1.15: Early Astronomers- Copernicus, Galileo, Kepler, and Newton - Geosciences

1.15: Early Astronomers- Copernicus, Galileo, Kepler, and Newton - Geosciences

Early Astronomers: Copernicus, Galileo, Kepler, and Newton

The geocentric model wasn't seriously challenged until Nicolas Copernicus who published a report in 1543 suggesting that the Sun, not the Earth, was the center of the Universe (called Copernican heliocentrism). Nicolaus Copernicus (1473-1543) was the first to explain the observed retrograde, looping phenomena of planet motion by replacing previously held theories of geocentrism (Earth being the center of the Universe) with heliocentrism (the Sun being the center of the observable Universe).

However, the Copernican system was also discovered to be flawed as telescopes were developed to see farther into space and astronomers began to grasp the immense scale of time and distance between our Solar System and other objects in our Milky Way Galaxy and the Universe beyond.

Italian physicist and astronomer, Galileo Galilei (1564-1642) used an early telescope and discovered four large moons of Jupiter (Figure 1.33). He also promoted the Heliocentrism Theory that the Sun, not the Earth, was the center of our Solar System. In 1615 he was subjected to the Roman Inquisition for his scientific inquiries. He was forced to publicly recant his beliefs and subjected to house arrest for the remainder of his life. (Note that the Roman Catholic Church eventually accepted his theory and officially forgave him in 1992!)

Figure 1.33. Galileo Galilei first used a telescope to examine the night sky.

From Copernicus to Newton

The term classical mechanics was first used early in the twentieth century to describe a branch of physics that was largely dominated by the physical laws formulated by the seventeenth century English physicist and philosopher Sir Isaac Newton (1642-1726). For that reason, classical mechanics is also often referred to as Newtonian mechanics.

As is invariably the case, Newton's work was based in no small measure on the work of his predecessors. In so far as the history of classical physics can be thought of as having a starting point, we probably need to go back to 1543 - almost one hundred and fifty years before Newton published his masterwork Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy).

In that year, the Polish astronomer Nicolaus Copernicus (1473-1543) published his book De revolutionibus orbium coelestium libri VI (Six Books Concerning the Revolutions of the Heavenly Orbs). Copernicus was already dying from the effects of a stroke at the time of publication, but allegedly regained consciousness on his deathbed just long enough to be presented with a printed copy of his great work, after which he promptly died.

Whilst this story is probably apocryphal, there can be no question as to the profound influence his work would have on the future of science. Copernicus had determined, not unreasonably, that the observed positions of the planets in the night sky would be much easier to explain if the Sun, rather than the Earth, were at the centre of the solar system.

The system of the entire created universe (Planisphere) according to the hypothesis of Copernicus exhibited in a planar view (illustrated in 1661 by Andreas Cellarius)

Unfortunately, not only did Copernicus' theories go against contemporary thinking, they raised a rather awkward question: If the Earth is careering through space, and at the same time spinning around its axis, why can we not detect this motion? The notion that the Earth was moving in such a fashion would have appeared nonsensical to a casual observer.

Copernicus died before he could offer anything in the way of proof to back up his ideas. Nevertheless, the events set in motion by Copernicus would become what is often referred to today as the scientific revolution. Finding an answer to the question that had now become so problematic for those who wished to pursue Copernicus' theories would fall to the Italian philosopher, astronomer and mathematician Galileo Galilei (1564-1642).

Galileo carried out numerous experiments to determine the nature of bodies in motion. In one experiment, he allowed a ball to roll down a slope, opposite which was a second slope. He noted with interest that the ball would roll up the second slope to almost the height from which it was released on the first slope furthermore, the respective angles of the slopes seemed to have little bearing on the height attained by the upward-moving ball.

Galileo deduced from this experiment that if, instead of encountering the second slope, the ball found itself on a continuous level plane, it would continue to move in the horizontal direction indefinitely. He concluded that a body that is already in motion in the horizontal direction will continue to move in that direction unless something impedes its progress, and that no additional force needs to be applied to the body in order to maintain its momentum.

This conclusion was later refined by the French philosopher, mathematician, and scientist René Descartes (1596-1650), who determined that the concept applied specifically to motion in a straight line this would later form the basis for Newton's first law - the law of inertia.

Galileo also experimented with falling bodies of different masses. He is famously alleged to have dropped two cannonballs, differing from one another in both size and mass, from the Leaning Tower of Pisa in order to demonstrate that they would both fall at the same rate regardless of their respective masses. Whether this experiment actually took place is the subject of some debate nevertheless, Galileo correctly determined that a freely falling body will accelerate uniformly, at a rate that does not depend on its mass.

Galileo also correctly surmised that the motion of a projectile was subject to movement in two principle directions simultaneously in addition to movement in the horizontal direction, the projectile was also moving in the downwards direction (a falling motion). He expressed this concept in his book Discorsi e dimostrazioni matematiche intorno a due nuove scienze attenenti alla meccanica (or Dialogues Concerning Two New Sciences), in which he states:

It has been observed that missiles and projectiles describe a curved path of some sort however no one has pointed out the fact that this path is a parabola. But this and other facts, not few in number or less worth knowing, I have succeeded in proving and what I consider more important, there have been opened up to this vast and most excellent science, of which my work is merely the beginning, ways and means by which other minds more acute than mine will explore its remote corners.

Those prophetic words would later be borne out by the work of Newton. Perhaps of more immediate significance, however, was the fact that Galileo had found an answer to the problem arising from Copernicus' theories, namely the question of why an observer on Earth experiences no sensation of motion, despite the fact the Earth is supposedly moving through space at high speed and revolves around its axis.

One of the arguments frequently made against the notion that the Earth was moving went something like this: If the Earth is moving, then surely a stone dropped from a tower should move away from the tower as it falls? Galileo could now argue that, since the stone must be moving in the same direction as the tower immediately before it is dropped, then it will continue to move in that direction unless some external force or entity prevents it from doing so.

Galileo later became even more convinced of the veracity of the heliocentric view of the solar system when the invention of the telescope in (circa) 1610 allowed him to look more closely at the motion of various objects in the night sky. Galileo's observations led him to the discovery of Jupiter's four largest moons (which he at first thought were stars). After studying these objects for several weeks he concluded that they must be orbiting Jupiter just as, according to Copernicus, the planets of the solar system must orbit the Sun.

A painting by Henry-Julien Detouche showing Galileo Galilei displaying his telescope to Leonardo Donato

Nevertheless, there was still a great deal of hostility towards the heliocentric view of the solar system, not least because it directly contradicted the official view of the Catholic church at the time, which was that the Earth was at the centre of the universe, and that the Sun, Moon and stars revolved around it. Indeed, Galileo's support of heliocentrism put him on a collision course with the church that eventually led to him being tried for heresy, and saw him forced to spend the last few years of his life under house arrest.

The Copernican view of the solar system was also endorsed by the German mathematician, astronomer, and astrologer Johannes Kepler (1571-1630), who was to become one of the key figures in the scientific revolution. Kepler learned of the Copernican system of planetary motion as a student, and became a dedicated supporter of Copernicus' ideas. Kepler had proved himself to be an outstanding mathematician, and when his studies ended he accepted a post teaching mathematics in Graz (the second largest city in Austria).

During Kepler's tenure in Gratz, and based on his knowledge of three-dimensional geometry, he gradually developed a working theory concerning the geometrical ordering of the planets in the solar system. These ideas appeared in his first major astronomical work Mysterium Cosmographicum (The Cosmographic Mystery), which was originally published in 1596. A greatly expanded edition, which included a number of corrections and improvements, was published in In 1621.

Copper engraving illustrating Johannes Kepler's Geometrical Model of the Copernican System, 1597

In pursuance of his theories, Kepler sought the opinions of many other astronomers of the period. He entered into a correspondence with the Danish nobleman and astronomer Tycho Brahe (1546-1601) - imperial mathematician to the Holy Roman Emperor (and King of Hungary) Rudolf II. Brahe was renowned for his accurate and comprehensive astronomical and planetary observations.

In 1600, Kepler met with Brahe in Prague. As a result of that meeting, he accepted a post as Brahe's assistant, and was assigned the task of analysing the observational data that Brahe provided. When Brahe died rather unexpectedly in 1601, Kepler succeeded him as imperial mathematician. His brief was to complete Brahe's unfinished work, and to provide astrological services to the Emperor.

Kepler remained in Prague until 1612, and spent those years analysing the extensive observational data that Brahe had gathered. It was in 1610, towards the end of his tenure there, that Galileo discovered the moons of Jupiter. Galileo sought the opinion of Kepler on this matter, who was happy to lend his support to Galileo's findings and later published his own observations of Jupiter's moons.

Kepler's work had a number of important outcomes. One of these was the Tabulae Rudolphinae (Rudolphine Tables) - a star catalogue and a set of planetary tables based on Brahe's observational data, named for the Emperor and eventually published by Kepler in 1627. In 1609, Kepler published his book Astronomia nova the full title of which (in English) is New Astronomy, Based upon Causes, or Celestial Physics, Treated by Means of Commentaries on the Motions of the Star Mars, from the Observations of Tycho Brahe, Gent.

