AST 301 Fall 2007-Scalo Review sheet for exam #7Exam 7 covers sec. 24.3 (Hubble’s Law), and chapters 25 (NOT 25.4), 26, and 27. As onprevious exams, emphasis is on understanding the basic ideas and their implications and connections, noton memorization of details or on numerical values. I will not test you on any of the “More Precisely” or“Discovery” sections except Discovery 26-1, p. 752. Read them if you are interested (e.g. you will learnhow strange “string theory” is).There will be a number of questions related to deuterium and helium as produced in the era ofnucleosynthesis and how those provide tests of cosmological models. However you do not have tomemorize any of the nuclear reactions involved.As usual, a few of the exam questions will be versions of some of the questions found at thetextbook web site multiple choice self-tests. Also as usual, I strongly suggest that you do not try thesequestions until you have thoroughly studied. Another suggestion that bears repeating: Test yourself byseeing if you could explain most of the material, or the answers to the questions at the end of the chapter,to someone who hasn’t taken the course, without consulting the book at all. Not being able to do this(and it should be pretty clear when you can’t) is a sure sign that you don’t understand the material enoughand need further study.The end-of-chapter questions are also useful review tools. I am unable to give you a list of whichones are most important. You should look through all of them and see if you are familiar enough toanswer them.Liubin Pan (our TA) will have office hours Thursday 2-4 (unless I send you an email note tellingyou differently--I have not checked with him on this yet). I will have office hours on Thursday from 4 to6. I’ll have to send you email if there is some meeting that day that I have forgotten to put on mycalendar.If you want to meet on Wed., let me know--2:30 or 4:45 are possibilities.I will be available for phone consultation from 9am to 9pm Wed. and Thurs., if I amhome—otherwise, leave a message, feel free to call back, etc.; you won’t be disturbing me because I’lljust be reading or working. But please don’t call after 9 pm.Sec. 24.3. This is a leftover from the last exam, but one of the most important topics you’llencounter. Here the Hubble Law is introduced as a “standard candle” that can be used to obtain distancesto very distant galaxies. Later, it is revisited in another role, as the first evidence suggesting a model forthe evolution of the universe called the Big Bang.Chapter 25. You should read and study all this material except for sec. 25.4, Black Holes inGalaxies. You might find it interesting to look it over, because it describes observations and theoriesabout the supermassive black holes that lurk in the centers of galaxies, but I will not include it on the test.However you are responsible for the long section at the end of the chapter discussing the evidence fordark matter, including mapping dark matter with gravitational lens techniques. Don’t worry if you don’tquite understand gravitational lensing, as long as you are willing to accept that it happens.We began with sec. 25.5 (p. 696), on mapping a large part of the observable universe usingdifferent techniques, finding evidence for clustering up to extremely large scales. We then returned tosec. 25.1, which presents still more evidence for even larger scale structure and “dark matter.” You shouldbe able to explain in simple words what this evidence is—generally it is all the same kind of evidence(except for using gravitational lensing), but using different objects.A new theme in this chapter is looking back in time by observing very distant galaxies to learnsomething about how they have evolved. How are galaxies at large redshifts (means very distant—reviewthe Hubble relation if this is not clear to you!) different from nearby galaxies? This is the crucial clueabout how the Hubble sequence of galaxy types (ellipticals, spirals, irregulars) are related. Notice theemphasis on starburst galaxies, and galaxy collisions when you go back to sections 25.2 and 25.3. Youshould be familiar with the role these play in the formation and evolution of galaxies, as well as be able todescribe the various lines of evidence we have now amassed for dark matter (sec. 25.1) and how its masscompares to the mass of “normal” (“baryonic”) matter in the universe.If “baryonic” is confusing, just remember that many people think that dark matter consists ofexotic fundamental particles that exist in quantum theory but have not yet been produced in accelerators,and that we are made of “normal” matter—neutrons, protons, electrons—those are “baryons.”Chapter 26 (Cosmology). I won’t enumerate the sections--all of them are important. Don’t betoo worried if you feel like you don’t understand the material on the curvature of space: very few peoplereally understand that. But do remember the 2-dimensional analogies so that you’ll know what we’retalking about if you encounter the terms “closed” and “open” universe, the significance of Hubble lawand CBR discovery.Chapter 27 (The Early Universe). This is a challenging but extremely interesting chapterbecause of all the strange phenomena and physical conditions discussed. Sec. 27.2 is probably the mostdifficult, but don’t worry about the zoo of fundamental particles and types of particles that areintroduced—they are just trying to explain how particles form as the energy (temperature) passes throughthe energy that corresponds to the particle’s mass (E = mc^2). I am mostly concerned that you get thebasic ideas—I realize it is too much to digest in a week. In particular, you don’t have to memorize thenumerical or other details of Table 27-1 (and I won’t ask you about much terminology, like what is ahadron or a lepton, etc.). But we did go over a simpler version of this “time line” in detail in class, so I doexpect you to know what went on and when (i.e. roughly how old the universe was when this or thatoccurred) during the following key phases:1. Inflation; 2. Nucleosynthesis; 3. Decoupling of matter and radiation (and why that implies thatthere must be a cosmic background radiation); and 4. The formation of structure from fluctuations.Basically, understanding the significance of these eras of the universe, and the observationalevidence they are
View Full Document
Unlocking...