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