# data[].attributes.body
Galileo had five siblings, but only 3 lived long lives. One that was fairly notable was a young boy named Michelangelo, who was a musician like their father. Though Galileo wasn’t a musician like his father urged him to be, their relationship remained fairly well,

Galileo had no children, and had never once been married, but it is said how he had a brief affair with a woman named Marina Gamba, someone he had met on his many trips to Venice.
(Other Source Is http://galileo.rice.edu/bio/narrative_5.html)

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Galileo di Vincenzo Bonaiuti de’ Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( GAL-il-AY-oh GAL-il-AY, GAL-il-EE-oh -⁠, Italian: [ɡaliˈlɛːo ɡaliˈlɛːi]) or simply Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a polymath. He was born in the city of Pisa, then part of the Duchy of Florence.[3] Galileo has been called the father of observational astronomy,[4] modern-era classical physics,[5] the scientific method,[6] and modern science.[7]

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Galileo created a new way of experimenting, so that it was no longer simply verbal without it being proven correct, but now mathematical and a recognized method. Including the law of if an object is heavier, it will fall faster. If it is lighter, it will fall slower.

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Galileo died in Arcetri, near Florence, Italy, on January 8, 1642, after suffering from a fever and heart palpitations.

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Who Was Galileo?

Galileo was an Italian astronomer, mathematician, physicist, philosopher and professor who made pioneering observations of nature with long-lasting implications for the study of physics.

He also constructed a telescope and supported the Copernican theory, which supports a sun-centered solar system. Galileo was accused twice of heresy by the church for his beliefs, and wrote a number of books on his ideas.

Early Life

Galileo Galilei was born in Pisa in the Duchy of Florence, Italy, on February 15, 1564.

Galileo was the first of six children born to Vincenzo Galilei, a well-known musician and music theorist, and Giulia Ammannati. In 1574, the family moved to Florence, where Galileo started his formal education at the Camaldolese monastery in Vallombrosa.

Education

In 1583, Galileo entered the University of Pisa to study medicine. Armed with prodigious intelligence and drive, he soon became fascinated with many subjects, particularly mathematics and physics.

While at Pisa, Galileo was exposed to the Aristotelian view of the world, then the leading scientific authority and the only one sanctioned by the Roman Catholic Church.

At first, Galileo supported this view, like any other intellectual of his time, and was on track to be a university professor. However, due to financial difficulties, Galileo left the university in 1585 before earning his degree.

Career as a Professor

Galileo continued to study mathematics after leaving the university, supporting himself with minor teaching positions.

During this time he began his two-decade study on objects in motion and published The Little Balance, describing the hydrostatic principles of weighing small quantities, which brought him some fame. This gained him a teaching post at the University of Pisa, in 1589.

While there, Galileo conducted his fabled experiments with falling objects and produced his manuscript Du Motu (On Motion), a departure from Aristotelian views about motion and falling objects. Galileo developed an arrogance about his work, and his strident criticisms of Aristotle left him isolated among his colleagues. In 1592, his contract with the University of Pisa was not renewed.

Galileo quickly found a new position at the University of Padua, teaching geometry, mechanics and astronomy. The appointment was fortunate, for his father had died in 1591, leaving Galileo entrusted with the care of his younger brother.

During his 18-year tenure at Padua, he gave entertaining lectures and attracted large crowds of followers, further increasing his fame and his sense of mission.

Daughters and Son

In 1600, Galileo met Marina Gamba, a Venetian woman, who bore him three children out of wedlock: daughters Virginia and Livia, and son Vincenzo. He never married Marina, possibly due to financial worries and possibly fearing his illegitimate children would threaten his social standing.

Galileo worried his daughters would never marry well, and when they were older, had them enter a convent. In 1616, at the San Mateo Convent, Virginia changed her name to Maria Celeste and Livia became Sister Arcangela, when they became nuns. Maria Celeste remained in contact and supported her father through letters until her death.

No letters from Arcangela survive. His son's birth was eventually legitimized and he became a successful musician.

