Astronomy 161: Review Guide for Midterm


The midterm will occupy the entire class period on Friday, April 29. It will consist of 40-50 multiple choice questions. The level will be similar to those of the quizzes, but some of the questions will be broader in scope, and some will be more challenging.

You may bring one page (both sides) of handwritten notes. You may bring a calculator, but you are unlikely to need it. Please bring a number 2 pencil.

If you have an unavoidable conflict with the midterm, you must let me know in advance in order to be allowed to take the makeup. The makeup midterm will be short answer instead of multiple choice.

Review Sessions

There will be two optional review sessions:
Wednesday, April 27, 5:30-6:30 pm, 4054 McPherson Lab, with David Weinberg.
Thursday, April 28, 6:00-7:00 pm, 4054 McPherson Lab, with Jaiyul yoo.
These will be question and answer review sessions: come with your questions, and we will do our best to answer them. Of course, it should also be useful to hear your classmates' questions and our answers. We will not answer questions of the form "will x be on the exam," though we can offer guidance on whether a particular topic is central or peripheral.


The quiz will cover the material through Lecture 10, Universal Gravity Part II.

Names to know: Aristotle, Eratosthenes, Aristarchus, Ptolemy, Copernicus, Tycho, Kepler, Galileo, Newton.

As with the quizzes, it is useful to go through the "key questions" that introduce each lecture.

As you go through the history that we have covered, pay particular attention to the logic of arguments. What kinds of information enabled astronomers to figure out the size of the Earth, the relative sizes of the Earth, Moon, and Sun, and the periods and orbital radii of planets? Why were new ideas (epicycles, a heliocentric model, elliptical orbits) introduced? How did new discoveries provide evidence for or against one theory or another? What role did new observational technologies (Tycho's instruments, the telescope) play in these discoveries? In retrospect, which arguments were good and which were flawed?


There are four equations that you should know and understand:

You should know what physical or geometrical idea these equations encode, and you should know what quantities the variables in the equations (P, G, etc.) stand for. Note that "a" stands for something different in each of the first three equations.

I will not ask you to do any complicated calculations on the midterm, but I will expect you to be able to use these equations to answer questions like: "If the Moon were twice as far away from the Earth as it is now, would the gravitational force of the Earth on the Moon be four times higher, two times higher, the same as it is now, two times smaller, or four times smaller?" And you should certainly be able to answer questions like: "I apply the same force to two objects, one low mass and one high mass. Is the acceleration of the low mass object larger, the same, or smaller?"

You should also be sure that you understand what an ellipse is and what Kepler's equal area law is.

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Updated: 2005 April 24[dhw]