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Seeing Stars!★ by Huijun, Hui Wen, Vanessa, Letitia, Jin****gwen, Valerie** 1543: Publication of Copernicus' //De revolutionibus orbium coelestium (the Revolutions of the Celestial Orbs).// 1609: Invention and Development of Telescope and observation of the Milky Way by Galileo 1609: Publication of Kepler’s Astronomia Nova, which documented his findings of the Three Laws of Planetary Motion 1610: (7 Jan) Observation of Galilean Moons by Galileo 1610: (March) Publication of Galileo’s //Sidereus Nuncius (The Starry Messenger)//,documenting his observations and discoveries made from the telescope. 1610: (December) Observations of the phases of Venus by Galileo 1611: Copernicus’ publications put on the Index of Forbidden Books 1612: Observation of sunspots by Galileo 1613: Publication of Galileo’s //Letters on the Sunspots//, documenting his discoveries about sunspots. 1616: Galileo’s publications put on the index of Forbidden Books 1633: Galileo was tried by the Church, being accused of heresy and was convicted of his crime on June 16. 1835: Copernicus’ and Galileo’s works were removed from the Index of Forbidden Books.
 * Timeline: **

Nicolaus Copernicus
__A Biography of the Great Guy__



Nicolaus Copernicus (1473-1543) was born in Torun, Poland. He studied in the University of Cracow before he went to Italy to study canon law and medicine. In addition, he learnt Greek and developed his interest for Astronomy there too! In 1503, he returned to Poland and worked as an administrative canonry of Frombork where his uncle was also a bishop and remained in the diocese (a district under the pastoral care of a bishop in the Christian Church) for the rest of his life.

Galileo Galilei
__Biography of Great Guy Number 2__



Galileo Galilei was born on the 15 February, 1564 in Pisa, Italy. He died on the 8th of January, 1642. His father was a musician and a wool trader. Galileo had six younger siblings. Galileo was expected to study medicine to earn more money. At eleven years old, Galileo was sent off to study in a jesuit monastery. Four years later, Galileo announced that he wanted to become a monk. This shocked his father and therefore Galileo was withdrawn from the monastery. Galileo attended the University of Pisa to study medicine in 1581 at the age of seventeen. However, Galileo left the University of Pisa without a degree as he was not interested in it. Galileo started tutoring students mathematics to earn a living. He did experiments with floating objects and even developed a balance that could tell that for example, gold was 19.3 times heavier than the same volume of water. During this time, Galileo also campaigned for his life’s ambition: a position on the mathematics faculty at a major university.

Johannes Kepler
__Biography of Great Guy Number 3__



Johannes Kepler (December 27, 1571 – November 15, 1630) was born at Weil der Stadt, near Stuttgart and studied at the University of Tubingen. He was a German mathematician, astronomer and astrologer, and key figure in the 17th century scientific revolution.His works also provided one of the foundations for Issac Newton’s theory of universal gravitation. He also did fundamental work in the field of optics, invented an improved version of the refracting telescope, and helped to legitimize the telescopic discoveries of his contemporary Gallileo. In 1593, the authorities nominated Johannes to teach mathematics in Graz and Kepler, left with no choice, complied.

** Major achievements and discoveries: **

**__The Heliocentric Model__ **

From a long time ago, people believed in Aristotelian and Ptolemic concept of the Earth as the centre of Universe, with the Sun and other planets revolving around it. Copernicus was the first to come up with the opposing idea that the Earth, along with all other planets, revolves around the sun. Ptolemy created the Ptolemaic Universe to solve the problem of the planets going through precession. However, in the book, Copernicus realized that this problem of precession can be answered by questioning and challenging the fundamental assumption made when Ptolemy created the Ptolemaic Universe - The Earth was the center point of the revolution of the Heavenly Bodies (The Planets and the Stars). Copernicus then attempted to solve the problem by using the simplest possible solution - He moved the Sun to the center of the Universe and by doing so, he found out that almost all the problems with planetary precession had disappeared along with it. Therefore, the heliocentric Copernican Universe was created. In the book, Copernicus summarized his theory on his heliocentric theory:

1. There is no one center of all the celestial circles or spheres.

2. The center of the earth is not the center of the universe, but only of gravity and of the lunar sphere.

3. All the spheres revolve about the sun as their mid-point, and therefore the sun is the center of the universe.

4. The ratio of the earth's distance from the sun to the height of the firmament (outermost celestial sphere containing the stars) is so much smaller than the ratio of the earth's radius to its distance from the sun that the distance from the earth to the sun is imperceptible in comparison with the height of the firmament.