Telescope

In July 1609, Galileo learned about a simple telescope built by Dutch eyeglass makers and soon developed one of his own. In August, he demonstrated it to some Venetian merchants, who saw its value for navigation and spotting ships. The merchants gave Galileo a salary to manufacture several of them.

Galileo's ambition pushed him to go further, and in the fall of 1609 he made the fateful decision to turn his telescope toward the heavens. Using his telescope to explore the universe, Galileo observed the moon and found Venus had phases like the moon, proving it rotated around the sun, which refuted the Aristotelian doctrine that the Earth was the center of the universe.

He also discovered Jupiter had revolving moons that didn't revolve around planet Earth. In 1613, he published his observations of sunspots, which also refuted Aristotelian doctrine that the sun was perfect.

Books

Galileo published a number of books throughout his career, including:

The Operations of the Geometrical and Military Compass (1604), which revealed Galileo's skills with experiments and practical technological applications.

The Starry Messenger (1610), a small booklet revealing Galileo's discoveries that the moon was not flat and smooth but a sphere with mountains and craters.

Discourse on Bodies in Water (1612), which refuted the Aristotelian explanation of why objects float in water, saying that it wasn't because of their flat shape, but instead the weight of the object in relation to the water it displaced.

Dialogue Concerning the Two Chief World Systems (1632), a discussion among three people: one who supports Copernicus' heliocentric theory of the universe, one who argues against it, and one who is impartial. Though Galileo claimed Dialogues was neutral, it was clearly not. The advocate of Aristotelian belief comes across as the simpleton, getting caught in his own arguments.

Two New Sciences (1638), a summary of Galileo's life's work on the science of motion and strength of materials.

What Did Galileo Discover?

In addition to the telescope and his numerous mathematical and scientific discoveries, in 1604 Galileo constructed a hydrostatic balance for measuring small objects.

That same year, he also refined his theories on motion and falling objects, and developed the universal law of acceleration, which all objects in the universe obeyed. He also devised a type of simple thermometer.

Thermometer

A simple glass-bulb thermometer known as a Galileo thermometer wasn't invented by Galileo, but was based on his understanding that the density of liquids changes based on its temperature.

A thermoscope that Galileo designed (or helped to design) is similar to modern-day thermometers. Inside the thermoscope, a liquid rises and falls in a glass tube as the temperature of the liquid rises or falls.

DOWNLOAD BIOGRAPHY'S GALILEO FACT CARD

Galileo and the Church

After Galileo built his telescope in 1609, he began mounting a body of evidence and openly supporting the Copernican theory that the earth and planets revolve around the sun. The Copernican theory, however, challenged the doctrine of Aristotle and the established order set by the Catholic Church.

In 1613, Galileo wrote a letter to a student to explain how Copernican theory did not contradict Biblical passages, stating that scripture was written from an earthly perspective and implied that science provided a different, more accurate perspective.

The letter was made public and Church Inquisition consultants pronounced Copernican theory heretical. In 1616, Galileo was ordered not to "hold, teach, or defend in any manner" the Copernican theory. Galileo obeyed the order for seven years, partly to make life easier and partly because he was a devoted Catholic.

In 1623, a friend of Galileo, Cardinal Maffeo Barberini, was elected as Pope Urban VIII. He allowed Galileo to pursue his work on astronomy and even encouraged him to publish it, on condition it be objective and not advocate Copernican theory. This led Galileo to publish Dialogue Concerning the Two Chief World Systems in 1632, which advocated the theory.

Church reaction was swift, and Galileo was summoned to Rome. Galileo's Inquisition proceedings lasted from September 1632 to July 1633. During most of this time, Galileo was treated with respect and never imprisoned.

However, in a final attempt to break him, Galileo was threatened with torture, and he finally admitted he had supported Copernican theory, but privately held that his statements were correct. He was convicted of heresy and spent his remaining years under house arrest.

Though ordered not to have any visitors nor have any of his works printed outside of Italy, he ignored both. In 1634, a French translation of his study of forces and their effects on matter was published, and a year later, copies of the Dialogue were published in Holland.

While under house arrest, Galileo wrote Two New Sciences, published in Holland in 1638. By this time, Galileo had become blind and was in poor health.

