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 * Seeing Stars:**
 * From Copernicus to Galileo**
 * Done by: Chia Shi Mei (5), Li Churen (16), Sara Ang (26), Stacy Young (30), Tan Heng** **Yeng (31)**


 * Timeline of Key Events**

Ptolemy describes a geocentric universe.
 * 150**

Nicholas Copernicus publishes his theory that Earth travels around the Sun (heliocentric).
 * 1543 **

A brilliant comet (Supernova) is observed by Tycho Brahe, who proves that it is travelling beyond Earth's atmosphere and therefore provides the first evidence that the heavens can change.
 * 1577 **

Johannes Kepler announces his two laws of planetary motion. First Law, that the orbit of a planet is an ellipse (replacing the circular orbits of Plato). Soon thereafter he discovers the Second Law, that planets move on the ellipse to sweep equal areas in equal times. Almanacs based on his laws prove to be highly accurate.
 * 1609 **

The telescope was introduced to astronomy in 1609 by Italian scientist Galileo Galilei. Galileo did not invent the telescope but he was among the first to improve it and use it to examine the heavens. He carried out important observations of the Sun, Moon, Planets, and Stars.

Johannes Kepler discovers Third Law, that there is a precise mathematical relationship between the time it takes a planet to orbit the sun, and the size of its orbit.

Galileo Galilei publishes Sidereus  Nuncius  describing the findings of his observations with the telescope he built. These include spots on the Sun. craters on the Moon, and four satellites of Jupiter. Proving that not everything orbits Earth, he promotes the Copernican view of a Sun-centred universe. Kepler discovers laws of planetary motion. Working with Tycho's observations, Kepler answers questions about shapes of planetary orbits, how the speed of a planet varies as it orbits the Sun, and the relationship between orbital distance and orbital period.
 * 1610 **

Francis Bacon suggests that Earth's continents move about. Bacon noticed that the eastern and western shores of the Atlantic were parallel and could be fitted together.
 * 1620**

Descartes develops concept of inertial motion. Descartes believed that all motion resulted from collision with particles called "corpuscles". In the absence of such collisions, a body remains at rest. An object in motion continues to move in the same direction at the same speed.
 * 1630**

Galileo published a book entitled ‘The Dialogue’ describing the merits of the heliocentric and geocentric models of the solar system. It was a powerful argument for the ideas of Copernicus. Galileo was brought before the inquisition and spent the last 9 years of his life under house arrest.
 * 1632**

Isaac Newton 1668 builds the first reflecting telescope, his Newtonian telescope.
 * 1668 **

<span class="wiki_link_ext">Isaac Newton establishes the theory of gravitation and laws of motion. He explains Kepler's laws of planetary motion and allows astronomers to understand the forces acting between the Sun, the planets, and their moons
 * <span class="wiki_link_ext">1687 **

Astronomy made great strides during the scientific revolution, a time period in which Copernicus, Galileo, Isaac Newton and others studied. These men made great contributions to the science of astronomy, developing new technology for studying the stars and planets.
 * Short biological write-up - Astronomers**

__Short biological write-up:__ Nicholas Copernicus (19 February 1473 – 24 May 1543) was a Pole. He was a devout Christian and also a physician, a Catholic cleric, a governor, a military leader and more. Astronomy was only a hobby for <span class="wiki_link_ext">Copernicus. He attended Krakow University, University of Ferrara, University of Padua and Bologna University.
 * Nicholas Copernicus**

__Contributions:__ He was the first astronomer to put forth the theory that the Earth was not the centre of the universe. This theory, discussed in his book "On the Revolutions of the Celestial Spheres," stimulated scientific investigation and is often referred to as the starting point of the Scientific Revolution.

__Short biological write-up:__ Tycho Brahe (14 December 1546 – 24 October 1641) was born in Knudstrup, which currently is in southern Sweden but was a part of Denmark at the time. While attending the universities of Copenhagen and Leipzig to study law and philosophy, he became interested in Astronomy and spent most evenings studying the stars.
 * <span class="wiki_link_ext">Tycho Brahe **

__Contributions:__ One of Tycho Brahe’s first contributions to astronomy was the detection and correction of several grave errors in the standard astronomical tables. Then, in 1572, he discovered a supernova located in the constellation of Cassiopeia. Eventually, his fame led to an offer from King Frederick II of Denmark & Norway to fund the construction of an astronomical observatory.

During his life, Tycho Brahe did not accept Copernicus’ model of the universe. He attempted to combine it with the Ptolemaic geocentric model. He proposed that the five known planets revolved around the sun, which, along with those planets, revolved around the earth each year. The stars, then, revolved around the Earth, which was immobile.

Of course, Tycho Brahe’s theories were incorrect, but the data he collected during his lifetime was far superior to any others made prior to the invention of the telescope.

