Images, Resonances, Echoes, take 3
Some reverberations, some new ripples
Images- of multi-step arguments, unpacked, a graphical language, meta-physics
Many driving factors encourage pushing ever onward(I've experienced nerves, classroom management strategies, statement packed specifications). Yet, in encouraging a critical response to knowledge, you'll need to make rather a lot explicit and so open to comment and inspection. Otherwise , there is little to get a grip on. But continually shifting perspective to point out the structure of the argument can get wearing, particularly if talk has to carry all of the burden (the channel gets congested: bandwidth overload). Here is a moderate suggestion for using diagrams to represent the structure of the argument. There is a hope that used often enough it'll available as a resource to support discussion without having to be explicitly injected into the word-stream.
Start with distinguishing between the physical and the conceptual, choosing a defensible boundary: I'd suggest that every useful step of an argument can be put in one of these two buckets.
Physical (green): tangible, identifiably and uncontroversially a part of the lived-in world, with only a little structuring.
Conceptual(blue): a part of the imagined world of physics – precise created entities interact in defined ways.
Next consider the kinds of transitions from step to step. You might get away with as few as four. SupportingPhysicsTeaching showed that this can be done with: intervene, evolve, redescribe, step.
A moderate number is better(to support familiarity and therefore easy recognition), but this schema may be too parsimonious for you.
An intervene transition emphasises some intervention by an experimenter, so the panes either side are likely to represent the change between the "before" and the "after".
An evolve transition suggests that the process goes along by itself, without such outside interference, that we're watching the process evolve, so the panes either side might represent snapshots in that process.
The redescribe transition moves from one kind of description to another, for example from using forces to using energy, or from a physical to a conceptual description. Perhaps "now see it like this".
The step transition is a kind of catch-all, for when complexity or internal logic suggest inserting a break in the flow, but without any particular conditions being satisfied. You could think of it as a graphical paragraph marker.
And embedded in the distinctions is a view of what doing physics is: that too needs to be defensible, but as philosophies of physics differ don't expect a unique set to be self-evident. Maybe, for our purposes, the most important criterion is whether your particular schema is heuristically useful, or not.
It may be that an underlay showing just the structure makes more plain the forest-scale landscape of what thinking in physics is all about, blurring the trees.
Such diagrams can be hand drawn, but you might be better of having to hand a library of representations: here is one such, to get the ball rolling.
Of course you might prefer the flexibility of code (also enabling interactive diagrams, in which case a set of primitives like such as:
acceleration(magnitude,rotation,acolour) power(value) circuitParallel(kind) bulb(label)might form better building blocks with different granularities. But maybe that's a story for another time.
More reading
Ogborn 1996 Explaining Science In The Classroom Paperback Open University Press
Resonances- an account of why things float or sink
This is a classic multi-step argument, so long as you avoid the dead end of the traditional formulation of "the upthrust is equal to the weight of fluid displaced". The quantity and quality of physical insights in this sequence is itself a good reason to avoid that formulation.
You might start with a very physical experience of making a hole in water by pushing a ballon into a pail of water, and experiencing upthrust.
Then maybe supplement this with doctored bottles, some with holes in the side so that the bottles don't make holes in the water, others without such holes so that they do makes holes in water.
Then develop a line of argument somewhat like this:
You're going to think about making holes in water, using boats. Making these holes results in a buoyancy force on the boat, which supports the boat and its cargo. Buoyancy forces only occur in fluids, so you'll be thinking about pressure and the particles of the fluid bombarding the surfaces of the boat. To think about bombardment on surfaces, we'll choose to make a simple boat. You'll be concentrating on the surfaces at the sides and the bottom.
Let's make a really simple boat, to reason with.
In a fluid, pressure increases with depth. So the sides of the boat will be at the same pressure, but the top and bottom will be a different pressures.
As the pressure increases with depth, so the bombardment gets more intense. Therefore you might expect different surfaces of the boat, at different depths, to experience different bombardments on each piece of exposed area.
Focus on a surface, and vary the pressure on either side. Increasing the pressure increases the bombardment. A difference in bombardment results in a force.
Note that there are both the bottom surface and the two surfaces that make up the sides of the boat to think about.
You could wrap all of these together, as a sequence of panes, with guides to link panes. Not to replace teaching, but maybe a resource for a flipped classroom?
More reading
Scott McCloud’s infinite canvas
Echoes - an experiment and things past
A sideways thought, putting that well known supply of absorbers, textbooks, to use. Show fractional decay with a microwave source and detector by placing increasing numbers of textbooks between source and detector.
I liked this for a fractional decay show and tell, to accompany the books:
As final reverberation for waves, combine the ideas of multiple step arguments, of story spaces to support flipped classrooms, to get:
That leaves the steps and superposition branch rather less developed. But IRE01 provided a sound basis for developing that line of thinking.
I've been wondering about the role of questioning in explanation. It strikes me that the formalism described above might be aimed more at teachers and making sure we've understood all the important points we need to explain. But then the actual explanation will be different and might hinge on some key questions. Watching videos of explanations I'm struck by how the best ones seem to ask lots of questions or say nothing. The worst ones seem to be the ones where they attempt a whole scale transfer of the picture in the teachers head into the students head. Asking questions seems to be more like highlighting crux issues you need to understand. An analogy might be a rock climb. We want to know whether we did the climb in the guide book. But we only need to know whether we did the same route as described, we don't need to have put our hands in the exact places as the first ascender or subsequent ones. By asking questions like "did you come out over that edge?" we can ascertain whether the climb was done. But of course a good description of the climb is needed to start with. It isn't enough to state that you started at point A at the bottom and emerged at point B at the top.
Also, I wonder if all good explanations start with a description of the scenery; this linking of conceptual to physical. As physics teachers I think we very often take for granted the symbolism we use. Like when you have one of those "oh.....we're viewing it from above....I thought..." moments.