As mentioned on the front page, the target audience for this website is amateurs -- people who are interested in physics, and are interested in relativity, but who are not professional physicists.

It is my fond hope that this site may help some visitors to better understand the subject of relativity, or at the least will provide some interesting reading.

The goal of relativity is to render all physical laws in a form which is relative to the observer:  the laws should be independent of any motion of the observer or (in the case of radiant energy) of the source.  Special relativity treats the special case of uniform motion; general relativity treats the more general case of accelerated motion.  General relativity also provides an answer to the question, "Why are inertial and gravitational mass always present in a fixed ratio?" or, equivalently, "Why does everything fall at the same rate?"

If you are setting out to learn relativity, then I have a bit of hard-won advice.  Start by asking yourself:

1. Rock solid!  I invert matrices in my head for fun!
2. OK, I guess.
3. Boy I hated that subject -- skipped all the homework and just crammed for exams
4. Algebra?  Huh?  You mean, like the quadratic formula 'n stuff?
If you answered (3) or (4), go find an algebra book and spend some time with it.  Artin's "Algebra" is pretty readable, if you haven't already got a good text lying around.  Ideally you should at least know what a symmetric bilinear form is before you tackle relativity.

GR requires tensor calculus, but introductory GR texts tend to cover it as they go, so it's not really a problem.  But they seem to assume you already know the algebra cold.

### About Units and Conventions Used on This Website

Throughout this website, I use the convention that C = 1, and hence multiplication by C can be ignored.  If time is measured in seconds, then lengths are measured in light-seconds; if time is measured in years, then distances are measured in light-years.  This simplifies a number of formulas considerably, though at some occasional cost in clarity.

Except as noted, the Lorentz metric is assumed to be diag(-1,1,1,1).

### About Me, and Contact Info

I'm a professional programmer with a long-time interest in math and physics.  I finally decided I wanted to understand something about general relativity.  So I blew a bunch of money on text books, and since then I've spent lots of my free time studying (or arguing with various people on sci.physics.relativity).

If you want to get in touch for any reason, please email me.

The derivations and proofs on this site are my own.  Though I have tried to be careful, the conclusions here have not, for the most part, been checked against published books or articles, so it's quite possible that there are errors either in the reasoning or in the conclusions.  If you happen to run across anything you think is incorrect, please let me know.

### About the Website:  Technical Details

Most of the pages on this site were authored using Mozilla (which was capable of producing far more sophisticated websites than anything I ever asked it to do -- the simple site design and primitive formatting are by choice, not by necessity).  Since Mozilla got canned, recent pages have been authored with a mix of Kompozer (a variant on NVU) and Seamonkey, depending on whose bugs I find the most annoying on any particular day.  The illustrations were done with Gimp.  Most of the equations were edited with OpenOffice, but recently I've gotten sick of the never-fixed bugs and limitations in OO Math and have switched to LaTex (which has a completely different set of problems).  Graphs were either drawn with splines in Gimp (when the curves were not critical) or were produced by Gnuplot.  The inline Greek text uses a mix of pictures and HTML Unicode characters, which may be unreadable in some browsers.  Links and image dimensions are checked with home-brew Perl scripts before uploading, and most pages have been validated using the W3C validator.  If you have problems with anything on the site please email me.  The pages are served by Apache running on a Linux box, on space owned by the good folks at ServerSnap.com.

Except for photographs of Einstein, all text, images, and computer code on this site, unless otherwise noted on the individual pages, are copyright © 2004-2012 by Stephen A. Lawrence.  If you copy anything from this site at least have the good grace to send me email telling me about it.  (In any case my employer probably is the legal owner, since like most of us I signed away my rights when I took a job.  Whatever.)

It's hard for me to imagine how anyone who studies the general theory of relativity could fail to conclude that Einstein, Hilbert, and Riemann were brilliant.  Einstein, obviously, also had a sense of humor.

Page last updated 11/16/06