PHY 313: Modern Astrophysics
Dr. Tony Crider
What exactly is astrophysics?
Astronomy is the science (sometimes the art) of observing things in space from the Earth. Humans have been doing this for as long as we have been humans. By contrast, astrophysics is the relatively modern practice of taking what we’ve learned about the Universe from physics experiments and using it to explain what we see in space. While you didn’t ask, I should also mention that space physics is when you try to figure out what is going on in space by actually going there (or sending a robot) rather than simply using telescopes to look at it from Earth. Since our robots can’t yet travel at warp speeds, space physicists almost always study things within our solar system. Astrophysicists tend to study the stuff outside of our solar system, such as stars, galaxies, and the Universe as a whole. Just to make it confusing, when talking to the public, scientists tend to use the word astronomy to mean observational astronomy, astrophysics, and space physics. (Ask me to draw you a Venn diagram, if you’re confused.) Finally, for completeness, I should point out that astrology is when people try to take what they see in the sky and use it to explain why they’re having a bad day.
Ok, let me rephrase. What are you we going to cover in Introduction to Astrophysics?
While the title of the course and the big orange book we’re using both include the word astrophysics, what we will really be doing is an introduction to astronomy for physicists. When we’re done, you should be able to explain how we know the most basic things there are to know about astronomy, such as:
Since this course is meant to serve as a bridge between freshman physics and Modern Physics, we’ll be doing quite a bit of the physics, math, and computer programming that professional astronomers do when facing these topics.
How are you going to calculate the grade?
The daily closed-book reading quizzes given at the beginning of class will be worth 20% of your grade. Each quiz will be given a grade of 5 for A-level responses, a grade of 4 for B/C-level responses, and a grade of 3 for D/F-level responses. After the first exam, each student will give a presentation on a section of the textbook. These talks will be worth 15% of your grade with your practice being worth 5% and your in-class talk being worth 10%. I’ll provide a rubric for these talks later in the semester. The end-of-chapter homework problems I assign collectively will be worth 25% of your grade. These homework sets will generally involve a problems with varying difficulty and point value. There will be three exams, each worth 10% of your grade. All of these will culminate in a group practicum worth 10% of your grade.
Let’s get to the point. Am I going to get an A?
Probably not. Usually, only one or two students in my classes get a straight A. Doing the assignments correctly will really only get you to a B, maybe a B+. To earn an A or A-, your work really needs to be amazing. Inevitably, in every class there are students that pull this off. Likewise, if your work is merely correct and complete, you’ll likely end up with a C. If you want to hear me wax poetic about grading policies, ask me to lunch sometime.
When are your office hours?
My office hours will be set in the near future. You can phone me there and leave me voice mail (336-278-6268) or e-mail me (acrider@elon.edu). Of course, whenever you see my office door open (MCMI 003L), feel free to pop in.
What is the homework like?
I typically assign five problems on the homework sets. Three are simple C-level problems worth 25 points each. Two are more challenging B-level problems worth 10 points each. One problem is difficult A-level problem worth 5 points. If you are no able to do this problem, you can still earn up to 95% of the points. Most of your homework assignments will be turned in as Excel or Google Docs spreadsheets with a separate tab for each problem. I also expect that each solution you turn in should be capable of being understood by someone unfamiliar with the course. (I’ll explain why I do this in class.) Thus, for full credit, an A-level solution should include the following:
Any solution that does not include these may receive point penalties. I’m encouraging you to work with other students on the homework sets. A lot of education research shows that you learn better from other students than from a professor. That said, when you’re working with a group I expect you to follow a few simple rules for this class:
Breaking any of the rules could result in an honor code violation for this class, and I really, really don’t want to have that happen in Modern Astrophysics.
How will I grade the reading quizzes and homework?
Very often, part of the reading quizzes (and the exams) is figuring out what the question is asking. You will need to learn to “unpack” a question that sounds simple. On the first day of class, you’ll do a “reading quiz” asking you, “Who is Darth Vader?” We’ll then discuss the difference between C-level answers (e.g. “Darth Vader is the villain in Star Wars.”), B-level answers, and A-level answers.
Shortly before the first homework set is due, we’ll talk in class about what you should have for it. Since this is a sophomore-level class, you are expected to do more than a freshman-level class (i.e. showing your work and the solution) but less than a junior-level class (i.e. writing a full paper about a single topic). For full credit, you will need to write out the problem, describe your approach, show your work (using the spreadsheet for calculations, when appropriate), write out a sentence stating your final answer, and then interpret the significance of the answer (perhaps by comparing the value to some other relevant number). You will be doing far fewer problems than you did in University Physics but you’ll need to write a lot more for each question. This will start to prepare you to write full, scientific papers in your junior year.
What are the exams like?
The exams typically have just a few short questions. Usually, the required solutions are also very short. The exams are both open-book, open-homework, and open-web (but not open-friend; you may NOT contact other people). What makes the exams difficult is that you must combine what you learned from the homework with what you learned from the in-class projects. You must also be able to reformulate a somewhat vague question into a question that can be answered scientifically.
Where is all the boilerplate material that is normally in a course syllabus, like the schedule and stuff about the Elon Honor Code?
I decided to try something different for this syllabus. Most of the mundane information about the course is found on-line at the course website (http://astrophysicswithcrider.blogspot.com/). As for the Honor Code, you can and should read it at least once per year, since it has changed a lot at Elon in the past few years. If I suspect that you have broken the code, I’ll ask you to come talk to me about it. Hauling a student to the Provost’s office for a hearing is one of my least favorite things to do as a professor, but I seem to get stuck doing that at least once every other year. Please don’t let that student be you.