Familiarity and Lies-to-Children

One of the interesting things to come out of the switch to Matter & Interactions for our intro classes has been some discussion among my colleagues of how the books treat specific topics. A couple of people have raised concerns that the coverage of certain topics is different from the traditional presentation, in a way that isn’t entirely accurate.

This is interesting to me not because it calls the books into question, but because the standard treatments of these things aren’t entirely accurate, either. Both the new book and the older book are full of lies-to-children.

“Lies-to-children” is a term that I attribute to Terry Pratchett (via one of the Science of Discworld books), and it’s distinct from an ordinary lie. A lie-to-children is a simplified story you tell to people who aren’t ready for the full picture.

An ordinary lie, as I said in class the other day, is “I did the homework, I just don’t have it with me.” A lie-to-children is, for example, the story we tell elementary school kids about how a bill becomes a law:

“Somebody proposes a law, it’s debated in Congress, both houses vote, then the President signs it, and it becomes a law.” It’s a wonderful, comprehensible story, but it’s also a lie-to-children. There’s nothing in there about subcommittee hearings, or lobbyists, or earmarks, or filibusters, or signing statements, or judicial review, or…

The reality of our legislative process is much more complex, and much more sordid. But kids watching cartoons aren’t ready to hear that sort of thing– many adults can barely get their heads around it– so they get the simple version first. It gives them enough information to understand the broad outlines of the world, and start to function as citizens, and when they’re ready to know more, they can learn more.

Physics is full of lies-to-children. Newton’s Laws are a lie-to-children– they’re a wonderful description of the motion of macroscopic objects at low speeds, but they fail utterly when dealing with very small objects, or objects moving at speeds close to that of light. We teach first-year college students about classical mechanics alone, because that’s enough to get the basic idea, and if they want to know more, then we let them in on Special Relativity and the Schroedinger Equation. Which are themselves lies-to-children, standing in for General Relativity and the Dirac Equation, and so on.

What’s interesting about the Matter & Interactions books is not that they’re full of lies-to-children, but that they use a different set of lies-to-children than the standard texts we all grew up with. And people’s reaction to this is really interesting– some of the concerns people have expressed are really fine technical points, having to do with things that M&I covers that more traditional books skip completely– a microscopic picture of the flow of current, for example.

I’m not trying to run down my colleagues, here– they’re not raising objections just to be difficult. They’re sincerely concerned that the inaccurate points in the new book might create some student confusion later on these points. They may even be right (though I’m not convinced it would matter, for some of the points raised).

What’s fascinating to me, though, is that I don’t think that the conventional treatment is really all that much better at avoiding things that are technically untrue, particularly on the sort of technical points that people have raised in discussion. It’s just that we all took classes under a traditional curriculum, and we’ve all taught classes in a traditional curriculum, so the lies-to-children that we tell when teaching from those books are familiar and comfortable, while the lies-to-children we tell in the new curriculum are unfamiliar, and thus unsettling.

There might be some insight here into the unending debate about communication strategies here in blogdom. Lots of the objections to “framing” and the like are phrased as objections to “lying” about science. But really, the “lies” in question are lies-to-children, and scientific education is all about lies-to-children. It’s just that the lies-to-children suggested by advocates of alternate communication strategies are different than the lies we’re used to telling, and that makes some people uncomfortable.

(I don’t think that’s the whole story– I think it’s really a question of differing goals– but that could be a part of it.)


  1. #1 Daryl McCullough
    May 1, 2008

    I forgot who it was who said this, (maybe RealLibertarian(tm) Jim Henley), but somebody said that he considers the Santa Claus myth to be a very important lesson to teach children: That even people who love you sometimes lie to you, often with your best interest at heart. (or something like that) For a kid to discover for himself that there is no Santa Claus and that he was lied to about it, and that that doesn’t mean that his parents are evil people, is an important step in developing a mature outlook towards life. Whoever it was, also thought that disbelieving in Santa was good practice for disbelieving in God.

  2. #2 Daryl McCullough
    May 1, 2008


    What’s an example of a new lie introduced by “Matter & Interactions”?

  3. #3 CCPhysicist
    May 1, 2008

    Yeah, just from looking at their info on the web I would agree it is more about differing goals … which are then reflected in which simplification you choose to use.

    Now I know I want to look at that book, if only for some additional insight on the “lies to children” we tell. (F=ma, lie, F=dp/dt, connects well to relativity, not needed if you are building bridges, quite helpful if you are engineering for a car crash.) The one about current is interesting because the electrical engineering of chips is getting into the small numbers limit for conduction at frequencies where the wires on the chip are really wave guides with corners.

    Pointing out where simplifications are being made is one of my teaching tactics. I use it to help students see that there will be more to learn on top of what we have introduced. One simple example is that we only treat steady state AC circuits in intro physics, nothing about the transient behavior determined by the phase of the source at t=0 when you connect it to the circuit. Ditto for ignoring the effect of a beam bending or a door deforming when it is under load when doing statics problems. “You need to do this problem like you solve y=mx+b if you want to kick ass when you move on to the next level at Wannabe Flagship U.”

    Of course, I can use “the little guy with attitude” at my CC in a way that you can’t at Union! Or maybe you can, with Harvey Mudd and Harvard as reference points for the competition to get into grad school.

  4. #4 Uncle Al
    May 1, 2008

    Three pieces of adding machine tape with a line drawn down the center on both sides. “Cut something entirely in half and obtain two pieces.”

    1) Make a hat band by taping a lap join. Only cut along the line, all the way around. Obvious result.
    2) Make a Moebius strip by adding a half-twist before joining. Cut. Classic result.
    3) Make another Moebius strip and cut half-way between the line and the edge, all the way around. Instructions are short, explanations are long.

    All the fun is in the footnotes. All compositions of matter validate the Equivalence Principle, now to 5×10^(-14) relative. Do chemically identical left and right shoes validate the Equivalence Principle? Somebody should look.

    The proper test of spacetime geometry is mass distribution geometry – enantiomorphic crystallographic space groups P3(1)21 and P3(2)21 alpha-quartz test masses contrasting the relative positions of their nuclei in space with a 0.484 nm chirality emergent scale. Somebody should look.

  5. #5 Paul King
    May 1, 2008

    IIRC the “lies to children” term is found in the sections written by Jack Cohen and Ian Stewart.

  6. #6 Laelaps
    May 1, 2008

    I always liked the Simpsons’ “Amendment to Be” song better…

  7. #7 Ron
    May 1, 2008

    Do you follow the discussions with the authors on the M&I e-mail list?

  8. #8 Pseudonym
    May 1, 2008

    A lot of scientists don’t understand that people think and speak almost exclusively in metaphor.

    I found Daryl McCullough’s comment interesting about Santa Claus, but I can’t help bringing up another Terry Pratchett observation: That people need to believe in the “little lies” (like the Hogfather; the Discworld’s Santa Claus) so that they can believe the big ones, like justice.

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