11TodayToday’’s agendas agenda• Brief review of celestial sphere concepts• Cosmic Voyage Part I• Lecture: foundations of modern-dayastronomy• Planetarium: finish exercise; solar system,orbits, and more.• Planetarium (if time): zooming out fromEarth; overview of celestial objects; sampletours2Foundations of Modern-Foundations of Modern-Day AstronomyDay AstronomyFrom a geocentric cosmos ruled byastrology and the precise predictionsof planetary positions to a heliocentricone that obeys comprehensive laws.3Learning goalsLearning goals∆Explain what Ptolemy’s model containedand why it was accepted for so long.∆List the basic contributions of Copernicus,Galileo, Brahe, and Kepler.∆Summarize the change in thinking,technology, and/or methods that led to theacceptance of a heliocentric universe.4Early astronomy: Plato and AristotleEarly astronomy: Plato and Aristotle(Plato Plato on the left) – Geometry was themeans by which to understand theuniverse, the very principle upon whichthe universe exists.Aristotle (384Aristotle (384––322 BC)322 BC)• Universe is perfect• Uniform, circular motion representsdivine perfection• Everything revolves around the Earth• Heavens composed of concentric,rotating crystalline spheres to which thestars and planets were attached.• Outermost sphere, the "Prime Mover,"got the rest going• Only ONE grand mechanism25AristotleAristotle’’s models model6What AristotleWhat Aristotle’’s model could not explain:s model could not explain:Retrograde motion of the planets.Varying size of the Moon.Celestial objects “crashing”through the celestial sphere.7http://people.scs.fsu.edu/~dduke/nmars.html http://people.scs.fsu.edu/~dduke/nvenus.html8PtolemyPtolemy’’s model inconsistent with Aristotles model inconsistent with Aristotle’’ssPtolemy adopted instrumentalist view:Model is only an accurate calculator topredict the planet motions; reality isAristotle's model.Seeming conflict OK.http://people.scs.fsu.edu/~dduke/nptolemy.html39PtolemyPtolemy’’s model was convincings model was convincingANCIENT ASTRONOMERS convinced that theirelaborate scheme was correct because they hadingrained beliefs that:• All motion in the heavens is uniform circularmotion.• The objects in the heavens are made fromperfect material.• Objects cannot change their intrinsic properties.• The Earth is at the center of the Universe.Ptolemy’s model worked; he published his Almagest (the greatest)10∆Explain what Ptolemy’s model contained andwhy it was accepted for so long.11NicholausNicholaus Copernicus: Copernicus:ONE mechanism. Perfect circular motion. Sunneeded to be put in its rightful place. Nicolas Copernicus (b. 1473 d. 1543)became familiar with the works of Aristotle,Ptolemy, and others.Mathematician, astronomer, jurist, physician,classical scholar, Catholic cleric, governor,military commander, diplomat, economistScholars, theologians, others became“Copernicans” or “anti-Copernicans.”BUT – he had no new observations, anddid not make any himself; he hesitated topublish; model no better than Ptolemy’s.12Galileo 1564 - 1642Galileo 1564 - 1642Galileo did notGalileo did not PROVE the PROVE theCopernican system, butCopernican system, but his hisobservations provided the twistobservations provided the twistof the knife thatof the knife that led led to the to theacceptance of the heliocentricacceptance of the heliocentricmodelmodel. He DISPROVED parts. He DISPROVED partsof the geocentric model.of the geocentric model.Was first to develop and useWas first to develop and usescientific method.scientific method.Galileo (1564-1642);(1564-1642); Brahe ((1546 1546 –– 1601 1601)); Kepler ((1571 1571 –– 1630) 1630)413Moon was Moon was damaged -- Sun was not perfect!damaged -- Sun was not perfect!14Moons of Moons of JupiterJupiter werewereobserved andobserved andconclusion made thatconclusion made thatnotnot everything orbited everything orbitedEarth.Earth.Sky View Cafe15Contradictory phases of VenusContradictory phases of Venus: You choose!: You choose!http://www.youtube.com/watch?v=OlnlbZHP-jkhttp://www.youtube.com/watch?v=0Z_v7Tag4fg&NR=116TychoTycho Brahe Brahe (1546 (1546 –– 1601) 1601)Uraniborg•Born into high nobility•Designed, built, andperiodically calibratedhis instruments•Methodical in obtainingcomplete dataGalileo (1564-1642);(1564-1642); Brahe ((1546 1546 –– 1601 1601)); Kepler ((1571 1571 –– 1630) 1630)517Johannes Johannes KeplerKepler (1571 (1571 –– 1630) 1630)•Published a letter of support for Galileo•Observations of Jupiter’s satellites boostedGalileo’s work•Thirty-years war interrupted his position andthus his work.•Pulled his 3 laws from Tycho’s data“The Earth sings Mi, Fa: you may infereven from the syllables that in this ourhome misery and famine hold sway.”Galileo (1564-1642);(1564-1642); Brahe ((1546 1546 –– 1601 1601)); Kepler ((1571 1571 –– 1630) 1630)18∆List the basic contributions of Copernicus,Galileo, Brahe, and Kepler.19∆ Summarize the change in thinking, technology,and/or methods that led to the acceptance of aheliocentric
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