Rhett over at Dot Physics is not quite happy about the way magnets are being taught to his young niece:
The other question came from my niece – who is an extremely bright girl (not sure exactly what grade – maybe 5th). She was at home and didn’t have her science textbook, so she asked me the following:
“What happens to the electrons in a metal when it becomes a magnet”
I always worry about magnet questions because magnets are not that simple to understand at a fundamental level. Sure, there are some things you can do with magnets – especially if you want to do some experiments. However, asking questions like this or like “why can iron be a magnet, but not aluminum” to a 5th grader is like asking me how gravity works.
How gravity works might not sound hard either, but at the fundamental general relativistic level it’s exceptionally difficult and at the quantum level nobody has any idea. The problem is this: when discussing things like gravity at the introductory level, it’s possible to give a correct and useful classical description. Air resistance aside – and that too is easily understandable if mathematically difficult – finding trajectories and orbits is easy. It’s one of the first things we teach in into physics classes. The gory relativistic details just aren’t important at any energy scale the students will ever have to deal with. This is true all through the physics of daily life. You don’t need quantum electrodynamics to explain a light bulb, you don’t need the full canonical ensemble treatment to explain hot and cold, so and and so forth.
But magnets? Almost uniquely among everyday phenomena, anything even resembling a remotely accurate explanation is a blisteringly complicated quantum mechanical affair. Even first year textbooks for physics majors tend to gloss over the actual answer to “why are some things magnets?” questions with a few paragraphs of non-mathematical handwaving.
I don’t like this, but nature is what it is. My advice to teachers of 5th graders science is to mostly skip the “why” in the case of magnets and focus on what magnetic materials do. Some things are ferromagnetic, they do this. Some things are diamangetic, they do that. I hate hate hate giving that advice, but I just don’t think it’s possible to simplify magnets to that level without creating additional confusion down the road. Once the students are advanced enough – maybe high school – then start with some non-mathematical simplifications of the quantum origin of magnetism.
Which, come to think of it, might be a good thing to talk about around here…