Lookback Lab
Published on Apr 30, 2007 at 8:53 pm.
No Comments.
Filed under college teaching.
This is the last week of the classes at my college. Next week is final exams. For our last laboratory exercise, I like to do something easy and fun (and very easy to grade!).
Some of our labs involve observations, other labs involve lots of computations. So, I thought that I’d do something very simple and fun. I have students pick a constellation. They then use software available in the lab to determine the distances to a half dozen or so stars in the constellation. Then, I have them think about what was going on on Earth when the light that is just now arriving left that star. So, if the star is a distance of 23 lightyears away, that meant that the light would have started on its journey 23 years ago. That would be 1984. What was happening in 1984? Who was president? What was big news then? Well, I can remember 1984 — I was in graduate school then. But many of my students were too young (or not even born!) in 1984. And, many don’t know much of recent history. And what about a star 156 lightyears away? When you look at that star tonight you see that light started towards us in 1851. What was going on in 1851? I want them to think about just how long that light was traveling before it got here. The stars are FAR away. But, to do that, I want them to think about what was going on here on Earth, but how can I get them to find out what was going on in those years?
What we need is perhaps Mr. Peabody and his WABAC machine (growing up I always thought it was the “Wayback” machine, since that is how it is pronounced). Hmm. How many of my students used to watch Rocky and Bullwinkle?
So, since I don’t have a WABAC machine, I have to find out some other way for the students to find out what was happening in the past. Well, I’ve found a couple of good websites that give timelines of history, and these sites are very useful in this exercise. One of these sites is Hyperhistory Online. There are several buttons there that take you to a timeline. or a list of events by year, or several other interesting lists of historical things. Another good site is Timelines of History. This site has a less appealing look to it, but it is packed with interesting historical tidbits. So, I direct students to these sites.
The important thing here is to stress that the activity shows that the great distance to the stars. When we go out and look at these stars, the light that is currently arriving started towards us long ago. Just saying that a star is so many lightyears away doesn’t have the same impact as saying that the light that is just now arriving, moving at 186,000 miles each second (300,000 kilometers per second), started when Theodore Roosevelt was president! But, you have to be careful to make sure that the students realize that the light now arriving started then, but that the star itself didn’t start then. A common mistake among the weaker students, if you are not careful, is to think that the star is only that old.
But, it is a fun, and very easy lab to do. And, I have them share some of the more colorful stars with their classmates. So, they get to have fun, and they don’t work hard, and I have an easy lab to grade during the horribly busy time of the semester for me!
So, anyone teaching astronomy out there who is looking for a very easy end-of-the-semester exercise, here’s one for you! It makes a nice break from the labs with lots of calculating, plotting, and measuring.
-Astroprof
(Mr. Peabody and Sherman, courtesy of Jay Ward Productions)