The book contains the results of Kepler's investigation of the motion of Mars, from which he concluded that Mars follows an elliptical orbit around the Sun. The Astronomia nova is considered one of the most important books in the history of astronomy, and presents convincing evidence for heliocentrism. It was also the publication in which Keppler stated his first two laws of planetary motion, which can be summarised as follows:

  • The planets move in elliptical orbits, with the sun at one focus
  • A line joining a planet and the Sun sweeps out equal areas in equal intervals of time

Keppler's third law of planetary motion, along with the first two laws, would appear in the first volume of his textbook Epitome astronomiae Copernicanae (Epitome of Copernican Astronomy), published in 1615. The third law describes the relationship between the distance of a planet from the Sun and its orbital period it states that the square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

Kepler's textbook was to become perhaps his most influential work. In fact, during the twenty year period following Kepler's death in 1630, Epitome astronomiae Copernicanae was probably the most widely read astronomy text in Europe. Kepler's work went a long way towards legitimising Copernicus' notions of a heliocentric solar system. Although his rules concerning planetary orbits were widely accepted, however, there was far less enthusiasm for his ideas concerning the physical causes of these motions.

In 1665, thirty five years after Kepler's death, a twenty-three year old Isaac Newton returned from his studies at Trinity College Cambridge to his home in Woolsthorpe, Lincolnshire, the college having been temporarily closed down as a precaution against an outbreak of bubonic plague that was affecting Southern England, including parts of East Anglia, at that time. In Cambridge, Newton had been become familiar with the work of - among others - Descartes, Galileo and Kepler.

Although Newton would not publish his Principia until 1687, many of the ideas and theories for which he is so well known were developed over the next two years during his time at Woolsthorpe. During this period he developed the branch of mathematics we know today as calculus, did a considerable amount of work in the field of optics, and formulated his ideas on gravitation.

The credit for developing infinitesimal calculus is today generally acknowledged to belong jointly to Newton and the German polymath and philosopher Gottfried Wilhelm Leibniz (1646-1716), who independently developed his own version of the calculus during the same period. At the time, however, both Newton and Leibniz claimed to have developed the calculus first, leading to a bitter intellectual dispute that lasted many years and continued even after Leibniz's death in 1716.

The calculus was of critical importance because it provided the mathematical tools that made it possible to study phenomena in which the parameters undergo continuous change - in much the same way that geometry provides us with the tools to study two- and three-dimensional shapes, and algebra allows us to work with quantities whose value is unknown. Calculus is today used extensively in just about every branch of science.

It is often claimed that Newton's theories concerning gravity were inspired by an event that allegedly took place whilst he was sitting beneath an apple tree in his mother's garden in Woolsthorpe, in which an apple fell on his head. Newton himself never wrote of the incident, but the following account is given by the English antiquarian William Stukeley (1687-1765) in his biography of Newton "Memoirs of Sir Isaac Newton's Life":

"After dinner, the weather being warm, we went into the garden & drank thea under the shade of some appletrees, only he, & myself. Amidst other discourse, he told me, he was just in the same situation, as when formerly, the notion of gravitation came into his mind. 'Why should that apple always descend perpendicularly to the ground,' thought he to himself: occasion'd by the fall of an apple, as he sat in contemplative mood: 'Why should it not go sideways, or upwards? But constantly to the Earth's centre? Assuredly, the reason is, that the Earth draws it. There must be a drawing power in matter. & the sum of the drawing power in the matter of the Earth must be in the Earths centre, not in any side of the Earth. Therefore does this apple fall perpendicularly, or towards the centre. If matter thus draws matter, it must be proportion of its quantity. Therefore the apple draws the Earth, as well as the Earth draws the apple."

Newton's theory of gravitation is thought to have been inspired by an apple falling from a tree

The question that occupied Newton, who had a particular interest in the Moon and its orbit around the Earth, was not whether gravity existed, but whether its effects extended so far that it could be the force responsible for holding the Moon in its orbit. He finally came to the conclusion that the gravitational attraction between two bodies must extend over great distances, and that the strength of the gravitational attraction between two bodies was inversely proportional to the distance that separated them.

This conclusion was generally in agreement with Keppler's third law, which stated that the period of a planet's orbit was dependent only on its distance from the Sun. Newton was eventually able to show that gravity was responsible for the orbital motions of all of the planets in the solar system, prompting him to name it "universal gravitation".

By applying his theories regarding gravitational forces, Newton was able to derive Keppler's three laws of planetary motion mathematically, removing any lingering doubts about the validity of a heliocentric model of the solar system (although his inability to explain the physical nature of gravity led to accusations from some quarters that he was bringing "occult agencies" into science).

Newton's work laid the foundations of classical mechanics as we understand it today, and culminated in the publication, in 1687, of his master work, Philosophiæ Naturalis Principia Mathematica. In it Newton states his law of universal gravitation, and the three laws of motion which describe the relationship between an object, the forces acting upon it, and the object's resulting motion.

Newton's influence on the development of classical mechanics, and his contribution to science generally, make him one of the most important figures in the history of science. He nevertheless had the modesty to acknowledge the debt he owed to those upon whose work he built, including that of Galileo and Keppler. In a letter written in 1676 to fellow English scientist Robert Hooke (1635-1703), he famously wrote:

Copernicus, Kepler and Galileo

Despite its suppression, still alive among a few intellectuals was the theory by Nicolaus Copernicus (Koppernigk), said today to have been the founder of modern astronomy. Copernicus (1474-1543) had been a brilliant Catholic cleric in Poland. For relaxation he painted, translated poetry from ancient Greek into Latin and dabbled in celestial observations with the naked eye. From his observations he theorized that the earth, rather than standing still, rotated around its axis daily and traveled around the sun yearly &ndash resurrecting what had been known among Hellenistic intellectuals in ancient times. The Catholic Church and Martin Luther, more common in brain power, considered themselves better informed on the matter than Copernicus. Luther described Copernicus as an "upstart astrologer " trying to be clever. He is reported to have quipped that sacred scripture tells us that Joshua commanded the sun to stand still, not the earth (Joshua 10:12-13). The Catholic Church also claimed that Copernicus's claim defied common sense.

Nicolaus Copernicus, brilliant and obedient

Giordano Bruno, burned at the stake February 17, 1600

Rotating Earth. For ages people looking at the sky thought the heavens were spinning rather than the earth.

Opposition from the Church led Copernicus to shelve his theory, but Church opposition did not kill the idea. A student of astronomy mentioned the idea to a young Protestant German named Johann Kepler, who in the late 1500s and into the early 1600s was trying to figure out the changing distances between planets. Kepler discovered that Mars was moving about the sun not in a perfect circle but in an ellipse &ndash contradicting Plato's belief about perfection and the heavens. Kepler proposed that laws about materiality that applied to things on earth applied also to the heavens.

Around the year 1608, in Holland, the telescope was invented &ndash a tube with a convex lens at one end and a concave lens on the other. The invention has been described as a collaboration between two makers of spectacles and a third person who was a mathematician. A 35 year-old scientist named Galilei Galileo, from Pisa Italy, heard about the invention, and in 1609 he made his own telescope, with a magnifying power of eight. The telescope as the writer Steven Johnson points out was part of a chain of developments connected to printing, the rise of literacy and lens-making for eye glasses. And now lenses would contribute to science regarding what was viewed as the heavens and eventually to science regarding the microscopic.

Galileo was a Catholic and a progressive thinker. Aristotle's views, previously considered radical in Europe, had become the conservative point of view, and, like Francis Bacon, Galileo was opposed to Aristotelian ideology. Galileo was interested in the mechanics of motion, and he was at odds with Aristotelian professors talking of things sinking or floating according to their will or essential natures and of things falling because they wanted to return home, as if the inanimate contained spirit and will. Galileo had grasped the idea of force as mechanical. He drew revolutionary conclusions that in the 20th century would seem common sense: that bodies in motion continued to move except as slowed by some force. His views annoyed theologians, but his ideas interested those wanting to measure the flight of cannon balls.

In 1610, with his telescope, Galileo discovered the moons of Jupiter, and soon afterward he found spots on the sun and the hills and valleys on the surface of the moon. This ability to see where others could not got him into trouble with the Church, whose authorities put ideology ahead of scientific, or empirical discovery. Their theology was deemed correct, and it was for Galileo to conform to it, not for the Church to adopt the science of Galileo or anyone else's science. Galileo had demonstrable evidence that Copernicus had been correct. And among some of the Aristotelians of the old scholastic school of thought – who forgot Aristotle's admonition to investigate &ndash came condemnation of the telescope.

In 1611, Galileo visited Rome and exhibited the wonders of the telescope to the pontifical court. He tried to produce scriptural confirmation of the view that the earth went around the sun. The Church warned him that he should limit himself to study of the physical world and to avoid applying his ideas to theology. In 1616 the Church condemned as absurd and heretical the view that the earth moved around the sun, and the Church made expressions of this view forbidden reading. Pope Paul V instructed Galileo to refrain from teaching the doctrine, and Galileo promised to obey.

The Church, meanwhile, had been burning a few at the stake for their heresies. Giordano Bruno had been burned to death in Rome for his Pantheism. Another Pantheist, Lucilio Vanini, was condemned as an atheist and burned at the stake in 1619 in Toulouse, in southern France.

