Photons, Schmotons

John Baez and Michael Weiss


Did you ever wonder "What the heck is a photon, anyway?"

Well, this question quickly gets you into pretty deep waters. Not only do you need to understand Maxwell's equations and quantum mechanics, you need to understand how they fit together into a marvelous theory called "quantum electrodynamics".

These webpages won't teach you quantum electrodynamics. But they'll give you a little nudge in the right direction.   

List of Figures:

And guess what! The above stuff is just the first part of a two-part conversation between Michael Weiss and John Baez. The second part has not been made into webpages yet, but you can read it as a PDF file - or as GIF files, which are like a poor man's HTML.

Can't get enough?

For the original conversation in its raw entirety, read the threads on sci.physics.research entitled Photons, Shmotons and later Photons, Schmotons. You might also want to look at the thread entitled Photons, Schmotons: for Oz. After reading this stuff, you might want to try my introduction to renormalization. Maybe someday all these expositions will fit together into a unified, elegant whole... but not now!

Various formats

This stuff is available in lots of formats - but alas, part 2 is not yet available in HTML, only GIF. If you create HTML for part 2, I'll give you a nice present! I'll also reward anyone who creates HTML of Part 1 that includes the Greek letters.

The PDF and Postscript have much nicer typesetting than the HTML files.

There is also a tar file containing this entire website. If you place this in some directory and untar it there, it will create a subdirectory "photon" and put all the files there. There's also a gzipped tar file if you prefer that:

But actually I'm lying: these tar files contain everything on this website except the tar files themselves, since that would make them too large... infinitely large, in fact.

Who did what

Michael Weiss did the really hard work: he created the LaTeX files and turned part 1 into HTML as well. He tried converting these notes from LaTeX into HTML using latex2html, but he had problems, so the version you see is something of a compromise. Barry Brent kindly volunteered to turn part 2 into GIF format. More recently, Tiaan Geldenhuys cleaned up the figures and included them in the LaTeX files.

What binds us to space-time is our rest mass, which prevents us from flying at the speed of light, when time stops and space loses meaning. In a world of light there are neither points nor moments of time; beings woven from light would live "nowhere" and "nowhen"; only poetry and mathematics are capable of speaking meaningfully about such things. - Yuri Manin

2005 John Baez and Michael Weiss