Chapter 3 The Science of Astronomy Copyright 2009 Pearson Education Inc Internet The American Astronomical Society finds itself at an important tipping point Funding in Washington DC is declining and yet we are training more and more astronomers As your Vice President I will bring Bold Fresh ideas to help the membership deal with these substantial issues As my new Bold Fresh approach I would work to bring back Disembowelment and Human Sacrifice to astronomy as was once practiced by the great astronomers At one time we had the ears of kings and Gods as we guarded the astronomical secrets from the unwashed We had the funding agencies and GS workers build palaces and temples to our knowledge and we got to wear cool hats and stuff with red feathers We have lost this momentum and I will work to bring back our former glory It is important to insure that historically underrepresented groups such as women solar astronomers and string theorists would be encouraged to participate By narrowing the human sacrifices to astronomers that by consensus could easily be decapitated we would also reduce the total number of members as we regain the prestige and funding we so obviously deserve I have no doubt that the society at large could easily nominate astronomers for this important service to our profession starting perhaps with department chairmen thesis advisors Deans or the guy that wrote IRAF Anything you write or post assume can be read on internet Be careful Copyright 2009 Pearson Education Inc Copyright 2009 Pearson Education Inc Tycho s star was the real revolution Tycho showed that the new star which appeared for a few months had no parallax and thus was farther away than the Moon in contradiction to Aristotle and the Church Aristotle was wrong and the Church was not infallable Copyright 2009 Pearson Education Inc Kepler s Three Laws Planets revolve on elliptical orbits Planets sweep out equal areas in equal times Semi major axis cubed equals period squared P2 a3 Copyright 2009 Pearson Education Inc Question if the period is 16 years what is the semi major axis A 64 years B 4 light years C 36 years D 32 years trick question 16 2 a3 or a3 256 a 6 35AU Understand how to do this formula Copyright 2009 Pearson Education Inc How did Galileo solidify the Copernican revolution Galileo 1564 1642 overcame major objections to the Copernican view Three key objections rooted in the Aristotelian view were the following 1 Earth could not be moving because objects in air would be left behind 2 Noncircular orbits are not perfect as heavens should be 3 If Earth were really orbiting Sun we d detect stellar parallax Copyright 2009 Pearson Education Inc Overcoming the first objection nature of motion Galileo s experiments showed that objects in air would stay with a moving Earth Aristotle thought that all objects naturally come to rest Galileo showed that objects will stay in motion unless a force acts to slow them down Newton s first law of motion nbs s opinion both were right they just had different theories Copyright 2009 Pearson Education Inc Overcoming the second objection heavenly perfection Tycho s observations of comet and supernova already challenged this idea Using his telescope Galileo saw Sunspots on the Sun imperfections Mountains and valleys on the Moon proving it is not a perfect sphere Copyright 2009 Pearson Education Inc nbs s opinion I have never understood how anyone could think the Moon was perfect To my eye it clearly has splotches Overcoming the third objection parallax Tycho thought he had measured stellar distances so lack of parallax seemed to rule out an orbiting Earth Tycho miscalculated the effects of refraction from the Earth s atmosphere among other small errors Galileo showed stars must be much farther than Tycho thought in part by using his telescope to see that the Milky Way is countless individual stars If stars were much farther away then lack of detectable parallax was no longer so troubling nbs s opinion this is all well and good but it is a difficult theory to find other predictions if the stars are indeed very far away Copyright 2009 Pearson Education Inc Galileo also saw four moons orbiting Jupiter proving that not all objects orbit Earth This was the killer argument This was just like the Solar System with a similar law to Kepler s 3rd Law Copyright 2009 Pearson Education Inc Galileo s observations of phases of Venus proved that it orbits the Sun and not Earth The recent Kepler results have seen this in a planet around another star There they see a small increase in brightness before the planet goes behind the star which would not happen in a geocentric theory It also means that with really good measuremnets we should be able to Copyright 2009 Pearson Education Inc In 1633 the Catholic Church ordered Galileo to recant his claim that Earth orbits the Sun His book on the subject was removed from the Church s index of banned books in 1824 Galileo Galilei Copyright 2009 Pearson Education Inc Galileo was formally vindicated by the Church in 1992 What have we learned How did Copernicus Tycho and Kepler challenge the Earth centered idea Copernicus created a Sun centered model Tycho provided the data needed to improve this model Kepler found a model that fit Tycho s data What are Kepler s three laws of planetary motion 1 The orbit of each planet is an ellipse with the Sun at one focus 2 As a planet moves around its orbit it sweeps out equal areas in equal times 3 More distant planets orbit the Sun at slower average speeds p2 a3 Copyright 2009 Pearson Education Inc What have we learned How did Galileo solidify the Copernican revolution His experiments and observations overcame the remaining objections to the Sun centered solar system Copyright 2009 Pearson Education Inc 3 4 The Nature of Science Our goals for learning How can we distinguish science from nonscience What is a scientific theory Copyright 2009 Pearson Education Inc How can we distinguish science from nonscience Defining science can be surprisingly difficult Science comes from the Latin scientia meaning knowledge But not all knowledge comes from science Copyright 2009 Pearson Education Inc The idealized scientific method Copyright 2009 Pearson Education Inc Based on proposing and testing hypotheses Hypothesis educated guess nbs this is a nice ideal for science that rarely happens If this were the case science would be as exciting as accounting But science rarely proceeds in this idealized way For example
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