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life, the universe, and everything
Hank Dolben
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Mon, 2003 Jun 30
If You're Reading this, Then You Know the 'Blog Moved
As long as the location of my personal web pages was moving because of the change from attbi.com to comcast.net domain, I decided to also change the "user" to "nothingisperfect" to cut down on email address harvesting from this weblog. Obviously, I won't be reading any email addressed to nothingisperfect@comcast.net. Note that there are some internal links (where one post is linked to another) that are now broken since blosxom doesn't interpret a URL base within a posting.
As it turned out, despite my fears, Comcast handled the transition smoothly by automatically redirecting HTTP from home.attbi.com to home.comcast.net.
Mon, 2003 Jun 23
The Restaurant at the End of the Universe (or just before Uranus)
On my bike tour of the solar system I had planned to eat in the neighborhood of the Sun, but, having started early, arrived in Presque Isle mid-morning, so decided to have a Gatorade "energy bar" and find lunch on the way back to Houlton. In the town of Bridgewater, about halfway out to Pluto and just sunward of Uranus, I spotted the Country Bakery on the right side of the road. I dropped out of hyperspace and, peering in through the door, saw that they had subs; just what I wanted. I stepped in, ordered a 12" classic, and downed a bottle of PowerAde while the sandwich was being assembled.
Wandering around the little shop, I spotted a brochure, amongst various promotional literature, of The Maine Solar System Model. What luck! I hadn't found one in Houlton since I had left before the Visitor Information Center room had opened. Now I had some reading material to peruse during my meal. The brochure is quite well done and a handy reference to have along for the ride, better than my handwritten notes cribbed from the website.
A 12" sub was more than I could eat right then, but the shopkeeper was kind enough to wrap half of it to go as well as refilling one of my water bottles. I left with the brochure and 6" of grinder added to my back pockets and zoomed (did I mention the tailwind?) past Uranus and Neptune on my way back to Pluto. At the rest area in Houlton, I enjoyed the beautiful weather as I sat at a picnic table in the shade under pine trees, and finished the rest of my sandwich.
Sun, 2003 Jun 22
The Bike Rider's Guide to the Solar System (Model in Maine)
Friday, as promised, I biked the Maine Solar System Model, from Pluto at the Visitor Information Center in Houlton, around the Sun at the Northern Maine Museum of Science at the University of Maine at Presque Isle, and back out to Pluto again; an 80 mile roundtrip. Given that the scaled speed of light is seven miles per hour, I was in hyperspace while on the bike, breaking the comet metaphor.
The gas giants are striking and hard to miss, while the inner planets, being so small, are not easy to see, but not hard to find, since they are all within a mile and a half of the Sun and their locations are well described in the guide (Earth: mostly harmless). Pluto and Charon are inside the Visitor Center, in the corridor between the restrooms and the information area.
I was pleased that this turned out to be a good ride. U.S. Route 1 rolls over the gradual hills of Aroostook County - always going up or down, never severely, though enough that there are climbing lanes on many of the uphill sides - with the crests from about one to three miles apart, and with an insignificant elevation gain from Houlton to Presque Isle. Since this is farm country, open views of the surrounding fields and hills abound. The rode is generally very good with full-lane, well paved shoulders for the southern 25 miles, except where there are climbing lanes, and three foot paved shoulders elsewhere, allowing plenty of clearance between bicyclist and traffic, which while light has a large fraction of trucks roaring by at a good clip in the 55 mph speed limit that prevails for all but the middle of a few towns.
At present, there is road construction, covering about a mile just north of the center of Mars Hill. You might wish that you had your mountain bike for this nasty section as the whole thing is wet, and dirt except for one part that is one lane and covered with fist size crushed rock, where I felt as though I was in the Paris-Roubaix, but with loose, sharp pavé. If not for the fact that this comes between Saturn and Uranus - a long way from Mars, in spite of the town's name - this might be considered the asteroid belt that's missing from the model.
