# Lies Your Physics Teacher Told You?

He of uncertain principles asks Which do you prefer: transverse waves, or longitudinal waves? The fact builder chimes in with a clarification of a common misconception.

Myself, certainly I’m going to go for transverse waves. Not only are all the cool waves transverse (well sort of), electromagnetic waves, gravitational waves, stadium waves, etc, but you can’t surf on a longitudinal wave.

And of course, how cool are gravitational waves? So cool they produce this mesmerizing action on a ring of particles:

Interestingly while light is often used as the quintessential example of transverse waves, (the example being give is usually that of plane waves of light) if you talk about light beams with finite diameter, longitudinal modes appear. (For example, see here) But I don’t fault my physics teachers for not teaching me this: learning physics is really just a series of less lying anyway isn’t it?

1. #1 Ian Durham
May 21, 2009

> learning physics is really just a series of less lying
> anyway isn’t it?

I always thought that until I started using Tom Moore’s text to teach physics. He spends the time to get it right the first time and still make it comprehensible to students.

2. #2 Chris
May 22, 2009

I’d like to think my physics teachers told me truth, for all practical purposes that is. The real lies started in grad school. If we survive the next revolution, will we not realize that learning physics was a series of steps in order to understand the ultimate lie?

3. #3 David
May 22, 2009

You know, I think I *finally* get [circular] polarization.

4. #4 Aaron
May 22, 2009

Dave: Did you not have to do the waveguide sections of Jackson?

5. #5 Dave Bacon
May 22, 2009

Thank you Aaron for reminding me of that painful experience. Yes I had that, but not before they lied to me in physics 1 (actually I didn’t go to class enough to tell whether they lied or not ðŸ™‚ )

6. #6 Neil B â™ª
May 26, 2009

Yeah, I think a lot of the problem has to do with both semantics and visualization (the latter well dissected at BoF.) People, even scientists, aren’t the best “framers of issues.” I think the decoherence scam (IMHO) is one of the worst examples.

I think another “lie” is that mechanics is all sorted out. Well, not the relativistic mechanics of extended bodies. Consider that arguments over correct solution of the right-angle-lever paradox, Thomas Precession etc. kept popping into Am. J. Phys. or Il Nuovo Cimento into the 70s. I’ve been working on an issue I call “the referred force problem” in relativity. I explain in my latest blog post, “Challenging electromagnetic paradox of relativistic forces.” There’s so much attention paid to particles, few realize that it’s messy hashing out what happens to extended bodies subject to forces with points of application that move upon them (like, on currents) and then considering those bodies in motion.

7. #7 Jonathan Vos Post
May 27, 2009

I agree with Neil B that many simple cases of extended bodies subject to forces, in General Relativity, are still unsolved. Kip Thorne confirmed that there is, for example, no published solution of a “rigid” (as redefined for GR) disk under angular acceleration.

More generally, almost all education is a lie, in the sense that each wave of instruction is merely a less-oversimplified treatment. Children are taught positive integers. Then negative. Then told that negatives have no square root. Then taught imaginary numbers. Then told of other square roots of 1 (quaternions), then matrix solutions…

This is true in particular for Science and Math, under the pedagogy of “spiraling” and “scaffolding.”

Yet the student-teacher relatiosnhip is purportedly based on truth and trust. I take my job as a teacher as seriously as my job as a scientist. So my classroom narratives all come with disclaimers.