5. Whatever motion appears in the firmament arises not from any motion of the firmament, but from the earth's motion. The earth together with its circumjacent elements performs a complete rotation on its fixed poles in a daily motion, while the firmament and highest heaven abide unchanged.

6. What appear to us as motions of the sun arise not from its motion but from the motion of the earth and our sphere, with which we revolve about the sun like any other planet. The earth has, then, more than one motion.

7. The apparent retrograde and direct motion of the planets arises not from their motion but from the earth's. The motion of the earth alone, therefore, suffices to explain so many apparent inequalities in the heavens.

Through geometry, mathematics, physics and cosmology, he was able to find concrete evidence to deduce the positions of planets and other celestial bodies. Thus, for the first time, there was a scientific theory made, not one that was based on thinking and philosophy. Although in the past there had been heliocentric ideas surfaced, Copernicus was the first person to create a complete and general explanation the heliocentric concept.

As quoting from Copernicus, past astronomers ‘have not been able to discover and infer the chief point of all - the structure of the universe and the true symmetry of its parts. But they are just like someone taking from different places hands, feet, head and the other limbs, no doubt depicted very well but not modeled form the same body and not matching one another - so that such parts would produce a monster rather than a man.’ Copernicus felt that Ptolemy did not manage to present the integrated and a whole picture of the cosmos through the Ptolemaic Universe. As such, Copernicus saw the Ptolemaic Universe as a model which different components do not fit well with each other and hence he rejected Ptolemaic cosmology because of Ptolemy’s equant, saying that such theories “were not adequate unless they also conceived certain equalizing circles, which made the planet appear to move at all times with uniform velocity neither on its deferent sphere nor about its own center”. There were also disparities which Copernicus felt were out of the way such as the absurd variations in the apparent size of the Moon in the Ptolemaic Universe, and hence being aware of such defects, he wondered if there were a better arrangement for the celestial bodies. Rejecting the equant would otherwise suggest a return to Aristotelian theories, hence Copernicus set about carefully constructing his own theory. Therefore, after developing his interest for astronomy, he decided to pursue this particular interest for him through creating a new model to solve the problems about the Universe. 

**__Empirical use of the telescope to observe the Universe__** The telescope was invented by some lens makers in the Netherlands. However, it was Galileo who tinkered with the invention and pushed the magnifying technology to its limits to reach a factor of 33 times. That was the instrument with which, in 1609-10, Galileo made his revolutionary discoveries. For the first time in history, there were empirical evidence in various theories. Through the telescope, Galileo made several significant and revolutionary observations: - Galileo's observations of sunspots. In 1611, there were several people who observed the mysterious dark areas on the Sun through the telescope, and some, such as Cristoph Scheiner, thought that these patches could be objects orbiting the Sun. This held true with the original perception that the Sun was flawless and perfect. However, through Galileo's observations, he discovered that they were the dark spots that appeared on the Sun temporarily.

- Galileo's observations of rings of Saturn. However, at that time, Galileo called them “discs” because his telescope was not advanced enough to observe that they were rings.

- Galileo's observations of the Moon through the telescope: Aristotle had earlier claimed that the Moon was a perfect sphere, and that the dark spots observed on the Moon was either some sort of contamination or a reflection of parts of Earth. However, through Galileo’s observations of the Moon using the telescope, he observed the changing shapes of the dark lunar spots and other patterns of light and shadow on the Moon’s surface. This led him to believe that the Moon was filled with mountains and craters, and he could even use Mathematics and Physics to estimate these mountains’ heights.. Using Mathematics and his observations, Galileo concluded that the Moon, once believed to be a perfect sphere, was actually full of potholes.

- Galileo's observations of Venus: Galileo looked at Venus through the telescope and saw its visible shape changing like that of the moon, exhibiting various phases such as gibbous, crescent and full. This indicated that Venus was revolving around the Sun. For example, Venus would become a crescent when Venus was between the Earth and the Sun, a time when most of its sunlit half faced away from Earth, and as its position around the Sun changed, it would display different phases. His observations served to validate Copernicus’s heliocentric theory as it showed the planets like Venus did revolve around the Sun.

