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ISP205 Section 2, Section ID: 577649 My notes: Lecture #3 on Tuesday 1-16-01 12:40pm – 2:00 pm Handouts: Quiz Kepler Bubble sheet Bring: Syllabus and schedule Topics: 1. Review previous lecture 1. Homework: dont need paper 2. Ecliptic: path of the sun along the celestial shpere (west to east) 3. Planets and Moon move on or close to the ecliptic. Planets show retrograde motion. 4. Milky way (galactic equator) almost vertical 5. Precession: North celestial pole moves around every 26000 years. 2. Example for scientific method – evolution of heliocentric model of solar system go through history. 1. Aristotele (384 BC - 322 BC) Work based on a priori philosophical speculation, not observation, but mixed in observations (earth is not moving, heavier bodies fall faster, but earth is a sphere as everything tends to move towards its center and observation of lunar eclipses which show bend shadow !!!) 2. Aristarchos of Samos 310 BC – 230 BC DEMO: show picture from Redshift (the Greeks, Pg. 5,6) pull sun forth and back to show dependence, say need distance to moon - later determined distance to the sun measuring angle between moon and sun at exactly first quarter (sun-moon and moon-earth axis perpendicular). Moon distance known from parallax across earth. First heliocentric model of solar system (maybe because he knew from distance of sun that it has to be so much bigger and can therefore not revolve around something much smaller). Result: 6 times to close ! 3. Eratosthenes 276 BC - 196 BC skip( mention briefly and point to book) but say- greeks new how big earth and how far away from sun … (would be the Greeks, Pg 14,15,16,20 in Presentation) determined circumference of earth by using difference of angle of sunlight at 2 different places – at one place deep well – perpendicular sun rays – then at Alexandria stick showed 7 degree. So know that its 7 degree latitude difference ! so Columbus could have known how far it is to India the other way around the earth – and in fact some people at the time could have told him probably. 4. Claudius Ptolemy (100AC – 160AC) Almagest: foundation of theory of solar system for next centuries Tetrabiblios: foundation of astrology. Integration of planet astrology of Babylonians with zodiac astrology of Egyptians. Epicycles explained movements of planets by preserving the circle as the standard shape. Earth centered because of absence of parallax – scientific argument !!! Redshift demo: Ptolemy: Epicycles: The greeks, Pg24 Parallax: Student demo, (SKIP ! The greeks Pg 11) 5. Nicolas Copernicus (1473 – 1543) picture Redescovered Aristarchos idea of heliocentric solar system as a quote in Archimedes writings. Noticed that all observations could be explained much easier and that calculations of solar system movements, also calendars, would be much simpler. Still needed a few epicycles as he still used circles as planetary orbits. Published it as a simplification scheme – not truth – and only banned 70 years later by catholic church because written in Latin. 6. Galileo Galilei (1564-1642) picture Founded modern scientific method of careful observations to test a hypothesis. First man to use a telescope to look into the night sky. Found phases of Venus ahich proved that venus orbits the sun. Found hints that Copernicus ideas could be correct a. Milky Way individual stars b. Moon not some heavenly thing, but an object with a landscape like earth - Redshift Presentation: C&G Pg. 9 c. Sunspots (not helio centr. Model – maybe skip) Redshift C&G Pg. 10 d. Moons of Jupiter (saw 4 of them, there are 16). Proves that something can orbit around an object that itself is orbiting another object without being left behind Redshift C&G Pg. 11 e. Phases of Venus First Proof that Prolemy’s model is wrong (but Brahes compromise could still work) Redshift C&G Pg 14: original observation Scanned image for origin of phases of venus ask: which one heliocentric, which one earth centered (vote ?) Point: sometimes venus between earth and sun, but sometimes not. Wanted to promote heliocentric model, but could not explain lack of parallaxe. Used his wrong theory of tides to prove that earth is moving around the sun (could not explain 2 tides !!!). Pope Urban VIII was well educated man and admirer of Galileo and argued with him about tide theory. Galileo wrote his “Dialogue” bashing the church not buying his arguments for a heliocentric model – pope Urban VIII happened to be away when manuscript was sent to him and his chief censor did not understand it and let it pass. Pope was angry and banned book (doing Galileo a favor because it prevented embarassment with wrong theory of tides) arguing that there is no evidence for it and that tide theory is wrong – so he did not want to reinterpret bible based on that. Galileo did not revoke – lifelong house arrest. Other things Galileo found: foundation of mechanics (discussed later) (with Newton) 7. Tycho Brahe (1546-1601) picture Most accurate observer of his time, without telescope but nice observatory of an Danish island Hveen (picture) . Countless observational data of movements of planets and positions of stars (1004 star positions published in a catalog). Thought if Copernicus is right he must find a parallaxe. Didn’t find it – assumed earth is center and sun moves around earth. BUT he accepted the simplifications in Copernicus idea and assumed all other planets move around sun. This compromise was accepted by catholic church, which had point of view that reinterpretation of bible was ok if enough evidence was presented. Purely scientific arguments !! Dec 10, 1566 he gets into an argument with a danish noble man Manderup Parsberg about who’s the best mathematician. At Dec 29 Tycho loses part of his nose in a duel with Parsberg. He then wore a silver replacement for the rest of his life. His death is also debated – some rumours say he had a rupture of his bladder after a too large meal (others mercury poisoning) 8. Johannes Kepler (1571-1630) Astrologer and Mathematician. Sought employment with Brahe because of his bad eye sight, because of his strong interests in stars he wanted to use his observational data. But Brahe was difficult character and after another fight with Danish King he left Denmark and whent to Prague. There Kepler managed to become hi sassitant, but he did not let him use the data. When Brahe died, papers had to go to legal heirs, but Kepler stole the papers. Discovery: After 10 years trying he found Keplers Laws about the Planets a. The orbit of the planets around the sun is an ellipse, with the sun being at one focus. Show picture of ellipse b. The straight line joining a planet and the Sun sweeps out equal areas in space in equal amounts of time Show picture First: Redshift Presentation: Keplers Laws, pg 6 Means: at shorter distance planet moves faster !!! Then show picture of areas c. The orbital period of a planet is related to the semi major axis of its elliptical orbit. If we measure period P in years and the semi major axis in AU (average distance earth-sun) then simple: (semi major axis)3 = (period)2 or A3=P2 - the further away the planet the slower (remember Redshift demo Do an example: Jupiter 5.2AU then P2 = 5.23 therefore P=11.86 years !!! 