In 1624, Galileo went to Rome and received permission from the Pope to write a description of the rival Copernican and Ptolemaic theories. Pope Urban VIII gave him permission on condition that he do so without favoring the Copernican system and that he write a conclusion that expressed the view of the Church. Galileo returned to Florence and set to work, and in January 1632 his work was published. It was applauded by intellectuals across Europe, and it was too popular to suit the Church. Jesuits complained that Galileo's book was a bad influence. It says something about the common attitude of the time that friends of Galileo criticized him for being in love with his own genius and showing little respect for others by pursuing ideas not commonly accepted nor approved by their Church.

In August, 1632, the Church prohibited further sales of the book. And, in October, Galileo was ordered to appear before the Inquisition in Rome. Galileo arrived in Rome in February 1633 as ordered. He was treated with deference and not jailed. Galileo appeared before ten judges, at the same spot where Bruno had heard his sentence of death. The Inquisition accused Galileo of having violated the ruling by the Church in 1616 that he refrain from "teaching or discussing" Copernicanism in any way. The agreement Galileo had received from Urban VIII in 1624 was described as having been received under false pretenses, that the permission had been an extortion. Galileo recanted his beliefs that the earth moved around the sun. His sentence of imprisonment was changed to banishment. He was ordered to recite once a week for three years the seven Penitential Psalms, and he remained confined to his estate just outside Florence, where he lived until his death in 1642.

A History of Science and Its Relations with Philosophy and Religion, by Sir William Dampier, 1948

Nicholas Copernicus and Johannes Kepler, Astronomers

Nicolaus Copernicus (19 February 1473 – 24 May 1543) was the first astronomer to formulate a comprehensive heliocentric cosmology, which displaced the Earth from the center of the universe.

Copernicus’ epochal book, De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), published just before his death in 1543, is often regarded as the starting point of modern astronomy and the defining epiphany that began the scientific revolution. His heliocentric model, with the Sun at the center of the universe, demonstrated that the observed motions of celestial objects can be explained without putting Earth at rest in the center of the universe. His work stimulated further scientific investigations, becoming a landmark in the history of science that is often referred to as the Copernican Revolution.

Among the great polymaths of the Renaissance, Copernicus was a mathematician, astronomer, physician, quadrilingual polyglot, classical scholar, translator, artist, Catholic cleric, jurist, governor, military leader, diplomat and economist. Among his many responsibilities, astronomy figured as little more than an avocation – yet it was in that field that he made his mark upon the world.

At original publication, Copernicus’ epoch-making book caused only mild controversy, and provoked no fierce sermons about contradicting Holy Scripture. It was only three years later, in 1546, that a Dominican, Giovanni Maria Tolosani, denounced the theory in an appendix to a work defending the absolute truth of Scripture. He also noted that the Master of the Sacred Palace (i.e., the Catholic Church’s chief censor), Bartolomeo Spina, a friend and fellow Dominican, had planned to condemn De revolutionibus but had been prevented from doing so by his illness and death.

It was not until six decades after Spina and Tolosani’s attacks on Copernicus’s work that the Catholic Church took any official action against it. In March 1616, in connection with the Galileo affair, the Roman Catholic Church’s Congregation of the Index issued a decree suspending De revolutionibus until it could be “corrected,” on the grounds that the supposedly Pythagorean doctrine that the Earth moves and the Sun does not was “false and altogether opposed to Holy Scripture.” The same decree also prohibited any work that defended the mobility of the Earth or the immobility of the Sun, or that attempted to reconcile these assertions withScripture. The corrections to De revolutionibus, which omitted or altered nine sentences, were issued four years later, in 1620. This censorship was not lifted until 1835.

Johannes Kepler (December 27, 1571 – November 15, 1630) was a German mathematician, astronomer and astrologer, and key figure in the 17th century scientific revolution. He is best known for his eponymous laws of planetary motion, codified by later astronomers based on his works Astronomia nova,Harmonices Mundi, and Epitome of Copernican Astronomy. They also provided one of the foundations for Isaac Newton’s theory of universal gravitation.

During his career, Kepler was a mathematics teacher at a seminary school in Graz, Austria, an assistant to astronomer Tycho Brahe, the imperial mathematician to Emperor Rudolf II and his two successors Matthias and Ferdinand II, a mathematics teacher in Linz, Austria, and an adviser to General Wallenstein. He also did fundamental work in the field of optics, invented an improved version of the refracting telescope (the Keplerian Telescope), and helped to legitimize the telescopic discoveries of his contemporary Galileo Galilei.

Kepler lived in an era when there was no clear distinction between astronomy and astrology, but there was a strong division between astronomy (a branch of mathematics within the liberal arts) and physics (a branch of natural philosophy). Kepler also incorporated religious arguments and reasoning into his work, motivated by the religious conviction that God had created the world according to an intelligible plan that is accessible through the natural light of reason.

Johannes Kepler’s first major astronomical work, Mysterium Cosmographicum (The Cosmographic Mystery,1596), was the first published defense of the Copernican system. As he indicated in the title, Kepler thought he had revealed God’s geometrical plan for the universe. Much of Kepler’s enthusiasm for the Copernican system stemmed from his theological convictions about the connection between the physical and the spiritual the universe itself was an image of God, with the Sun corresponding to the Father, the stellar sphere to the Son, and the intervening space between to the Holy Spirit. His first manuscript of Mysterium contained an extensive chapter reconciling heliocentrism with biblical passages that seemed to support geocentrism.

The extended line of research that culminated in Astronomia nova (A New Astronomy)—including the first two laws of planetary motion—began with the analysis, under Tycho’s direction, of Mars’ orbit. Based on measurements of the aphelion and perihelion of the Earth and Mars, he created a formula in which a planet’s rate of motion is inversely proportional to its distance from the Sun by late 1602 Kepler reformulated the proportion in terms of geometry: planets sweep out equal areas in equal times—Kepler’s second law of planetary motion. He then set about calculating the entire orbit of Mars, using the geometrical rate law and assuming an egg-shaped ovoid orbit. After approximately 40 failed attempts, in early 1605 he at last hit upon the idea of an ellipse, which he had previously assumed to be too simple a solution for earlier astronomers to have overlooked. Finding that an elliptical orbit fit the Mars data, he immediately concluded that all planets move in ellipses, with the sun at one focus—Kepler’s first law of planetary motion.

Kepler was convinced “that the geometrical things have provided the Creator with the model for decorating the whole world.” In Harmonices Mundi (Harmony of the Worlds), he attempted to explain the proportions of the natural world—particularly the astronomical and astrological aspects—in terms of music. Among many other harmonies, Kepler articulated what came to be known as the third law of planetary motion. He then tried many combinations until he discovered that (approximately) “The square of the periodic times are to each other as the cubes of the mean distances.” When conjoined with Christian Huygens’ newly discovered law of centrifugal force it enabled Isaac Newton and othersto demonstrate independently that the presumed gravitational attraction between the Sun and its planets decreased with the square of the distance between them.

In 1615, he completed the first of three volumes of Epitome astronomia Copernicanae (Epitome of Copernican Astronomy). Despite the title, which referred simply to heliocentrism, Kepler’s textbook culminated in his own ellipse-based system. The Epitome became Kepler’s most influential work. It contained all three laws of planetary motion and attempted to explain heavenly motions through physical causes. It was read by astronomers throughout Europe, and following Kepler’s death it was the main vehicle for spreading Kepler’s ideas. In the late 17th century, a number of physical astronomy theories drawing from Kepler’s work—notably those of Giovanni Alfonso Borelli and Robert Hooke—began to incorporate attractive forces (though not the quasi-spiritual motive species postulated by Kepler) and the Cartesian concept of inertia. This culminated in Isaac Newton’s Principia Mathematica (1687), in which Newton derived Kepler’s laws of planetary motion from a force-based theory of universal gravitation.

Ancient astronomers sought to discover rules for the motions of planets. One of the more fanciful theories was that of the ancient Greek astronomer Eudoxus, who thought that the planets traveled in celestial spheres, which made heavenly music as they turned.

During the European Renaissance, astronomers began to question whether the Earth was the center of the Universe as previously believed. With his telescope, Galileo Galilei observed the four moons of Jupiter now known as the Galilean moons, Io, Europa, Ganymede, and Calisto (shown at left in a NASA composite photo, from left to right, top to bottom) orbiting around Jupiter. He presented this discovery as evidence to an unreceptive world that everything did not revolve around the Earth.

One phenomenon that was difficult to explain was retrograde motion: the time when a planet appears to pause, then to start moving backwards through the sky. Niklas Koppernigk (who later wrote his name Nicolaus Copernicus, shown in a painting at left) was born in 1473. He took an early interest in astronomy and medicine.

Copernicus realized that if the Sun were at the center of the Solar System, and the planets revolved around the Sun, then the planets always moved in the same direction. Copernicus knew that his idea was radical and that it would be unpopular. Friends who heard of his discovery pleaded with him to make his findings public. Fearing arrest or worse punishment, Copernicus waited thirty-six years to publish his theories.

Copernicus, a Roman Catholic priest by the end of his life, finally sent a copy of his manuscript, entitled De revolutionibus orbium coelestium, to a Lutheran printer in 1543 as he was dying. The Lutheran Church did not support a heliocentric Solar System model, but would be less punitive than the Roman Catholic Church.

