Some of the teachers in UE2 seem to think of us physics PhDs as repositories of knowledge and of themselves as ignorant. I think it's safe to say that typical professional development reinforces this conceptualization: the attitude from university people toward teachers is, "We know what you need to know." (That's what I had experienced before coming here, and I've heard teachers say that is their experience.) Our hope is that the professional development offered here does not take that attitude. I am trying to cultivate the attitude in myself that they know what we need to know.
I want to confess that this is nontrivial for me - it's an attitude I aspire to, but it's not how I was raised. In order to help make this mindset deeper and more automatic for myself I am trying to articulate specifically what physics I have learned from the teachers so far this week.
First of all, they are right about something, which is that they do not give me physics answers that I didn't already have. They do, however, give me questions I didn't have. And if you believe that questions indicate learning, which I do, then I have learned physics from them. Then, sometimes I get the fun of answering those questions; so I wind up with more answers than before, even though the teachers didn't give me the answers. Here are some of the questions the teachers have pushed for me this week.
1. What is energy? Okay, this is not this week, and I learned it with the whole SPU team, but still: Only because I personally was pressed on this over and over by teachers, and only because I was challenged to stop being evasive, I articulated for myself that: Energy is stuff that makes things happen. It is invisible, massless, and can permeate objects. It moves from one place/object to another, without any of it going away or appearing out of nowhere. That's what energy is to me. I didn't know that before.
2. What is force? Many teachers are calling repeatedly for better distinctions between energy and force. Much as I have thought in terms of forces and even studied the teaching and learning of forces, I do not have a succinct conceptual statement of what force is that feels as satisfying to me as my energy statement. Here's what I've got for now: Forces are pushes or pulls. They are interactions between two objects that can (sometimes) cause those objects' motion to change. Forces are different from energy in that forces are not stuff; they are more like arrows. They can appear and disappear, they do not travel from one place to another but rather are associated with specific objects the whole time they are in existence. This still feels too long and messy; I'm working on it. I would not have been working on it had I not been pressured by teachers to do so.
3. What does it mean to say that energy comes in different forms? This is a question that is very much still active for me. Forms seem to me to be categories of evidence for the presence of (or changes in) energy. In this sense they seem conceptually highly useful, since they are the kinds of things we see that tell us that energy is present (or changing). What could be more pedagogically or scientifically significant than the nature of the visible evidence of the invisible stuff? On the other hand, I have not yet met a categorization of energy forms that I like (any normal-length list has forms missing that I care about); I don't know what would constitute a valid basis for categorization or for making up forms that aren't on whatever list you've been handed; and the "kinds of things we see" are tied in with our perceptual and technological capacities, which isn't what I had originally meant to be talking about. K-12 teaching about energy seems to me to be very forms-oriented, so I want to have a clear understanding of forms, and I don't.
4. Might it be possible to have a different, coherent, explanatory model, in which energy is created out of nothing? Today Lisa (UE2) wanted to explore the possibility that when you lift something away from the earth (in her case an elevator), gravitational energy is created in the object. She also had a complete and correct energy story in which energy was conserved, so it wasn't that she lacked understanding, it was that she wanted to explore a possible alternative model. (And I found that I have some sympathy for her intuition, that there is something energy-like created by pulling attracting things apart. can anyone help me with that? does that come from somewhere?) I don't see Lisa as having been merely creative or rebellious; devising and testing alternative models of a phenomenon is critical to science. This really has me thinking. What might that model look like, fleshed out? Would there be anything wrong with it? Would it be equivalent to some other model - would it make energy more like some other physics quantity? I think that my own model for energy is only as strong as the alternative models that it's better than, if you follow the grammar of that.
Maybe I will get a chance to share some of this with them. Unfortunately I think it might be surprising for them to learn that I am learning anything from them (other than how ignorant they supposedly are), and maybe having examples would help.
Comment on 3: I like your idea of trying to come up with a valid basis for determining a criterion for a new category of form. I think to answer it we have to look at when people invent new forms, which is when they're trying to explain something. Historically in science, new forms have often been invented when the known forms didn't add up in a way that satisfied energy conservation. So surely one criterion is that you have to have enough forms to account for all the energy in whatever scenario you're looking at. This criterion actually seems pretty straightforward.
ReplyDeleteBut then there also needs to be a criterion that has to do with how you subdivide form: e.g. are sound energy and growth energy different from kinetic energy, or the same thing? This criterion seems much more slippery than the first. Basically, we come up with finer distinctions when we need them to explain something and lump things together when the finer distinctions aren't useful to us. As Krishna pointed out earlier, physicists are constantly switching between models with finer and courser grains of distinction. Sometimes it makes sense to say that kinetic and potential are the only two forms of energy and sometimes it's really important to distinguish between vibrational and rotational and translational kinetic energy. In this case, I don't think we can come up with any general rule, just that we subdivide as necessary.
In conclusion: My criteria form how many and which forms we need is: We need to have enough forms to account for all the energy in whatever scenario we're looking at, and we need to subdivide it into enough categories to distinguish all the features we care about.
Comment on 4: I think Lane said this yesterday, but I'll say it again here: Gravitational potential energy *is* being created when you lift an object, but not out of nothing, out of some other kind of energy.
ReplyDeleteMaybe this is a problem with the phrase "energy is never created or destroyed." We actually do talk about new forms of energy being created, when what we really mean is that some other form of energy transformed into this new form. Is turning something into something else the same as creation? Certainly in everyday language we say we create a painting, when really all we did was put together canvas and paint in a new configuration.
I keep thinking of gluons popping out of the vacuum when you try to pull quarks apart. Are we creating gluons or just turning the energy we're using to pull the quarks apart into gluons?
On Wednesday afternoon in UE1, Heather said repeatedly that she didn't think energy could be created, but she thought maybe you could turn less energy into more energy. I found myself getting really annoyed because in my mind these two statements are identical and I wanted her to see that they are identical. But they are different to her. My annoyance probably stemmed from my frustration at not being able to understand why they are different to her.
Rachel, this is so good. I really, really like it, and I'm wondering whether you'd consider turning it into a short TPT paper.
ReplyDeleteIf you like this idea, it might also be fun (?) to add a piece about what teachers (both pre- and inservice) have taught you (us) about _teaching_. I'd be happy to mull over this with you (or add something from my experience), because I feel like I'm learning a whole lot from the LAs about this.
And...did you get to share this with the teachers, as you suggested that you might? If so, what was their response?
ReplyDeleteI did share this with the teachers, verbally, on a special brown-bag-lunch day in which we invited them to ask us any questions they wanted about the videotaping or the research. Sam prepared a letter to all of them (posted here: http://scherrenergyproject.blogspot.com/2011/07/open-letter-from-videographers-to.html), we wore the microphones, they held the cameras, and we had what I remember as a wonderful conversation. It should be on video!
ReplyDeleteThanks, Rachel. I'll look for the video this week! Exciting.
ReplyDeleteI've been thinking more today about whether or not I think a contribution from me about what I've learned from LAs this quarter is an appropriate addition to the paper I proposed. I think your paper would be stronger without it, actually, and I think that the LA piece would be better saved for a different paper/presentation.
I'll let you know what I find in terms of video and whether there's anything that strikes me as interesting or relevant to a paper. :)