In time, however, the Church couldn't deny the truth in science. In 1758, it lifted the ban on most works supporting Copernican theory. It wasn't until 1835 that the Vatican dropped its opposition to heliocentrism altogether.

In the 20th century, several popes acknowledged the great work of Galileo, and in 1992, Pope John Paul II expressed regret about how the Galileo affair was handled.

How Did Galileo Die?

Galileo died after suffering from a fever and heart palpitations on January 8, 1642, in Arcetri, near Florence, Italy.

Galileo's contribution to our understanding of the universe was significant not only for his discoveries, but for the methods he developed and the use of mathematics to prove them. He played a major role in the Scientific Revolution and earned the title "The Father of Modern Science."

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Galileo was an Italian astronomer, mathematician, physicist, philosopher and professor who made pioneering observations of nature with long-lasting implications for the study of physics. He also constructed a telescope and supported the Copernican theory, which supports a sun-centered solar system.

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Galileo heavily doubted the idea that heavier objects fall faster, and lighter objects fall slower. So, he conducted his own experiments and discovered that the balls ‘boasted the same acceleration independent of their mass’, according to Space.com

He also designed and built the first Pendulum Clock, to help people keep better track of time.

# data[].attributes.attachment_link.readable_text
Italian astronomer Galileo Galilei provided a number of scientific insights that laid the foundation for future scientists. His investigation of the laws of motion and improvements on the telescope helped further the understanding of the world and universe around him. Both led him to question the current belief of the time - that all things revolved around the Earth.

[See also our overview of Famous Astronomers and great scientists from many fields who have contributed to the rich history of discoveries in astronomy.]

Galileo's experiments

The Ancient Greek philosopher, Aristotle, taught that heavier objects fall faster than lighter ones, a belief still held in Galileo's lifetime. But Galileo wasn't convinced. Experimenting with balls of different sizes and weights, he rolled them down ramps with various inclinations. His experiments revealed that all of the balls boasted the same acceleration independent of their mass. He also demonstrated that objects thrown in the air travel along a parabola.

At the same time, Galileo worked with pendulums. In his life, accurate timekeeping was virtually nonexistent. Galileo observed, however, that the steady motion of a pendulum could improve this. In 1602, he determined that the time it takes a pendulum to swing back and forth does not depend on the arc of the swing. Near the end of his lifetime, Galileo designed the first pendulum clock.

Galileo's telescope

Galileo is often incorrectly credited with the creation of a telescope. ( Hans Lippershey applied for the first patent in 1608, but others may have beaten him to the actual invention.) Instead, he significantly improved upon them. In 1609, he first learned of the existence of the spyglass, which excited him. He began to experiment with telescope-making, going so far as to grind and polish his own lenses. His telescope allowed him to see with a magnification of eight or nine times. In comparison, spyglasses of the day only provided a magnification of three.

It wasn't long before Galileo turned his telescope to the heavens. He was the first to see craters on the moon, he discovered sunspots, and he tracked the phases of Venus. The rings of Saturn puzzled him, appearing as lobes and vanishing when they were edge-on - but he saw them, which was more than can be said of his contemporaries.

Of all of his telescope discoveries, he is perhaps most known for his discovery of the four most massive moons of Jupiter, now known as the Galilean moons: Io, Ganymede, Europa and Callisto. When NASA sent a mission to Jupiter in the 1990s, it was called Galileo in honor of the famed astronomer.

In his book " Sidereus Nuncius" ("Starry Messenger"), published in 1610, Galileo wrote:

"On the 7th day of January in the present year, 1610, in the first hour of the following night, when I was viewing the constellations of the heavens through a telescope, the planet Jupiter presented itself to my view, and as I had prepared for myself a very excellent instrument, I noticed a circumstance which I had never been able to notice before, namely that three little stars, small but very bright, were near the planet; and although I believed them to belong to a number of the fixed stars, yet they made me somewhat wonder, because they seemed to be arranged exactly in a straight line, parallel to the ecliptic, and to be brighter than the rest of the stars, equal to them in magnitude . . . When on January 8th, led by some fatality, I turned again to look at the same part of the heavens, I found a very different state of things, for there were three little stars all west of Jupiter, and nearer together than on the previous night."

