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Unformatted text preview: The UK has over 100 henge monuments and over 900 ceremonial circles Stonehenge (built 2700 1700 BC) Stonehenge Stonehenge predict seasons Predict seasons: e.g., the Sun rises over the Heelstone at the summer solstice. Stonehenge predict eclipses?
Fred Hoyle was able to develop a method to use Stonehenge to predict eclipses ! The nature of Stonehenge is still debated How were the 25 ton lintels (crossstones) laid? Archaeologists ceremonial circle Some Astronomers great observatory with predictive power Are Hoyle's rules to predict eclipses (56 post holes divided by 3) an example of an arbitrarily complex theory, similar to epicycles? Greek Astronomy and the Dawn of Modern Astronomy: Astronomers, Mathematicians, and Philosophers Thales circa 600 BC emphasized metaphysics; one of the first to propose a model of the Universe, namely that the Earth was a disk afloat on a great sea. Pythagoras circa 540 BC emphasized mathematics; used numbers and geometry to express relationships in nature. Thales' Idea Astronomers, Mathematicians, and Philosophers Plato circa 380 BC emphasized metaphysics; the pupil of Socrates and Aristotle's teacher; he emphasized the importance of the circle in models. Aristotle circa 350 BC emphasized metaphysics; he is credited with developing a wellthoughtout model of the Universe (an Earth centered geocentric model) that persisted until the 1500s. Aristotelian World View: Geocentric (EarthCentered) Astronomers, Mathematicians, and Philosophers Aristarchus circa 280 BC he was a great Greek astronomer and mathematician who actually put forth a Suncentered heliocentric model of the Universe, but it was not accepted (mainly because stars didn't exhibit parallax, which was expected if the Earth went around the Sun because people incorrectly assumed the stars were relatively nearby); he applied geometry calculations to observations to deduce the relative sizes and distances of the Sun and Moon. Astronomers, Mathematicians, and Philosophers Eratosthenes circa 250 BC emphasized mathematics; he made observations of the angle of the Sun with respect to zenith (overhead) at different latitudes which enabled him to accurately calculate the circumference of the Earth. Astronomers, Mathematicians, and Philosophers Hipparchus circa 150 BC emphasized mathematics; one of the first to catalog the brightnesses and positions of stars in a comprehensive way; credited with introducing the concept of epicycles. Ptolemy circa 140 AD emphasized mathematics; he refined the Aristotelian model of the Universe with a system of epicycles that could explain retrograde planetary motion; he also wrote the famous Almagest. Emphasis on Metaphysics Thales Plato Aristotle Emphasis on Mathematics Pathagoras Hipparchus Ptolemy Astronomers, Mathematicians, and Philosophers Alighieri (Dante) circa 1300s he made drawings which showed the location of heaven and hell in the Aristotelian Universe based on theological teachings of Thomas Aquinas; this became one of the foundations of the Christian church at that time. A Theocratic View Emerges from the Dark Ages Aquinas Dante Aristotelian World View: Geocentric (EarthCentered) The stars and planets were attached to crystalline spheres. Ptolemaic World View: Geocentric but with epicycles to fix backward looping planet motions Circles on Circles The influence of Plato Sun's angle at noon at different latitudes gives the circumference (or diameter) of Earth Eratosthenes determination was precise, accurate to 3%. Why no parallax? the stars are too far away to observe it (Copernicus)! World Views Aristotelian [Earthcentered (geocentric) model which used rotating crystalline spheres] Ptolemaic [Earthcentered (geocentric) model which used epicycles to explain the planets' retrograde motions] Theocratic [Earthcentered (geocentric) based on the theology of Thomas Aquinas, including a place for heaven and hell] Copernican [Suncentered (heliocentric) which used a rotating Earth and more naturally explained the planets' retrograde motions] Theocratic World View: largely based on Aristotelian ideas The synthesis of Saint Thomas Aquinas: a place for hell, purgatory, angels, and heaven. Astronomers, Mathematicians, and Philosophers Copernicus 14731543 AD he was the first to propose a comprehensive Suncentered (heliocentric) model of the Universe that became widely accepted. Rheticus he prompted Copernicus to publish his great work, De Revolutionibus. Copernicus (14731543) Afraid of ridicule, but agreed to publish De Revolutionibus on his death bed Astronomers, Mathematicians, and Philosophers Digges one of the first to seriously introduce the concept of infinity into a model of the Universe. Bruno he was the first to suggest that we live in a Universe with the Sun not at its center and that each star (possibly an infinite number of them) represent different solar systems. Bruno burned at the stake in 1600! He was more of a mystic than scientist, but his views are consistent with modern scientific views. Astronomers, Mathematicians, and Philosophers Brahe (Tycho) 15461601 AD although he never used telescopes, he is considered one of the greatest observational astronomers of all time; he made very accurate observations of planetary motions, especially Mars, which enabled Kepler to develop his 3 laws of planetary motion. Kepler 15711630 AD he showed that the Sun centered (heliocentric) model of the Universe worked better if the planets were in elliptical orbits about the Sun instead of circular orbits. Tycho Brahe (15461601) Lost his nose in a duel! Tycho's Uraniborg Castle Kepler (15711630) Kepler was Tycho's assistant. One of Kepler's earlier attempts to explain Tycho's observatins involved using nested spheres. Astronomers, Mathematicians, and Philosophers Lippershey Dutch lens maker often credited as the first to build a refracting telescope (but not for astronomy). Galilei (Galileo) 15641642 AD he did important experiments which helped reveal the laws of falling bodies; he also made observations with a telescope (he put together the first refracting telescope used for astronomical observation) which supported the heliocentric theory. Galileo (15641642) Galileo made the first astronomical telescope a refracting telescope that used lenses. Dialogue Chaos in the Church Galileo's Dialogue of the Two Chief World Systems caused chaos in the Church. Galileo has 3 scholars (clearly representing Aristotle, Ptolemy, and Copernicus) argue the merits of their views. Aristotle was named "Simplico." Galileo is brought before the Inquisition Astronomers, Mathematicians, and Philosophers Hooke great scientist of his time, but he often wrongly criticized Newton. Halley prompted Newton to publish his great work, Principia ; discovered "Halley's Comet." Newton received encouragement and criticism Halley Hooke Astronomers, Mathematicians, and Philosophers Newton 16421727 AD great synthesizer of experiments and observations who put forth the Theory of Gravity (for example, he explained Kepler's empirical 3rd Law and modified it so that it could be used to calculate the mass of a body); he also invented the reflecting telescope, calculus, and did important experiments in optics and light along the way. Isaac Newton (16421727) Many believe he was the greatest scientist of all time. World Views continued concept of an infinite Universe (Digges) concept of many solar systems (Bruno) Keplerian [circular orbits replaced by elliptical orbits] the use of astrology (many) Newtonian [gravity theory explains motions on Earth and in the sky] Aristotelian World View: Geocentric (EarthCentered) Copernican World View: Heliocentric (SunCentered) An Infinite Copernican Universe Digges modification (right) to the Copernican Heliocentric Universe (left). ...
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- Spring '08