Archive for May, 2010

Vocabulary isn't Enough


So Far Away

SWAB: How Far to the Stars?

Lather and Rinse

Tell and Repeat courses

Aka student regurgitation. To avoid this, one must come up with questions which test for understanding, rather than information chucking in the vertical direction.

Anyway, Rhett mentions a wonderful conceptual question, and one I had not run across before, as an example.

The only bad thing about this question is that they aren’t trivial to create. Oh snap – well, I just gave away an awesome question. Truthfully, this question has been “out in the wild” for a long time. It is still a great question and you could probably use it on a test. The problem with a question being in the wild is that students can just memorize the solution – this means that question no longer tests for understanding.

One solution is to have a large number of questions, so that simple memorization is difficult, but these questions are hard to come by. Another is to have modular questions, so that you could ask about the same concept in different ways, but that’s far easier with algebraic results, where you change what information is given and which variable you want the students to solve for. I’m not sure to what extent it’s possible with a discussion question. Rhett’s example changes a variable, certainly, but not in the same way as an algebraic problem.

Another, I think, is to phrase a situation with a contradiction and have the students find out what the problem is with the phrasing of the question — a “why isn’t this possible?” kind of problem, or “find the fish flaw.” I see this all the time in crackpot discussions; once you remove the rigor of math, it’s easy to state a model which has some unphysical aspect and contradicts itself, which is why thought experiments alone can never disprove some phenomenon, and why perpetual motion machines are easy to describe but never work.

Here’s a classical physics example: you swing a bucket in a big circle which passes over your head. You adjust the speed so that the bucket comes to stop, with the string taut, directly overhead, at which point the bucket and water fall on your head. Is that possible?

A student may think so, because from a conservation of energy standpoint all you need is to have the kinetic energy at the bottom be equal to the potential energy at the top, so that the kinetic energy vanishes, and presto! You’re wet. But this ignores the requirement of the taut string: in order for that to be true, there must circular motion (not uniform, because v will be changing, but still circular) and this requires that there be tangential movement. Even as the tension tends toward zero, there is still gravity, so at the apex you would still have a centripetal acceleration, and thus v cannot go to zero. The bucket cannot come to a stop directly overhead with a taut string. (and yet it was so easy to state that it would happen …)

SEO Codswallop

DF: Tynt, the Copy/Paste Jerks

I’ve picked at this nit already, but Gruber explains what’s going on when you get the annoying “read more” blurb when you copy/paste from certain sites (which also apparently sends analytics back to a server too, to report on what was copied). It’s all due to a company named Tynt.

It’s a bunch of user-hostile SEO bullshit.

Everyone knows how copy and paste works. You select text. You copy. When you paste, what you get is exactly what you selected. The core product of the “copy/paste company” is a service that breaks copy and paste.

Whatever their justification for using Tynt is, I’ll bet it involves repeated use of the phrase “biz dev”. All they’re really doing is annoying their readers. Their websites are theirs, but our clipboards are ours. Tynt is intrusive, obnoxious, and disrespectful. I can’t believe some websites need to be told this.

A pox on thee, Tynt.

To All of My Fan(s)

Look Closely, Doctor: See the Camera?

The Truman show delusion, as well as other related modern-era afflictions.

One of Dr. Gold’s patients told him, “My family and everyone I knew were actors in a script, a charade whose entire purpose is to make me the focus of the world’s attention.”

Another patient traveled to New York City and showed up at a federal building in downtown Manhattan seeking asylum so he could get off his reality show, Dr. Gold said.

The patient reported that he also came to New York to see if the Twin Towers were still standing, because he believed that seeing their destruction on Sept. 11 on television was part of his reality show. If they were still standing, he said, then he would know that the terrorist attack was all part of the script.

I suffer from no such delusion, because

1. My blog would be enough to show any would-be exec that a reality show based on my life would not be economically viable, i.e. my reality show is probably pre-canceled

2. I think I have the kind of friends that would tell me if such a show existed.

3. Even if such a show were to actually exist, the existence of a production company would shield me from lawsuits exacting payment for boring people to death, so I wouldn’t stress out over it.

A New Group Meeting Experience

A new meeting experience on Thursday: a meeting with, essentially, footnotes. This was not a presentation, mind you — no rehearsed talk, no powerpoint, no written materials. Just an impromptu discussion, where someone used some ad-hoc terminology. Rather than deviate off on a tangent (or possibly a secant) and immediately delineate its origins, he waited until finishing the somewhat extended train of thought, and only then did he explain the etymology of the phrase he had used. I can’t recall that happening before, at least with the length of discussion involved. It was probably five minutes between the phrase and the explanation. I’ve only seen that in prepared talks.

The mention of footnotes then led into a brief discussion of David Foster Wallace (who apparently was very aggressive in his use of them)

Someone at the table: What kind of author is he?

Me: Dead

Our group meetings tend to meander a bit. But then, I’m usually a little punchy by Thursday afternoon, so I am an instigator of that behavior.

The Answer, My Friend

Blowing the wind.

May 27, 1931: Wind Tunnel Lets Airplanes ‘Fly’ on Ground

In a massive building covering more than two acres, the wind tunnel used a pair of 35-foot propellers connected to 4,000-horsepower electric motors. Air was sucked through large funnel-like structures that directed a smooth flow of air past the staging area where airplanes, helicopters, race cars and even a Navy SEAL submarine were tested.

No Accounting for Taste

Amazon reviewers think this masterpiece sucks

Not everyone loves the classics.

Charlotte’s Web:

It is because of this horrid book that I eat sausage every morning and tell my dad to kill every spider I see. It is a traumatic, coma-enducing story that has changed my life forever. In conclusion I feel no one should be put through such torture and this book should be banned from every school, library, and bookstore in the Milky Way.

MiB Redux

Oh, wait — wrong MiB. We were never here *flash*

Motion Induced Blindness

Steady fixation favours disappearance, blinks or gaze shifts induce reappearance. All in all reminiscent of the Troxler effect, but stronger and more resistant to residual eye movements.

I’ve previously linked to an effect with Troxler fading

Toil and Trouble

Bubble Chamber Art

The Bubble Chamber is a generative painting system of imaginary colliding particles built with Processing. A single super-massive collision produces a discrete universe of four particle types. Particles draw their positions over time resulting in the construction of oddly familiar patterns.

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