Thursday, August 31, 2006
Tuesday, August 29, 2006
When you've forgotten the combination to your lock...
Actually, that isn’t quite right. Duplicates are allowed, so you aren’t really taking permutations of 40 numbers. But that isn’t the subject of this post. The point is that with three numbers, each of which can be one of 40, there should be 64,000 possible “combinations.” That means that the probability that two locks will have the same combination is small enough not to worry about. It also means that it would take you a long time to try every possibility if you forget what your combination is. Let’s suppose you can try five possible combinations per minute, which seems reasonable, then it should take 12,800 minutes, which is 213 hours. At eight hours per day, we’re talking about 27 days of work, or over five solid weeks if you give yourself weekends off.
That seems pretty secure, doesn’t it? Clearly nobody will devote that amount of time.
Actually, that’s the worst-case scenario. You might, after all, hit on the correct combination in your first try. So we need the expected value, which is half the previous figure: on the average it should take less than three weeks. Still ridiculous.
But Liam Bowen has shown that there’s a way to get the expected value down to a very manageable ten minutes, still at five tries per minute! In other words, the worst case becomes 100 trials rather than 64,000. In his interesting and much linked-to article, he uses modular arithmetic and lock knowledge (occasionally confusing numbers with digits) to explain how to do this. But let me quote and emphasize Bowen’s caution:
PLEASE don’t use this to break into anything other than your own stuff.
Sunday, August 27, 2006
Although not great literature in any sense, Cold Moon is a gripping page-turner. Despite a few inaccuracies and a number of implausibilities that risk the reader’s suspension of disbelief, it’s a fine crime novel that’s a combination of a police procedural, a standard detective story, and a psychological mystery. Read it when you have a couple of days with several hours of free time (not on a school night).
Saturday, August 26, 2006
I Heart Huckabees
I definitely enjoyed the unconventional film I Heart Huckabees, but it’s more than merely unconventional. I can’t do better than to quote a few sentences from Roger Ebert’s review:
...the moment a movie is over, everybody asks you what you thought about it. I said, “I didn’t know what I thought.” Then how did it make you feel? “It made me feel like seeing it again.” You mean you liked it so much you want to see it twice? “No, I’m still working on seeing it the first time.”Yeah. What he said.
Now I have seen it twice. The movie is like an infernal machine that consumes all of the energy it generates, saving the last watt of power to turn itself off. It functions perfectly within its constraints, but it leaves the viewer out of the loop. This may be the first movie that can exist without an audience between the projector and the screen. It falls in its own forest, and hears itself...
Oh — you want to know what it’s about? Nah, that wouldn’t help. I could tell you that it’s about an environmentalist organization, a large department store that pretends to support it, an environmentally conscious firefighter, and an existential detective agency; but that wouldn’t help you much. I could tell you that it stars Jason Schwartzman, Jude Law, Naomi Watts, Dustin Hoffman, Lily Tomlin, and Dorchester’s own Mark Wahlberg, but that wouldn’t help you much either. Just rent the DVD and see it. Maybe twice.
Thursday, August 24, 2006
Hackers and Painters
A person who enjoys exploring the details of programmable systems and how to stretch their capabilities, as opposed to most users, who prefer to learn only the minimum necessary. RFC1392, the Internet Users’ Glossary, usefully amplifies this as: A person who delights in having an intimate understanding of the internal workings of a system, computers and computer networks in particular.The popular press has conflated this with cracker, whose meaning has now become the meaning of hacker in most people’s minds:
One who breaks security on a system. Coined ca. 1985 by hackers in defense against journalistic misuse of hacker.Anyhow, now that you’re straight on what Graham means by hacker, you’re going to start wondering whether painter also means something you didn’t expect. It all depends, of course, on what you expected: it’s painter in the sense of a visual artist, not in the sense of a house painter.
Computer programmers share some important characteristics with artists — much more than they share with accountants, say. Programming a computer is a creative act, having much in common with painting a picture. Read this book if you want to find out what it’s like to create and build a large software project — spam detection and online stores in Graham’s case, but those are more by way of example than major themes. The major themes are really the big ideas of software development. When you read the book, you’ll learn a lot about programming languages and other tools. Take Graham’s admittedly biased view with several grains of salt, but do realize that he speaks with the voice of experience in both software development and art, not with the voice of academia. I won’t disclose his biases here; suffice it to say that his professional experience leads him to some well-considered judgments on certain popular operating systems and programming languages.
