It's Like Building a Bridge

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Uncertain Principles: Physics Is All About Analogies

I’ve got a little speech about this that I give when I talk about simple harmonic oscillators in the intro mechanics class, that I started giving because I got sick of the students giving me pitying looks when I went on about masses on springs. Because, really, who gives a damn about masses on springs?

Of course, any physicist knows that the reason we spend time talking about masses on springs is not because masses on springs are inherently fascinating, but because so many systems that are interesting can be made to look like masses on springs. That is, there is an analogy to be made between the behavior of a really simple system that we can solve exactly (the mass-on-a-spring problem) and much more complicated systems that we would really like to be able to solve exactly.

This goes along with Every Problem Looks Like a Nail, my link to brief comment on an xkcd cartoon: To first order, everything is an harmonic oscillator.

In science, we build models. Analogies are pre-fab models, based on an already-existing floor plan. Or, in the Feynman context of discussing magnets

I really can’t do a good job, any job, of explaining magnetic force in terms of something else that you’re more familiar with, because I don’t understand it in terms of anything else you’re more familiar with.

to put a concept in terms of concepts you do understand, and to use another analogy, it’s a bridge to a concept you understand.

3 thoughts on “It's Like Building a Bridge”

  1. Shouldn’t it be “to second order, everything is a harmonic oscillator?” I mean, it is technically the second-order term of the Taylor expansion, though it is the first non-zero correction…

  2. 1) When all you have is BNC connectors, all your problems look coaxial.
    2) When all you have is a hammer, everything looks like a screw. A hammer is a perfectly good screwdriver. Use a 5 lb baby sledge.
    3) A Slinky is a dispersive medium for transverse waves.

    Uncle Al’s high school physics teacher Mr. Harnik had high standards. He bought an infinitely long Slinky to demonstrate wave action. How do you remove an infinitely long slinky from its box? You open it from the bottom! Then some nit put it in the storage closet and we never did find its ends.

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