ASTRONOMY 202 Spring 2007: Solar System Exploration Instructor: Dr. David Alexander Web-site: www.ruf.rice.edu/~dalex/ASTR202_S07 Class 8: The Science of Astronomy [2/5/07] Announcements The First Modern Scientist: Galileo • Discoveries • The Inquisition The Hallmarks of Science Objectivity vs. Subjectivity Discussion & Questions? Chapter 3 Announcements Homework 2 Issues • Show working • Coordinate systems • Circumpolar stars Homework 3 due Wednesday Feb 7 Homework 4 available online – due Mon Feb 12 The First Modern Scientist “And perhaps this planet [Saturn] also, no less than horned Venus, harmonizes admirably with the great Copernican system, to the universal revelation of which doctrine propitious breezes are now seen to be directed towards us, leaving little fear of clouds or crosswinds.” - Letters on Sunspots , Galileo, 1613 “You cannot help it Mr. Sarsi, that it was granted to me alone to discover all the new phenomena in the sky and nothing to anybody else. This is the truth which neither malice nor envy can suppress.” - Il Saggiatore , Galileo, 1623 Galileo Galilei [1564-1642] Galileo, often wrote in Italian rather than the standard Latin for scholarly works. He also Galileo died the same year that employed a Socratic approach by making his Isaac Newton was born. arguments in the form of a dialogue between the brilliant Sagredo and the not so brilliant Simplicio with the occasional help from a third ‘neutral’ See Rice’s own Galileo Project at interlocuter, Salviati. http://es.rice.edu/humsoc/Galileo/ The Great Observer Although Galileo did NOT discover sunspots, he was the first to argue that they were a solar phenomenon. Observations of Jupiter showed 4 ‘stars’ which changed their position with time leading Galileo to determine that they orbited the planet. Galileo’s telescope observations demonstrated that the Moon’s surface was not perfectly smooth. The Phases of Venus Aristotlian System Copernican System The observation of the full cycle of the phases of Venus was proof that at least one object in the solar system orbited the Sun. Ptolemaic System Tycho System Stellar Parallax Heliocentric World View finally confirmed by observation of stellar parallax The Hallmarks of Science A word on Occam’s Razor: Modern science has ‘corrupted’ the original maxim and turned it into a ‘law of The scientific method parsimony ’. The original allowed for ‘plurality ’ when ‘necessary ’. Summary of Chapter 3 Concepts Geocentric vs. Heliocentric • Plato, Aristotle and Aristarchus • Ptolemy and the need for epicycles • Copernicus and the need for epicycles Kepler ’s Laws • Empirical Laws • Elliptical orbits • Planets sweep out equal areas in equal times • Relationship between period and semi -major axis: p 2=a 3 Galileo and the heliocentric ‘universe ’ • Sunspots, mountains on moon – challenged perfect heavens • Jupiter ’s moons – challenged Earth as single center of everything • Phases of Venus – challenged idea that Venus went around the Earth Hallmarks of Science.