Monday, February 21, 2011

Elementary science education, Part 2

Distinguish a force that acts by direct contact with an object (e.g., by pushing or pulling) from a force that can act without direct contact (e.g., the attraction between a magnet and a steel paper clip).
NJCCCS, Standard for 2nd Grade

You cannot, of course. We "feel" forces the same way--it's a push or a pull.

I could dive into the specifics--a few cells get squished, a Pacinian corpuscle gets agitated enough to open up an ion channel,  an action potential runs down an axon or two, joins the signals from myriad sources, and we interpret the feeling as a "push"--but that tells us nothing, really, about what a force is beyond its paradoxically simple definition: a push or a pull that can change the speed, direction, or shape of an object.

A second grader can easily see (or feel) that a magnet has "special" qualities--it can push or pull without direct contact with another object. The force itself, however, is still a pulling.

This hardly seems like a big deal, true, but I get high school students who do not know what a force is. Or what matter is. Or that none of us truly have a great grip on either.

(Matter is stuff with inertia, inertia is the tendency of a particular blob of matter to resist change when, well, pushed or pulled. That's just the way things work. Newton called inertia vis insita, the innate force of matter.)

A second grader, of course, need not (and, at any rate, could not) master Newtonian physics. Still, a second grader has Pacinian corpuscles and a cerebellum, and can think. She can figure out that magnets can push or pull,  just as she can push and pull, and that a magnet's pull feels just like any other pull.

What can be distinguished is that magnets, for whatever reason, do not need to "touch" the other object to do this. This is interesting, but I would not make it the heart of the lesson--at least not to a 7 year old. I might point out that the Earth pulls us, but again focus on what force is--again, a pull or a push.

If the child infers that the Earth acts like a magnet, well, depending on what a child's view of magnet is (an object that pulls other objects towards it), she is right. Her knowledge is incomplete, of course, but in science it will always be incomplete. The pull of the Earth feels no different than the pull of a magnet or of your mother's hand. (Your mother's hand exerts its pull on a more specific area, but the pull itself is the same feeling.)

It gets down to language and perceptions at this level. At higher levels, a child has more vigorous scaffolding (the history of millions of experiments building on existing models) and more vigorous tools (calculus), but even then, our models depend on language.


I'll give the state this much. The standard above is eminently testable. But it's not science.

I've been (again and obviously) on a Feynmann kick. The following video is a wonderful look at a happy man who loves looking at how the world works. And yes, I borrowed heavily from him. I want Dr. Feynman in my elementary schools.

Again, another random photo.


Laurence Baclin said...

What I'll remember from your post? Random pictures are good, standard curriculum are bad ;o)

doyle said...

Dear Laurence,

Thanks for the words, I think....

Jenny said...

Feynman would likely be top on my list of people I wish I had ever had a chance to share a meal with. Science has probably always been my least favorite subject (which doesn't really say too much because I love all of it) but I'll struggle through Feynman's lectures just for his voice and respect for the learner.

I'm grateful to know that in some places those in power manage to pick good people to form the curriculum. I'll be very interested in seeing the final product from ya'll's work.

doyle said...

Dear Jenny,

Ain't he grand?

I'll be glad to send you what we end up with--I'm glad I'm doing it, just wish we had a few more hours in a day to get done what needs getting done....

Anonymous said...

Well, what a force IS is really difficult. You are describing what it does - the effect. Even looking at "contact" forces vs. "non-contact" forces - on an atomic level, how does this "contact" happen? And it's only contacting in one place, not all the atoms.
I'm not suggesting you teach this, I am suggesting that we begin to encourage this sort of honesty.

Anonymous said...

oops and then I got the video to play...
but he still doesn't acknowledge that we don't really know what a force IS, does he? Only that it is.

doyle said...

Dear Anonymous,

Yep, and that's the point. I start each year telling my class I hope that they'll know less by the end of the year than they did at the start.

Science uses measurable (or at least observable) effects to create models to predict.

I have no idea what matter is--the kids don't believe me when I say this in September.

I agree that we need to teach honestly--which means leaving gaping holes in our current curriculum. I can live (even thrive) with that, but it makes some students (and a few parents & administrators) a bit uneasy.

You know when students get it when they have trouble walking after being immersed in this stuff.