Early Astronomers: Ptolemy, Aristotle, Copernicus, and Galileo 

One thing humans have never actually understood fully is astronomy. Of course, there has always been mythological theories but never an explained theory. Astronomy usually serves as a technique to keep time and predict the future. The word astronomy is defined as a natural science that studies objects and phenomena to explain the origin of objects and their evolution. Before astronomers created theories about the universe, people usually believed earth was at the center of the universe. In the 1920s, people actually did not know anything factual about astronomy. Decades later, people finally realized that the galaxy was one in many in this expansive universe. Soon, people noticed that the galaxies actually were moving apart from each other in every direction and or speed.

Ptolemy was an ancient astronomer, geographer, astrologer, mathematician, cartographer, and writer that considered the earth as the center of the universe. Claudius Ptolemy supposedly lived in Alexandria during the Roman province of Egypt in the 2nd century and discovered many scientific treatises. Ptolemy was born in 100 AD and died in 168 AD by Alexandria, Egypt.

Back in this time period, the earth was called geo in Greek. So this idea would be called the geocentric theory. Disregarding his false theory, Ptolemy was able to connect the star movement with mathematics, to predict the motion of the planets. Ptolemy’s theory was that the earth was the center of the universe including the sun revolved. In order to make the estimated guesses correct, Ptolemy tested out that planets must circulate in epicycles and small circles, so the earth itself could move along an equant. Considering that none of this information was valid, it made up for the math portions of his prediction. This flawed view of the earth was accepted for many centuries.

Ptolemy’s well known work was named the Almagest, a treatise in thirteen books. The contribution that the Almagest had to science was important because it gave in detail, the mathematical theory of the movements of the sun, moon, and planets. Ptolemy made his most original contribution by presenting details for the movement of each of the planet. The theories that were all presented, were not superseded until a century after Copernicus presented the heliocentric theory in 1543. Ptolemy justifies his interpretation of the universe, based on the earth centered system described by Aristotle. It is a perspective of the world based on the earth around which the sphere of the fixed stars, circulates every day. Ptolemy used mathematical models to estimate the locations of the sun, moon, and planets, using combinations of circular motions known as epicycles. According to the MacTutor History of Mathematics, Ptolemy discovered this theory on the 6th of March, 127 and the last discovery was made on the 2nd of February, 14.

Ptolemy thought that all celestial objects including the planets, sun, moon, and stars orbited around earth. Earth, in the center of the universe actually did not move at all. Copernicus thought that the planets orbited the sun, and that the moon orbited earth. The sun in the center of the universe, did not move, nor did the stars. Copernicus was correct about some things but wrong about others. The sun is not in the center of the universe and it does move, as well as the stars. Also, both Copernicus and Ptolemy thought the orbits of the planets were circular but now, both know that they are elliptical. Copernicus debunked Ptolemy’s theory sometime between 1507 to 1515 but was able to develop the physics to prove that he was correct by the 1600s.

As some people know, Aristotle was an ancient Greek philosopher and scientist that is considered one of the greatest thinkers in politics, psychology and ethics. Besides astronomy, he enjoyed teaching and writing. The love he had for philosophy encouraged him to start his own school based on philosophy and aristotelian traditions. Aristotle was born in 384 B.C. in Stagira in northern Greece and died in 322 B.C. in Chalcis, Greece. Being born in the colony of Stagira, Aristotle lost his parents at an early age. Very much information is hidden about his parents but his father was the court physician to the king of Macedon. When he was young, he was sent to the Athens to attend Plato's Academy and was a student for 20 years and eventually became a teacher.

Years later, he eventually got married to a lady named Pythias and had two children, a son and a daughter. After he began his school, he started writing about astronomy, law, government, logic, and medicine, etc. Most of the writings were in the perspective of a western thought. Aristotle wrote approximately 170 books, 47 of which still are available after more than two thousand years later. Aristotle soon retired in Chalcis, and died the next year, 322 from a stomach disease.