Unfortunately Graham also takes several forays into the worlds of politics and philosophy, I say “unfortunately” because they will detract from the book if you’re turned off by his libertarian views. Don’t let Graham’s politics deter you from taking his software development ideas seriously: there’s only the most tenuous connection between his politics and his views on software. Read the book anyway, and just argue mentally with the author. You will still enjoy the large majority of the chapters, especially when you think about pointy-haired bosses and their ilk. Speaking of chapters, Hackers and Painters is really a collection of semi-independent essays rather than a monolithic book. The first essay, “Why Nerds are Unpopular,” is especially recommended to middle- and high-school teachers and students: Graham writes from his own experience from when he was a teenage nerd (or geek — take your pick), and his analysis definitely rings true. Other recommended essays include “What You Can’t Say,” which is mostly about political correctness; “Good Bad Attitude,” which argues in favor of breaking the rules; and “The Road Ahead,” which explores the idea of web-based rather than desktop-based software.
One customer on Amazon says that “These essays help me maintain my sanity and inspire me to produce beauty while I code.” What more could one want? I don’t usually recommended taking the time to read reviews on Amazon, but in this case they’re well worth reading, even though of course some of the reviewers’ opinions are incorrect.
Wednesday, August 23, 2006
Vacationing in Lexington, Newton, and Quincy
The highlights included the National Heritage Museum in Lexington, the Newton Historical Society, the Quincy Historical Society, and the Adams National Historical Park. All were worth it in their own way, and I got a number of ideas for our own Dorchester Historical Society. I felt like a Manhattanite who has never seen the Statue of Liberty, since this was my first visit to the Adams National Park despite having lived in the Boston area for the past 41 years.
Tuesday, August 22, 2006
So what do we expect? Let’s see:
- Diversity in ethnicity, class, and gender? Check.
- Kids who are externally driven by ressure from parents? Check.
- Kids who are internally driven by their own needs and values? Check.
- Kids who are still normal kids despite it all? Check.
- One kid with Asperger’s? Check.
Monday, August 21, 2006
Unaccustomed excitement at the Museum
A loud siren went off, and a voice on the PA system said that there was an emergency and everyone was to leave the building immediately by the nearest exit. No explanation, nothing but repeats of the message over and over again. There were a lot of foreign visitors, many of whom were understandably confused. We got to the escalators, with a couple of hundred people ahead of us, and noticed that everyone was slowly lined up waiting patiently for the down escalator, while the up escalator was dutifully carrying nobody on its way upstairs. So we promptly pushed the red stop button and walked down, followed by half of other guests. Why didn’t anyone else think of that?
Outside we found that most people were clustered all too close to the building. What if it was a real fire? Well, the building looks pretty fire-proof. But what if there was a bomb? Surely standing fifty feet from the building wouldn’t be good enough. And then a fire truck appeared. And another. And another. But still there were people standing right in the fire lane!
By time we gave up and left, six fire trucks had arrived, including a hook and ladder. One firefighter rapidly ascended the ladder onto the roof of the museum, axe out in his hand, and promptly disappeared.
Oddly enough, I could find no follow-up anywhere. So what really happened?
Sunday, August 20, 2006
This year we decided to cut back on the number of topics
So we learned our lesson. We decided to go for more depth and less breadth in 2006. Aiming to focus on interdisciplinary applications of math that didn’t duplicate what the students were learning in their regular schools, we cut out Visual Representations of Data and Probability. We also renamed the Game Theory unit to Conflict and Cooperation. These changes were definitely successful: the summer was less frantic, and there was time to concentrate on applications in depth. The only downside was that some students perceived the two-summer course as less mathematical, since it contained very little material that was familiar from their regular math courses. (The irony is that the most traditionally mathematical activities, such as using systems of linear equations to solve mixed-strategy game theory problems, were the least successful.)
Saturday, August 19, 2006
Ruth Rendell: Thirteen Steps Down
Usually I prefer to write my own reviews rather than refer readers to others’, but in this case I have to let Fiona Walker speak for me, as I really have nothing to add to her comments... so go read them!