"I therefore concluded, and decided unhesitatingly, that there are three stars in the heavens moving about Jupiter, as Venus and Mercury around the Sun; which was at length established as clear as daylight by numerous other subsequent observations. These observations also established that there are not only three, but four, erratic sidereal bodies performing their revolutions around Jupiter."

Galileo may also have made the first recorded studies of the planet Neptune, though he didn't recognize it as a planet. While observing Jupiter's moons in 1612 and 1613, he recorded a nearby star whose position is not found in any modern catalogues.

"It has been known for several decades that this unknown star was actually the planet Neptune," University of Melbourne physicist David Jamieson told Space.com. "Computer simulations show the precision of his observations revealing that Neptune would have looked just like a faint star almost exactly where Galileo observed it."

Copernican system

In Galileo's lifetime, all celestial bodies were thought to orbit the Earth. Supported by the Catholic Church, teaching opposite of this system was declared heresy in 1615.

Galileo, however, did not agree. His research - including his observations of the phases of Venus and the fact that Jupiter boasted moons that didn't orbit Earth - supported the Copernican system, which (correctly) stated that the Earth and other planets circle the sun.

In 1616, he was summoned to Rome and warned not to teach or write about this controversial theory. But in 1632, believing that he could write on the subject if he treated it as a mathematical proposition, he published work on the Copernican system. He was found guilty of heresy, and was placed under house arrest for the remaining nine years of his life.

Galileo quotes

"And yet it moves."

"I have never met a man so ignorant that I couldn't learn something from him."

"I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use."

"You cannot teach a man anything, you can only help him find it within himself."

"It is a beautiful and delightful sight to behold the body of the Moon."

"Wine is sunlight, held together by water."

- Find other quotes at GoodReads.com.
Additional resources

# data[].attributes.attachment_link.title
Galileo Galilei: Biography, Inventions & Other Facts

# data[].attributes.attachment_link.description
Italian astronomer Galileo Galilei provided a number of scientific insights that laid the foundation for future scientists. His investigation of the laws of motion and improvements on the telescope helped further the understanding of the world and universe around him. Both led him to question the current belief of the time - that all things revolved around the Earth.

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Galileo was one of the first people to support and believe Nicolaus Copernicus theory of the Earth revolving around the Sun, instead of the other way around. This eventually sent him to imprisonment in 1633, (house arrest) being convicted of heresy (he believed something that the Church did not, this was a personal offense.).

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Wow!

Galileo discovered four of Jupiter's moons almost four hundred years ago.

Galileo Galilei was an Italian physicist and astronomer. He was born in Pisa on February 15, 1564. Galileo's father, Vincenzo Galilei, was a well-known musician. Vincenzo decided that his son should become a doctor.

In 1581, Galileo was sent to the University of Pisa to study medicine. While a student at the university, Galileo discovered that he had a talent for mathematics. He was able to persuade his father to allow him to leave the university to become a tutor in mathematics. He later became a professor of mathematics.

In 1609, Galileo heard about the invention of the spyglass, a device which made distant objects appear closer. Galileo used his mathematics knowledge and technical skills to improve upon the spyglass and build a telescope. Later that same year, he became the first person to look at the Moon through a telescope and make his first astronomy discovery. He found that the Moon was not smooth, but mountainous and pitted - just like the Earth! He subsequently used his newly invented telescope to discover four of the moons circling Jupiter, to study Saturn, to observe the phases of Venus, and to study sunspots on the Sun.

Galileo's observations strengthened his belief in Copernicus' theory that Earth and all other planets revolve around the Sun. Most people in Galileo's time believed that the Earth was the center of the universe and that the Sun and planets revolved around it.

