileo had stopped here, and become a man of wealth and leisure, he might be a mere footnote in history. Instead, a revolution started when, one fall evening, Galileo trained his telescope on an object in the sky that all people "knew" must be a perfect, smooth, polished heavenly body--the Moon. We can only imagine Galileo's astonishment on finding a surface that was "uneven, rough, full of cavities and prominences." A surface full of features much like those that could be found on Earth. This was tremendously exciting news, although there were still plenty of people who insisted that Galileo was wrong. Some of their arguments were very clever, like the mathematician who insisted that even if Galileo was seeing a rough surface on the Moon, that only meant that the entire moon had to be covered in invisible, transparent, smooth crystal.

Months passed, and Galileo's telescopes improved. On January 7, 1610, Galileo turned his 30 power telescope towards Jupiter, and found three small, bright stars near the planet. One was off to the west, the other two were to the east, all three in a straight line. The following evening, Galileo once again took a look at Jupiter, and found that all three of the "stars" were now west of the planet, still in a straight line!

Observations over the following weeks lead Galileo to the inescapable conclusion that these small "stars" were actually small satellites that were rotating about Jupiter. THESE SATELLITES DID NOT MOVE AROUND THE EARTH! If there were satellites that didn't move around the Earth, wasn't it possible that the Earth was not the center of the universe? Couldn't the Copernican idea of the Sun at the center of the solar system be correct?

Just like any modern scientist, Galileo published his findings--as a small book titled The Starry Messenger." 550 copies were published in March of 1610, to tremendous public acclaim and excitement. We can imagine what it was like for people--probably something like when people learned that the Earth was round, not flat. Or, more recently, what it was like to discover that our galaxy was only one of billions!

And there were more discoveries: the appearance of bumps next to the planet Saturn (Galileo thought they were companion stars; the "stars" were actually the edges of Saturn's rings), spots on the Sun's surface (though others had actually seen the spots before Galileo), and seeing Venus change from a full disk to a sliver of light.

The Vatican's Reaction

The great detective Sherlock Holmes once said that "Whether the Earth goes around the Sun or the Sun around the earth makes not a penny-worth of difference to me or my work." For Galileo, saying that the Earth went around the Sun made a huge difference, since he was contradicting the teachings of the Church. While some of the Church's mathematicians wrote that Galileo's observations were clearly correct, many members of the Church believed that Galileo must be wrong.

In December of 1613, one of Galileo's friends told him how a powerful member of the nobility said that she could not see how Galileo's observations could be true, since they would contradict the Bible. The lady quoted a passage in Joshua where God causes the Sun to stand still and lengthen the day. How could this mean anything other than that the Sun went around the Earth?

Galileo was a religious man, and he agreed that the Bible could never be wrong. However, he said, the interpreters of the Bible could make mistakes, and it was a mistake to assume that the Bible had to be taken literally. The true meaning of a Biblical verse might not be obvious at all, and wise scholars would have to work hard to find the true meanings. After all, a cardinal in the Church itself had once said that the intention of the Holy Spirit is to teach us how one goes to heaven, not how heaven goes! He ended with an explanation of how the miracle could not possibly have taken place if the Sun went around the Earth.

This might have been one of Galileo's major mistakes. At that time, only churchmen were allowed to interpret the Bible, or to define God's intentions. It was absolutely unthinkable for a mere member of the public to do so.

And some of the clergy started responding, accusing Galileo of heresy. One friar quoted from the New Testament "O ye men of Galilee, why stand ye gazing up into heaven?" Another churchman went to the Inquisition, the Church court that investigated charges of heresy, and formally accused Galileo. This was a very serious matter. In 1600, a man named Giordano Bruno was convicted of being a heretic for believing that the earth moved about the Sun, and that there were many planets throughout the universe where life--living creations of God--existed. Bruno was burnt to death.

This time, Galileo was found innocent of all charges, and cautioned not to teach the Copernican system. 16 years later, all that would change.

The Final Trial

The following years saw Galileo move on to work on other projects. He watched the movements of Jupiter's moons, wrote them up as a list, and then came up with a way to use these measurements as a navigation tool. There was even a contraption that would allow a ship captain to navigate with his hands on the wheel. That is, assuming the captain didn't mind wearing what looked like a horned helmet!

As another amusement, Galileo started writing about ocean tides. Instead of writing his arguments as a scientific paper, he found that it was much more interesting to have an imaginary conversation, or dialogue, between three fictional characters. One character, who would support Galileo's side of the argument, was brilliant. Another character would be open to either side of the argument. The final character, named Simplicio, was dogmatic and foolish, representing all of Galileo's enemies who ignored any evidence that Galileo was right. Soon, Galileo wrote up a similar dialogue called "Dialogue on the Two Great Systems of the World." This book talked about the Copernican system.

"Dialogue" was an immediate hit with the public, but not, of course, with the Church. The pope suspected that he was the model for Simplicio. He ordered the book banned, and also ordered Galileo to appear before the Inquisition in Rome for the crime of teaching the Copernican theory after being ordered not to do so.

Galileo was 68 years old and sick. Threatened with torture, he publically confessed that he had been wrong to have said that the Earth moves around the Sun. Legend then has it that after his confession, Galileo quietly whispered "And yet, it moves."

Unlike many less famous prisoners, Galileo was allowed to live under house arrest in his house outside of Florence. He was near one of his daughters, a nun. Until his death in 1642, he continued to investigate other areas of science. Amazingly, he even published a book on force and motion although he had been blinded by an eye infection.

The Story Continues.....

The Church eventually lifted the ban on Galileo's Dialogue in 1822--by that time, it was common knowledge that the Earth was not the center of the Universe. Still later, there were statements by the Vatican Council in the early 1960's and in 1979 that implied that Galileo was pardoned, and that he had suffered at the hands of the Church. Finally, in 1992, three years after Galileo Galilei's namesake had been launched on its way to Jupiter, the Vatican formally and publicly cleared Galileo of any wrongdoing.

Additional Reading and Resources

Galileo
Leonard Everett Fisher
MacMillan Publishing Company, 1992

A wonderful and concise children's book, suitable for ages 8-12.

Galileo
James Reston Jr.
HarperCollins 1994

A recent book that discusses Galileo's conflict with the Church in detail.

The Starry Messenger
Galileo Galilei
Translated by Stillman Drake

Galileo's original writings on his observations of Jupiter.

The Institute and Museum of the History of Science of Florence, Italy Galileo Galilei Artifacts is available for virtual exploration. Many of the inventions described in this article--telescopes, a machine to raise water, and others--can be seen, along with portraits of Galileo, and even one of Galileo's fingers!