Friday, August 18, 2006
But that’s not really the subject of today’s post. Here I just want to comment on Twiki, the platform upon which we built CSAconnect, a multipurpose wiki that we used (and continually modified) throughout the session. The theory was that CSAconnect would provide many capabilities, including describing and listing resources for courses; posting, submitting, and grading assignments; keeping records; and creating online journals, homepages, and links. My friend Meredith wrote the software; I served as liaison, tester, and occasional bug-fixer. We learned a valuable lesson from this process: don’t use TWiki! The combination of access control issues, poor documentation, and unacceptable performance added up to an extremely frustrating experience. I’ve never found anything so difficult to use.
Thursday, August 17, 2006
More From Polymath
For example, consider a discussion of whether 0^0 should be 0 (because zero to any power is 1) or 1 (because anything to the zero power is 1). Or is it indeterminate? Or undefined?
And on the non-mathematical front, do read the long review of Ruth Reich’s Garlic and Sapphires.
Wednesday, August 16, 2006
Why .999... really does equal 1
Tuesday, August 15, 2006
Cell phones: good or bad?
I am surprised at the opposition to cell phones among a vocal minority of my baby-boomer friends. Sure, they admit that cell phones are useful at times and even essential in case of emergencies. But on the balance they definitely label cell phones as “bad.” In our current world of terrorist threats, both external and internal, this reaction strikes me as short-sighted. Cell phones clearly reduced the number of deaths at Columbine. An article in Education World pointed out the following:
People watched and heard as cell phones linked victims and potential victims to their loved ones and the outside world. Parents now wanted to be in closer contact with their children, and argued to school districts that cell phones were necessary for safety.
And what about the recent attack in Mumbai? As pointed out by Bruce Schneier, America’s leading security expert, “Cell phones are useful to terrorists, but they're more useful to the rest of us.”
Monday, August 14, 2006
World's best version of Life
Sunday, August 13, 2006
S is for Silence
Anyway, since Grafton has clearly latched onto a successful formula, she feels constrained to continue to follow it for the most part, but she also makes a number of changes in S is for Silence. Although it’s all nominally a first-person report — as always — it also contains frequent flashbacks in the form of chapters that take place fifty years ago. (That’ fifty years ago compared to the “present” of the mid-80s, where Grafton’s books are still taking place. Like most long-lasting series, the action doesn’t advance in the real-time calendar of publishing dates.) Conflict and character development place more of a role than they do in most mysteries, and some of the familiarities of previous installments fade almost into the background here. I don’t know what it would be like to read S is for Silence if you weren’t familiar with the rest of the series, but definitely read it if you’re a faithful Sue Grafton fan.
Friday, August 11, 2006
McCall Smith in Germany
When I was a kid, I learned the definition of an expert as someone who knows more and more about less and less, and I resolved never to become that sort of expert. Perhaps that’s why I became somethng of a polymath. But von Igelfeld is definitely that sort of expert, knowing everything about Romance philology and nothing about anything else. These blinders lead to dozens of comic situations — chuckle-to-oneself comic, not laugh-out-loud comic — as von Igelfeld and his colleagues attempt to deal with a panoply of real-life situations in the first two volumes and fantasy situations in the third. My favorite scene is one in which the three German professors attempt to learn how to play tennis by reading a textbook.
Like the other two series, the von Igelfeld novels frequently raise philosophical questions, often in the guise of moral dilemmas. These books are not for everyone, but they’re fun to read and provide a useful perspective for those of us whose worlds are often academic, in both senses of the word.
Thursday, August 10, 2006
McCall Smith in Botswana
Tuesday, August 08, 2006
Saturday, August 05, 2006
Mathematical Gangsta Rap
Wednesday, August 02, 2006
Suddenly a new car
Tuesday, August 01, 2006
End of hiatus!
I am very much looking forward to the new vesion of Blogger, which will permit labels on posts to denote categories. This feature will help viewers who are interested in only some of the topics I write about, say education and math but not Dorchester or travel. Unfortunately there is no migration path yet, so at the moment it's only for new blogs. Stay tuned...
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