Friday, April 25, 2008

Galaxy Collisions in the Classroom

The internet not only lets you show your students images of galaxy collisions, but it also let you simulate the events.

Around this time of the semester, I am covering galaxies, large-scale structure, and cosmology. The other day, the folks at the HST released a wonderful webpage filled with the best Hubble images of galaxy collisions I have ever seen. Scroll to the bottom of that page to see links to the individual images.

Showing pretty pictures in class is one way to interest students. When it comes to colliding galaxies, you don't have to just show the static pictures though. Some astronomers at CWRU and the University of Oregon have developed a web-based applet, called GalCrash, that simulates the dynamics of colliding galaxies. You can choose many different parameters for the simulation, including number of stars and mass, etc.

What I like about this applet is that you can run a simulation and achieve a result that is similar to the morphology shown in the actual images of galaxy collisions. Just pause the applet and show the comparison to students! I think it's a neat way to connect physical theory with observations.

~Paul Robinson

Saturday, April 5, 2008

Clickers vs. Flash Cards: Research in Peer Instruction

New action research, published in the April issue of The Physics Teacher, discusses the use of clickers versus flash cards in the aid of peer instruction.

The first time I attended a Center for Astronomy Education (CAE) Teaching Excellence workshop was also the first time I had really seen the technique of peer instruction. By "peer instruction", I mean the kind promoted by Eric Mazur: A class discusses a topic, or receives a short lecture, and then a series of multiple choice questions are posed. The results of the voting influences how the teacher will give instruction.

But how to vote? Certainly anonymous voting is nice, taking pressure off the students who are nervous or shy about revealing their answers in front of everybody. One way of voting is to use your hands: vote with your fingers. Multiple choice answer "A" is one finger; "B" is two fingers, and so on. Placing your vote on your chest prevents the students behind you from seeing your vote.

Another way to vote is using flash cards. In this way, colored flash cards printed with a letter on them are held up to indicate a vote.

In my own classroom, I use multiple choice questions a lot, and my students vote with their fingers.

In the last fifteen years or so, electronic devices have been introduced into the voting classroom. "Clickers" are remote devices that resemble tv remotes that can transmit a student's answer to the professor's computer.

Also in my first CAE workshop, I recall Ed Prather voicing skepticism as to whether or not it mattered if a student used flash cards or a clicker. Certainly, there is evidence that students are excited about using the technology, but does the use of clickers in voting change the pedagogical landscape? Or is it just as good to use flash cards (or fingers)?

Some new data has come in. Nathaniel Lasry of John Abbott College has an article in this month's Physics Teacher entitled Clickers or Flashcards: Is There Really a Difference?. I'll let you read the article, but Lasry's main conclusion is that there is no pedagogical difference between the two tools, provided that the same method of peer instruction is given. This makes sense to me, since there doesn't seem to be a way cognitive load would change between using a clicker or using a flash card.

The main advantage of using clickers is the electronic culling of voting data. Some clicker systems are so advanced that they can collect the data, analyze it and generate webpages in which you can view class and individual student performances across class sessions and entire semesters. Voting with your fingers doesn't allow this.

One thing seems clear from this: lack of technology should not stop you from introducing peer instruction into your classroom.

~Paul Robinson