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. 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.

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.

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. 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. 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.

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.

Death

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."

Who Was Isaac Newton?

Isaac Newton was a physicist and mathematician who developed the principles of modern physics, including the laws of motion and is credited as one of the great minds of the 17th-century Scientific Revolution. In 1687, he published his most acclaimed work, Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), which has been called the single most influential book on physics. In 1705, he was knighted by Queen Anne of England, making him Sir Isaac Newton.

Early Life and Family

Newton was born on January 4, 1643, in Woolsthorpe, Lincolnshire, England. Using the "old" Julian calendar, Newton's birth date is sometimes displayed as December 25, 1642. Newton was the only son of a prosperous local farmer, also named Isaac, who died three months before he was born. A premature baby born tiny and weak, Newton was not expected to survive. When he was 3 years old, his mother, Hannah Ayscough Newton, remarried a well-to-do minister, Barnabas Smith, and went to live with him, leaving young Newton with his maternal grandmother. The experience left an indelible imprint on Newton, later manifesting itself as an acute sense of insecurity. He anxiously obsessed over his published work, defending its merits with irrational behavior. At age 12, Newton was reunited with his mother after her second husband died. She brought along her three small children from her second marriage.

Isaac Newton's Education

Newton was enrolled at the King's School in Grantham, a town in Lincolnshire, where he lodged with a local apothecary and was introduced to the fascinating world of chemistry. His mother pulled him out of school at age 12. Her plan was to make him a farmer and have him tend the farm. Newton failed miserably, as he found farming monotonous. Newton was soon sent back to King's School to finish his basic education. Perhaps sensing the young man's innate intellectual abilities, his uncle, a graduate of the University of Cambridge's Trinity College, persuaded Newton's mother to have him enter the university. Newton enrolled in a program similar to a work-study in 1661, and subsequently waited on tables and took care of wealthier students' rooms.

Scientific Revolution

When Newton arrived at Cambridge, the Scientific Revolution of the 17th century was already in full force. The heliocentric view of the universe—theorized by astronomers Nicolaus Copernicus and Johannes Kepler, and later refined by Galileo—was well known in most European academic circles. Philosopher René Descartes had begun to formulate a new concept of nature as an intricate, impersonal and inert machine. Yet, like most universities in Europe, Cambridge was steeped in Aristotelian philosophy and a view of nature resting on a geocentric view of the universe, dealing with nature in qualitative rather than quantitative terms. During his first three years at Cambridge, Newton was taught the standard curriculum but was fascinated with the more advanced science. All his spare time was spent reading from the modern philosophers. The result was a less-than-stellar performance, but one that is understandable, given his dual course of study. It was during this time that Newton kept a second set of notes, entitled "Quaestiones Quaedam Philosophicae" ("Certain Philosophical Questions"). The "Quaestiones" reveal that Newton had discovered the new concept of nature that provided the framework for the Scientific Revolution. Though Newton graduated without honors or distinctions, his efforts won him the title of scholar and four years of financial support for future education. In 1665, the bubonic plague that was ravaging Europe had come to Cambridge, forcing the university to close. After a two-year hiatus, Newton returned to Cambridge in 1667 and was elected a minor fellow at Trinity College, as he was still not considered a standout scholar. In the ensuing years, his fortune improved. Newton received his Master of Arts degree in 1669, before he was 27. During this time, he came across Nicholas Mercator's published book on methods for dealing with infinite series. Newton quickly wrote a treatise, De Analysi, expounding his own wider-ranging results. He shared this with friend and mentor Isaac Barrow, but didn't include his name as author. In June 1669, Barrow shared the unaccredited manuscript with British mathematician John Collins. In August 1669, Barrow identified its author to Collins as "Mr. Newton ... very young ... but of an extraordinary genius and proficiency in these things." Newton's work was brought to the attention of the mathematics community for the first time. Shortly afterward, Barrow resigned his Lucasian professorship at Cambridge, and Newton assumed the chair.

Discoveries & Inventions

Newton made discoveries in optics, motion and mathematics. Newton theorized that white light was a composite of all colors of the spectrum, and that light was composed of particles. His momentous book on physics, Principia, contains information on nearly all of the essential concepts of physics except energy, ultimately helping him to explain the laws of motion and the theory of gravity. Along with mathematician Gottfried Wilhelm von Leibniz, Newton is credited for developing essential theories of calculus.

Newton's first major public scientific achievement was designing and constructing a reflecting telescope in 1668. As a professor at Cambridge, Newton was required to deliver an annual course of lectures and chose optics as his initial topic. He used his telescope to study optics and help prove his theory of light and color. The Royal Society asked for a demonstration of his reflecting telescope in 1671, and the organization's interest encouraged Newton to publish his notes on light, optics and color in 1672. These notes were later published as part of Newton's Opticks: Or, A treatise of the Reflections, Refractions, Inflections and Colours of Light.