The Catholic Church, which was very powerful and influential in Galileo's day, strongly supported the theory of a geocentric, or Earth-centered, universe. After Galileo began publishing papers about his astronomy discoveries and his belief in a heliocentric, or Sun-centered, Universe, he was called to Rome to answer charges brought against him by the Inquisition (the legal body of the Catholic Church). Early in 1616, Galileo was accused of being a heretic, a person who opposed Church teachings. Heresy was a crime for which people were sometimes sentenced to death. Galileo was cleared of charges of heresy, but was told that he should no longer publicly state his belief that Earth moved around the Sun. Galileo continued his study of astronomy and became more and more convinced that all planets revolved around the Sun. In 1632, he published a book that stated, among other things, that the heliocentric theory of Copernicus was correct. Galileo was once again called before the Inquisition and this time was found guilty of heresy. Galileo was sentenced to life imprisonment in 1633. Because of his age and poor health, he was allowed to serve his imprisonment under house arrest. Galileo died on January 8, 1642.

A Question

Why did the Inquisition sentence Galileo to life imprisonment?

The StarChild site is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA/GSFC.

StarChild Authors: The StarChild Team
StarChild Graphics & Music: Acknowledgments
StarChild Project Leader: Dr. Laura A. Whitlock
Curator:J.D. Myers
Responsible NASA Official: Phil Newman

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Wow! Galileo discovered four of Jupiter's moons almost four hundred years ago. Galileo Galilei was an Italian physicist and astronomer. He was born in Pisa on February 15, 1564. Galileo's father, Vincenzo Galilei, was a well-known musician. Vincenzo decided that his son should become a doctor.

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People have also believed that Galileo may have actually been the first person in history to discover Neptune, though he didn’t consider it a planet at first. He only believed that it was a faint star. University of Melbourne physicist David Jamieson says, "Computer simulations show the precision of his observations revealing that Neptune would have looked just like a faint star almost exactly where Galileo observed it."
He was said to have found it in 1613, three years after using the telescope.

# data[].attributes.attachment_link.readable_text
Italian astronomer Galileo Galilei provided a number of scientific insights that laid the foundation for future scientists. His investigation of the laws of motion and improvements on the telescope helped further the understanding of the world and universe around him. Both led him to question the current belief of the time - that all things revolved around the Earth.

[See also our overview of Famous Astronomers and great scientists from many fields who have contributed to the rich history of discoveries in astronomy.]

Galileo's experiments

The Ancient Greek philosopher, Aristotle, taught that heavier objects fall faster than lighter ones, a belief still held in Galileo's lifetime. But Galileo wasn't convinced. Experimenting with balls of different sizes and weights, he rolled them down ramps with various inclinations. His experiments revealed that all of the balls boasted the same acceleration independent of their mass. He also demonstrated that objects thrown in the air travel along a parabola.

At the same time, Galileo worked with pendulums. In his life, accurate timekeeping was virtually nonexistent. Galileo observed, however, that the steady motion of a pendulum could improve this. In 1602, he determined that the time it takes a pendulum to swing back and forth does not depend on the arc of the swing. Near the end of his lifetime, Galileo designed the first pendulum clock.

Galileo's telescope

Galileo is often incorrectly credited with the creation of a telescope. ( Hans Lippershey applied for the first patent in 1608, but others may have beaten him to the actual invention.) Instead, he significantly improved upon them. In 1609, he first learned of the existence of the spyglass, which excited him. He began to experiment with telescope-making, going so far as to grind and polish his own lenses. His telescope allowed him to see with a magnification of eight or nine times. In comparison, spyglasses of the day only provided a magnification of three.

It wasn't long before Galileo turned his telescope to the heavens. He was the first to see craters on the moon, he discovered sunspots, and he tracked the phases of Venus. The rings of Saturn puzzled him, appearing as lobes and vanishing when they were edge-on - but he saw them, which was more than can be said of his contemporaries.

Of all of his telescope discoveries, he is perhaps most known for his discovery of the four most massive moons of Jupiter, now known as the Galilean moons: Io, Ganymede, Europa and Callisto. When NASA sent a mission to Jupiter in the 1990s, it was called Galileo in honor of the famed astronomer.