Fri, 2003 Jun 13
The Demystification of Rotation Matrices
Even for people who use them, rotation matrices seem somewhat magical. Direct understanding is largely obscured by the fact that there are a few key steps to the derivation, and that presentation methods are usually hopelessly general. In an effort to counter that trend here's a short explanation that boils it all down to the essential parts in one place. For now, I won't show the math. I think that those with some background will understand all the easier without having to follow the formalisms.
A rotation matrix is most often used to transform a vector in one coordinate system into the vector in another coordinate system, which is rotated from the first. The transformation is accomplished by simply multiplying the vector by the matrix. By definition, the process of multiplication can be broken down into taking the dot product of each row in the matrix with the vector, where each dot product results in a coordinate of the vector in the rotated system.
Each row of a rotation matrix is the unit vector of an axis of the rotated system expressed in the coordinates of the first system. The dot product of a unit vector and a second vector results in the length of the projection of the second vector on the unit vector; exactly the definition of a coordinate for some axis. This correspondence between the dot product and the geometrical relationship of two vectors is the nub of the magic, a theorem equivalent in power and beauty to that of Pythagorus.
The dot product result, in turn, mainly depends on a little trigonometry which can be easily shown: given an angle T, equal to A - B, cosT = cosA cosB + sinA sinB.
Later, I'll write a little longer explanation that includes the math, especially that "easily shown" theorem of trigonometry on which the whole edifice rests.
Thu, 2003 Jun 12
Prentice Hall Advanced Algebra: Tools for a Changing World
by Allan Bellman et al., 1998, ISBN: 0-13-419011-4, is the textbook that I thought was so good when my son Will used it in High School, and from which I got the geometric presentation of completing the square used in my appreciation. Thanks to Will and Mrs. Chadwick, the head of the Mathematics Department at St. Thomas who provided the information. One of these days, I'll copy that paper into another word processor so that I can add the reference.
Change from AT&T to Comcast Will Break these Web Pages on July 1
I expect that the URLs for this web site will change on July 1. Comcast bought AT&T's cable service division and will be making a service transition then. I don't have much faith that it will work smoothly since the information Comcast has provided has been sketchy at best. For example, I haven't seen anywhere what the server name is for personal web pages. I knew this was coming when I started this 'blog and so am treating this month as experimental.
Back-to-Back 50 Milers, Yesterday and Today
OK, the truth is that I cut yesterday's bike ride short, to 49 miles, because of rain, but made up for it today by riding 53.
A Derivation of the Quadratic Formula by Completing the Square
About two and a half years ago (circa Dec. 2000), when my son Will was in high school, my helping him with a little algebra homework led to the writing of an appreciation of completing the square, and its application to a derivation of the quadratic formula. I was very impressed with the clarity of his algebra textbook and now wish that I had done two more things in my document: dated it, and credited the book. I'll see if my son can find a reference for the book. At this point, I can't change the document since I have it only in PDF and don't have an application that can edit that.
My First Dip of the Season
As forecast, a southwest breeze had come up in the early afternoon, producing, along with a temperature in the high 70s, very comfortable conditions for lake sailing, especially for mid-May. From the Point of Pines, the best place to head in that kind of wind is the small bay south of Hay's reef, off the state beach. There I was, catching a pretty good puff and barreling along, hiked out on a close reach when the Laser fell headlong into a hole, leaving me to scramble to leeward trying to keep from going over backwards. I failed to keep the boat from capsizing and so ended up gasping in the very chilly water.
Generally, one proves his or her stalwart constitution by taking a quick dip around Memorial Day. In a year when the winter had been very cold and the ice went out rather late, I was beating that by a good week. Worse, as I was getting my reaction to the cold under control the boat turned completely upside down, allowing the centerboard to fall out. Now I had to haul the boat back on its gunwale by working from the bottom, then swim around to the topside and push the centerboard back in so that, returning to the bottom I could use the protruding centerboard to right the boat - not what you would call a quick dip. But once I was back onboard and sailing again under the bright, thin clouds, I could not have been happier.
