# July 19 2000

Math lesson

Thanks, Craig, for the math lesson today!

Craig points to the tesseract, a four-dimensional cube. Cool animation, it’s very illustrative. And here are the Quaternions for the Masses. I learned about the Quaternions in Linear Algebra II, a few years back. A fascinating mathematical object! (I liked the complex numbers when they were first introduced in my last year at school, and the quaternions seemed kind of like “complex numbers for advanced students” to me.)

The tessaract and the quaternions are only a few pages of Harry J. Smith’s Fun with Mathematics!.

Craig had another interesting link, but I’m afraid it will take me a while to look through The Geometry Junkyard.

One thing I found there is this page of 3D Strange Attractors and Similar Objects. Mathematics can be beautiful!

New Design

Sheila has a new design, which I think is great! I especially like the ‘Buglight’ font.

Wann kommt der Sommer?

The weatherforecast has been promising that it’s going to be warm and sunny today. Nope. It was cloudy and even rained a little. Not very warm either.

I went to Cologne today to do some shopping. I also had my camera with me because I thought this was a good chance to take some photos of the wonderful cathedral in Cologne (“Dom St. Peter”) in the sunny weather. But since the weather was everything but great, the photos don’t look very good. This one shows the upper part of a side entrance. Here’s another one of the towers.

The cathedral is more than 750 years old, but it took a long time to build it: It was finished in 1880 and needs constant renovation, nowadays mostly because air pollution destroys the sandstone it is built of.

The WDR (West German Broadcasting) has a webcam that shows the cathedral: Domcam.

If you want to see some more pictures of the ‘Dom’, go here. Click on any link to see some pictures. A click on the pictures leads you to a larger version, and click on ‘weiter’ to see the next picture. ‘Abschnitte’ brings you back to the overview.

Der Dom hat auch eine offizielle Homepage (auf deutsch): Kölner Dom online.

P.S.: Sorry, Jörg, heute gibt’s keine geklauten Links von Dir!