It must be karma.

Earlier today, I was over at Mentat Wiki. If you're into brain-oriented feats and haven't already checked it out, do so now.

I was adding a page about doing logarithms in your head. This is a pretty geeky topic, and not generally useful, but it can be a great tool to impress your math teachers and fellow geeks.

Once I finished editing the logarithm article, I headed over to ThinkGeek, one of my favorite on-line stores. Lo and behold, I find out that they've just added a newly-found cache of slide rules!

For those who haven't heard of them, slide rules were a simple and elegant calculating device used before the pocket calculator became common. As ThinkGeek writes:

Most of you just don't know how lucky you have it these days. Can you imagine going through advanced Trigonometry without a calculator? No, you probably can't. Can you believe that the cigar-smoking NASA mission-control engineers during the sixties had to make split-second super-mega-advanced calculations using nothing but a slide rule? Probably not. They did.

Slide rules used logarithms to enable the user to perform an amazing array of calculations, including problems involving exponents and roots. Among our geek forefathers, they were a badge of honor.

You can find out more about slide rules at, not surprisingly, Eric's Slide Rule Site, and even try a virtual slide rule out at JavaSlide.