Sun, 2003 Jun 08
The comet ride, biking the solar system
When I was quite young, my mother took my sister and me to the Children's Museum in Boston, which used to be in a big, old house on the Jamaicaway. In one of the cramped rooms, in a glass case, was a model of the solar system, which at first I found exciting, but then disappointing when a guide explained that the model was not to scale, as it would be problematic to show any interesting features and fit the thing in the museum.
For years, as I've noticed while bicycling through Rye, New Hampshire, scaled distances of the planets from the Sun have been marked on Wallis Road starting from in front of the Junior High School and extending towards the beach. The little boy in me who yearned for a better model has silently appreciated Ms. Adams, the teacher behind that nice creation.
Now, some folks in Maine have created a model of the solar system that finally fulfills the dream of that young model aficionado, with a scale of one mile to an Astronomical Unit and stretching from the Northern Maine Museum of Science at the University of Maine at Presque Isle along U.S. Route 1 to Houlton with scale models of the planets and major moons mounted on stands along the way.
I won't be able to attend the unveiling on June 14th, but plan to make a comet-like 80 mile roundtrip bike ride from Houlton around the Sun in Presque Isle and back out past Pluto again, one day in the following week.
I have to thank Slashdot for this one.
Sat, 2003 Jun 07
Mail servers could be responsible for prohibiting spam.
I suggest that one way to stop spam is to make mail services responsible for prohibiting their clients from spamming. The service administration process would insure that the identity of its client is well known. Clearly this is already the case for services where the clients are paying customers or employees, but is problematic for free services such as Yahoo!. Then, through its usage policy the service imposes deterrent costs, including revocation of privileges, for spamming. Finally, the mail server is certified (by a chain of digital certificate authority) to implement sufficient standards. The certification process is completely in the hands of the service providers, who are technically capable of administering it.
Then such a server only accepts email, addressed to one of its clients, from another server that is certified. When clients receive messages that look like spam, they notify their service provider who continues the process by notifying the senders' service provider, who in turn verifies the spam and takes action against the sender.
The existence of a service enhanced in this way would provide a competitive advantage so that all services would be forced to adopt the policies and technology. A transition could be handled by allowing uncertified messages that are flagged so that a client can treat them differently.
Fri, 2003 Jun 06
'Blogging
Every 'blog has to start with something and starting with an explanation of this one seems as irresistible as it is conventional.
I've known about 'blogging for a while and learned to appreciate RSS once I started using an application (e.g., NetNewsWire Lite) that automatically checks for new posts to selected feeds. This is particularly great for feeds where the posting is infrequent (as you can expect this one to be), but even pays off for others such as the New York Times by differentiating the posts that have been seen from those that have not.
To 'blog or not to 'blog? I wouldn't say, "I 'blog, therefore I am." But, what the heck, every now and then I have something to say and I like this method of communicating. Also, there are some web sites, for example, Mount Everest news, that would be well served by an RSS feed, making me wonder how hard it would be.
Since my ISP (AT&T, really Comcast, though not yet in name) doesn't support CGI for personal web sites, I need to be able to generate the HTML and RSS after posting an article, and then ftp the files to the server, instead of having a CGI script generate the stuff on demand. It turns out that blosxom supports that mode, as well as being free and simple to use.
100k Bike Ride
Today I got in a 100 km bike ride, my second of the season, the first being a week ago. That gets me up to 825 miles for the season, with eight weeks to go to the Pan-Mass Challenge. I'm usually motivated to ride on Friday if I haven't gotten much mileage in the early part of the week. The weather was about as good as it's been this spring; sunny, in the upper 70s, dew point 52, though a little on the windy side. It always makes me feel good to be able to ride 100k. It's not so long that it wipes me out, but long enough to be a good day's exercise.
D-Day
June 6th has always meant something special to my family. To begin with, my parents were married on June 6th, two years before D-Day, on the day that my father was commissioned in the Army Air Force. Then there was D-Day, when my father-in-law stormed one of those famous beaches in France. After the war, my father's father died on June 6th. In my mind this always seems more like Memorial Day than the last Monday in May.