| Background | Pythagoras |
| Ptolemy | Copernicus |
| Johannes Kepler | Galileo Galilei |
| Sir Isaac Newton | Edmund Halley |
| Albert Einstein | Stephen Hawking |
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One of the most powerful creations of Greek science was the mathematical astronomy created by Hipparchus in the second century B.C. and given final form by Ptolemy in the second century A.D. Ptolemy's work was known in the Middle Ages through imperfect Latin versions. In fifteenth-century Italy, however, it was brought back to life. George Trebizond, a Cretan emigre in the curia, produced a new translation and commentary. These proved imperfect and aroused much heated criticism. But a German astronomer, Johannes Regiomontanus, a protege of the brilliant Greek churchman Cardinal Bessarion, came to Italy with his patron, learned Greek, and produced a full-scale "Epitome" of Ptolemy's work from which most astronomers learned their art for the next century and more. Copernicus was only one of the celebrities of the Scientific Revolution whose work rested in large part on the study of ancient science carried out in fifteenth-century Italy. (The Revival Of An Ancient Science) A pre-Socratic Greek philosopher, Pythagoras of Samos, Ionia, is mostly known through his work as recorded by his followers, the Pythagoreans. His followers believed that everything in the universe, including abstract ideas, could be quantified and expressed in numerical values. Perhaps what Pythogoras is most noted for is his discovery of the Pythagorean theorem. Essentially, the theorem helped other mathematicians including Euclid to form assumptions and help advance the mathematics. In the field of the rising science of pre-astronomy, Pythagoras paved a path for a new astrology that included an element of concrete mathematics, which would prove helpful in the future of astronomy.
The Pythagorean Theorem proves that the sum of the squares of the lengths of the sides of a right triangle is equal to the square of the length of the hypotenuse. This proof became very helpful in the calculation of astronomical distances. Ptolemy is the Greek who left the greatest legacy to the future of astronomy. He is the third of the legendary Alexandrian men, living near 150 A.D. He had access to the wealth of knowledge left by earlier scientists, and from this, he synthesized the first comprehensive model of the universe. Aristotle gave the philosophical framework, and Ptolemy built a specific mathematical model based upon his teachings. Ptolemy was bothered that the current universe view could not reproduce or predict accurately certain observed phenomena, such as planetary retrograde motion, and the fact that Mars appears dimmer at times. So he began to devise a new system, whereby he applied Euclid's geometry to the universe. Under the Ptomlemaic system, planets orbited around the Earth on a deferent, which is simply a circle around Earth. But Ptolemy said that the deferent did not have the earth at the center, but were instead eccentric. An eccentric is a deferent with the earth slightly off-center. Ptolemy said that planets appear to speed up and slow down because they do not revolve around the earth at a uniform rate. Instead, he found a point, the equant, which was equal and opposite the earth from the center. If one were to stand at the equant, he would see the planet going around at a uniform rate. Finally, to explain retrograde motion, Ptolemy decided that the planet traveled along an epicycle, or a sub-orbit. This epicycle travelled along the deferent.
This model, first appearing in Ptolemy's book Almagest, was the first to tackle apparent incongruities in the Aristotelian model. It is complicated because Ptolemy felt the need to keep Plato and Aristotle's law that planets move in uniform circular motion at a uniform rate. His model allowed this to happen while still explaining why eccentric observations occur, and was the standard text for astronomical study until Copernicus. Michael Maestlin, the tutor of Johannes Kepler, actually owned a copy of Almagest, and Kepler was brought up with Ptolemy's world view.  Nicolaus Copernicus (1473-1543)
Latinized form of Niclas Kopernik, the name of the founder of the heliocentric planetary theory; born at Torun (Thorn), 19 February, 1473, died at Frauenburg, 24 May, 1543. Copernicus proposed that a rotating Earth revolving with the other planets about a stationary
central Sun could account in a simpler way for the same observed phenomena of the daily rotation of the heavens, the annual
movement of the Sun through the ecliptic, and the periodic retrograde motion of the planets. He was encouraged to publish his theories, but he was reluctant to do so. However, he relented and did publish them; they were handed to him the very day he died (Important Physicists and Astronomers)  Johannes Kepler (1571-1630)
The German astronomer was the first strong supporter of the heliocentric theory of Copernicus and the discoverer of the three laws of planetary motion. Always guided by the concept of beauty in the structure of the universe, and specifically by a theory of harmony in geometric figures, numbers, and music, Kepler, in his Harmonices mundi (Harmonies of the World, 1619), announced his third law--a
relationship between the orbital periods and the distances of the planets from the Sun. His belief that the Sun regulates the
velocity of the planets was a milestone in scientific thought, laying the foundation for Newton's theory of universal gravitation. The posthumous Somnium on which Kepler labored until shortly before his death, is indicative of his fertile mind. In this work, Kepler describes a journey to the Moon and discusses the existence of lunar inhabitants. A crucial link between the thought of Copernicus and that of Newton, Kepler was an important figure in the 17th-century scientific revolution (Important Physicists).  Galileo Galilei (1564-1642) Galileo studied medicine at the university of Pisa, but his real interests were always in mathematics and natural philosophy. He is chiefly remembered for his work on free fall, his use of the telescope and his employment of experimentation. In 1592 Galileo was appointed professor of mathematics at the university of Padua (the university of the Republic of Venice). There his duties were mainly to teach Euclid's geometry and standard (geocentric) astronomy to medical students, who would need to know some astronomy in order to make use of astrology in their medical practice. However, Galileo apparently discussed more unconventional forms of astronomy and natural philosophy in a public lecture he gave in connection with the appearance of a New Star (now known as 'Kepler's supernova') in 1604. In a personal letter written to Kepler (1571 - 1630) in 1598, Galileo had stated that he was a Copernican (believer in the theories of Copernicus). No public sign of this belief was to appear until many years later.