9. Summary evidence for heliocentric solar system a. Simpler, and with Kepler only accurate description of planet motions (epicycles had still small deviations !!!) b. Landscapes on Moon: Earth could be a celestial object as well (so far some claimed that celestial bodies are something completely different than the earth) c. Moons around Jupiter: something that moves can still have other objects orbiting around it (Moon is not left behind my moving earth !!!) d. Phases of Venus: other planets orbit sun. Why not earth ?? But final proof had to wait until: 1. James Bradley 1728: found Abberration (final proof of moving earth) (starlight comes under angle when earth moves, but angle is opposite if opposite direction, so stars describe ellipse on sky (~20.48’’ diameter) bigger effect than parallax !!! 10. F.W. Bessel 1838 First detection of stellar parallax (additional proof of moving earth) from star 61 Cygni (0.29 arc sec) – 66 trillion miles Material: Board and pen for aberration demo Backup: To do: Overview History of Astronomy: 2. Aristotele (384 BC - 322 BC) Work based on a priori philosophical speculation, not observation, but mixed in observations (earth is not moving, heavier bodies fall faster, but earth is a sphere as everything tends to move towards its center and observation of lunar eclipses which show bend shadow !!!) 3. Aristarchos of Samos 310 BC – 230 BC determined distance to the sun measuring angle between moon and sun at exactly first quarter (sun-moon and moon-earth axis perpendicular). Moon distance known from parallax across earth. First heliocentric model of solar system (maybe because he knew from distance of sun that it has to be so much bigger and can therefore not revolve around something much smaller). Result: 6 times to close ! 4. Eratosthenes 276 BC - 196 BC determined circumference of earth by using difference of angle of sunlight at 2 different places – at one place deep well – perpendicular sun rays – then at Alexandria stick showed 7 degree. So know that its 7 degree latitude difference ! 5. Hipparcos 190 BC – 120 BC discovered precession by comparing his star catalogue to observations made 150 years earlier. Also established magnitude system 6. Claudius Ptolemy (100AC – 160AC) Almagest: foundation of theory of solar system for next centuries Tetrabiblios: foundation of astrology. Integration of planet astrology of Babylonians with zodiac astrology of Egyptians. Epicycles explained movements of planets by preserving the circle as the standard shape. Earth centered because of absence of parallax – scientific argument !!! 7. Nicolas Copernicus (1473 – 1543) Redescovered Aristarchos idea of heliocentric solar system as a quote in Archimedes writings. Noticed that all observations could be explained much easier and that calculations of solar system movements, also calendars, would be much simpler. Still needed a few epicycles as he still used circles as planetary orbits. Published it as a simplification scheme – not truth – and only banned 70 years later by catholic church because written in Latin. 8. Tycho Brahe (1546-1601) Most accurate observer of his time, without telescope but nice observatory of an Danish island Hveen. Countless observational data of movements of planets and positions of stars (1004 star positions published in a catalog). Thought if Copernicus is right he must find a parallaxe. Didn’t find it – assumed earth is center and sun moves around earth. BUT he accepted the simplifications in Copernicus idea and assumed all other planets move around sun. This compromise was accepted by catholic church, which had point of view that reinterpretation of bible was ok if enough evidence was presented. Purely scientific arguments !! Dec 10, 1566 he gets into an argument with a danish noble man Manderup Parsberg about who’s the best mathematician. At Dec 29 Tycho loses part of his nose in a duel with Parsberg. He then wore a silver replacement for the rest of his life. His death is also debated – some rumours say he had a rupture of his bladder after a too large meal (others mercury poisoning) 9. Johannes Kepler (1571-1630) Astrologer and Mathematician. Sought employment with Brahe because of his bad eye sight, because of his strong interests in stars he wanted to use his observational data. But Brahe was difficult character and after another fight with Danish King he left Denmark and whent to Prague. There Kepler managed to become hi sassitant, but he did not let him use the data. When Brahe died, papers had to go to legal heirs, but Kepler stole the papers. Tried several shapes and after 10 years of study found the ellipse. Could explain all of Brahes observations ! 3 Laws of Kepler ! 10. Galileo Galilei (1564-1642) Founded modern scientific method of careful observations to test a hypothesis. First man to use a telescope to look into the night sky. Found phases of Venus ahich proved that venus orbits the sun. Wanted to promote heliocentric model, but could not explain lack of parallaxe. Used his wrong theory of tides to prove that earth is moving around the sun (could not explain 2 tides !!!). Pope Urban VIII was well educated man and admierer of Galileo and argued with him about tide theory. Galileo wrote his “Dialogue” bashing the church not bying his arguments for a heliocentric model – pope Urban VIII happened to be away when manuscript was sent to him and his chief censor did not understand it and let it pass. Pope was angry and banned book (doing Galileo a favour because it prevented embarassement with wrong theory of tides) arguing that there is no evidence for it and that tide theory is wrong – so he did not want to reinterpret bible based on that. Galileo did not revoke – lifelong house arrest. 11. Isaac Newton (1643-1727) 3 laws of Newton explain all Keplers laws 12.