- Galileo's observations of Galilean moons: Through his telescopic observations, Galileo saw that there were three very bright objects orbiting Jupiter. He observed this for a number of nights and found that a fourth bright object became visible. Galileo reasoned that there were four satellites that revolved around Jupiter and Jupiter with its satellites revolved around the sun. Thus, Galileo discovered the four moons of Jupiter, Io, Europa, Ganymede and Callisto, which were later termed as the Galilean moons in honour of Galileo. The fact that a planet had four Moons orbiting it thus put down the geocentric theory that all celestial bodies should be orbiting around the Earth, which was at the center of the universe. This again provided empirical evidence for the Heliocentric Model.

- Galileo's observations of the stars: People had orginally observed the Milky Way as a nebulous mass and believed it to be clouds. However, through the telescope, Galileo observed that the Milky Way was actually numerous stars very closely positioned together that to the naked eye they seemed like clouds. Moreover, Galileo also saw through the telescope several stars too far off to be seen by the naked eye.

** __Kepler's Three Laws of Planetary Movements__ ** 1. The orbit of every planet is an ellipse with the Sun at a focus. (He had originally calculated Mars’ orbit while assuming that planets revolved around the Sun in circular orbits. However, there were inaccuracies in the results of his repeated calculations and Kepler finally realized that planets moved in an elliptical orbit. This overthrew the original assumption that planets and celestial bodies moved in circular orbits.) 2. A line joining a planet and the Sun sweeps out equal areas during equal intervals of time. 3. The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

=Significance of discoveries and achievements:=

__**Wrong Perception #1**__ <span style="font-family: Tahoma,Geneva,sans-serif; line-height: 115%;">- The Universe was a very small place. - Their microscopy of the Universe can be seen in this example: When someone climbs a tower, they were not just getting a better view of the stars, they thought that they were literally getting closer to the stars. - In the largest version, the Universe can fit within the orbit of Pluto. This is because even though the people in the 16th century knew that the Universe moves in a circular motion around a center point, they believed that the Universe could not be a big place because the outer parts of the Universe will then have to travel at a speed of billions per hour. - Hence since nothing could have survived and travel at speeds like that, they believed that the Universe was small because the outer edges of the Universe must be very close to the Earth.

__**Wrong perception #2**__ -The stars move in a circular motion around the Earth. - If Earth was moving in a circular orbit around the Sun, they thought that Earth must then be moving at a very fast speed, like maybe 1000 miles per hour. Therefore, if someone were to jump, they would then land 10 or 20 miles away from the spot they first started because the Earth is moving. However, they realized that you will land on the same spot when you jump into the air. - Hence they deduced that the Earth must not be in obituary motion, and thus Earth must be the center of the Universe.

__**Wrong perception #3**__ - The Ptolemaic Universe created by Ptolemy, an ancient greek astronomer. - There was a problem with the theory of the Earth being the center of the Universe and that is that even though the planets are seen to be moving in circular motion in the sky, they are sometimes observed to be moving backwards (Precession). Ptolemy decided to come up with a solution that will solve this problem and still make Earth the center of the Universe. Firstly, he made the elliptical orbits eccentric. He took them out of their orbit path and concluded that the planets are spinning around a moving point, each planet having a different center of rotation. These extra orbital orbits are called epicycles. - Ptolemy created a new geocentric Universe that shows the planets orbiting around points that orbited the earth in uneven and unbalanced elliptical orbits. Even though it may be nonsensical, the astrologers and astronomers of the Islamic world believed that the Ptolemaic Universe was an accurate depiction of the motion of the universe, hence when Arabic Science entered the European world in the 12th and 13th centuries, many people gradually began to believe the Ptolemaic Universe and this remained unchallenged for many years until Nicolaus Copernicus came along. Evidence to back up that the Ptolemaic Universe was nonsensical: When King Alfonso of Spain was first introduced to the Ptolemaic Universe, he said: “If God had made the universe thus, he should have asked me for advice first.”

__**Wrong perception #4**__ - The sky/heaven was made of crystal spheres. - It was thought that the sun, moon and planets, made of aither (ancient greek personification of the clear upper air of the sky) would have a naturally circular motion, because a circular motion is the simplest motion that keeps repeating. They figured that the stars and Earth were in spheres, and the larger sphere of stars rotated about the Earth-sphere every 24 hours. And because the stars were very much visible, it was taken that the sphere they were inside was transparent (crystal). In total Aristotle figured that the sky was made up of //fiftyfive// concentric spheres. Aristotle thought the crystal spheres actually existed. - The crystal sphere theory worked out because they thought that aither (which the celestial bodies were thought to be made of) could only move in circular motions. This was entirely dismissed by latter philosophers, because surely if the spheres were made of crystal and the Universe of the time was much smaller, the sky would have shattered when a canon ball was fired into the sky.