Copernicus received his published book back from the printer on May 24, 1543 &mdash the last day of his life. His radical idea that the planets revolved around the Sun (not the Earth), backed up with analysis of observations, began what we call today the Copernican Revolution.

Galileo Galilei (1564-1642) was a mathematician and astronomer. He pioneered the use of mathematics in analyzing experimental physics data. With such measurements, he accurately approximated the Earth's gravitational attraction by timing the rolling of balls on inclined planes with water clocks. He also discovered the mathematical law for the rate of swing of a pendulum, finding that it only depended on the pendulum's length rather than the weight at the end or the height from which it started.

He first got the idea that lighter objects could not fall slower than heavier objects by seeing that hail stones appeared to fall at the same rate whether they were large or small. Benedetti Giambattista had already demonstrated this fact in 1553, and published his results, but Galileo performed further experiments. Legend has it that Galileo dropped cannon balls of different weight from the Leaning Tower of Pisa. Although experimenters before him, and even one of his students did drop balls of different weight from the Tower, there is no actual record of Galileo performing such an experiment.

To Galileo, his work on gravity would not have appeared related to his observations in astronomy. Several years later though, Sir Isaac Newton would tie the two together, showing that planetary motion could be explained by the law of gravitational attraction. In fact, Newton used Galileo's Law of Inertia (showing that the force required to move an object was proportional to the object's mass) in his First Law of Motion. Galileo Galilei died in 1642, the year that Isaac Newton was born.

While a professor of astronomy at the University of Padua, Italy in 1609, Galileo heard of the microscope and "spyglass." Working from a vague description, he produced his own "spyglass" that had thre times magniication, then built another wth ten times magnification. He presented this to his city's government as a military aid.

Galileo became the first person to study the stars and planets through glass lenses. He began by using his spyglass to examine the Moon, where he discovered craters. He found that the Milky Way was actually a collection of thousands of closely spaced stars, "almost too numerous for belief."

On the fateful night of 7 January 1610, he trained a new 30 power telescope on Jupiter and discovered three of the four easily visible moons of Jupiter, now known as the Galilean Moons. The next night he observed them again, and saw that one of the moons had traveled to the other side of Jupiter, so all three were on the same side. He reasoned that the motion of these moons around Jupiter proved that not everything revolved around the Earth.

Galileo also discovered the rings of Saturn, but died not knowing that they were rings. He saw them at first, then saw them disappear as Saturn's rings were on edge as seen from Earth, then saw them reappear a couple of years later. After that, he saw them as seemingly two cup handles. It wasn't until after his death that telescopes became powerful enough to resolve these mysterious objects as rings.

Galileo supported the theory of Copernicus, that planets and the Earth revolved around the Sun. This, and his experiments that disproved other Aristotlan beliefs, brought him under investigation by the Roman Catholic Church in 1633. He was condemned for his beliefs and imprisoned, though this was later commuted to house arrest for life. In 1954, the Church deleted his works from the Banned Book List of the Inquisition. In 1992, Pope John Paul II declared that Galileo Galilei was "unjustly condemned" for supporting the Copernican model of the Solar System.

Another astronomer familiar with Copernicus' De revolutionibus orbium coelestium, Tycho Brahe, Imperial mathematician in Prague in the late 1500s, made painstaking observations of the Sun, Moon, and planets throughout much of his life. He is shown at left in an illustration from his Astronomiae insstauratae mechanica (1598).

Tycho Brahe did not support the new heliocentric theory of Copernicus. However, he did believe that philosophical arguments were not as valid as real observational data. Driven by a desire to solve the mystery of planetary orbits, he constructed the most accurate observatory that existed before the telescope's invention. His data was the most accurate that had ever been recorded at the time.

He published a paper in 1573, De nova stella, that described a supernova observation. This observation refuted the common belief that the heavens were fixed, never changing. His careful observations of the Moon allowed him to determine formulas for lunar motion with unprecedented accuracy. Tycho Brahe published his findings on the Moon's motion a year before his death.

After publishing his lunar observations, he began work on a theory that would explain his decades of careful planetary observations. He had already found that the Earth did not remain a constant distance to the Sun throughout a year, in 1591. However, he was not able to explain or further investigate this phenomenon before his death on October 24, 1601. To the end, he believed that Copernicus was at least entirely correct. As he was dying, Tycho Brahe said to his assistant, Johannes Kepler, "Do not let me have lived in vain." While Kepler showed that Brahe's geocentric beliefs were not true, it was only by using his highly accurate data spanning decades that Kepler was able to develop his own theories of planetary motion. In that sense, Tycho Brahe had not endeavored all those years in vain, for he laid the groundwork necessary for Kepler's amazing mathematical discoveries.

Johannes Kepler (shown in a painting at left) had been interested in astronomy most of his life. He sought theories that would explain planetary motions, and knew that testing theories would require a collection of astronomical observations. The greatest astronomical records in the world were those of Tycho Brahe. At the same time, Brahe needed someone with Kepler's mathematical abilities to analyze his extensive data. Kepler joined him as an assistant in February 1600, the year before Tycho Brahe's death.

Kepler believed in the Copernican system, which placed the Sun at the center of the Solar System. He had begun investigating the motion of Mars before Tycho Brahe's death. Kepler's understanding of planetary motion accelerated when he realized that the orbit of Mars was in a plane tilted slightly from the plane of the Earth's orbit around the Sun. He published his observations on Mars in 1609.

Why was predicting the orbit of Mars such a great achievement? It was because no other planet exhibits as severe retrograde (backwards) motion as Mars when viewed from the Earth. Mercury and Venus always stay close to the Sun. Jupiter and Saturn, the other known planets at the time, are further away. Mars is the closest planet to the Earth that is farther from the Sun than the Earth, and so its retrograde motion appears the greatest. There was no other planetary orbit that was more difficult to predict than the orbit of Mars.

  • K1: The planets orbit the sun in an elliptical orbit, with the Sun at one of the focus points of the ellipse.
  • K2: The planets sweep across an equal area between themselves and the Sun in an equal amount of time.
  • K3: The squares of the periods of two planets orbiting the Sun are proportional to the cubes of their semi-major axes (half of the long axis of their orbital ellipse).

Kepler proposed that planetary motion was caused by magnetic force from the Sun.

Astronomers calculated reference ephemerides by using elliptical orbits for almost 400 years after Kepler's discovery. It wasn't until the 1970s that computer technology and NASA's need to accurately send spacecraft to planets that more accurate computer simulations of mutual gravitational attraction of Solar System bodies became practical. To this day, positions of asteroids of unknown mass are still calculated using Kepler's elliptical orbits.

Later in the 1600s, Sir Isaac Newton (shown in a painting at left) formulated the principles of gravitational attraction. Newton's breakthrough came from contemplating Kepler's Third Law. He said that he first found in 1680 that the pattern of a planet under gravitational attraction from the Sun would be an ellipse with the Sun at one focus. Unfortunately, he lost the proof in his office. At the urging of his friend, astronomer Edmond Halley (of Halley's Comet fame), in 1684 Newton spent three months reconstructing the proof.

Then, in a burst of inspiration from 1685-86, Newton wrote his revolutionary Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosopy), commonly referred to as Principia Mathematica or simply Principia.

In his Principia, Newton first outlined three axioms, or Laws of Motion:

  1. Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed thereon.
  2. The alteration of motion is ever proportional to the motive force impressed and is made in the direction of the right line in which that force is impressed.
  3. To every action there is always opposed an equal reaction or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.

Newton held that Space and Time were fixed, rigid, never changing. By the 1900s, telescopes became powerful enough to observe one more revolutionary principle that changed all that: Einstein's Theory of Relativity, which he built upon earlier work by his friend Hendrick Lorentz showing that objects could not travel faster than the Speed of Light.

In his Theory of Relativity, Albert Einstein demonstrated mathematically that the force of gravitational attraction could be viewed as a distortion of space and time around an object, so that another object (or light) was curved by following a path of least resistance in this warped space-time continuum. At one point in unravelling the relationship between gravitational attraction and relativity, showing that Space and Time were not at all constant, Einstein said: "Newton, forgive me."

Einstein first proposed a test of his Theory of Relativity by observing stars during the Total Solar Eclipse of 29 May 1919. The eclipse was observed from Brazil and West Africa under the direction of the astronomer Sir Arthur Eddington. The observations verified Einstein's Theory of Relativity. Today, ultra-accurate observations take this relativistic bending of light into account. The Sun bends the light of a nearby star by less than two arcseconds. Atmospheric refraction bends light far more, so this effect is not easy to observe.

Tycho, Kepler, and Galileo

The critical tradition began with Copernicus. It led directly to the work of Tycho Brahe, who measured stellar and planetary positions more accurately than had anyone before him. But measurement alone could not decide between Copernicus and Ptolemy, and Tycho insisted that the Earth was motionless. Copernicus did persuade Tycho to move the centre of revolution of all other planets to the Sun. To do so, he had to abandon the Aristotelian crystalline spheres that otherwise would collide with one another. Tycho also cast doubt upon the Aristotelian doctrine of heavenly perfection, for when, in the 1570s, a comet and a new star appeared, Tycho showed that they were both above the sphere of the Moon. Perhaps the most serious critical blows struck were those delivered by Galileo after the invention of the telescope. In quick succession, he announced that there were mountains on the Moon, satellites circling Jupiter, and spots upon the Sun. Moreover, the Milky Way was composed of countless stars whose existence no one had suspected until Galileo saw them. Here was criticism that struck at the very roots of Aristotle’s system of the world.

