9 6 10 Astro 201 Sept 2 2010 Do on line prac ce quiz 2 see d2l Homework 2 posted on web page aHer class Today Ancient Greeks Ptolemy V Copernicus retrograde mo on Galileo Astronomical basis for calendars Tycho Kepler Newton Despite Aristarchus for 2000 years a GEOCENTRIC model of the Universe was favored STARS a xed to the celes al sphere Moon Planets and the Sun are between the EARTH and STARS EARTH at the center 1 9 6 10 PTOLEMY 90 168 AD Ptolemy s ALMAGEST was translated into La n in 1496 GEOCENTRIC Earth at center Copernicus 1473 1543 Heliocentric Model Sun at the center 2 9 6 10 Ptolemy s Epicycles In order to understand the mo on of the planets in the sky Ptolemy s model had to be modi ed In terms of the heliocentric model the planets orbit the Sun in ellipses not circles Retrograde mo on of the planets with respect to the stars required EPICYCLES Eclip c the fact that the planets orbit the Sun in a plane means that they always appear to lie on a great circle on the sky called the eclip c 3 9 6 10 Retrograde mo on The planets some mes appear to be traveling west to east unlike the stars and Sun which always go east to west Next slide anima on Astronomy Picture of the Day for Dec 20 2001 Jupiter and Saturn showing retrograde mo on Combining 23 pictures taken at 2 week intervals from June 2000 May 2001 Planet wanderer 4 9 6 10 Ptolemy s explana on for retrograde mo on of the planets 5 9 6 10 Earth O Center Earth Equant Epicycle Deferent The planet moves along its epicycle as the epicycle moves along the deferent around the Earth To make the observa ons as accurate as possible it was necessary to place the Earth slightly o center of the orbits but to preserve symmetry that meant that there was an equal place Equant opposite the Earth from the center The combined mo on of the planet and the resul ng retrograde mo on are shown Copernicus explana on for retrograde mo on 6 9 6 10 Copernicus On the Revolu on of the Heavenly Spheres Published at the me of his death in 1543 Major Conclusions 1 The planets orbit the Sun 2 The apparent daily mo on of the Sun and stars is the result of the Earth s rota on 3 The stars are much farther away than the Sun Heliocentric model distance from Sun to stars must be much greater than distance from Sun to Earth Since Earth orbits Sun stars should show parallax a shiD in apparent posiEon over the course of half a year 7 9 6 10 OBSERVATION Parallax of stars is TOO SMALL to be seen by the naked eye Not observed un l 1800s ImplicaEon distance to stars is several thousand mes Earth Sun distance Parallax Unit of distance the PARSEC A star which is one parsec from Earth shows a parallax of one arcsecond 1 d p Remember 360 degrees in a circle 60 arcminutes per degree 60 arcseconds per arcminute 8 9 6 10 Reac ons to Copernicus On March 5 1616 Copernicus work was banned from being taught and discussed by the Congrega on of the Index un l corrected It stayed on this list of prohibited books and teachings un l 1822 MarEn Luther 1483 1546 Copernicus is a fool who wishes to reverse the en re scheme of astronomy but sacred scripture tells us that Joshua commanded the Earth to stand s ll not the Sun Giordano Bruno 1548 1600 burned at the stake for advoca ng that stars are suns in their own right and that there is a plurality of worlds like the Earth Cosmological Models Version 1 0 Superdome model Version 2 0 Geocentric model Version 3 0 Heliocentric model v 1 0 v 2 0 v 3 0 9 9 6 10 Which is right Occam s Razor Pluralitas non est ponenda sine neccesitate plurality should not be posited without necessity Given a set of otherwise equivalent models of a phenomenon the simplest one is the best Keep it simple stupid William of Occam 1285 1349 English philosopher from Ockham Franciscan Monk Got into trouble with the Pope for advoca ng apostolic poverty Died of the Black Death while in exile Advocated Epistomological Parsimony c f Ontological parsimony Epistomology theory of knowledge Ontology what exists 10 9 6 10 Galileo Galilei 1564 1642 Italian First to use a telescope to look at the sky 1610 Siderius Nuncius The Starry Messenger Spots on the Sun the Sun rotates The Moon has mountains craters rocky surface with imperfec ons The planet Jupiter is not a pinpoint star but a disc in the sky WITH MOONS that orbit it Venus has PHASES like the MOON Galileo Galilei 1564 1642 Spots on the Sun The Sun rotates Eventually went blind 11 9 6 10 Galileo Galilei 1564 1642 The Moon Has Mountains and Valleys Galileo Galilei 1564 1642 Phases of Venus Galileo observed that Venus showed phases en rely like those of the moon from full to crescent which it must do if the Copernican theory was correct According to the Ptolemaic theory Venus would have to be a perpetual crescent 12 9 6 10 Observa ons consistent with Copernicus inconsistent with Ptolemy Galileo Galilei 1564 1642 Jupiter Has Moons Galilean Moons 4 Largest moons of Jupiter Io Europa Callisto Ganymede 13 9 6 10 Galileo Galilei 1564 1642 1632 Dialogo Dei Massimi Sistemi Dialogue on the Two Chief World Systems In Italian Not Latin For the common people Two people one representing the view of Ptolemy and other the view of Copernicus present their arguments before an intelligent layman The Pope Urban II thought that Simplico the character who upheld the views of Ptolemy in the book was a deliberate and insul ng caricature of himself 1633 Trial by Church threatened with instruments of torture forced to recant views Eppur Si Muove And yet it moves 1633 Galileo is ordered to his house in Arcetri under house arrest where he remains for the rest of his life The book remained on the index of forbidden books un l 1822 Pope John Paul II nally gave an address that admived that there had been errors in the treatment of Galileo by the church in 1992 ASIDE Contrast Galileo with Nicolas Steno 1638 1686 who laid the groundwork for the interpreta on of the fossil record See The Seashell on the Mountaintop by Alan Cutler 14 9 6 10 Modern Scien c Method 1 Observa ons and Experiments Data which describes the physical world 2 Theory Hypotheses Models Organize Facts from experiment observa ons Unifying principles Make testable predic ons Crea onism and Intelligent Design vs Evolu on The example of gravity as a scien c theory Newton s Law c 1700 AD Einstein s theory of General Rela vity c 1916 Photon versus wave descrip on of light The most interesEng scienE c quesEons to work on for a professional scienEst are those …