Between 1665 and 1667, Newton returned home from Trinity College to pursue his private study, as school was closed due to the Great Plague. Legend has it that, at this time, Newton experienced his famous inspiration of gravity with the falling apple. According to this common myth, Newton was sitting under an apple tree when a fruit fell and hit him on the head, inspiring him to suddenly come up with the theory of gravity. While there is no evidence that the apple actually hit Newton on the head, he did see an apple fall from a tree, leading him to wonder why it fell straight down and not at an angle. Consequently, he began exploring the theories of motion and gravity. It was during this 18-month hiatus as a student that Newton conceived many of his most important insights—including the method of infinitesimal calculus, the foundations for his theory of light and color, and the laws of planetary motion—that eventually led to the publication of his physics book Principia and his theory of gravity.

Isaac Newton’s Laws of Motion

In 1687, following 18 months of intense and effectively nonstop work, Newton published Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy), most often known as Principia. Principia is said to be the single most influential book on physics and possibly all of science. Its publication immediately raised Newton to international prominence. Principia offers an exact quantitative description of bodies in motion, with three basic but important laws of motion:

• First Law: A stationary body will stay stationary unless an external force is applied to it.

• Second Law: Force is equal to mass times acceleration, and a change in motion (i.e., change in speed) is proportional to the force applied.

• Third Law: For every action, there is an equal and opposite reaction.

Theory of Gravity

Newton’s three basic laws of motion outlined in Principia helped him arrive at his theory of gravity. Newton’s law of universal gravitation states that two objects attract each other with a force of gravitational attraction that’s proportional to their masses and inversely proportional to the square of the distance between their centers. These laws helped explain not only elliptical planetary orbits but nearly every other motion in the universe: how the planets are kept in orbit by the pull of the sun’s gravity; how the moon revolves around Earth and the moons of Jupiter revolve around it; and how comets revolve in elliptical orbits around the sun. They also allowed him to calculate the mass of each planet, calculate the flattening of the Earth at the poles and the bulge at the equator, and how the gravitational pull of the sun and moon create the Earth’s tides. In Newton's account, gravity kept the universe balanced, made it work, and brought heaven and Earth together in one great equation.

Final Years

Toward the end of this life, Newton lived at Cranbury Park, near Winchester, England, with his niece, Catherine (Barton) Conduitt, and her husband, John Conduitt. By this time, Newton had become one of the most famous men in Europe. His scientific discoveries were unchallenged. He also had become wealthy, investing his sizable income wisely and bestowing sizable gifts to charity. Despite his fame, Newton's life was far from perfect: He never married or made many friends, and in his later years, a combination of pride, insecurity and side trips on peculiar scientific inquiries led even some of his few friends to worry about his mental stability. By the time he reached 80 years of age, Newton was experiencing digestion problems and had to drastically change his diet and mobility. In March 1727, Newton experienced severe pain in his abdomen and blacked out, never to regain consciousness. He died the next day, on March 31, 1727, at the age of 84.

Legacy

Newton's fame grew even more after his death, as many of his contemporaries proclaimed him the greatest genius who ever lived. Maybe a slight exaggeration, but his discoveries had a large impact on Western thought, leading to comparisons to the likes of Plato, Aristotle and Galileo. Although his discoveries were among many made during the Scientific Revolution, Newton's universal principles of gravity found no parallels in science at the time. Of course, Newton was proven wrong on some of his key assumptions. In the 20th century, Albert Einstein would overturn Newton's concept of the universe, stating that space, distance and motion were not absolute but relative and that the universe was more fantastic than Newton had ever conceived. Newton might not have been surprised: In his later life, when asked for an assessment of his achievements, he replied, "I do not know what I may appear to the world; but to myself I seem to have been only like a boy playing on the seashore, and diverting myself now and then in finding a smoother pebble or prettier shell than ordinary, while the great ocean of truth lay all undiscovered before me."

Who Was Copernicus?

Circa 1508, Nicolaus Copernicus developed his own celestial model of a heliocentric planetary system. Around 1514, he shared his findings in the Commentariolus. His second book on the topic, De revolutionibus orbium coelestium, was banned by the Roman Catholic Church decades after his May 24, 1543 death in Frombork.

Early Life and Education

Famed astronomer Nicolaus Copernicus (Mikolaj Kopernik, in Polish) came into the world on February 19, 1473. The fourth and youngest child born to Nicolaus Copernicus Sr. and Barbara Watzenrode, an affluent copper merchant family in Torun, West Prussia, Copernicus was technically of German heritage. By the time he was born, Torun had ceded to Poland, rendering him a citizen under the Polish crown. German was Copernicus' first language, but some scholars believe that he spoke some Polish as well.

During the mid-1480s, Copernicus' father passed away. His maternal uncle, Bishop of Varmia Lucas Watzenrode, generously assumed a paternal role, taking it upon himself to ensure that Copernicus received the best possible education. In 1491, Copernicus entered the University of Cracow, where he studied painting and mathematics. He also developed a growing interest in the cosmos and started collecting books on the topic.