At the same time Galileo was searching the heavens with his telescope, in Germany Johannes Kepler was searching them with his mind. Tycho’s precise observations permitted Kepler to discover that Mars (and, by analogy, all the other planets) did not revolve in a circle at all, but in an ellipse, with the Sun at one focus. Ellipses tied all the planets together in grand Copernican harmony. The Keplerian cosmos was most un-Aristotelian, but Kepler hid his discoveries by burying them in almost impenetrable Latin prose in a series of works that did not circulate widely.

What Galileo and Kepler could not provide, although they tried, was an alternative to Aristotle that made equal sense. If the Earth revolves on its axis, then why do objects not fly off it? And why do objects dropped from towers not fall to the west as the Earth rotates to the east beneath them? And how is it possible for the Earth, suspended in empty space, to go around the Sun—whether in circles or ellipses—without anything pushing it? The answers were long in coming.

Galileo attacked the problems of the Earth’s rotation and its revolution by logical analysis. Bodies do not fly off the Earth because they are not really revolving rapidly, even though their speed is high. In revolutions per minute, any body on the Earth is going very slowly and, therefore, has little tendency to fly off. Bodies fall to the base of towers from which they are dropped because they share with the tower the rotation of the Earth. Hence, bodies already in motion preserve that motion when another motion is added. So, Galileo deduced, a ball dropped from the top of a mast of a moving ship would fall at the base of the mast. If the ball were allowed to move on a frictionless horizontal plane, it would continue to move forever. Hence, Galileo concluded, the planets, once set in circular motion, continue to move in circles forever. Therefore, Copernican orbits exist. Galileo never acknowledged Kepler’s ellipses to do so would have meant abandoning his solution to the Copernican problem.

Kepler realized that there was a real problem with planetary motion. He sought to solve it by appealing to the one force that appeared to be cosmic in nature, namely magnetism. The Earth had been shown to be a giant magnet by William Gilbert in 1600, and Kepler seized upon this fact. A magnetic force, Kepler argued, emanated from the Sun and pushed the planets around in their orbits, but he was never able to quantify this rather vague and unsatisfactory idea.

By the end of the first quarter of the 17th century Aristotelianism was rapidly dying, but there was no satisfactory system to take its place. The result was a mood of skepticism and unease, for, as one observer put it, “The new philosophy calls all in doubt.” It was this void that accounted largely for the success of a rather crude system proposed by René Descartes. Matter and motion were taken by Descartes to explain everything by means of mechanical models of natural processes, even though he warned that such models were not the way nature probably worked. They provided merely “likely stories,” which seemed better than no explanation at all.

Armed with matter and motion, Descartes attacked the basic Copernican problems. Bodies once in motion, Descartes argued, remain in motion in a straight line unless and until they are deflected from this line by the impact of another body. All changes of motion are the result of such impacts. Hence, the ball falls at the foot of the mast because, unless struck by another body, it continues to move with the ship. Planets move around the Sun because they are swept around by whirlpools of a subtle matter filling all space. Similar models could be constructed to account for all phenomena the Aristotelian system could be replaced by the Cartesian. There was one major problem, however, and it sufficed to bring down Cartesianism. Cartesian matter and motion had no purpose, nor did Descartes’s philosophy seem to need the active participation of a deity. The Cartesian cosmos, as Voltaire later put it, was like a watch that had been wound up at the creation and continues ticking to eternity.

Copernicus, Galileo, and the Church: Science in a Religious World

During most of the 16th and 17th centuries, fear of heretics spreading teachings and opinions that contradicted the Bible dominated the Catholic Church. They persecuted scientists who formed theories the Church deemed heretical and forbade people from reading any books on those subjects by placing the books on the Index of Prohibited Books. A type of war between science and religion was in play but there would be more casualties on the side of science.

Nicholas Copernicus and Galileo Galilei were two scientists who printed books that later became banned. Copernicus faced no persecution when he was alive because he died shortly after publishing his book. Galileo, on the other hand, was tried by the Inquisition after his book was published. Both scientists held the same theory that the Earth revolved around the sun, a theory now known to be true. However, the Church disapproved of this theory because the Holy Scriptures state that the Earth is at the center, not the Sun. As the contents of the Bible were taken literally, the publishing of these books proved, to the Church, that Copernicus and Galileo were sinners they preached, through their writing, that the Bible was wrong.

Nicholas Copernicus (1473 - 1543), mathematician and astronomer, established a model of the universe with the sun, rather than earth, at its center. His most notable book, On the Revolutions of Heavenly Bodies, was highly controversial when it was published in 1543 but nevertheless became a fundamental turning point in the history of science.

Copernicus published his book On the Revolutions of the Heavenly Bodies (hereafter referred to simply as Revolutions) in 1543 shortly before his death.1.) In Revolutions, Copernicus states that the Sun is at the center and the Earth revolves around it while rotating on its axis daily.2.) Like all scholarly authors, Copernicus wrote in Latin, which only educated people could read, effectively minimizing the number of readers to a select few.3.)

The phrasing Copernicus utilized was &ldquothat if the earth were in motion then the observed phenomenon would result.&rdquo4.) This phrasing is extremely important as it means the Copernicus himself could deny he believed it he merely fashioned it in such a way that it was a hypothesis that would allow astronomers to correct mathematical errors they came across while observing the heavens. By writing in this fashion, Copernicus would have been able to deny that he himself believed in heliocentrism because he phrased it as nothing more than a hypothesis and as a result, would be able to slip past the Church's dislike of heliocentrism.

Copernicus' theories are not fully formed, meaning there are several flaws that make the heliocentric hypothesis appear weak and ill-contrived. According to Giovanni Tolsani in 1546, a member of the Dominican Order, &ldquoalmost all the hypotheses of this author Copernicus contain something false&rdquo5.) and he &ldquoseems unfamiliar with Holy Scripture since he contradicts some of its principles.&rdquo6.) Revolutions was not placed on the Index of Prohibited Books until 1616, seventy-three years after it was first published.7.)

A censored version with some sections changed or omitted was released four years after it was prohibited.8.) It is possible that Revolutions was not banned immediately because of its hypothetical nature and weak arguments. However, Tolsani also wrote, a papal authority &ldquohad planned to condemn his [Copernicus'] book. But, prevented at first by illness, then by death, he could not carry out this [plan].&rdquo9.) After his death, the Church was heavily involved in the Council of Trent during the years 1545 to 1563 and other matters10.) . Thus, Revolutions escaped prohibition for many years and eventually influenced Galileo Galilei, who read it and wrote on the subject himself.

In 1616, Galileo was issued an injunction not to &ldquohold, defend, or teach&rdquo heliocentrism.11.) When he began writing Dialogues in 1624, he intended to present both arguments equally. However, he wrote the arbitrator in such a way that he decided the Copernican speaker had the most points that made logical sense, thus supporting Copernicanism throughout his book.12.)

When Galileo originally tried to print Dialogues in 1630, he was ordered to have it printed in Rome. However, he left Rome because of the outbreak of plague and communicated with the Master of the Sacred Palace, the chief censor, through writing. The Master of the Sacred Palace ordered Galileo to have someone the Master chose review the manuscript to ensure it was fit for publishing.

Father Master Giancito Stefani was chosen to review the manuscript and the publisher followed all instructions from the Father Master.13.) Galileo said, during his trial in 1633, that he did not believe what he wrote, that he let his vanity influence his words and phrasing to make him appear more intelligent to his readers but this plan failed when his readers came to the conclusion that he believed the Copernican hypothesis to be true because of his powerful phrasing.14.)

Galileo wrote and published Dialogue on the Two Chief Systems of the World, Ptolemaic and Copernican (Dialogues) in 1632 Pope Urban VIII issued an order almost immediately to prevent the publisher from printing more copies.15.) It was printed in Italian, not in Latin like Revolutions, so all of Italy was able to read it.16.) The original title had been Dialogue on the Ebb and Flow of the Sea but it was changed so it would not appear that Galileo was pushing the fact that the tides supported his opinion and the new title also appeared more theoretical.

Galileo Galilei (1564 - 1642) made significant contributions to the scientific revolution, specifically by making improvements to the telescope and by making astronomical observations that supported Copernicus's findings.

Also, the title with the sea in it might have made the Church feel threatened that Galileo was supporting heliocentrism, which would have resulted in Galileo being charged with heresy. Dialogues was structured as several conversations between a supporter of Ptolemy, a Copernicus supporter, and a neutral arbitrator. The Copernican supporter spoke Galileo's mind and the Ptolemaic supporter was called Simplicio, simpleton in Italian.17.) Urban was infuriated when he read the book and saw that the phrase he required in order for the book to be published, about God's omnipotence, was said by Simplicio.

In the Pope's mind, Galileo was making a caricature of him by having Simplicio say that phrase. Personal vanity is believed to have led the Pope to cry for a committee to be made to determine if Galileo should be tried by the Inquisition and to determine how the book was published and not censored.18.) Galileo also insulted people who did not believe in Copernicanism a fact which did not escape the notice of Pope Urban VIII's advisory committee.19.) Because Galileo did not phrase his words as hypothetical, readers thought Galileo held the theory that the Earth revolved around the Sun.20.) The committee created by the Pope also came to the same conclusion: Galileo knew what he was doing and must be disciplined for it.

