## Feynman Fysics

Without any new MythBusters popping up lately, I’ve had to find another outlet for my science geek needs.

Fortunately, the library had Feynman’s lectures available, and I’ve got volume one checked out again.  I’ll try to share some thoughts as I relentlessly plow my way through the book.

First off, I’m really enjoying the depth, breadth, and brevity of the topics he covers in such a short time.  It’s neat and depressing how many basic concepts he can walk us through from the ground up; it was definitely “easier” to make multiple really earth-shattering discoveries back in the day.  It feels like most of the low-hanging fruit has been had; of course, we’ll only probably feel that way until the next simple yet elegant discovery is made.

If I were to right an introductory physics text, this is exactly what I would want to do, I just wouldn’t be able to do it.  That being said, I have just a few critiques.

As Dr. Feynman walks the reader through Newton’s laws of dynamics, he isn’t as precise with the notation as I’d prefer.  He is very consistent in his description of vector quantities, but does not distinguish vector values from scalar values in the notation. It is not uncommon to see

$F=m\frac{dv}{dt}=ma$.

I mean, granted, LaTeX probably hadn’t been invented, and the type-setting wasn’t too stellar back in 1963, but at least use bold or something to distinguish between scalars and vectors.  This isn’t problematic for the reader already familiar with the concepts, but to new students, I can imagine it will cause at least a modicum of confusion.

In the same vein, he plays kind of loose and fast with units.  For instance, in dealing with the spring equation:

$-kx=m\frac{dv_x}{dt}$

he understandably wants to simplify it by picking convenient units to eliminate k and m.  So he says that he will use $k/m=1$.  Okay, but even these have to have some sort of units of inverse time squared; actually, he should have just stated $k/m=1\; sec^{-2}$, because when he uses the equation later, he uses seconds.  Why is this important?  Because the equation he works with reduces to

$\frac{dv_x}{dt}=-x$.

Which is problematic, since there are units of acceleration on the left, and distance on the right.  It would have made me feel much better if he had instead written

$\frac{dv_x}{dt}=-\frac{x}{sec^2}$.

Or something.  Again, it’s not a problem for people comfortable with the material, but may throw some wrenches at somebody still developing mastery.  As opposed to vectors and scalars, he doesn’t really address this inconsistency, which may make it more problematic.

What do you think?  Am I being picky, or are these things to be concerned about?

### 2 Responses to “Feynman Fysics”

1. Shaz says:

I think you are being picky and rightfully concerned. My biggest gripe with science literature in general is that there is little to no concern to make it readable/understandable to the non-PhD. A good undergrad should be able to understand this stuff quickly. Mixing units is bad form at any level. If it wasn’t Feynman I’d think he didn’t know what he was talking about.

Also, I’ve finally started reading your posts. You’ve officially made it to my RSS feed and the “Interesting Links” portion of my own page. That’s kind of a big deal.

• K-Mob says:

I’m honored.

To be fair, he goes on to explain vectors quite thoroughly a couple chapters later, using bold symbols to designate them.

That still doesn’t absolve him of his units negligence.

I think for the most part it is a great read for an interested non-Ph.D. Which is probably why I like it…