Syllabus (the book)

I just read Syllabus by Lynda Barry. It is a set of syllabi and daily in-class instructions, along with some reflections, from a few years of teaching cartooning and writing at Wisconsin. It is a combination of hilarious and insightful, both about learning to draw and cartoon, but also about the practice of teaching.

A page from Lynda Barry's Syllabus.

The syllabi and daily exercises include many great practices. For example, when students are listening to something (being read or previously recorded), she has them either draw tight spirals in their notebooks or else color in a line drawing. She has the students sketch in non-photo blue pencil and ink in later; it reduces inhibitions. She has simple forms for students to write daily diary or journal entries so that they make close observations of the world, in words and pictures. She loves most the students who have never drawn (since childhood), and she makes exercises that capitalize on their newness (and defeat those who are more experienced at rendering), like forcing them to do drawings in increasingly short time intervals.

The book is hilarious in part because she shows lots of great student work (it is not clear she has proper permissions here, because she does not individually credit each student drawing), and because the whole book is a collage of drawings, writings, and found objects, in the Lynda Barry style. I doubt there is another book out there on teaching that makes you laugh out loud all the way through.

A great question for me is what of Barry's practices could carry over to a class in Physics?

Make it Stick

I just read Make it Stick, about research-based results in how people learn and the implications for education. I loved it; it is filled with simple, straightforward ideas that will be useful in the classroom. For example, it is better to do many low-stakes quizzes than a few high-stakes exams. For another, it isn't useful for students to re-read the textbook, and it is useful for the lectures and the textbook to be misaligned. For another, students' perception of their learning is often wrong and misguided. For another, it is useful to interleave topics and not just do “massed practice”. It points out that it is very adaptive for learners to believe that their brains are plastic and their abilities are not innately limited. Luckily this also appears to be true. All of these things will come into my next pre-health (or other big) class. And I will explicitly explain to the students why.

My quibbles with the book are few. One is that they slag off unschooling, and then immediately follow with a long profile of a Bruce Hendry, who is a perfect example of the power of unschooling (he is entirely self-taught through self-directed projects of great importance to himself!). I also found the writing repetitive and a bit slow. But the book is filled with good ideas. Also, it is not just informative, it is responsible: The authors clearly differentiate between research findings and speculations or over-generalizations of them. This is a great contribution to the literature on teaching and learning.

vector subleties

It is vectors all week this week, in my class, and in two classes I have taught for others. It is understandable that they confuse students, even physics majors with good backgrounds. Here are some subleties that I like to point out:

• Vectors have a magnitude and a direction, but that is not sufficient. They also have a coordinate-free existence or description, and they form a linear space (with the usual linear operators). In this sense, despite what every textbook says, the unit vectors that define the coordinate system are not vectors!
• Although vectors carry around all this geometric baggage, they have a magnitude and a direction and nothing else. I can still confuse the physics majors by sliding around vectors on the board. There is no position associated with a velocity vector, and we confuse the students by always drawing the velocity as coming from the object that is moving.
• Multiplication of a vector by a scalar is usually conceived as changing the magnitude of the vector, which it does, but it also changes the units, in many cases of interest (for example when a displacement is multiplied by an inverse time to make a velocity). So it often produces a new vector that is not longer than the original vector, nor shorter, but really incomparable.
• There is a perfect symmetry between the relationship between velocity and position and the relationship between acceleration and velocity. However, it is far harder for students to understand that the acceleration vector can point perpendicular to the velocity vector than it is to understand that the velocity vector can point perpendicular to the position vector. No amount of class time spent on this point is wasted, in my experience.

weight, gravity, and contact force

On the final exam, I asked the following:

Explain why the astronauts in the Space Shuttle are weightless.

I was lenient in grading. But my position is actually at odds with most of the textbooks. Here's why.

The standard textbook answer is something like Actually, the astronauts on the Shuttle still have weight, since there are still gravitational forces acting on them. However, they feel like they are weightless because they are in an accelerating reference frame that is accelerating at the acceleration that the gravitational force is providing. This will be followed with various things about equivalence and plummeting elevators and non-inertial forces and so on.

My explanation is that the gravitational force on an object is not the weight of the object, when the word weight is properly understood. The weight of an object is not the gravitational force but rather the contact force that holds the object up against gravity (and non-inertial forces). It is this contact force, after all, that a spring scale measures, because a spring scale does its job by providing a contact force. It is also this contact force, after all, that you perceive by having your feet pressed onto the floor or behind pressed into the seat of your chair. Indeed, gravitational forces can never be measured locally or internally (that's equivalence!), all you can measure is the stresses and strains required to oppose them in our non-inertial (by GR standards) frame.

My view makes the astronauts not misled but truly weightless. It also makes it true, not apparent, that one is lighter at the top of a hill and heavier at the bottom of a hill on a roller-coaster, and same for the related changes you experience in an elevator.

reading memos and the arrow of time

At the suggestion of my pedagogy mentor Sanjoy Mahajan (MIT), I assign reading memos, to be turned in before the class in which I expect the reading to be done. This encourages the students to do the reading (I give a small fraction of the grade for doing the memos), and it also gives me some exceedingly insightful feedback about what works and what doesn't in the book I am using (Chabay & Sherwood).

In Chapter 11 (this week's chapter), the book makes the requisite notes about the increase in entropy possibly having something to do with the advance of time, a subject I avoid for its capability of generating enormous quantities of speculation. In the reading memos, one of my students (John Morrow) asked:

A closed system will tend toward maximum entropy. Is it possible for it to reach maximum entropy before the rest of the universe? And if so wouldn't that imply that time would stop for the closed system?

Beautiful question! This either throws doubt on that whole crazy idea, or else implies that all systems that have or perceive time must be out of equilibrium? Insane! But of course that would be some of that speculation I abhor.

sheep–sheep collisions

A very nice paper appeared on the arXiv today on sheep–sheep collisions. It makes the point, which I stressed here, that collisions involve immense forces. It also makes some realistic estimates of the physical properties of the horns and skulls of bighorn sheep. But perhaps my favorite thing about the paper is that it begins by deconstructing a laughably wrong analysis in one of the many bad textbooks.