The committee created to charge Galileo determined that Galileo held heliocentrism as a matter of fact and violated the injunction issued to him.21.) With that decision, it was determined that Galileo would be tried by the Inquisition. The Inquisition did not need to decide if Galileo was innocent or guilty, they already knew he was guilty. The Inquisition wanted to determine what Galileo's intentions were. Galileo tried to delay going to Rome for the trial, most likely due to the Inquisition's infamous methods. He wrote to the Inquisitors and said he would be happy to answer questions by mail. He cited his failing health for his reluctance to take the 200 mile journey and had three doctors write to the Inquisition to say that he was unable to travel without risking his life. Continued on Next Page »

The Science: Orbital Mechanics

Kepler&rsquos Laws of Planetary Motion

While Copernicus rightly observed that the planets revolve around the Sun, it was Kepler who correctly defined their orbits. At the age of 27, Kepler became the assistant of a wealthy astronomer, Tycho Brahe, who asked him to define the orbit of Mars. Brahe had collected a lifetime of astronomical observations, which, on his death, passed into Kepler&rsquos hands. (Brahe, who had his own Earth-centered model of the Universe, withheld the bulk of his observations from Kepler at least in part because he did not want Kepler to use them to prove Copernican theory correct.) Using these observations, Kepler found that the orbits of the planets followed three laws.

Like many philosophers of his era, Kepler had a mystical belief that the circle was the Universe&rsquos perfect shape, and that as a manifestation of Divine order, the planets&rsquo orbits must be circular. For many years, he struggled to make Brahe&rsquos observations of the motions of Mars match up with a circular orbit.

Eventually, however, Kepler noticed that an imaginary line drawn from a planet to the Sun swept out an equal area of space in equal times, regardless of where the planet was in its orbit. If you draw a triangle out from the Sun to a planet&rsquos position at one point in time and its position at a fixed time later&mdashsay, 5 hours, or 2 days&mdashthe area of that triangle is always the same, anywhere in the orbit. For all these triangles to have the same area, the planet must move more quickly when it is near the Sun, but more slowly when it is farthest from the Sun.

This discovery (which became Kepler&rsquos second law of orbital motion) led to the realization of what became Kepler&rsquos first law: that the planets move in an ellipse (a squashed circle) with the Sun at one focus point, offset from the center.

Kepler&rsquos third law shows that there is a precise mathematical relationship between a planet&rsquos distance from the Sun and the amount of time it takes revolve around the Sun. It was this law that inspired Newton, who came up with three laws of his own to explain why the planets move as they do.

Newton&rsquos Laws of Motion

If Kepler&rsquos laws define the motion of the planets, Newton&rsquos laws define motion. Thinking on Kepler&rsquos laws, Newton realized that all motion, whether it was the orbit of the Moon around the Earth or an apple falling from a tree, followed the same basic principles. &ldquoTo the same natural effects,&rdquo he wrote, &ldquowe must, as far as possible, assign the same causes.&rdquo Previous Aristotelian thinking, physicist Stephen Hawking has written, assigned different causes to different types of motion. By unifying all motion, Newton shifted the scientific perspective to a search for large, unifying patterns in nature. Newton outlined his laws in Philosophiae Naturalis Principia Mathematica (&ldquoMathematical Principles of Natural Philosophy,&rdquo) published in 1687.

Law I. Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed theron.

In essence, a moving object won&rsquot change speed or direction, nor will a still object start moving, unless some outside force acts on it. The law is regularly summed up in one word: inertia.

Law II. The alteration of motion is ever proportional to the motive force impressed and is made in the direction of the right line in which that force is impressed.

Newton&rsquos second law is most recognizable in its mathematical form, the iconic equation: F=ma. The strength of the force (F) is defined by how much it changes the motion (acceleration, a) of an object with some mass (m).

Law III. To every action there is always opposed an equal reaction: or the mutual actions of two bodies upon each other are always equal, and directed to contrary parts.

As Newton himself described: &ldquoIf you press a stone with your finger, the finger is also pressed by the stone.&rdquo


Within the pages of Principia, Newton also presented his law of universal gravitation as a case study of his laws of motion. All matter exerts a force, which he called gravity, that pulls all other matter towards its center. The strength of the force depends on the mass of the object: the Sun has more gravity than Earth, which in turn has more gravity than an apple. Also, the force weakens with distance. Objects far from the Sun won&rsquot be influenced by its gravity.

Newton&rsquos laws of motion and gravity explained Earth&rsquos annual journey around the Sun. Earth would move straight forward through the universe, but the Sun exerts a constant pull on our planet. This force bends Earth&rsquos path toward the Sun, pulling the planet into an elliptical (almost circular) orbit. His theories also made it possible to explain and predict the tides. The rise and fall of ocean water levels are created by the gravitational pull of the Moon as it orbits Earth.

Einstein and Relativity

The ideas outlined in Newton&rsquos laws of motion and universal gravitation stood unchallenged for nearly 220 years until Albert Einstein presented his theory of special relativity in 1905. Newton&rsquos theory depended on the assumption that mass, time, and distance are constant regardless of where you measure them.

The theory of relativity treats time, space, and mass as fluid things, defined by an observer&rsquos frame of reference. All of us moving through the universe on the Earth are in a single frame of reference, but an astronaut in a fast-moving spaceship would be in a different reference frame.

Within a single frame of reference, the laws of classical physics, including Newton&rsquos laws, hold true. But Newton&rsquos laws can&rsquot explain the differences in motion, mass, distance, and time that result when objects are observed from two very different frames of reference. To describe motion in these situations, scientists must rely on Einstein&rsquos theory of relativity.

At slow speeds and at large scales, however, the differences in time, length, and mass predicted by relativity are small enough that they appear to be constant, and Newton&rsquos laws still work. In general, few things are moving at speeds fast enough for us to notice relativity. For large, slow-moving satellites, Newton&rsquos laws still define orbits. We can still use them to launch Earth-observing satellites and predict their motion. We can use them to reach the Moon, Mars, and other places beyond Earth. For this reason, many scientists see Einstein&rsquos laws of general and special relativity not as a replacement of Newton&rsquos laws of motion and universal gravitation, but as the full culmination of his idea.

The Hidden Option Of The Geocentric Globe Earth

Flat earthers proclaim that the enemy has deceived us about the design of the universe, and they are right. I now believe that the enemy has created a deception to deceive people into believing that life on Earth was a product of chance and time, and not a Creator.

The enemy has done that by causing astronomers to proclaim that the universe is heliocentric. They do this not because they have any proof that the Earth is moving, but because it fits into their worldview.

You will see below that the Earthly perspective of the planets and universe is the same, regardless of whether it’s heliocentric or the Tychonic geocentric model.

“I can construct for you a spherically symmetrical universe with Earth at its center, and you cannot disprove it based on observations. You can only exclude it on philosophical grounds.” George F.R. Ellis

Scientific proofs for the geocentric earth were published in 2013, and then the geocentric earth documentary movie called The Principle came out in 2014.

After that, information about the flat earth skyrocketed on YouTube and Facebook because the enemy wanted to cause people to reject anyone who believes in the geocentric earth.

The enemy has created a false dichotomy by positioning the debate as ‘heliocentric globe earth vs. flat earth’ but there is another option that has been hidden by the enemy, the geocentric globe earth.

If you believe that the earth is flat, please know that I’m in agreement with you about the sun not being the center of the universe, and that the Earth is not flying through space.

You can reject my explanation and click away but if you’re really searching for truth, and not just seeking to defend a belief, then I pray that you will read this article.

Note: the point of this page is to provide basic information about the geocentric Earth.

My goal is not to answer every question and/or overcome every objection. If you’re searching for truth, then read this summary, and then read the below book and judge for yourself for only in getting the full explanation can you make a right judgment.

I also provide Bible verses which show that the sun is moving around the earth, so that by the dual witness of scientific evidence and Scripture we can see that the earth is geocentric.

I’m not declaring that the earth is geocentric, as I can’t prove it scientifically but when you look at how Bible verses seem to point to a geocentric earth, it’s an option that we need to consider. Read through the website, and you decide.

Robert A. Sungenis,‎ PhD wrote a book called ‘Geocentrism 101 – An Introduction into the Science of Geocentric Cosmology‘ first published in November 2013.

Here is a summary from the book:

The newest cosmological evidence puts Earth at the center of the universe, and this is admitted by man popular scientists.

Experiential evidence from over one hundred years ago to the present day shows the Earth is motionless is space.

Einstein’s Special Theory of Relativity was invented precisely to counter the many experiments in the late 1800s that showed the Earth was standing still in space.

Einstein’s General Theory of Relativity was invented to cover the weaknesses of the Special Theory, but in doing so the General Theory allowed the Earth to be motionless in the center of the universe.

In addition to Einstein’s General Theory of Relativity, other theories of physics, such as Newton’s law of motion and Mach’s Principle, say that a universe rotating around a fixed Earth is as scientifically valid as a rotating Earth in a fixed universe.