__Short biological write-up:__ Galileo Galilei (15 February 1564 – 8 January 1642) was an Italian <span class="wiki_link_ext">physicist, <span class="wiki_link_ext">mathematician  , <span class="wiki_link_ext">astronomer  , and <span class="wiki_link_ext">philosopher  who played a major role in the <span class="wiki_link_ext">Scientific Revolution.
 * Galileo**

__Contributions:__ During his life, Galileo made a number of contributions to the science of astronomy, including advancing the telescope. Galileo, the first to conduct systematic studies of uniformly accelerated motion, also discovered the four largest satellites of Jupiter. The phrases "the father of modern observational astronomy," "the father of science" and the "father of modern physics" have all been used to describe <span class="wiki_link_ext">Galileo.

__Short biological write-up:__ Johannes Kepler (December 27, 1571 – November 15, 1630) was a <span class="wiki_link_ext">German mathematician, <span class="wiki_link_ext">astronomer  and <span class="wiki_link_ext">astrologer  , and key figure in the 17th century <span class="wiki_link_ext">scientific revolution. He was a religious man, who found a way to credit God for each and every discovery he would make, not to mention his own life and career paths. He lived in poverty, and died in poverty.
 * <span class="wiki_link_ext">Johannes Kepler **

__Contributions:__ After Tycho Brahe’s death, his assistant, <span class="wiki_link_ext">Johannes Kepler used Tycho Brahe’s observations to calculate his own three laws of planetary motion. (Contributed a mathmatical law of motion to astronomy) Kepler was able to make so significant a contribution to astronomy and physics because of the precise data he had acquired from Tycho Brahe. 1. The __orbit__ of every __planet__ is an __ellipse__ with the sun at one of the foci. An ellipse is characterized by its two focal points; see illustration. Thus, Kepler rejected the ancient Aristotelean and Ptolemaic and Copernican belief in circular motion. 2. A __line__ joining a planet and the sun sweeps out equal areas during equal intervals of time as the planet travels along its orbit. This means that the planet travels faster while close to the sun and slows down when it is farther from the sun. With his law, Kepler destroyed the Aristotelean astronomical theory that planets have uniform __velocity__. 3. The __squares__ of the __orbital periods__ of planets are directly __proportional__ to the __cubes__ of the __semi-major axes__ (the "half-length" of the ellipse) of their orbits. This means not only that larger orbits have longer periods, but also that the speed of a planet in a larger orbit is lower than in a smaller orbit.

__Short biological write-up:__ Sir Isaac Newton (4 January 1643 – 31 March 1727 was an <span class="wiki_link_ext">English physicist, <span class="wiki_link_ext">mathematician  , <span class="wiki_link_ext">astronomer  , <span class="wiki_link_ext">natural philosopher  , <span class="wiki_link_ext">alchemist  , and <span class="wiki_link_ext">theologian  who is considered by many scholars and members of the general public to be one of the most influential men in <span class="wiki_link_ext">human history.
 * Isaac Newton**

__Contributions:__ Newton advanced the Scientific Revolution with his "Mathematical Principles of Natural Philosophy" that described the three laws of motion and universal gravitation. Newton was the first to use the Latin term gravitas (weight) to describe the force of gravity. The refracting telescope was invented by him.


 * Major discoveries and achievements**

Nicholas Copernicus discovered that the sun was the centre of our solar system, not Earth as previously believed.
 * Heliocentric Worldview**

This changed the entire perception of the universe and with this we were able to make more advances in astronomy and science. However, this angered the Catholic Church as they believed, as it brought about uncertainty about the human role in the universe, which was believed to be the most dominant, as God had created humans. This also questioned God’s location in the universe.
 * Significance of introduction of heliocentric Worldview**

A man named Hans Lipperhey invented the telescope but Galileo was the one who improved it to a magnification of 30x as well as introduce it to the rest of the world.
 * Invention of Telescope**

Galileo was the first astronomer to use it to observe the heavens. This invention made it possible for scientists to see further into the heavens then before, thus paving the way for future discoveries. Previously, scientists had used inferential and deductive reasoning to figure out the way of the skies and stars but with the invention of the telescope, science started taking on a more observational approach, which resulted in a more reliable and accurate Scientific Method.
 * Significance of invention of telescope**

Isaac Newton formulated the theory of Gravity in 1666 and this explained many earlier phenomenon observed by astronomers and scientists, for example planetary motion. Gravity refers to the force of attraction between all masses in the universe; especially the attraction of the earth's mass for bodies near it.
 * Newton’s discovery of Gravity**

Gravity explained the orbit of the planets and how the Sun affected the speed of planetary motion, which was a phenomenon that had been puzzling astronomers for years. It also served as further proof for the heliocentric view of the universe.
 * Significance of theory of Gravity**

__space.about.com__ [|www.aboutseti.com/articles/famous-astronomers/index.php] __en.wikipedia.org/wiki/Timeline_of_astronomy__ [|www.mhhe.com/physsci/astronomy/arny/.../timeline2.mhtml] [|http://www.wsu.edu/~dee/ENLIGHT/SCIREV.HTM] [|http://mars.wnec.edu/~grempel/courses/wc2/lectures/scientificrev.htm] [|http://wikipedia.com]
 * References**