## December 21, 2006

### Lectures on Classical Mechanics

#### Posted by John Baez

In the Spring of 2005 I taught a graduate course on classical mechanics, and Derek Wise took beautifully precise notes. I started with the Lagrangian approach, with a heavy emphasis on action principles, and derived the Hamiltonian approach from that.

Now, as a Christmas present to the world, Blair Smith has converted them into a beautiful typeset PDF document, adding extra material:

Enjoy! And, please report any typos or other errors that you find!

This is a great example of the new open-source approach to collaboratively writing expository papers.

The LaTeX source code is available here. If you correct 10 or more typos in a way that I can use, I will thank you in the final version of these lecture notes!

If you wish to correct large numbers of typos, please consider downloading source code, making corrections, and sending the corrected code to me. Please don’t make changes to the format, so I can run ‘diff’ to see what changes you’ve made without being drowned by inessential changes.

There are many nuances of style and content that I need to adjust before these notes are ready for publication. So, I’ll be making changes too, but doing my best to keep the above source code up to date.

Posted at December 21, 2006 7:30 PM UTC

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### Re: Lectures on Classical Mechanics

This is one instance where I would really like to have a wiki whose pages are all LaTeX documents, so that we could all work together on fixing the bugs we catch. For example, take the first line of the Preface:

These course notes for a mathematics graduate course on classical mechanics.

This sentence no verb.

(I have also wished that Thomas Pynchon had published his most recent novel, Against the Day, as a wiki. This is only because the errata list is distressingly long. As far as I know, I was the first person to notice that the dust jacket flap copy had Nikolai Tesla instead of Nikola…)

Posted by: Blake Stacey on December 21, 2006 7:59 PM | Permalink | Reply to this

### Re: Lectures on Classical Mechanics

Blake wrote:

This is one instance where I would really like to have a wiki whose pages are all LaTeX documents, so that we could all work together on fixing the bugs we catch.

It would be nice. Alas, I don’t know how to set up a wiki, so for now I’m making the LaTeX files available as described above.

I fixed the first typo you found, and a bunch more in the first few pages. I also changed the discussion of Lagrangian vs Hamiltonian approaches to more closely fit what I think kids at this stage need to know. Right now most of the long passages of text were written by Blair — who, while a great guy, has the unfortunate habit of not being me.

Posted by: John Baez on December 22, 2006 11:38 PM | Permalink | Reply to this

### Re: Lectures on Classical Mechanics

Hm… “This Wiki’s Finds”?

Anyhow, I’ve seen a lot out there running Wikipedia’s own MediaWiki. At a glance it doesn’t look too difficult to maintain.

Posted by: John Armstrong on December 23, 2006 12:36 AM | Permalink | Reply to this

### Re: Lectures on Classical Mechanics

It’s worth noting that preface.tex is not in the source code directory, so you get a file-not-found error message when you run LaTeX on classical.tex. Doesn’t seem to be a fatal flaw, though.

The problem with MediaWiki is that it has its own markup language (“wikitext”), which has to be converted to LaTeX. This part could be done with regular expressions, changing double apostrophes to \em commands and so forth. More significantly, the math support in MediaWiki is rather like a vermiform appendix: while it’s easy to throw an equation into a wikitext page here and there, doing the systematic work necessary to make an actual physics paper is much more difficult. You put all equations inside $ and $ tags, so not only would one have to change all those tags over to equation environments, but also the convenient features of LaTeX like equation numbering just don’t exist.

Converting bibliographic citations from MediaWiki’s <ref>-tag system over to BibTeX poses another problem of comparable complexity.

Ideally, we’d have wiki software which stores pages in straight-up LaTeX and allows for all (or almost all) the features of the language. Until then… .

Posted by: Blake Stacey on December 23, 2006 1:41 AM | Permalink | Reply to this

### Re: Lectures on Classical Mechanics

Blake wrote:

It’s worth noting that preface.tex is not in the source code directory.

Fixed - thanks!

There are lots of easy things that need doing, like turning \emph to \textbf for all defined terms. So far I’ve only done this for Chapter 1. I also tried to make the tone of voice more like mine in this chapter.

Posted by: John Baez on December 23, 2006 2:56 AM | Permalink | Reply to this

### Re: Lectures on Classical Mechanics

There are lots of easy things that need doing, like turning \emph to \textbf for all defined terms.

Damn straight. Definitions should be findable!

For the benefit of those benighted souls who want their definitions nigh-invisible, I would suggest changing them instead to \defn, which can be newcommanded as one wishes.

Posted by: Allen Knutson on December 23, 2006 3:52 AM | Permalink | Reply to this