Every scientific proof for an Earth revolving around the sun has been discredited, and there has never been an experiment that has provided proof that the Earth is moving.

Recent data from satellite probes sent up in the 1900s and 2000s show that the whole universe is aligned with both the Earth-sun ecliptic and the Earth’s equator, showing that our universe is geocentrically oriented with Earth at the center.

Recent data from telescopes show that galaxies and many other celestial objects such as quasars and gamma ray bursts, are oriented around the Earth in concentric spheres.

Neither Copernicus, Galileo, Kepler, Newton, Einstein nor anyone else has ever provided the world with proof that the Earth revolves around the sun.

Few are aware that a year before he died Galileo renounced, quite dramatically, all his claims that the Earth went around the sun.

Here’s some notable quotes from Geocentrism 101:

“We cannot feel our motion through space, nor has any physical experiment ever proved that the Earth actually is in motion.” Historian Lincoln Barnett, foreward by Albert Einstein

“I have come to believe that the motion of the Earth cannot be detected by any optical experiment” Albert Einstein

“A great deal of research has been carried out concerning the influence of the Earth’s movement. The results were always negative.” Henri Poincare

“No physical experiment has ever proved that the Earth actually is in motion.” Lincoln Barnett.

“Thus, even now, three and a half centuries after Galileo’s condemnation by the Inquisition, it is still remarkably difficult to say categorically whether the Earth moves.” Julian Barbour, a world-class physicist in England.

“What was the conclusion of the Michelson-Morley experiment? The implication is that the Earth is not moving.” Richard Wolfson

The Geocentrism 101 book comes with a CD that has graphical models, which compare the heliocentric and geocentric earth model so that you can see that the perspective of the solar system doesn’t change.

People are not able to prove whether the earth is heliocentric or geocentric, as the models show the planets and stars appearing in the same places of the sky.

The sun revolves around the earth, and the planets revolve around the sun. The weight of the solar system keeps it all in balance.

Here’s a snapshot of the comparison of the annual cycle. From the earth view, the perspective looks the same on both models.

Here’s a snapshot of the comparison of the daily cycle. Again, from the earth view, the perspective looks the same on both models.

Astronomers and Physicists confirm that we on Earth cannot tell the difference between the heliocentric model or the Tychonic geocentric model.

“the Earth-centered system is in reality absolutely identical with the system of Copernicus and all computations of the places of the planets are the same for the two systems.” J.L.E. Dryer, Astronomer

“Whether the Earth rotates once a day from west to east, as Copernicus taught, or the heavens revolve once a day from east to west, as his predecessors believed the observable phenomena will be exactly the same. This shows a defect in Newtonian dynamics, since an empirical science ought not to contain a metaphysical assumption, which can never be proved or disproved by observation.” Dennis Sciama, Physicist

“So which is real, the Ptolemaic or Copernican system? Although it is not uncommon for people to say that Copernicus proved Ptolemy wrong, that is not true… One can use either picture as a model of the universe, for our observations of the heavens can be explained by assuming either the earth or the sun to be at rest.” Stephen Hawking.

“There is no planetary observation by which we on Earth can prove that the Earth is moving in an orbit around the sun.” I. Bernard Cohen, Physicist

Here is a video demonstrates that you cannot determine between heliocentrism and geocentrism by simply observing the planets, the sun moons etc.

Tycho Brahe and other astronomers promoted a geocentric earth, not a flat earth.

Tycho Brahe (1546 – 1601) was a Danish nobleman, astronomer, and writer known for his accurate and comprehensive astronomical and planetary observations.

Well known in his lifetime as an astronomer, astrologer and alchemist, he has been described as “the first competent mind in modern astronomy to feel ardently the passion for exact empirical facts.”

As an astronomer, Tycho worked to combine what he saw as the geometrical benefits of the Copernican system with the philosophical benefits of the Ptolemaic system into his own model of the universe, the Tychonic system. His system correctly saw the Moon as orbiting Earth, and the planets as orbiting the Sun.

In this depiction of the Tychonic system, the objects on blue orbits (the Moon and the Sun) revolve around the Earth. The objects on orange orbits (Mercury, Venus, Mars, Jupiter, and Saturn) revolve around the Sun. Around all is a sphere of fixed stars.

But the enemy propped up other astronomers, to counter their explanations, and point to the heliocentric model.

Kepler did not want to promote Tycho’s model, so after he died, Kepler made arrangements to obtain his 40-years worth of planet-charting that was originally meant to support the geocentric system, and used it for the heliocentric system.

Modern scientists freely admit that heliocentrism – the system which has the Earth rotating on its axis and revolving around the sun – is merely their preferred model of cosmology, and their preference for it is based purely on philosophical grounds, not scientific ones.

The Michelson-Morley Experiment confirmed that the Earth is motionless.

By all experimental indications, the Earth was found to be standing still in space, and modern science was confronted with its most astounding yet devastating evidence that had the potential to destroy its very foundation – the Copernican Principle.

In 1958, referring to the 1887 Michelson-Morley experiment and the dozens of other similar experiments performed through the 1930’s that yielded same results, the famous physicist Wolfgang Pauli admitted to what he called “The failure of the many attempts to measure terrestrially any effects of the earth’s motion…”

Science historian and physicist John D. Bernal stated: “The Michelson-Morley experiment was the greatest negative result in the history of science.” In other words, they were expecting it to prove that the Earth was moving in space, but they proved the very opposite.

In a book by Lincoln Barnett called “The Universe And Dr. Einstein” which Albert Einstein endorsed by writing the foreword, it says: “The experiment was tried again by Morley and by others, with the same conclusion: the apparent velocity of the Earth through the ether was zero.”

“This conclusion directly contradicts the explanation… which presupposes that the Earth moves.” Albert Michelson

“The data (of Michelson-Morley) were almost unbelievable… There was only one other possible conclusion to draw – that the Earth is at rest.” Bernard Jaffe, Physicist

Then the enemy had physicists such as George Fitzgerald and Hendrick Lorentz, create creative solutions to Michelson’s astounding results in an attempt to cover over the evidence.

Cosmic microwaves show that the Earth is in the center of the universe.

In 1989, the Cosmic Background Explorer (COBE) proved the radiation of the universe was lined up with the Equator of the Earth which put the earth are or near the center of the universe.

A second probe, the Wilkinson Microwave Anisotropy Probe (WMAP) was sent up in 2001. It was much more sensitive than the COBE probe and was able to provide a more focused picture of the universe’s microwave distribution.

It confirmed that there is a systematic and very organized distribution of microwaves aligned with and coming right towards the Earth from the furthest reaches of the universe.

The radiation data shows that the whole universe is divided into two, with a northern hemisphere and a southern hemisphere all of which lines up with the Earth’s equator.

Then to test to see if any contamination may have affected the data from the Wilkinson Microwave Anisotropy Probe, the European Space Agency sent up another prove in 2009. It was named the “Planck” probe, in honor of the 20th century physicist, Max Planck.

But it produced the same results as the WMAP probe, only with much better detail and clarity so the results could not be dismissed.

“A great deal of research has been carried out concerning the influence of the Earth’s movement. The results were always negative.” Henri Poincare, Physicist

All in all, there are three basic alignments of the Earth with the universe:

The cosmic microwave radiation’s dipole is aligned with the Earth’s equator.

The cosmic microwave radiation’s quadrupole and octupole are aligned with the Earth-Sun ecliptic.

The distant quasars and radio galaxies are aligned with the Earth’s equator and the North Celestial Pole.

Essentially, these three alignments provide the X, Y and Z coordinates to place Earth in the very center of the known universe.

Not only are the spin axes of galaxies and the cosmic microwave radiation aligned with Earth, but the distribution of galaxies shows that they lie mainly in concentric spheres around the Earth.

In his 1975 paper published in Astrophysics and Space Science, Y.P. Varshni said, “The Earth is indeed the center of the universe. The arrangement of quasars on certain spherical shells is only with respect to the Earth. It implies that a coordinate system fixed to the Earth will be a preferred frame of reference in the universe.”

One important fact about the cosmic radiation alignment with the Earth-Sun ecliptic is that it fits perfectly with the Neo-Tychonic geocentric model.

Since the Neo-Tychonic geocentric model has both the stars and the polarity of the cosmic microwave radiation aligned with the Sun, which all revolve around the fixed Earth, it is the only model that fits all of the cosmological data.

The Coriolis Effect

Essentially, Ernst Mach showed that the Coriolis Effect can be created either by a rotating Earth in a fixed star field or by the star field rotating around the fixed Earth.

The bulge of the Earth

Arthur Eddington, a famous scientist in the days of Einstein, said “The bulge of the Earth’s equator may be attributed indifferently to the Earth’s rotation or to the outward pull of the centrifugal force introduced when the Earth is regarded as non-rotating.”

The Big Bang was invented to suppress geocentrism, and cause scientists to take the heliocentric viewpoint.

The Big Bang was the brain child of the Belgian priest and scientist, Fr. Georges Lemaitre (1894-1966).

After a classical education at a Jesuit secondary school, the Collège du Sacré-Coeur, in Charleroi, Lemaître began studying civil engineering at the Catholic University of Leuven at the age of 17.

A Jesuit-trained person creating the Big bang theory, go figure!

