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History of Astronomy “ Renaissance”

History of Astronomy “ Renaissance”. The Copernican revolution!!!. Nicolaus Copernicus, 1473-1543. Polish physician and lawyer Revived Aristarchus’ idea of a Sun-centered ( Heliocentric ) universe Planets move in circular orbits about Sun Retrograde motion explained automatically;

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History of Astronomy “ Renaissance”

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  1. History of Astronomy“Renaissance” The Copernican revolution!!!

  2. Nicolaus Copernicus, 1473-1543 • Polish physician and lawyer • Revived Aristarchus’ idea of a Sun-centered (Heliocentric) universe • Planets move in circular orbits about Sun • Retrograde motion explained automatically; • No need for epicycles and deferents, etc. • Measured relative sizes of planets’ orbits

  3. Nicolaus Copernicus,Continued • Ideas did not find ready acceptance • His model did not give much better agreement with observation than Ptolemy’s • Blame lies partly on choice of circle—the perfect curve • Model implies parallax shift in star position but none seen • Earth feels at rest; no sensation of motion • Authority of Aristotle and the Church

  4. Copernicus’s Heliocentric DiagramPrinted in De Revolutionibus

  5. Forbidden • In 1616 the Catholic Church placed Copernicus’ work on its list of forbidden books “until corrected” by local ecclesiastical censors, where it remained until 1835. • Martin Luther described him as “an upstart astrologer…This fool wished to reserve the entire science of astronomy. But sacred scripture tells us that Joshua commanded the Sun to stand still, and not the Earth.”

  6. Tycho Brahe,1546-1601 • Danish nobleman; owned an island castle • Imperial Mathematician to the Holy Roman Emperor, Rudolph II • Built instruments of high accuracy (no telescopes yet) • Made precise measurements of planet positions • Observed a “new” star in 1572 (supernova) • Heavens are changeable! • The supernova showed no parallax; much farther than planets

  7. A “New Star”

  8. Tycho’s Observatory Tycho’s observatory at Uraniborg, Denmark. Tycho is seen showing the mural quadrant, a marked quarter circle on the wall, that he used to measure the altitudes at which the stars and planets crossed the meridian.

  9. Tycho Brahe, Continued • Studied path of a comet in 1577 • The comet would have had to pass through many of the perfect crystalline spheres • Liked Copernicus’ model but could not get over the “lack of stellar parallax” objection. • Compromise model • Planets circle the Sun • Sun circles the Earth Interesting Fact: Lost nose in a duel, wore a metal one.

  10. Johannes Kepler1571-1630 • Tycho’s assistant; came from a desperately poor background • Kepler’s Cosmic Mystery • “Inherited” Tycho’s notebooks • Very carefully analyzed records for Mars and concluded that … • Mars and other planets move in elliptical orbits, not circular ones • The Sun is at the focus of the ellipse, not at its center

  11. Kepler: Mystery of the Cosmos“Mysterium Cosmographicum”, 1596 • Kepler’s Cosmic Mystery – The spheres of the six planets nested in the five perfect solids of Pythagoras and Plato. • The outermost perfect solid is a cube.

  12. Kepler’s LawsFirst Truly Mathematical Description • All planets move in elliptical orbits, with the Sun at one focus of the ellipse • Line from the Sun to a planet sweeps out equal areas in equal intervals of time • Square of period (in years) = cube of orbit size (in AU) P2 = R3

  13. The Laws

  14. Kepler’s First Law & Some Geometry

  15. More on Geometry

  16. Kepler’s Second Law The two shaded sectors are equal in area.

  17. A Third Law Example • We know from observations that it takes Jupiter 11.86 years to revolve around the Sun. What is Jupiter’s distance from the Sun? P2 = R3 • Let P = 11.86 years • Then P x P= 11.86 x 11.86 = 140.66 • Therefore, R x R x R = 140.66 R = 5.2 A.U.

  18. Geosynchronous Orbit

  19. Galileo Galilei1564-1642 • Italian scientist and scholar • Studied motion of objects, but did not drop stones from the Leaning Tower of Pisa • First one to look at the sky with a telescope, 1609 • Saw craters and hills on Moon • It’s a piece of rock, not something special • Saw spots on the Sun; spots shifted in time • Sun is neither perfect, nor unchanging

  20. The Moons of Jupiter • 1610 - Galileo publishes Sidereus Nuncius (Message from the stars) which describes the astronomical discoveries he has made with his telescopes. • Harriot also observes the moons of Jupiter but does not publish his work. Observed four moons moving around Jupiter • There are other centers of motion besides “us”

  21. Galilean Moons

  22. Galileo’s Moon Drawing

  23. Sunspots Observed by Galileo

  24. Dialogue Concerning the Two World Systems • Saw immense numbers of stars in the Milky Way Existing conceptions of universe too limited • Saw phases of Venus Phases, position and apparent size of Venus could only mean that it orbited the Sun Ran into serious trouble with the Church; Galileo recanted then; the Church in 1992!

  25. Phases of Venus

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