__** Conclusion **__ For a long time, people had been strictly conforming to the Aristotelian and Ptolemic concept of the Earth as the centre of Universe, accepting their philosophical theories as the truth, since their theories fitted in nicely with the Biblical concept of “Mankind” and "Earth" being the centre of Universe. The Roman Catholic Church, being the most trusted and unchallenged source of authority and knowledge at that time, promoted this belief and thus the geocentric theory was widely accepted and unquestioned.

Any phenomena or circumstance that could not be explained or understood was credited to divine intervention, magic, religion or witchcraft. Hence, there was little or no empirical evidence at all supporting the various philosophical theories produced by the various thinkers of the age, and no one questioned their authority as long as they were sanctioned by the Church.

However, Copernicus came up with the heliocentric model that went against the accepted belief of the time. He removed Earth from the centre of the Universe. Galileo then followed up on his findings by capitalizing on the lens technology to validate Copernicus' heliocentric model. Because this starkly opposed the religious teachings and beliefs and that time, their works were condemned as perverting the nature of things. This, however, was significant in that it was perhaps the first time that the teachings of the Church and the great philosophers of that time were openly challenged, and this time there was empirical and scientific backings to their claims, unlike the usual philosophical theories put forth in the past.

This introduced the people to a whole new perspective of things as concrete evidence was now used to substantiate claims, and there were rational explanations to things rather than the belief that divine intervention resulted in various phenomena. These discoveries sparked off great dispute and Galileo was eventually persecuted and sentenced by the religious order to life imprisonment for persisting with his beliefs. His sentence was commuted to house arrest for the last nine years of his life. Eventually though, they were finally embraced by society and their works were acknowledged as significant and groundbreaking discoveries. In 1835, their works were removed from the Index of Forbidden Books. These discoveries also ignited the pursue for empirical explanations for various theories formulated and laid the basis of scientific research for future scientists like Francis Bacon, Rene Descartes and Sir Isaac Newton.

=<span style="font-family: Arial,Helvetica,sans-serif; line-height: 115%;">References: = <span style="font-family: Arial,Helvetica,sans-serif; font-size: 132%; font-weight: normal;">__Websites__ 1. Eric Weisstein, (2007). //Copernicus, Nicholaus (1473-1543) -- from Eric Weisstein's World of Scientific Biography//. Retrieved from []. 2. Abby Cessna, (2009, June 22). //Heliocentric Model//. Retrieved from []. 3. Wendy Kahler, (2002). //The achievements of Galileo//. Retrieved from []. 4. Wikipedia: i. //Galileo Galilei//. In [|Wikipedia]. Retrieved from [] ii. //Johannes Kepler//. In [|Wikipedia]. Retrieved from [] iii. //Nicolaus Copernicus.// In [|Wikipedia]. Retrieved from [] 5. University of Tennessee. //Galileo: The Telescope & The Laws of Dynamics//. Retrieved from []. 6. Nick Greene. //Johannes Kepler- Defender of Copernicus - Planetary Lawmaker//. Retrieved from []. 7. David P. Stern, (2005, March 23). //Kepler's Three Laws of Planetary Motion//. Retrieved from []. 8. Al Van Heiden, (2003, August 4). //The Galileo Project | Science | Copernican System//. Retrieved from []. 9. John O'Connor, Edmund F Robertson, (2002, November). //Galileo Summary//. Retrieved from [|http://www.gap-system.org/~history/Mathematicians/Galileo.html]. 10. Zephyrus (an independent company). //Galileo Galilei//. Retrieved from []. 11. Mary Bellis. //Galileo Galilei - Biography//. Retrieved from []. 12. Teacher's Domain, (2005, December 17). //Galileo: Sunspots//. Retrieved from []

<span style="font-family: Tahoma,Geneva,sans-serif; font-size: 120%;">__Books__ <span style="font-family: Tahoma,Geneva,sans-serif;"> 1. Hoskin, Michael. (2003). //The History of Astronomy: A Very Short Introduction//. United States, New York: Oxford University Press.

2. Hasan, Heather. (2005). //Kepler and the Laws of Planetary Motion.// United States, New York: Rosen Central Primary Source.

3. Sakolsky, Josh. (2005). //Copernicus and Modern Astronomy//. United States, New York: Rosen Central Primary Source.