Monday, June 28, 2010

Visualisation tools - Part I, resonance

For several years now, I've had the notion of writing a discussion of the characteristics of various musical instruments, with a particular focus on the primary resonator (string, air column, whatever) and ignoring, at least in the first instance, the effect of the modes of vibration of other bits of the structure (because that's complicated).

I plan, as a starting point, to consider a string, pinned at both ends. This has an infinite number of potential modes and which ones are excited depends on the mode of excitation: a guitar string starts with a displacement function and zero velocity; a piano string starts with zero displacement and a velocity that I suspect can be fairly well approximated by a Dirac delta function; I don't know about a violin string.

I'll then go on to discuss wind instruments, particularly flute and saxophone (because I have them lying about the house), before dealing with the most difficult of all, the humble harmonica. That's difficult because, even using the simplest Euler-Bernoulli model, you have to deal with hyperbolic functions.

An optional extra module will serve as a prequel to all of this - explaining Fourier analysis and synthesis.

I've been wondering how best to do the graphics. The two obvious candidates are VPython and Easy Java Simulations (EJS) - there's a good comparison at the brilliant Dot Physics. I've been using Python a lot lately, especially with NumPy, SciPy and matplotlib, and with all those great libraries it gives you essentially a free MATLAB. On the other hand, the fact that Java can run on pretty much any machine (except the IPhone), means EJS wins hands-down for an online demo.

Saturday, March 27, 2010

The origin of Sheldon?

I got a delivery from Amazon last week including From Eternity to Here by Sean Carroll - I enjoy his blog, and he gives a good lecture, so I thought I'd buy the book. I bought a few other books in the same order, so I haven't started reading it yet, but I'm looking forward to it.

I bought the book in spite of a particularly scathing review by Luboš Motl.  I had a look at Motl's other Amazon reviews. He really doesn't like Lee Smolin's The Trouble with Physics, but he does like Leonard Susskind's Black Hole War. I haven't read Black Hole War, but I've attempted a couple of other Susskinds. An Introduction to Black Holes defeated me. Don't be misled by the title; the tensor calculus starts on page one, and he doesn't say that it's tensors, he just assumes that the reader recognises them. In short, that book is aimed at readers with a better grounding in physics than I have (just a 19-year-old honours degree). On the other hand, Susskind's The Cosmic Landscape was superb. I read that and Smolin's The Trouble with Physics back-to-back last year, and I've been meaning to send Amazon reviews of both. I'd certainly give Smolin more than Motl's two stars, but all of this made me wonder "Who is this Motl guy?"

According to Wikipedia, Motl's a (former) string theorist who's left Harvard to return to his native Czech Republic where he writes a blog, in which he denies anthropogenic global warming, among other rants. He's also written a book (in French) commending the work of the Bogdanov brothers. I'll grant that Motl is better placed than I am to understand their work but I'm still convinced, as I wrote back in 2007, that it's nonsense. The most interesting snippet I've picked up on Motl, from an incoherent jumble of a blog, is that The Big Bang Theory's Sheldon was modelled on him. Actually, I should probably point to this clip; although it isn't just Sheldon, the views he espouses in it are Motl's.

While looking for links for this post I stumbled across this article, complete with comments by all the major players I've mentioned. I haven't finished reading it yet, but Motl is as tactful as ever.