Robert A. Sungenis,‎ PhD provides an amazing amount of evidence about astronomy, about the beliefs of astronomers, and about the cover-up by the enemy.

Don’t comment on this page, telling me that I’m wrong, until you’ve read the book ‘Geocentrism 101 – An Introduction into the Science of Geocentric Cosmology‘ by Robert A. Sungenis,‎ PhD. because you would be speaking out of ignorance.

If you really want to know the truth. If you really want to understand the enemy’s deception about the design of the universe, then you need to do your research about the geocentric globe earth.

It’s interesting that Robert didn’t write the book to counter the Flat Earth theory, as there is no mention of it in the book. He wrote it to counter the heliocentric view of the universe.

But shortly after he released the book, the flat earth theory was pushed on YouTube and Facebook no doubt in an attempt to cover over the truth about the geocentric globe earth.

Here’s some videos that discuss the proof of the geocentric model.

The Biblical Geocentric Model – Where Are We In the Universe?

Earth Is Center Of Whole Universe Part 1 by Rick Delano

Earth is Center of Whole Universe Part 2 by Robert Sungenis

Malcolm Bowden started posting videos which prove that the Earth is geocentric in 2010.

Here’s a video list for you to do more research.

Geocentricity Star parallax and redshift

Geocentricity explains the seasons

GEOCENTRICITY – An animated explanation of “Airy’s Failure” experiment.

Geocentricity – the unchanging orbits of the planets

Geocentricity: Christianity in the Woodshed by Gerardus D. Bouw, PhD.

Dr. Bouw has been writing about the geocentric Earth since 1992. This is the successor to Geocentricity and its predecessor, With Every Wind of Doctrine. This book is the most exhaustive and comprehensive book on the subject of geocentricity.

The book presents the geocentric nature of Scripture. It includes complete coverage of Joshua’s Long Day and Hezekiah’s sign. The role, function, and history of the firmament is covered extensively. The sun’s role in ruling the day is greatly extended in this book. Five appendixes are included in the book. One covers every scriptural reference to the geocentric creation. The last appendix derives the geocentric equations of motion that are commonly used in space travel only this derivation is strictly geocentric.

The book includes biographical sketches of most geocentrists from 1650 through 2013. Finally, the author traces the role that Copernicus’ heliocentric model played in the demotion of man from being created in the image of God to an evolved accident created in the image of an ape in rebellion against the God who created man in his own image.

He Maketh His Sun to Rise: A Look at Biblical Geocentricity, by Dr. Thomas M. Strouse, Dean of Bible Baptist Theological Seminary, Cromwell, CT.

Published in 2007, this book deals with geocentric verses in Scripture and exposes the fallacious arguments for heliocentrism and the unbiblical presuppositions that geocentricity’s creationist critics labor under.

See geocentricity through the eyes of a theologian expressed in the language of normal people.

The Bible and Geocentricity, by James N. Hanson, Professor Emeritus of the Cleveland State University,

He originally wrote the manuscript for this book in the 1980s.

It was serialized in the Biblical Astronomer in the early 1990s and has now been published in book form.

Rather than just being a reprint of the articles, the book has been revised and illustrated with figures hand-picked by the author.

With the geocentric globe earth in mind, we can see how Scripture confirms that the Earth is still and that the sun is moving.

Genesis 1:14 declares that the sun and moon are the markers/signs for days and for years, indicating that their movements reveal when the year, months and Holy Feast Days begin on the Scriptural calendar which means that the sun and moon are moving around the stationary Earth.

“And Elohim said, “Let lights come to be in the expanse of the heavens to separate the day from the night, and let them be for signs and appointed times, and for days and years”

Psalm 19:1-6 tells us that the sun is moving on the circular ecliptic, moving through the 12 constellations every year to tell the story of the Son of Righteousness, our Redeemer.

1 The heavens are proclaiming the esteem of Ěl And the expanse is declaring the work of His hand.
2 Day to day pours forth speech, And night to night reveals knowledge.
3 There is no speech, and there are no words, Their voice is not heard.
4 Their line has gone out through all the earth, And their words to the end of the world. In them He set up a tent for the sun,
5 And it is like a bridegroom coming out of his room, It rejoices like a strong man to run the path.
6 Its rising is from one end of the heavens, And its circuit to the other end And naught is hidden from its heat.

These verses describe the sun rising up or going down which proclaims that it is the sun that is moving, not the Earth:

The sun also ariseth, and the sun goeth down, and hasteth to his place where he arose. Ecclesiastes 1:5

He made the moon for appointed times The sun knows its going down. Psalm 104:19

From the rising of the sun to its going down, The Name of יהוה YHUH is praised. Psalm 113:3

Here’s some more verses: Genesis 15:12, Genesis 15:17, Genesis 19:23, Genesis 32:31, Exodus 17:12, Exodus 22:3, Exodus 22:26, Leviticus 22:7, Numbers 2:3, Numbers 21:11, Numbers 34:15, Deuteronomy 4:41, Deuteronomy 4:47, Deuteronomy 11:30, Deuteronomy 16:6, Deuteronomy 23:11, Deuteronomy 24:13, Deuteronomy 24:15, Joshua 1:15, Joshua 8:29, Joshua 10:27, Joshua 12:1, Joshua 13:5, Joshua 19:12, Joshua 19:27, Joshua 19:34, Judges 8:13, Judges 9:33, Judges 14:18, Judges 19:14, Judges 20:43, 2 Samuel 2:24, 2 Samuel 3:35, 2 Samuel 23:4, 1 Kings 22:36, 2 Chronicles 18:34, Psalm 50:1, Isaiah 41:25, Isaiah 45:6, Isaiah 59:19, Jeremiah 15:9, Daniel 6:14, Amos 8:9, Jonah 4:8, Micah 3:6, Nahum 3:17, Malachi 1:11, Matthew 5:45, Mark 16:2, Ephesians 4:26, James 1:11

These verses proclaim that the sun was moved backward ten degrees as a sign to Hezekiah that the Heavenly Father would add 15 years to his life.

“And Hezekiah said unto Isaiah, What shall be the sign that the LORD will heal me, and that I shall go up into the house of the LORD the third day? And Isaiah said, This sign shalt thou have of the LORD, that the LORD will do the thing that he hath spoken: shall the shadow go forward ten degrees, or go back ten degrees? And Hezekiah answered, It is a light thing for the shadow to go down ten degrees: nay, but let the shadow return backward ten degrees.” 2 Kings 20:8-11

“I am bringing the shadow on the sundial, which has gone down with the sun on the sundial of Aḥaz, ten degrees backward.” And the sun returned ten degrees on the dial by which it had gone down.” Isaiah 38:8

These verses proclaim that the sun stood still, which tells you that it is normally moving.

“Then spake Joshua to the LORD in the day when the LORD delivered up the Amorites before the children of Israel, and he said in the sight of Israel, Sun, stand thou still upon Gibeon and thou, Moon, in the valley of Ajalon. And the sun stood still, and the moon stayed, until the people had avenged themselves upon their enemies. Is not this written in the book of Jasher? So the sun stood still in the midst of heaven, and hasted not to go down about a whole day. And there was no day like that before it or after it, that the LORD hearkened unto the voice of a man: for the LORD fought for Israel.” Joshua 10:12-14

The sun and moon stood still in their habitation: at the light of thine arrows they went, and at the shining of thy glittering spear.” Habakkuk 3:11

In my opinion, there’s enough Scriptural and scientific evidence, to believe that the true design of the universe is the geocentric globe earth model.

And the grand deception of the enemy is that hardly anyone is talking about it.

Instead, the enemy is promoting the flat earth theory to deflect away from the truth and to cause people to reject anyone who talks about the geocentric earth.

1.15: Early Astronomers- Copernicus, Galileo, Kepler, and Newton - Geosciences

Ptolemy believed everything in the universe moves around ___________.

Galileo believed the _______ moved around the _____.

EARTH moved around the SUN?

Copernicus believed the sun traveled around the Earth.

Copernicus believed that Earth is a spinning planet that travels around the sun.

Which viewpoint did Newton believe: Geocentric or heliocentric?

Kepler believed the planets revolved around the ________.

THE SUN: heliocentric view

Ptolemy did not believe Earth moved.

Galileo used the telescope he made to study the heavens and saw that the moon's surface was


Copernicus's view of the solar system is called

HELIOCENTRIC VIEW: This view puts the sun at the center of our solar system.

Newton realized that the force that makes a pebble fall is the same force that keeps the moon traveling around Earth. This force is called

Kepler thought planets moved slower when they were closer to the sun.

FALSE: Kepler believed planets moved faster the closer they were to the sun.

The closer a planet is to the Sun, the stronger the Sun's gravitational pull on it, and the faster the planet moves. The farther it is from the Sun, the weaker the Sun's gravitational pull, and the slower it moves in its orbit.

Ptolemy's view of the solar system was widely accepted until the 1500s.

Galileo looked through his telescope and discovered this about Jupiter

Although Copernicus believed the Earth traveled around the sun, he DID NOT believe the Earth was spinning.

Copernicus believed the spinning motion of Earth is what makes the sun, the other planets, and the stars appear to move in the sky.

Newton is a famous scientists who was also a professor of _________ at Cambridge University.

Watch the video: The New Astronomy: Crash Course History of Science #13