Their was always a theory that Aristotle believed and was possibly correct. He believed that the earth was the center of the universe. Aristotle rejected Plato’s theory of forms, which states that properties such as beauty are abstract universal entities that exist independent of the objects themselves. Instead, he argued that forms are intrinsic to the objects and cannot exist apart from them, and so must be studied in relation to them. However, in discussing art, Aristotle seems to reject this, and instead argues for idealized universal form which artists attempt to capture in their work.

He, too, believed in a geocentric Universe and that the planets and stars were perfect spheres though Earth itself was not. He further thought that the movements of the planets and stars must be circular since they were perfect and if the motions were circular, they could go on forever. Today, the world now knows that none of this is the case, but Aristotle was so respected that these wrong answers were taught for a very long time.

Aristotle believed that the earth is round and smaller than the stars. With this being his theory he thought that everything surrounding it, revolves around it. This observation, although incorrect, is logical. Aristotle thought that if the earth moves, then the whole scheme of things would turn around. The stars, it would appear, are in their fixed places while the earth is in motion but least Aristotle was right for one thing, the earth is round. He asserted this belief by arguing that when a person goes to the north or to the south, he or she does not see the same stars in the evening or the same positions of the sky, in the day. Aristotle approximately made this theory in 325 B.C.

Later in his life, he also invented the telescope and microscope that would prove some of his own theories incorrect. According to research gate, Galileo disproved Aristotle’s theory between 384 B.C. and 322 BC. This greek philosopher has also made many significant and everlasting contributions to mostly every perspective of human knowledge.

His contributions have commanded sustained interest and have been largely translated and studied. According to jw.org “history professor James MacLachlan wrote that Aristotle's views of nature originated European thoughts for almost two thousand years”. Most of his views has influenced Catholic, Protestant, and Islam teachings. Aristotle’s contribution to astronomy lies between his codification and extension of past theories about celestial objects. This includes the fact that he was able to prove his theory of the universe with accurate information. He was able to combine what he saw from the stars movements with geometry to determine the movements of the planets.

Nicolaus Copernicus was one of the great astronomers of the sixteenth century. He was born on February 19th, 1473 in Torun, Poland. His real name was Mikolaj Kopernik although he is well known by his Latin name. His father was a wealthy merchant and he had there other siblings. In 1941, Copernicus went to University of Cracow and was their for about four years. He soon left in 1946 to study law at University of Bologna and became interested in astronomy.

Years later in 1501, he left Bologna to study medicine at University of Padua. During 1503 to 1510, he worked with his uncle but continued to study astronomy. Between this time period, an ancient Greek called Aristarchus accurately realized that the earth orbits the sun. This was around the time when Ptolemy announced his theory that he believed that the earth was in the center of the universe so Aristarchus theory was widely rejected.

Copernicus rejected his theory as well. The sun is the center of the solar system and the earth and other planets orbit it. This is called the heliocentric system for the Greek word sun, Helios. He also realized that the earth spins on an axis that is tilted. Aristotle announced that objects fall to the earth because it is at the center of the universe but Copernicus wondered what caused the objects to fall.

Copernicus soon discovered a new theory and manuscript but only distributed it between his close friends. This was set in place to make sure all mathematical calculations were correct before publishing his new theory to the public. By 1540 he was ready and announced his new theory in 1543. Shortly after his studies on astronomy he died on May 24, 1543.

After his death, he became well known throughout Europe. Based on my research, Galileo has debunked the Copernicus theory because he was the only person to prove Copernicus incorrect.Actually, Copernicus advanced the heliocentric theory that the sun, not the earth, is at the center, and that the earth goes around the sun. He did this more than half a century before Galileo. But Copernicus had no direct evidence, and he admitted that there were serious obstacles from experience that told against his theory. For instance, if the earth is moving rapidly, why don't objects thrown up into the air land a considerable distance away from their starting point? Galileo defended heliocentrism, but one of his most prominent arguments was wrong. Galileo argued that the earth's regular motion sloshes around the water in the oceans and explains the tides. In reality, tides have more to do with the moon's gravitational force acting upon the earth. In astronomy, Copernicus contributed to the heliocentric system. This system provided that the planets orbit around the sun including the earth. Besides orbiting the sun often, also turns once daily in the direction of the axis account for the precession of the equinoxes. He said out his model of the solar system and the path of the planets to prove his reasoning.