In his book " Sidereus Nuncius" ("Starry Messenger"), published in 1610, Galileo wrote:

"On the 7th day of January in the present year, 1610, in the first hour of the following night, when I was viewing the constellations of the heavens through a telescope, the planet Jupiter presented itself to my view, and as I had prepared for myself a very excellent instrument, I noticed a circumstance which I had never been able to notice before, namely that three little stars, small but very bright, were near the planet; and although I believed them to belong to a number of the fixed stars, yet they made me somewhat wonder, because they seemed to be arranged exactly in a straight line, parallel to the ecliptic, and to be brighter than the rest of the stars, equal to them in magnitude . . . When on January 8th, led by some fatality, I turned again to look at the same part of the heavens, I found a very different state of things, for there were three little stars all west of Jupiter, and nearer together than on the previous night."

"I therefore concluded, and decided unhesitatingly, that there are three stars in the heavens moving about Jupiter, as Venus and Mercury around the Sun; which was at length established as clear as daylight by numerous other subsequent observations. These observations also established that there are not only three, but four, erratic sidereal bodies performing their revolutions around Jupiter."

Galileo may also have made the first recorded studies of the planet Neptune, though he didn't recognize it as a planet. While observing Jupiter's moons in 1612 and 1613, he recorded a nearby star whose position is not found in any modern catalogues.

"It has been known for several decades that this unknown star was actually the planet Neptune," University of Melbourne physicist David Jamieson told Space.com. "Computer simulations show the precision of his observations revealing that Neptune would have looked just like a faint star almost exactly where Galileo observed it."

Copernican system

In Galileo's lifetime, all celestial bodies were thought to orbit the Earth. Supported by the Catholic Church, teaching opposite of this system was declared heresy in 1615.

Galileo, however, did not agree. His research - including his observations of the phases of Venus and the fact that Jupiter boasted moons that didn't orbit Earth - supported the Copernican system, which (correctly) stated that the Earth and other planets circle the sun.

In 1616, he was summoned to Rome and warned not to teach or write about this controversial theory. But in 1632, believing that he could write on the subject if he treated it as a mathematical proposition, he published work on the Copernican system. He was found guilty of heresy, and was placed under house arrest for the remaining nine years of his life.

Galileo quotes

"And yet it moves."

"I have never met a man so ignorant that I couldn't learn something from him."

"I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use."

"You cannot teach a man anything, you can only help him find it within himself."

"It is a beautiful and delightful sight to behold the body of the Moon."

"Wine is sunlight, held together by water."

- Find other quotes at GoodReads.com.
Additional resources

# data[].attributes.attachment_link.title
Galileo Galilei: Biography, Inventions & Other Facts

# data[].attributes.attachment_link.description
Italian astronomer Galileo Galilei provided a number of scientific insights that laid the foundation for future scientists. His investigation of the laws of motion and improvements on the telescope helped further the understanding of the world and universe around him. Both led him to question the current belief of the time - that all things revolved around the Earth.

# data[].attributes.body
Galileo Galilei was the first person to use the telescope to study the stars, though he did not invent it. With this telescope, however, he improved the spyglass and discovered four of Jupiter's moons (Io, Callisto, Europa and Ganymede), the rings of Saturn, and phases of the moon.

# data[].attributes.attachment_link.readable_text
Italian astronomer Galileo Galilei provided a number of scientific insights that laid the foundation for future scientists. His investigation of the laws of motion and improvements on the telescope helped further the understanding of the world and universe around him. Both led him to question the current belief of the time - that all things revolved around the Earth.

[See also our overview of Famous Astronomers and great scientists from many fields who have contributed to the rich history of discoveries in astronomy.]

Galileo's experiments

The Ancient Greek philosopher, Aristotle, taught that heavier objects fall faster than lighter ones, a belief still held in Galileo's lifetime. But Galileo wasn't convinced. Experimenting with balls of different sizes and weights, he rolled them down ramps with various inclinations. His experiments revealed that all of the balls boasted the same acceleration independent of their mass. He also demonstrated that objects thrown in the air travel along a parabola.

At the same time, Galileo worked with pendulums. In his life, accurate timekeeping was virtually nonexistent. Galileo observed, however, that the steady motion of a pendulum could improve this. In 1602, he determined that the time it takes a pendulum to swing back and forth does not depend on the arc of the swing. Near the end of his lifetime, Galileo designed the first pendulum clock.

