15 minutes a day...

I have a scheme going with an InternetFriend to encourage ourselves to get off our respective academic asses and get some things published. We have a deal where we will both write for 15 minutes a day. Not blog crap, not outlines, not sketches... real writing with real sentences for a real journal.

I did my first tonight. It's very exciting how easy it is to get 400 words on a page if you just force a 15 minute spew. Here they are... just for fun...

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Entropy is a Number

Most textbooks for high school students, as well as most conceptual physics texts for college students, treat entropy by suggesting it is some measure of "disorder". (references and examples?) This definition is fine for relating some of the basic implications of the Second Law, but it doesn't have the same precise feeling as most of the other physics concepts that the student has become familiar with - acceleration or force or energy for example. I've always had the impression that statement "entropy is disorder" can be a less-than-satisfying one for students.
(SAY WHAT THIS PAPER WILL DO HERE? OR LATER?)

Witness a conversation I had with a student one year in an introductory physics class.

I was making a statement about the relationship between entropy and information, and the student told me that "There is really no such thing as information. Information is just in our heads. Like when I look at this piece of paper, I see a bunch of information, but really it's just a bunch of random squiggles. The information isn’t on the paper, it's just in my mind."

It was difficult to convince the student that the difference between order and disorder was NOT some kind of fuzzy side-effect of human perception. The suggestion that disorder (and thus entropy) is somehow a subjective concept is difficult to escape without a more mathematical treatment of entropy.

Most introductory students will be unable to fully appreciate the full S = k ln W treatment of entropy. (In fact, many of them may not know what a logarithm is!) So, in my teaching, I have tried to find a middle ground - one which hints at the fact that entropy is a NUMBER, something you can calculate, even if the actual calculation that physicists normally use is just a bit beyond our grasp in an introductory class.

Most students have had enough experience with statistics to have seen the kind of Gaussian histogram that arises from rolling two dice. But even so, I begin by having students construct this graph experimentally in small groups. We then pool the results to produce a class histogram for the sum of 2 dice. (FIGURE 1) This opens the door to make a very important point in thermodynamics - even though the rolls of each individual die are essentially random, there is a predictability inherent in the system as a whole.

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Pretty cool, huh.

Also... I jogged today.

DID TOO!!