Theories of the Universe:
Describe with a diagram the model of the universe as described by Aristotle and Ptolemy.
The universe is like a giant living body, with its leading part being the stars and the Sun, but in which all parts are interconnected, so that what happens in one place affects what happens elsewhere. They also held a cyclical view of history, in which the world was once pure fire and would become fire again (an idea borrowed from Heraclitus).
Compare and contrast Copernicus’ model of the universe to that described by Aristotle and Ptolemy.
We noted earlier that 3 incorrect ideas held back the development of modern astronomy from the time of Aristotle until the 16th and 17th centuries: the assumption that the Earth was the centre of the Universe, the assumption of uniform circular motion in the heavens, and the assumption that objects in the heavens were made from a perfect, unchanging substance not found on the Earth.
Copernicus challenged assumption 1, but not assumption 2. We may also note that the Copernican model implicitly questions the third tenet that the objects in the sky were made of special unchanging stuff. Since the Earth is just another planet, there will eventually be a natural progression to the idea that the planets are made from the same stuff that we find on the Earth.
What did Kepler add to Copernicus’ model of the universe?
In 1543, twenty-eight years before Kepler 's birth, Copernicus published the landmark astronomical text De
Aristotle’s model of the universe was a geocentric universe. This meant that the Earth was at the centre of the universe and that all stars were on a celestial sphere. A celestial sphere is an imaginary sphere which acts as a dome around the Earth from which you can see the stars and the universe. Although Aristotle’s model was good for its time it could not explain retrograde motion of the planets.
Among these people were Copernicus who believed the sun was at the center of the world and the earth, stars and planets revolved around it. Danish astronomer Brahe helped contribute to this idea by contributing a large mass of data about the universe that he was able to discover. His student Kepler kept his ideas going, as he formulated many laws of planetary motion. He said the orbits around the sun were elliptical, planets don’t move in a uniform speed and the time a planet completes its orbit is related to its distance from the sun. Meanwhile, Florentine Galileo decided to use experiments to find out what happened and not what should happen, and discovered that a uniform force makes a uniform acceleration as well as inertia laws, that an object will be in motion forever unless stopped by another force.
Astronomy was a highly debated topic between scientists and the Roman Catholic Church. The Roman Catholic Church believed that the Earth was the center of the universe and there was a place for all of the gods/zodiacs in it. An astronomer from the Middle Ages, Ptolemy, created the drawing of the universe which depicted the Earth in the very center of the universe, or geocentric. The geocentric universe, also contained an outer name in latin translating directly to “The Empire of Heaven and the Home of God and the Elect( document C )”. Contrary to the beliefs of the Roman Catholic Church another astronomer from The Renaissance created a sun centered universe or heliocentric. This astronomers name was Copernicus, he created his universe based on observation of the movement of the planets and mathematics. During the Middle Ages it was strongly believed that the universe was geocentric, but now astronomers like Copernicus have disproved these beliefs with concrete
The Ptolemaic view of the motions of the stars was earth centric, or geocentric. Ptolemy believed that all the planets revolved around the earth, the earth was the center of the universe. Copernicus on the other hand held the belief that the universe revolved around the sun, or that the universe was heliocentric. Copernicus also only considered there to only be six planets, as he didn’t count the moon like Ptolemy. Kepler held similar beliefs t Copernicus, and believed that the reason why a god-created universe only had six planets instead of seven was based on Plato’s idea of the five Platonic Solids. That just like there are only five forms of matter and five platonic solids, the universe must have been intelligently created in a similar
Galileo’s Dialogue on the Two Chief World Systems uses powerful logic and simply described concepts to overcome the Aristotelian bias of the populous and argue in favor of Copernicus’ heliocentric view of the universe. Copernicus theorized that the earth, along with the other planets in the sky, is in motion around the sun. The Aristotelian’s geocentric worldview, that the earth is the motionless center of the universe, was deeply ingrained into the minds of the people and the teachings of the church. Galileo’s argument had to be not only incisive and logical to have any sway, but it also had to avoid offending or denying the ancient principles of thought proposed by Aristotle. He walked this delicate line between educating the public and
Galileo’s observational discoveries in astronomy allowed for the basis to begin discrediting the old ideas in favor of a new understanding of the universe. The longstanding way of thought in astronomy favored a spherically rotating universe around the Earth with unchanging and perfectly symmetrical constellations and planets. The contemporaries of Galileo believed, for example, that the moon had the face of a shiny, polished sphere, whereas Galileo showed that the surface of the moon to be imperfect with rough mountainous areas along with deep valleys (or “seas” as he called them) marked with dark sports (Frova 162). This surface very much paralleled the rough surface of the Earth (meaning that Earth’s surface was not unique). Also with his improved telescope, Galileo was capable of viewing the stars with much more clarity. Galileo discovered newly formed stars and star clusters, which challenged the Aristotelian philosophy of an ageless universe. Additionally, Galileo observed four of Jupiter’s largest moons orbiting around the planet (Frova 179). His observations of Jupiter’s satellites did not agree with the idea that all heavenly bodies must rotate around a central Earth. Finally, and arguably most important, Galileo showed Venus’s phases and
Review the Ptolemaic model and the Copernican model. Also, give a lecture on Nicolaus Copernicus and Ptolemy as individuals.
