Monday, June 28, 2010


I borrow the term ‘parsing’ from grammar:
To break (a sentence) down into its component parts of speech with an explanation of the form, function, and syntactical relationship of each part (The Free Online Dictionary, 2009).
In the sciences, the thing being parsed is not a sentence, but an experience or event. In class, I ask the students 'to draw what is going to happen next;' then I throw a piece of clay at the wall. It usually sticks. Representing this on paper is hard, very confusing, but very open and creative.

How would you do it?

Parsing would break such an experience into meaningful and analyzable 'components' or time intervals. Think about it a second: how would you draw everything that happened? Truth is, you can't. No one could. So, what do you do? You pick out the important parts, find where things change significantly, start making distinctions, make judgements about what to throw away. Bingo, the beginnings of scientific thinking.

However, most textbooks just jump right to the fictions: the ball instantly goes a constant velocity and then instantly stops. In truth—and students can easily see this—there is a period of acceleration while the ball is still in my hand, there is a period where it falls freely as it crosses the room, and there is some period of deformation. It might seem like this complicates the discussion, but I find that it clarifies it, makes it simpler to talk about, and the kids get quite engaged.

Passing along the tricks of the trade

The students can see where things change, but they grope for a way to capture it, to make it simpler. If they don't come to it themselves, I introduce the idea of ‘timestamps’ to parse the chronology of the event, and a standard tool of physics, ‘free-body-diagrams’, to help parse the relationships between objects. Math then becomes a great friend, a helpful language that really streamlines the conversation and enables thinking. We talk about who's pushing what, what direction, how hard, for how long. Student's typically find this kind of thinking fun, and excellence becomes breaking the world down into parts that are meaningful and can be analyzed with the math we know at that point.

The simplest things become fascinating

Another simple example of parsing for a class is analyzing the experience of pushing a toy cart a few inches with your hand and watching it slow down to a stop. I find this is very difficult for students, even the advanced AP Physics kids. Yet the exercise is very fruitful. They begin to bring up contradictions in their own thinking and begin to form real, workable questions. The 'granularity' of their experience becomes finer, and they realize they don't understand things as well as they would like to. Bingo: get curious, play, form a good question.


Pedagogy: the principles and methods of instruction. The main pedagogic difficulty is in keeping the teacher out of it while the students grapple with how to analyze the experience, and then, where to step in and give aid. Open-ended questions like “why did it slow down?” or “what made it move?” are baffling to students, but they tend to really enjoy the effort of figuring them out. They talk to one another. They get frustrated, confused.

'That's great.' I tell them. 'It's fine. That means you're really thinking.'

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