Did some work on the IF tonight.

I got a pair of Specialized Armadillo 700x25 through the team at a good discount, and mounted them tonight. I was a little worried they might not mount well, but they went on without any trouble. The Schwalbe Stelvios I had on it came with the bike: I've been running those since February, so with close to 6000 km on them, I figured it was time to put some new tires on. I really like the Stelvios: they have a good feel, and I've only had two flats in those 6000 km, so that's not bad. But lots of folks swear by the Armadillos as a winter tire, so I'm giving them a shot.

My rear wheel needed a little truing, so I did that too.

Tomorrow I'm leading an 80 km ride out to Issaquah and around Squak Mountain and back through May Valley. Weather looks like it will be excellent, though a bit chilly at the start.

I wrote this applet to illustrate a couple facts about the tangent lines to a parabola.

First, for every tangent line to a parabola, there is another tangent line to which it is perpendicular.

Second, the set of intersections of these perpendicular tangents is a line, perpendicular to the parabola's line of symmetry. This line happens to be the parabola's directrix.

If you take any differentiable curve and form the set of intersections of perpendicular tangents, you have what is known as the orthoptic of the curve. So the orthoptic of a parabola is a line. It's pretty easy to see that the orthoptic of a circle is a concentric circle. Many other orthoptics are hard to determine.

The more general concept is the isoptic, which is the set of intersections of tangents which form a constant (not necessarily pi over 2) angle. Wikipedia doesn't say much about this topic, but I have a nice old copy of "A Handbook on Curves and Their Properties" by Robert Yates which gives a number of examples. Few seem easy to derive: with even a simple curve, the orthoptic is often quite messy.

A couple of examples, without derivation (from page 140 of Yates).

• The orthoptic of the deltoid is its inscribed circle.
• The orthoptic of the cardioid is a circle and a limacon.
• The orthoptic of y²=x³ is the parabola 729y²=180x-16.

I think I'm going to try to post something every day during November.

I'll start by saying that I think November is my least favorite month of the year. It seems the darkest, though December is darker. But December has Christmas, and the winter solstice, so that by the end of the month, the days are getting longer, while during the entire month of November the days get shorter. Too, in Seattle, it rains a lot in November: the average rainfall in November is second only to December.

The other thing that makes December tolerable is that I don't work so much in December. This year, I'm giving final exams on December 12, which I have to grade of course, but I won't have to teach until January 4. That makes bad weather and short days much more tolerable.

And January, while colder than December or November, is, you know, the new year. New quarter starts, days are getting longer: it's practically like spring, or at least pre-spring.

So November is often the low point, but that doesn't mean it is all that bad. I'm not expecting a horrible experience over the next 30 days, just a dark, wet, somewhat cold one.

A good October it has been, cycling-wise.

I cranked out 579.75 km in October, my best October since 1995, and probably my best ever. So far this year, I've had my best ever January, February, April, August (best month ever!), and October. Not too bad. My record November and December are pretty low, so I think I ought to shoot for beating those records, too, but when the weather gets cold and wet, motivation is hard to get.

Also, my mileage for the year is already a record, so everything from now to Jan 1 is bonus.

I haven't used Processing in a while. Today I made an applet to illustrate the fact that normals to y = k x² will "miss" a chunk of the y-axis.

Check it out. Java required, naturally.

With the watching of Dodes'kaden, I've now watched exactly 50% (15 out of 30) of all of Kurosawa's films.

Dodes'kaden I thought was too light a flm for some of the topics it involves.

Here is perhaps my favorite shot in the film, Kurosawa's first in color:

Okay, so I'm trying to write a little script to check TCM's schedule a couple times a month and let me know if there is anything on it that I might want to check out.

I looked into doing this with Perl, and I found the LWP and LWP::Simple module, but it seems not to work as advertised.

For instance, this:

>perl -MLWP::Simple -e 'getprint "http://www.sn.no/"'

is supposed to return the source of the index file at www.sn.no. Instead, it returns nothing.

Now I know things are actually working pretty well, since it I do the same with a text file (rather than an html file) like this:

>perl _MLWP::Simple -e 'getprint "http://www.madandmoonly.com/doctormatt/mathematics/squares/rezz01.txt"'

it spews that text file all over standard out.

I'm stumped.

After brunch, in front of Cupcake Royale.

Once you have the frame images in gif format (say, 55.gif, 56.gif, 57.gif and 58.gif), you can use imagemagick to make them into an animated gif with 50/100 seconds interframe delay like this:

>convert -delay 50 55.gif 56.gif 57.gif 58.gif -loop 0 animated.gif

I watch a lot of movies on TCM (Turner Classic Movies). I love a lot of movies from the 30s and 40s, and there are lots on TCM. Often, I run across an actor, actress or director of whom I would like to see more. It would be awesome if I had a way to automatically be informed when movies by certain persons (or particular movies I know I'd like to see) are coming up.

TCM has a nice schedule page, updated each month, here. It ought to be simple to write a little perl script to grab this page and search it for names in a file I would maintain. I could have the script run automatically once a month, and somehow let me know the results (email?).

That sounds like a fun little project. I've never written any code that grabs stuff off the web, though I know people do it all the time, so how hard could it be?

I watched a lot of Simpsons in the 90s, but turned away after a number of horrifically disappointing episodes some time in the late 90s.

Today I watched an episode that made me notice how the character of Marge has been treated by the writers. In "Itchy and Scratchy and Marge", the 9th episode of the second season, there is this sequence:

Homer sees Marge making pork chops...

Marge: [making pork chops]
A dash of rosemary, a smidgen of thyme, a pinch of marjoram...
Homer: You know, Marge, you make the best pork chops in the whole world.
Marge: Oh, Homer, they're nothing special. The extra ingredient is care.
[continues her work]
A sprinkle of chervil, a teaspoon of tumeric, and a whisper of MSG.

Here, Marge is a competent, perhaps talented, cook.

In "El Viaje Misterioso de Nuestro Homer", the ninth episode of the eight season, Marge has a greatly diminished knowledge of spices; in particular she does not recognize the spice, oregano.

I think this can stand as an example of the general buffoonization of the Simpsons characters and the downfall of the series.

At least we can still watch the first four seasons.