Galileo's telescope

Galileo is often incorrectly credited with the creation of a telescope. ( Hans Lippershey applied for the first patent in 1608, but others may have beaten him to the actual invention.) Instead, he significantly improved upon them. In 1609, he first learned of the existence of the spyglass, which excited him. He began to experiment with telescope-making, going so far as to grind and polish his own lenses. His telescope allowed him to see with a magnification of eight or nine times. In comparison, spyglasses of the day only provided a magnification of three.

It wasn't long before Galileo turned his telescope to the heavens. He was the first to see craters on the moon, he discovered sunspots, and he tracked the phases of Venus. The rings of Saturn puzzled him, appearing as lobes and vanishing when they were edge-on - but he saw them, which was more than can be said of his contemporaries.

Of all of his telescope discoveries, he is perhaps most known for his discovery of the four most massive moons of Jupiter, now known as the Galilean moons: Io, Ganymede, Europa and Callisto. When NASA sent a mission to Jupiter in the 1990s, it was called Galileo in honor of the famed astronomer.

In his book " Sidereus Nuncius" ("Starry Messenger"), published in 1610, Galileo wrote:

"On the 7th day of January in the present year, 1610, in the first hour of the following night, when I was viewing the constellations of the heavens through a telescope, the planet Jupiter presented itself to my view, and as I had prepared for myself a very excellent instrument, I noticed a circumstance which I had never been able to notice before, namely that three little stars, small but very bright, were near the planet; and although I believed them to belong to a number of the fixed stars, yet they made me somewhat wonder, because they seemed to be arranged exactly in a straight line, parallel to the ecliptic, and to be brighter than the rest of the stars, equal to them in magnitude . . . When on January 8th, led by some fatality, I turned again to look at the same part of the heavens, I found a very different state of things, for there were three little stars all west of Jupiter, and nearer together than on the previous night."

"I therefore concluded, and decided unhesitatingly, that there are three stars in the heavens moving about Jupiter, as Venus and Mercury around the Sun; which was at length established as clear as daylight by numerous other subsequent observations. These observations also established that there are not only three, but four, erratic sidereal bodies performing their revolutions around Jupiter."

Galileo may also have made the first recorded studies of the planet Neptune, though he didn't recognize it as a planet. While observing Jupiter's moons in 1612 and 1613, he recorded a nearby star whose position is not found in any modern catalogues.

"It has been known for several decades that this unknown star was actually the planet Neptune," University of Melbourne physicist David Jamieson told Space.com. "Computer simulations show the precision of his observations revealing that Neptune would have looked just like a faint star almost exactly where Galileo observed it."

Copernican system

In Galileo's lifetime, all celestial bodies were thought to orbit the Earth. Supported by the Catholic Church, teaching opposite of this system was declared heresy in 1615.

Galileo, however, did not agree. His research - including his observations of the phases of Venus and the fact that Jupiter boasted moons that didn't orbit Earth - supported the Copernican system, which (correctly) stated that the Earth and other planets circle the sun.

In 1616, he was summoned to Rome and warned not to teach or write about this controversial theory. But in 1632, believing that he could write on the subject if he treated it as a mathematical proposition, he published work on the Copernican system. He was found guilty of heresy, and was placed under house arrest for the remaining nine years of his life.

Galileo quotes

"And yet it moves."

"I have never met a man so ignorant that I couldn't learn something from him."

"I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use."

"You cannot teach a man anything, you can only help him find it within himself."

"It is a beautiful and delightful sight to behold the body of the Moon."

"Wine is sunlight, held together by water."

- Find other quotes at GoodReads.com.
Additional resources

# data[].attributes.attachment_link.title
Galileo Galilei: Biography, Inventions & Other Facts

# data[].attributes.attachment_link.description
Italian astronomer Galileo Galilei provided a number of scientific insights that laid the foundation for future scientists. His investigation of the laws of motion and improvements on the telescope helped further the understanding of the world and universe around him. Both led him to question the current belief of the time - that all things revolved around the Earth.

# data[].attributes.body
Galileo Galilei was born February 15th, 1564 in Pisa, Italy, home of the Tower of Pisa, and attended at the University of Pisa in 1581 to study medicine, but ended up being endorsed in philosophy, astronomy, math, and many types of astronomy. His father was a famed musician, and even took part in some of Galileo's experiments from 1588 and 1589.

