What Can You Do With This? is the most fun I’ve had this school year. I could do week after week of times table review if my students and I were allowed just thirty minutes per week to sharpen our minds with mathematically rich multimediaIf you’re the sort who sees potential in these blog things for professional development then the fact that I developed this classroom fixture organically, spasmodically, like a wobbly baby giraffe, here on this blog, in full public view with full public input, might be a useful data point..

I have received two suggestions recently I wanted to address, two suggestions that would put us off a useful trail and into the bramble. Here is one.

FlickrCC Won’t Work

Scanning Creative Commons-licensed photography databases for math media simply isn’t a scalable solution. These media must be unaffected. The student must lift the heavy weights. The student must decide for herself what is important about an image, audio sample, or video. Most photographers, meanwhile, are very interested in artistic expression, in affectation, in imposing their own point of view on a scene, rather than stripping the scene of their point of view entirely, which is essential for classroom work. So instead of something unaffected, and artistically value-neutral like this:

You get expression like this:

… with the camera positioned at an artistically interesting but academically unhelpful angle. You can’t model a parabola onto this. You can’t model a circle onto this. The photographer was (naturally) unconcerned with measuring the scene, which rules out basic photogrammetry. It begs the question, “who shot this?” rather than an interesting question about the parabola itself.

This is a generalization, true, but a useful one. You can’t find the really effective WCYDWT? media. You can derive surface-scratchers like “what shapes do you see here?” from Creative Commons-licensed Flickr media but if you’re looking to propel a meaningful discussion or a rigorous activity, you have to make it yourself.

I pick up a huge static charge whenever six words, paired with the right a/v material, can motivate an hour of mathematical exploration.

Here is the opposite of that static charge, a loud sucking sound as my brain deflates, the old way of doing real-world relevance:

As a student, I’m like “cool, volleyball, volleyball’s fun” but the problem is already dumping questions and formulae and mathematical structure on top of me before I have ever once considered the reality that projectile motion follows a parabola.

You have to earn that.

So I shot four of these images [partial, full] – one that ultimately went long, one that went short, one that went in, and one that looked like it went in, but really veered to the side, provoking a discussion of errors in 3D projections onto a 2D plane.

I shot ’em plain. Nothing fancy, plenty of room along the edges, no soundtrack, no narration, nothing overtly helpful. I set them up so I could ask the students a clear, visceral question: “Will the ball hit the can?”These guidelines are all in the manual.

Because this is a question which everyone wants to answer, regardless of mathematical ability. Everyone has an opinion. Everyone gets invested. It’s also a question that has a visual answer, one which we can compare against their predictions. So the first thing I had the students do after they paired up in front of laptops was divide a piece of paper into quarters and make a bet on each throw. I gave them the digital files, next, on top of which they modeled parabolas in Geogebra, revising their guesses afterward.

Then we played the answer videos and called it a pretty good day.

Perhaps now that they’re really, really invested into the idea that projectile motion follows a parabola, now that they’re comfortable with Geogebra, we’ll take Geogebra away. We’ll change the constraints now, superimposing a grid or a protractor, deriving the parametrized equations, but I just want to impress upon you, if nothing else, that this is a very deliberate, very sacred (to me) process, a process which most textbooks desecrate whenever possible.

If one of my students could successfully answer that scanned textbook problem above, but hadn’t on her own wondered, “What if we knew the equations of the parabola, what then?” I really don’t know how accomplished I’d feel.