Document 3 shows how Galileo’s observations of the moon and laws of motion supported Copernicus’ heliocentric model. He discovered that the moon has craters, and is not a perfect sphere like Aristotle said. This was able to prove that Copernicus was correct. However, the Church disagreed and disliked his work. It was rejected by the Church and he was forced to recant or face execution.
1) Modern astronomy basically begins with the re-emergence of the heliocentric view of the universe by Copernicus. Who were the four other major contributors to the development of modern astronomy after Copernicus? Explain what those contributions were. Finally, why did it take so long for the geocentric view of the universe to be overthrown and what does that tell us about scientific research and our society, even today?
1. According to Ptolemy's diagram, how does the universe work? Where is the sun (solis) in his
During the 1500s, scientific ideas were primarily based on ancient and medieval ideas. Earlier ideas about the universe were based on Aristotle’s principles, which postulated that the earth was stationary and was at the center of the universe. Later Copernicus overturned the medieval idea of the universe by postulating that the earth revolved around the sun. Scholars like Brahe, Galileo refined the Copernicus model by experimenting and collecting evidence. Even though there were several fundamental breakthroughs by Galileo and other scientists, the new findings failed to explain the forces that controlled the movement of the planets and falling of objects on Earth, and Sir Isaac Newton challenged to solve this ambiguity.
On to the next portion of time which was called the renaissance astronomy period (1400-1650). Most renaissance astronomers did not accept the theories of the previous astronomers. So they decided to make their own. Starting off with the Polish astronomer Nicolaus Copernicus. He began a new era of astronomy when he concluded that the Sun was the center of the universe instead of the Earth. This inventive idea was not popular with the Church, but several other astronomers such as Brahe and Galileo helped to eventually prove that this model of the universe was more accurate. Speaking of Tycho Brahe he built an observatory from which he made the most accurate astronomical observations up to that time. His observatory contained equipment for mapping star positions, and for more than 20 years he made detailed records of his findings. He believed that the universe was a blend of the Ptolemaic and Copernican models, and created his own model in which the planets orbit the Sun and the Sun orbits the Earth. Moving on to the next big astromoner who was, in fact Tycho Brahes assistant, Johannes Kepler. He inherited Tycho’s collection of astronomical records, and used them to develop three laws of planetary
Aristotle had refuted heliocentricity , and by Galileo's time nearly every major thinker subscribed to a geocentric view. Copernicus had delayed the publication of his book for years because he feared not the censure of the Church, but the mockery of academics. It was the hide-bound Aristotelians in the schools who offered the fiercest resistance to the new science. Aristotle was the Master of Those Who Know; perusal of his texts was regarded as almost superior to the study of nature itself. The Aristotelian universe comprised two worlds, the superlunary and the sublunary. The former consisted of the moon and everything beyond; it was perfect and
Galileo Galilei was also a supporter of the Copernican Theory. Galileo believed the earth, and other planets, rotated on its axis around the unmoving sun. He used his new invention of the telescope to prove Copernicus’ theory. With the telescope, Galileo found sunspots on the earth’s moon, which gave proof to him that the heavens were not perfect and changeless but were more like the changeable earth. iv He also discovered Jupiter and the four moons that revolved around it. He only discovered one moon revolving around the earth. Galileo therefore stated if Jupiter were to revolve around the earth, then the earth would have to have at least four moons, and it doesn’t. v The Church objected Galileo’s theory because the Bible said the sun moved through the sky. Being totally rejected by the church, Galileo was forced to take back what he had written and was also prevented from any further teachings of his theory. Galileo was condemned by the Catholic Church for his ideas. The Church succeeded in silencing Galileo but couldn’t stop the advancements in science.
Aristotle’s model by today’s standards can easily be picked apart, but at the time, it was the best explanation that could be made with so little technology and insight. Although his theories have long since been replaced, they created a base for future scientists to work off of and challenge. Over time many great scientists began to question Aristotle’s theories. Nicolaus Copernicus (1473-1543), for example, contested the absolute significance of the earth, and he did not agree that it should be viewed as the center of the entire universe (Lizhi & Youquan, 1987). He plotted the earth at the center of the universe and created a heliocentric system just as mathematically complicated as the Ptolemaic system (one that also improved on Aristotle’s), but it explained a number of anomalies, including resolving the issue of retrograde motion (Ede, A. & Cormack, L., 2004). The problem was that Aristotle’s physics of ‘natural motion’ fell apart without the earth in the center of everything.