Galileo Galilei was born on February 15, 1564 in Pisa, Italy. He, himself is one of the few famous people known by his first name rather than his surname. His father was a musician but his were by no means wealthy. In 1581, Galileo began studying medicine at Pisa University. However he soon had a strong interest in mathematics and decided to learn to teach mathematics and philosophy. This decision was much against his father's wishes. Galileo soon left the university in 1585 and began having a private profession in mathematics. Quickly, he gained a reputation as a genius mathematician and in 1589 he became a professor in mathematics at Pisa University.

At that time the ancient Greek philosopher Aristotle was held in very high esteem and many people accepted his ideas without question, however Galileo did not. Aristotle said that if a heavy objects and a light object both fall from a height, the large one will reach the ground first. According to legend, Galileo tested the theory by dropping two different weights from the leaning Tower of Pisa and both hit the ground at the same time. Whatsoever, many people now believe this famous experiment is not valid. At the times, other scholars had already detected that Aristotle had an error in his theory. Yet, Galileo's criticism of Aristotle irritated the other personnel at the university and in 1592 his renewal of his contract was revoked. Alternatively, from 1592 to 1610 Galileo taught at the university of Padua. Soon after in 1609, Galileo heard of a new invention from Holland.

A gentlemen named Hans Lippershey invented the telescope. Galileo made his own telescope and soon improved it. Using a telescope, Galileo was able to see several things invisible to the bare eye. He could see many stars not visible without a telescope. He also discovered four small moons orbiting the planet Jupiter and at the time these were amazing discoveries. Until then nobody knew that any of the other planets, apart from Earth, had moons. Also during 1610, Galileo found out that Venus has phases like the Moon. This theory of Galileo was made in 1632. That year he was made mathematician and philosopher of the grand duke of Tuscany, Italy. At that time astronomers were debating sunspots. A German named Christoph Scheiner claimed that they were satellites of the sun. In 1613, Galileo argued that sunspots are actually on the surface of the sun. Meanwhile in 1543, a theory by the polish astronomer Nicolaus Copernicus was published until his time people believed that the sun, moon and planets orbit the earth.

Copernicus argued that the earth and the other planets orbit the sun. At first the church did not have a problem with his theory. However, this opinion gradually hardened and in 1616 the Copernican theory was declared heretical. There is a passage in the Old Testament where a prophet named Joshua commanded the sun to stand still in the sky. Some scholars said this meant the sun has to move. Joshua at the time knew nothing about astronomy. To him the sun appeared to move across the sky. Naturally he would command the sun to stand still and to him it would have appeared to stand still.

However, Galileo was a resolute supporter of the Copernican theory. In 1632 he published a book called “Dialogue Concerning the Two Chief World Systems”. As a result he was summoned to Rome to be examined. He arrived in January 1633. Galileo was threatened with torture until he renounced the Copernican theory. Nevertheless he was put under house arrest for the rest of his life. In 1634 Galileo published a book about mechanics called “Dialogue Concerning Two New Sciences”. Then in 1637, he noticed that the Moon moves slightly from side to side. Unfortunately in 1638 he went blind. Galileo Galilei died on January 8, 1642 at age seventy seven.

Based on my researches Galileo’s theory was absolutely correct because no person has been able to prove his theory incorrect. Galileo’s contribution to astronomy includes his newly invented telescope. This telescope discovered four of the moons surrounding Jupiter, the study Saturn, to observe the phases of Venus, and to study sunspots on the Sun. Galileo’s observations strengthened this belief in Copernicus’ theory that the Earth and all other planets revolve around the Sun.

In conclusion, the astronomers activities have remarkably transformed since the earliest ages to present titles. Their discoveries and theories shaped our beliefs of the universe in the present day because the information conducted by these astronomers were used to predict recent activities and foretell certain seasons. Later, astronomers sought to find explanations involving the versatile events which the heavens presented. These investigations have inspired interest and encouraged astronomers to conduct more studies with a view of presenting more pertaining the heavenly objects.