Archive for February, 2001

February 28 2001

Wednesday, February 28th, 2001


Ich demonstriere gerade einer Freundin, wie Manila funktioniert!

February 27 2001

Tuesday, February 27th, 2001

Email: It seems I can receive email via at the moment, though I’m not sure it will stay this way. Apart from the problem in the US it seems that the German Telekom is having problems at the moment as well…

By the way, if anyone has got a large digital image of Circle Limit IV by M. C. Escher (at least 1,000 x 1,000 pixels), please let me know!

circle limit 3: Hyperbolic Geometry

Hyperbolic Geometry is a strange world. There is more than one parallel to a straight line through a certain point, and the three angles of a triangle add up to less than 180°. There’s no way to build a real model for this geometry in our Euklidian world, but there is a model: The whole hyperbolic world fits into a disk.

To me, hyperbolic geometry is one of the most interesting branches of mathematics. One of the most beautiful works of art visualizing the hyperbolic plane is Circle Limit III by Maurits Cornelis Escher.

Science News: Visions of Infinity – Tiling a hyperbolic floor inspires both mathematics and art. By Ivars Peterson.

Helaman Ferguson, sculptor and mathematician:

“I chose to do creative math in a liberal arts college rather than an engineering school. Our society tends to compartmentalize people and professions, maybe with good reasons. Overcoming this compartmentalization has been a continuing battle for me.I refuse to be diminished by being described as just a mathematician, by being described as just a sculptor–I persist in both. Fortunately for me our society is diverse enough to permit both. […]

Mathematics, its ideas, symbols, and equations are an essential part of my personal design language. Much of my sculptural body of work celebrates the remarkable achievements of mathematics as an abstract art form–a human activity spanning thousands of years. “

Look at his hyperbolic quilt!

Douglas Dunham: Transformation of Hyperbolic Escher Patterns. The author also presents two colourful hyperbolic sculptures.

Spherical Geometry

is sort of the “opposite” of hyperbolic geometry. No parallels exist in the spherical world, and the angles of a triangle add up to more than 180°. I just received email from Dave Fisher (Thanks!), who wrote a poem about a spherical triangle: My Favourite Triangle.

As you may have gathered from the poem, spherical geometry is what’s happening on a sphere. Try to draw two straight lines on a sphere and have them not meeting anywhere! See, no parallels.

Note: straight lines on spheres are great circle paths. (The great circle path is the intersection of a spherical surface with a plane passing through the two points on the surface and the center of the sphere.)


Hal, it’s great to read that the CPAP is working for you. Although I guess it’s really pretty strange to have air blown up your nose all the time. But if it helps… fine!

February 26 2001

Monday, February 26th, 2001


Spicy Noodles mail is down again. Sorry.

Please use if you want to send me email.

Sorry for the lack of real updates. Busy with the thesis… Just give me another couple of days.

February 25 2001

Sunday, February 25th, 2001


Ich suche gerade nach einem schönen Spruch, den ich an den Anfang meiner Examensarbeit stellen kann. Er sollte entweder von einem großen Mathematiker (z.B. einer von den alten Griechen), M.C. Escher oder Einstein sein, sowas macht sich doch immer gut. Und was finde ich da bei Jörg?

“Die Mathematiker sind eine Art Franzosen: Redet man zu ihnen, so übersetzen sie es in ihre
Sprache, und dann ist es alsbald etwas anderes.”

Johann Wolfgang von Goethe

Wie wär’s?

Die Seite, auf der ich den Spruch gefunden habe, heißt Mathematikbücher, die Spaß machen!. “Der Zahlenteufel” von Enzensberger steht schon auf meiner Wunschliste.

In einem, lieber Jörg, muß ich Dir aber heftigst widersprechen: Die Menge der Mathematiklehrer und die Menge der Mathematikliebhaber sind keineswegs disjunkt! Mein Mathelehrer aus der 5. und 6. Klasse war eindeutig auch ein Matheliebhaber, und er verstand es auch, die Schüler für sein Fach zu begeistern. Oder jedenfalls mich.

In der Oberstufe hatte ich dann noch einmal einen ganz wunderbaren Mathelehrer, der nicht unschuldig daran ist, daß ich jetzt hier sitze, Mathe studiere und sogar meine Examensarbeit in Mathematik (statt Physik) schreibe.

(Was jetzt nicht heißen soll, daß mein Physiklehrer in der Oberstufe nicht gut war – er hat es mitverschuldet, daß ich nach dem Abi angefangen habe, Phsik zu studieren. Zur Mathematik kam ich erst ein paar Semester später wieder zurück.)

