Astro 203, Fall 2003 Practice Questions for Midterm 1. We recommend that you actually write out the answers to these questions. It really helps a lot. This is one facet of studying, not the entire diamond ring. 1) If the Sun is the size of your Kaler textbook, how far away is M31? 2) What is a light year? a light second? 3) If the Universe is 1.5x10**10 years old, and if a massive star only lives 1x10**6 years, how many generations of massive stars would be needed to span the age of the Universe? 4) What is the Solar System? the Milky Way? a cluster of galaxies? 5) What is an apparent property? an intrinsic property? 6) What do we mean when we say a theory is falsifiable? 7) What are the main motions in the sky, and how can we understand them as reflexes of motions of the Earth? Think about these in the context of your STARRY NIGHT work, even though we haven't given STARRY NIGHT back to you. 8) Explain parallax. On what does the measured parallax of an object depend? 9) Stars in the night sky also have (typically quite small) REAL MOTIONS of their own. Why? 10) How can we test that the laws of physics are the same everywhere? 11) How do you make light? 12) What are the main categories of light? What is the same about these categories? What's different? 13) Tell us about some of the experiments we did with the infrared camera. 14) What do telescopes give us that our human eyes don't? 15) What are the main forms of data from telescopes? 16) What experiments did we do with liquid nitrogen? 17) What is radiation? what is radioactivity? What is fission? What is fusion? What is convection? What is conduction? 18) Explain Wien's Law 19) Explain why scientists talk about temperature in Kelvins (Kelvin degrees). 20) Explain why the T**4 dependence in the Stefan-Boltzman law is important. 21) Explain WHY there is also an R**2 dependence of the Stefan-Boltzman law, and why/how we use it in this class. 22) State (and explain when you can) Kirchoff's Laws 23) How do we know the age of the Earth (tell me a process, not a word)? 24) How do you MEASURE if a star is red or if it's blue? 25) Why does the apparent brightness of light (and the strength of gravity) fall off as the square of the distance from the emitter? 26) What is the perfect gas law? Explain all the terms in the equation How does a gas make pressure (think about car tires)? How can a gas hold up a weight? 27) What does it mean that a star is in equilibrium? Does it somehow mean that you've turned off gravity? 28) What is the H-R diagram? How do we know masses of stars on it, how do we know radii? How do we know the luminosities? How do we know the temperatures? 29) How do we know lifetimes of stars? 30) Using just the H-R diagram, how do we know that a red giant is big? white dwarf is small? 31) What are the approximate ranges of luminosity and of mass on the H-R diagram? 32) Be prepared to do a "red star, blue star" problem 33) How do we know the Sun isn't made of coal? 34) What happens to the orbit of the earth is you replace our 1 solar mass sun with a hypothetical 1 solar mass black hole? (this is a law of gravity question) 35) What are the four forces of nature, and tell me as much as you can about them? 36) Explain the Bohr model of the atom. How does this model help us understand Kirchoff's laws? How does it help us explain the emission form thin gases? How does it help us explain the Solar spectrum? 37) How does the Bohr model of the atom help us learn the chemical composition of the Sun? 38) Why is the center of the Sun hotter than the edge of the Sun? Why doesn't the Earth's atmosphere fall down in a think little puddle on the floor? 39) How does an object make energy with Kelvin-Helmholtz contraction? Give a Solar System example? 40) Write down (memorize) the proton-proton cycle and explain what everythin in it is? 41) So, knowing what you know about gases and nuclear fusion, what's a main sequence star? 42) How does a gamma ray made in the center of the Sun get out of the sun (and how long does it take and why), and how does it get turned into mostly visible light? 43) Write an essay explaining stellar evolution as far as we've gotten in class 44) What's a planetary nebula and how does it get that way? 45) Why do we care about Solar Neutrinos? 46) From a stellar evolution point of view, tell me something about all of the required-reading stars in Kaler 47) Do all of the reading, including reading on the website. There's a lot of review material you'll find useful. Don't forget to read Ch 1 and 2 of Wheeler and the intro to Kaler. Don't forget to review all of your homeworks and labs. 48) Don't forget that there is no cookbook for this class. There are a lot of ideas that you have to fight with. You can fight with the ideas by taking advantage of the many many resources we've given you. Don't think that if you memorize the 1999 lines that Jane and I have written in the lecture section, that that's sufficient. Take advantage of everything we've given you. Come to the review session with thoughtful questions. Don't wait to start studying till the last moment. You'll want to have started in august!