Copernican Revolution: Nicolaus Copernicus (1473 - 1543) Heliocentric Model Tycho Brahe (1546 -1601) Galileo Galilei (1564 - 1642) Copernican Revolution Flaws of Ptolemaic System: Flaws of Ptolemaic System Uniform circular motion only approximates the actual motion of the planets Over centuries errors in predicted locations of planets accumulated To account for errors revisions to model get very complicated Epicycles on epicycles Philosophical view: Equant issue Moving the Earth away from the center compromises geocentricity To account for retrograde motion planets are circling imaginary points; what holds them there? NICOLAUS COPERNICUS (1473 - 1543) Father of Modern Astronomy: NICOLAUS COPERNICUS (1473 - 1543) Father of Modern Astronomy Invented Copernican Heliocentric Model All planets (including Earth) orbit the Sun! Inferior Planets : Mercury, Venus Superior Planets : Mars, Jupiter, Saturn Added Later: Uranus, Neptune, Pluto Copernicus’s Heliocentric System: Copernicus ’ s Heliocentric System Planets are in circular orbits undergoing uniform circular motion Inner planets move faster than outer planets Creates “ apparent ” retrograde motion when an inner planet overtakes an outer planet Advantages : Find sidereal periods of planets Find orbit sizes of planets (relative distances to Sun) Problem : Same accuracy problems in predictions as Ptolemaic Model Retrograde Motion in the Copernican Heliocentric System: Retrograde Motion in the Copernican Heliocentric System Geocentric vs. Heliocentric: Geocentric vs. Heliocentric Which is the center of the solar system: the Earth or the Sun? How do you know? (How can you prove it?) PowerPoint Presentation: Copernican Planetary System Eastern Quadrature Western Quadrature Inferior Planets: Inferior Planets Inferior Conjunction : Planet between Earth and Sun Superior Conjunction : Sun between Earth and planet Greatest Elongation ( Eastern or Western ) : Largest angle planet is from Sun as seen from Earth Mercury 22 Venus 46 Superior Planets: Superior Planets Opposition : Earth between Sun and planet Sun/planet 180 apart in sky Conjunction : Sun between Earth and planet Sun/planet 0 apart in sky Quadrature ( Eastern or Western ) : Planet is 90 from Sun as seen from Earth PowerPoint Presentation: Copernican Planetary System Eastern Quadrature Western Quadrature Which planet will never reach a conjunction as seen from the Earth?: Which planet will never reach a conjunction as seen from the Earth? Mercury Mars Jupiter Saturn All of these reach a conjunction Saturn is closest to the Earth during . . .: Saturn is closest to the Earth during . . . Opposition Inferior Conjunction Superior Conjunction Greatest Elongation Quadrature PowerPoint Presentation: Copernican Planetary System Eastern Quadrature Western Quadrature Periodicities: Periodicities Sidereal Period: Period of a planet ’ s rotation or revolution relative to stars (true period) Synodic Period: Period of a planet ’ s revolution or motion in sky as seen from Earth with respect to the Sun Time interval for the repetition of a particular configuration in the sky Example: Synodic period of Mars is from one opposition to the next opposition Synodic and Sidereal Periods of the Planets: Synodic and Sidereal Periods of the Planets Planet Synodic Period Sidereal Period Mercury 116 days 88 days Venus 584 days 225 days Earth ----- 1.0 year Mars 780 days 1.9 years Jupiter 399 days 11.9 years Saturn 378 days 29.5 years Uranus 370 days 84.0 years Neptune 368 days 164.8 years Pluto* 367 days 248.5 years *Dwarf Planet PowerPoint Presentation: Mars and Venus have the longest synodic periods. Why? Synodic Period of Mercury: Synodic Period of Mercury Note: Synodic Periods are not related to the stars at all! Why is Copernican model better than Ptolemaic model?: Why is Copernican model better than Ptolemaic model? Note: Could not make better predictions of celestial events! Can determine distances using trigonometry Distances to inferior planets Distances to superior planets Greatest Virtue: RELATIVELY SIMPLE Occam ’ s Razor : The simplest description of nature is most likely to be most correct and every description of nature should be as simple as possible. Average Distance of the Planets from the Sun: Average Distance of the Planets from the Sun Planet Copernican Value Modern Value Mercury 0.38 AU 0.39 AU Venus 0.72 AU 0.72 AU Earth 1.00 AU 1.00 AU Mars 1.52 AU 1.52 AU Jupiter 5.22 AU 5.20 AU Saturn 9.07 AU 9.54 AU Uranus ----- 19.19 AU Neptune ----- 30.08 AU Pluto* ----- 39.53 AU *Dwarf Planet Distances to Inferior Planets: Distances to Inferior Planets Measure angle of greatest elongation (angle W) Use trig: sin W = B/C B = Sun—Inferior planet distance C = Earth—Sun distance (1 A.U.) Sun Earth Inferior Planet W A B C Distances to Superior Planets: Distances to Superior Planets Measure the synodic period of the superior planet Determine sidereal period (S) Determine time it takes to go from opposition to eastern quadrature (T) T/S = Z/360 0 Use trig: cos Z = A/C C = Sun—superior planet distance A = Earth—Sun distance (1 A.U.) Sun Earth Superior Planet Z A B C Retrograde Motion: Copernicus vs. Ptolemy: Retrograde Motion: Copernicus vs. Ptolemy Ptolemy Copernicus Retrograde Motion & Opposition of Mars from 2010: Retrograde Motion & Opposition of Mars from 2010 YouTube: http://www.youtube.com/watch?v=72FrZz_zJFU Note: Why it happens (text and animation of Mars against background stars) Appearance of Mars in the sky Where opposition is in the retrograde loop TYCHO BRAHE (1546 - 1601): TYCHO BRAHE (1546 - 1601) Supported Geocentric System Sun and Moon orbited Earth Other planets orbited Sun Most accurate ever pre-telescopic observations of positions of stars and planets No evidence for stellar parallax!! Realized Copernican model could be correct if stars were 1000s times farther than Sun Rejected this idea as absurd (actually true!!) GALILEO GALILEI (1564 - 1642) The First Modern Scientist: GALILEO GALILEI (1564 - 1642) The First Modern Scientist Defended Copernican Heliocentric System First modern experimental physical scientist Carried out experiments to determine how nature works instead of appeal to prior authority Most people at this time appealed to the wisdom of Greek philosophers, primarily Aristotle First astronomer to use a telescope Built his first refracting telescope 1609 PowerPoint Presentation: Galileo ’ s Telescope Galileo’s Telescopic Discoveries: Galileo ’ s Telescopic Discoveries 4 brightest and largest moons of Jupiter Galilean Satellites: Io, Europa, Callisto, Ganymede Saw that the moons orbit Jupiter Surface features on Moon Craters, Mountains, Plains Called Plains “ Maria ” (Italian for “ seas) Phases of Venus Undergoes the same phases as the Moon Milky Way composed of many faint stars Planets are disks / Stars are points Sunspots Behaved erratically disappearing and appearing Showed Sun rotates approximately once per month Saturn ’ s Rings Galileo: Galileo What is Galileo ’ s single most important telescopic observation? Why? PowerPoint Presentation: Sunspots Phases of Venus Saturn Galileo's Sketches Moon Galileo’s Sketch of Jupiter and its Moons: Galileo ’ s Sketch of Jupiter and its Moons Galilean Satellites: Galilean Satellites View from a modern small telescope “ a small system like our own ” -- Galileo Venus and the Heliocentric Model: Venus and the Heliocentric Model Venus and the Ptolemaic Model: Venus and the Ptolemaic Model Phases of Venus: Phases of Venus Near Inferior Conjunction Large Crescent Phase Near Superior Conjunction Small Gibbous Phase How Galileo’s work undermined the Ptolemaic model: How Galileo ’ s work undermined the Ptolemaic model Moons of Jupiter move with Jupiter Earth is not the center of all motion “ A small system like our own ” Phases of Venus Must orbit Sun to see all phases Large crescent -- close to Earth (inferior conjunction) Small gibbous -- far from Earth (superior conjunction) Ptolemaic model requires crescent phase always Craters/Mountains on Moon Not perfect sphere imperfections Science vs. Religion: Science vs. Religion The Galileo Affair Galileo Biography : Galileo ’ s Daughter by Dava Sobel Videos : Starry Messenger Galileo ’ s Battle for the Heavens PowerPoint Presentation: “ In questions of science the authority of a thousand is not worth the humble reasoning of a single individual. ” -- Galileo Galilei (1564-1642) PowerPoint Presentation: “ I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use. ” -- Galileo Galilei (1564-1642) PowerPoint Presentation: “ The Bible tells us how to go to Heaven, not how the heavens go. ” -- Galileo Galilei (1564-1642) PowerPoint Presentation: Inferior Conjunction Opposition Conjunction Superior Conjunction Earth Orbit Earth Sun Copernican Planetary System Mercury is farthest from the Earth during . . .: Mercury is farthest from the Earth during . . . Opposition Inferior Conjunction Superior Conjunction Greatest Elongation Quadrature PowerPoint Presentation: Astronomers were full of emotions Trying to predict orbital motions. Copernicus solved the riddle: He put the Sun in the middle, And laid to rest all the other old notions .