Lecture_5 (1).pdf - ASTRONOMY 001 Section 1 Lecture 5...

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ASTRONOMY 001Section 1Lecture 5Mariangela Bernardi
HomeworkFirst homeworkOnCanvas, click on “Assignmentshomework_1.pdfIt covers Chapter 1-2-3It isDUE on Tuesday February 1!!!! No late homework will be accepted !!!!
TutorialsYou should have worked on the tutorialsrelated to chapters 1 to 3 (see syllabus)Scale of the UniverseSeasonsPhases of the MoonEclipseOrbits and Kepler’s LawsComplete the tutorials before the first midterm ….They will help you!
What have we learned?What was so mysteriousabout planetary motion in oursky?Like the Sun and Moon,planets usually drift eastwardrelative to the stars from nightto night; butsometimes, for afew weeks or few months, aplanet turns westwardin itsapparent retrograde motion.Easy for us to explain: occurswhen Earth passes a planet by(“laps it”) in its orbit. But difficultto explain if you think Earth isthe center of the universe.
What have we learned?Why did the ancient Greeks reject the realexplanation for planetary motion?They could not detectstellar parallax.Most Greeks concluded that Earth must bestationary, because they thought the starscould not be so far away as to make parallaxundetectable.
What have we learned?Why does modern science traceits roots to the Greeks?
How did the Greeks explainplanetary motion?
How did Copernicus, Tycho, and Keplerchallenge the Earth-centered idea?Copernicus (1473-1543):proposed Sun-centered model(published 1543)used model to determine layout ofsolar system (planetary distancesin AU)But . . .model was no more accurate thanPtolemaic model in predictingplanetary positions, because still usedperfect circles.
Nice try….But still not that good
Copernican ModelNot an Exact ModelPlanets orbit in circlesPlanets move at constant speedCould not predict the exact motion of theplanetsRequired epicycles (like Ptolemy) topredict motions of the planets
He made themost precise observationsthat had yet beenmade by devising the best instruments available before theinvention of the telescope.Hisobservations of planetary motion, particularly that ofMars, provided the crucial data for later astronomers likeKepler to construct our present model of the solar system.He made observations of asupernova(literally: nova= "newstar") in 1572It was a “real” star…..far away.The heavens were notimmutable.Brahe made careful observations of acometin 1577. Bymeasuring the parallax for the comet, he was able to showthat thecomet was further away than the Moon. Thiscontradicted the teachings of Aristotle, who had held thatcomets were atmospheric phenomenaHe made the best measurements that had yet been made inthe search forstellar parallax. Upon finding no parallax forthe stars, he (correctly) concluded that eitherthe earth was motionless at the center of the Universe,orthe stars were so far away that their parallax was toosmall to measure.

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Term
Fall
Professor
AGUIRRE
Tags
Galileo Galilei, Planet, Heliocentrism

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