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Galileo Galilei

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Galileo (born February 15, 1564, Pisa [Italy]-died January 8, 1642, Arcetri, near Florence) Italian natural philosopher, astronomer, and mathematician who made fundamental contributions to the sciences of motion, astronomy, and strength of materials and to the development of the scientific method. His formulation of (circular) inertia, the law of falling bodies, and parabolic trajectories marked the beginning of a fundamental change in the study of motion. His insistence that the book of nature was written in the language of mathematics changed natural philosophy from a verbal, qualitative account to a mathematical one in which experimentation became a recognized method for discovering the facts of nature. Finally, his discoveries with the telescope revolutionized astronomy and paved the way for the acceptance of the Copernican heliocentric system, but his advocacy of that system eventually resulted in an Inquisition process against him.

Early life and career

Galileo was born in Pisa, Tuscany, on February 15, 1564, the oldest son of Vincenzo Galilei, a musician who made important contributions to the theory and practice of music and who may have performed some experiments with Galileo in 1588-89 on the relationship between pitch and the tension of strings. The family moved to Florence in the early 1570s, where the Galilei family had lived for generations. In his middle teens Galileo attended the monastery school at Vallombrosa, near Florence, and then in 1581 matriculated at the University of Pisa, where he was to study medicine. However, he became enamoured with mathematics and decided to make the mathematical subjects and philosophy his profession, against the protests of his father. Galileo then began to prepare himself to teach Aristotelian philosophy and mathematics, and several of his lectures have survived. In 1585 Galileo left the university without having obtained a degree, and for several years he gave private lessons in the mathematical subjects in Florence and Siena. During this period he designed a new form of hydrostatic balance for weighing small quantities and wrote a short treatise, La bilancetta ("The Little Balance"), that circulated in manuscript form. He also began his studies on motion, which he pursued steadily for the next two decades.

In 1588 Galileo applied for the chair of mathematics at the University of Bologna but was unsuccessful. His reputation was, however, increasing, and later that year he was asked to deliver two lectures to the Florentine Academy, a prestigious literary group, on the arrangement of the world in Dante's Inferno. He also found some ingenious theorems on centres of gravity (again, circulated in manuscript) that brought him recognition among mathematicians and the patronage of Guidobaldo del Monte (1545-1607), a nobleman and author of several important works on mechanics. As a result, he obtained the chair of mathematics at the University of Pisa in 1589. There, according to his first biographer, Vincenzo Viviani (1622-1703), Galileo demonstrated, by dropping bodies of different weights from the top of the famous Leaning Tower, that the speed of fall of a heavy object is not proportional to its weight, as Aristotle had claimed. The manuscript tract De motu ( On Motion), finished during this period, shows that Galileo was abandoning Aristotelian notions about motion and was instead taking an Archimedean approach to the problem. But his attacks on Aristotle made him unpopular with his colleagues, and in 1592 his contract was not renewed. His patrons, however, secured him the chair of mathematics at the University of Padua, where he taught from 1592 until 1610.

Although Galileo's salary was considerably higher there, his responsibilities as the head of the family (his father had died in 1591) meant that he was chronically pressed for money. His university salary could not cover all his expenses, and he therefore took in well-to-do boarding students whom he tutored privately in such subjects as fortification. He also sold a proportional compass, or sector, of his own devising, made by an artisan whom he employed in his house. Perhaps because of these financial problems, he did not marry, but he did have an arrangement with a Venetian woman, Marina Gamba, who bore him two daughters and a son. In the midst of his busy life he continued his research on motion, and by 1609 he had determined that the distance fallen by a body is proportional to the square of the elapsed time ( the law of falling bodies) and that the trajectory of a projectile is a parabola, both conclusions that contradicted Aristotelian physics.

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Galileo | Biography, Discoveries, Inventions, & Facts

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Galileo, the brilliant Italian polymath, revolutionized our understanding of the universe through his groundbreaking discoveries in astronomy and contributions to scientific methodology.