Copernicus' Theory: Heliocentric Solar System

Throughout the time he spent in Lidzbark-Warminski, Copernicus continued to study astronomy. Among the sources that he consulted was Regiomontanus's 15th-century work Epitome of the Almagest, which presented an alternative to Ptolemy's model of the universe and significantly influenced Copernicus' research.

Scholars believe that by around 1508, Copernicus had begun developing his own celestial model, a heliocentric planetary system. During the second century A.D., Ptolemy had invented a geometric planetary model with eccentric circular motions and epicycles, significantly deviating from Aristotle's idea that celestial bodies moved in a fixed circular motion around the earth. In an attempt to reconcile such inconsistencies, Copernicus' heliocentric solar system named the sun, rather than the earth, as the center of the solar system. Subsequently, Copernicus believed that the size and speed of each planet's orbit depended on its distance from the sun.

Though his theory was viewed as revolutionary and met with controversy, Copernicus was not the first astronomer to propose a heliocentric system. Centuries prior, in the third century B.C., the ancient Greek astronomer Aristarchus of Samos had identified the sun as a central unit orbited by a revolving earth. But a heliocentric theory was dismissed in Copernicus' era because Ptolemy's ideas were far more accepted by the influential Roman Catholic Church, which adamantly supported the earth-based solar system theory. Still, Copernicus' heliocentric system proved to be more detailed and accurate than Aristarchus', including a more efficient formula for calculating planetary positions.

In 1513, Copernicus' dedication prompted him to build his own modest observatory. Nonetheless, his observations did, at times, lead him to form inaccurate conclusions, including his assumption that planetary orbits occurred in perfect circles. As German astronomer Johannes Kepler would later prove, planetary orbits are actually elliptical in shape.

Around 1514, Copernicus completed a written work, Commentariolus (Latin for "Small Commentary"), a 40-page manuscript which summarized his heliocentric planetary system and alluded to forthcoming mathematical formulas meant to serve as proof. The sketch set forth seven axioms, each describing an aspect of the heliocentric solar system: 1) Planets don't revolve around one fixed point; 2) The earth is not at the center of the universe; 3) The sun is at the center of the universe, and all celestial bodies rotate around it; 4) The distance between the Earth and Sun is only a tiny fraction of stars' distance from the Earth and Sun; 5) Stars do not move, and if they appear to, it is only because the Earth itself is moving; 6) Earth moves in a sphere around the Sun, causing the Sun's perceived yearly movement; and 7) Earth's own movement causes other planets to appear to move in an opposite direction.

Commentariolus also went on to describe in detail Copernicus' assertion that a mere 34 circles could sufficiently illustrate planetary motion. Copernicus sent his unpublished manuscript to several scholarly friends and contemporaries, and while the manuscript received little to no response among his colleagues, a buzz began to build around Copernicus and his unconventional theories.

Courting Controversy with the Catholic Church

Copernicus raised a fair share of controversy with Commentariolus and De revolutionibus orbium coelestium ("On the Revolutions of the Heavenly Spheres"), with the second work published right before his death. His critics claimed that he failed to solve the mystery of the parallax — the seeming displacement in the position of a celestial body, when viewed along varying lines of sight — and that his work lacked a sufficient explanation for why the Earth orbits the Sun.

Copernicus' theories also incensed the Roman Catholic Church and were considered heretical. When De revolutionibus orbium coelestium was published in 1543, religious leader Martin Luther voiced his opposition to the heliocentric solar system model. His underling, Lutheran minister Andreas Osiander, quickly followed suit, saying of Copernicus, "This fool wants to turn the whole art of astronomy upside down."

Osiander even went so far as to write a disclaimer stating that the heliocentric system was an abstract hypothesis that need not be seen as truth. He added his text to the book's preface, leading readers to assume that Copernicus himself had written it. By this time, Copernicus was ailing and unfit for the task of defending his work.

Ironically, Copernicus had dedicated De revolutionibus orbium coelestium to Pope Paul III. If his tribute to the religious leader was an attempt to cull the Catholic Church's softer reception, it was to no avail. The church ultimately banned De revolutionibus in 1616, though the book was eventually removed from the list of forbidden reading material.

Death & Legacy

In May 1543, mathematician and scholar Georg Joachim Rheticus presented Copernicus with a copy of a newly published De revolutionibus orbium coelestium. Suffering the aftermath of a recent stroke, Copernicus was said to have been clutching the book when he died in his bed on May 24, 1543, in Frombork, Poland.

Kepler later revealed to the public that the preface for De revolutionibus orbium coelestium had indeed been written by Osiander, not Copernicus. As Kepler worked on expanding upon and correcting the errors of Copernicus' heliocentric theory, Copernicus became a symbol of the brave scientist standing alone, defending his theories against the common beliefs of his time.