In the summer of 1609, Galileo heard about a spyglass that a Dutchman had shown in Venice. From these reports, and using his own technical skills as a mathematician and as a workman, Galileo made a series of telescopes whose optical performance was much better than that of the Dutch instrument. The astronomical discoveries he made with his telescopes were described in a short book called Message from the stars (Sidereus Nuncius) published in Venice in May 1610. It caused a sensation. Galileo claimed to have seen mountains on the Moon, to have proved the Milky Way was made up of tiny stars, and to have seen four small bodies orbiting Jupiter. These last, with an eye on getting a job in Florence, he promptly named 'the Medicean stars' (Galileo Galilei). There eventually followed some expression of interest by the Inquisition. According to the Holy Church, Copernicanism was in contradiction with Scripture, and in 1616 Galileo was given some kind of secret, but official, warning that he was not to defend Copernicanism. Just what was said on this occasion was to become a subject for dispute when Galileo was accused of departing from this undertaking in his Dialogue concerning the two greatest world systems , published in Florence in 1632. Galileo, who was not in the best of health, was summoned to Rome, found to be vehemently suspected of heresy, and eventually condemned to house arrest, for life, at his villa at Arcetri. He was also required to state an oath before the Holy Roman Church in which he was forced to renouce his belief that the Sun was at the center of the Solar system.  Microsoft Encarta Sir Isaac Newton was an English mathematician and physicist He is considered one of the greatest scientists in history, who made important contributions to many fields of science. His discoveries and theories laid the foundation for much of the progress in science since his time. Newton was one of the inventors of the branch of mathematics called calculus. He also solved the mysteries of light and optics, formulated the three laws of motion, and derived from them the law of universal gravitation. Newton's laws of motion are the most fundamental natural laws of classical mechanics. Sir Isaac Newton stated them in his book Principia Mathematica (1686). Taken together, Newton's three laws of motion underlie all interactions of force, matter, and motion except those involving relativistic and quantum effects.
Edmund Halley was a talented multidisciplinary scientist and was largely responsible for persuading Newton to publish his work. Halley's analysis of what is now known as Halley's comet is a perfect example of the scientific method in action. He observed that the comets of 1456, 1531, 1607, and 1682 followed similar orbital paths around the Sun and that each appearance was separated from the previous one by about 76 years -- which was the period predicted for the orbit by Kepler's Third Law. Halley hypothesis: These events were due to the reappearance of one object on an orbit which brought it close to the Sun once every 76 years. He then went on to predict that the comet would return again in 1758. The comet was sighted, on schedule, on Christmas Day 1758 and has since borne Halley's name.
Appearances of Halley's comet have been found in historic record as far back as 2000 years.  Courtesy History of Mathematics During the late 1800’s, the field of science desperately needed a new theory to revise the old Newtonian-based physics. The laws of Newtonian principles were beginning to show problems; for example, the precession of Mercury’s orbit could not be completely accounted for. Einstein revolutionized all aspects of science and modern thought through his theories of general and special relativity and idea of equivalence. Albert Einstein was taken seriously after rigorous testing of his theories. One example is the famous advance of Mercury's perihelion. Because Newton's law did not correctly predict this, Einstein's theory gained approval for a new revolution in science. Furthermore, the eclipse experiment of 1919 helped to prove his bending of light theory. These proofs helped him to gain wider acceptance of his theories. Einstein recieved the a Nobel Prize in 1921, not for his research on relativity, but for his 1905 work on the photoelectric effect.
It was brought to my attention that I was mistaken about Einstein's birthday. I did have it listed as 1896 instead of 1879 and, as Jim pointed out to me, that would have made him only 9 years old when he won the Nobel prize. Thank you Jim for keeping me on my toes!  Famous Physicists and Astronomers Dr. Hawking is a leading figure in modern cosmology. While studying physics and mathematics at the universities of Oxford and Cambridge, Hawking learned that he had the degenerative disorder of the nervous system known as Lou Gehrig's disease. Dr. Hawking was only given 2 1/2 years to live beyond 1966. He has beaten the odds and revolutionized modern science. When he Obtained his doctorate in 1966, he set out to link quantum mechanics and relativity, the two major theories of modern physics, by developing a quantum theory of gravity. Hawking's ongoing work indicates that quantum theory supports the model of the universe known as inflationary theory. His speculations include the existence of black holes no larger than elementary particles, and multiple universes linked by tiny quantum fluctuations in space that he calls "wormholes." In 1988, Hawking published a nontechnical explanation of his work called A Brief History of Time.
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Last Updated January 5, 2000
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