Und sogar in der Uni ist mir der eine oder andere Mathematiklehrer (oder zählen die Profs nicht dazu?) begegnet, der seine Begeisterung an uns Studenten weitergeben konnte. Der, der meine Examensarbeit betreut, gehört eindeutig auch dazu.

Und mein liebstes Mathematikbuch? “Geometrie des Universums – Von der göttlichen Komödie zu Riemann und Einstein”, von Robert Osserman, für Nichtmathematiker. Und für Fortgeschrittene ganz eindeutig dieses:

“Anschauliche Geometrie” von David Hilbert und Stephan Cohn-Vossen. Aus dem Klappentext:

“Anschauliche Geometrie: wohl selten ist ein Mathematikbuch seinem Titel so gerecht geworden, wie dieses außergewöhnliche Werk von Hilbert und Cohn-Vossen. Zuerst 1932 erschienen, hat das Buch nichts von seiner Frische und Kraft verloren. Hilbert hat sein erklärtes Ziel, die Faszination der Geometrie zu vermitteln, bei Generationen von Mathematikern erreicht.

Aus Hilberts Vorwort: ‘Das Buch soll dazu dienen, die Freude an der Mathematik zu mehren, indem es em Leser erleichtert, in das Wesen der Mathematik einzudringen, ohne sich einem beschwerlichen Studium zu unterziehen.'”

Hm… Sollte sich hier etwa meine Vorliebe für die Geometrie bemerkbar machen?

Around the world on recumbent bikes

Agence Future:

“The project combines social research with journalism and experiment. It consists of three main components. The first, in cooporation with the Free University of Brussels is a world wide study of popular and professional perspectives on the future. Specialist articles, reports, a video diary and a newsletter make the media component of the project. And last but not least, the undertaking is an adventure which takes a team of travellers around the world in the first ”

“We travel light, carrying our equipment -laptop, video and stills camera’s, camping gear and tools- on our recumbent bicycles. Our route is guided by our search for stories about the future and takes us in 11 stages to more than 30 countries across the planet. So far we have been in the UK, Egypt, the Benelux and Germany.”

Further info can be obtained at HPVelotechnik: Agence Future – Riding into the future. There’s also a travel log.

HP Velotechnik bietet auch Informationen auf deutsch an: Agence Future – Unterwegs in die Zukunft. Das Reisetagebuch kann man hier lesen.

Las Vegas, again!

I enjoyed David’s photos of his family trip to Las Vegas. They got to see much more of Las Vegas’s casinos, shows and attractions than André and I did, but then, we only spent one night in Las Vegas.

No News

It’s a boring day… at least in terms of webloging. Offline, I’m busy working on my thesis, which I hope to finish next week. Although I like the mathematics and geometry of my thesis, it is getting a bit boring… I want to move on to other things! But I guess I’ll have to deal with more than enough other stuff once I start preparing for the written and oral exams (which will be in August and November, respectively).

And although it’s pretty cold here in Bonn, it’s a lovely sunny day! I guess weather like this is best enjoyed from inside – you get the sun from outside and the warmth from the central heating. Heh.

February 24 2001

Saturday, February 24th, 2001


Wonderful black and white photographs in the Seattle Times: Traveling Light, story and photo gallery by Rosanne Olson.

“During the past four years, I have traveled in Europe, Mexico and the United States, taking pictures with my pinhole camera, which is essentially a box with a tiny pinhole to let in light.”

Link via Sheila.

Postscript graphics in LaTeX

Update to yesterday’s problem: I have recreated all my graphics with MetaPost, and it works now! facehappy:

I created some macros for this. If you want to know how I did it, look here:


The Wild Parrots of San Francisco’s Telegraph Hill. Sightings, stories, links, photos, FAQ, …


universum bremen: Gerade habe ich das Universum Science Center Bremen entdeckt. (Wieso ist der Name eigentlich deutsch und englisch gemischt? Entweder – oder!) Sieht so aus, als sei es ein ähnliches Museum wie das Exploratorium in San Francisco. Ich glaube, beim nächsten Besuch bei meinen Eltern muß ich mal einen Tagesausflug nach Bremen machen…

Las Vegas

Check out Susan’s photos – she went to Hoover Dam and Las Vegas!


Good morning! I jus tried to check my email, but it still is not working. André found out that it’s not the mail server and not the provider, but some bigger internet backbone route or something. Anyway, I don’t get any email and can’t send any either. Sigh… nothing to distract me from those graphics, it seems.

Oh, und danke für den Link zu Ghostscript, Jörg!

Have a nice day, everyone!