Showing posts with label physics. Show all posts
Showing posts with label physics. Show all posts

11.05.2009

Responses to Teach For America pre-interview readings

I applied to Teach For America last week and I made it to the phone interview phase, which will be Monday for me. Before the interview, there are a couple of short articles you're supposed to read. To help organize my thoughts, I will discuss them a little here. Comments welcome, of course.

The first article is all about the Achievement Gap, which basically means the fact that students in certain groups (namely, those from low-income families, African-American, and Hispanic students) tend to perform worse than others, according to several different measures of performance. It cites lots of statistics to demonstrate the problem, and then tackles the questions of why the gap exists, and what we can do about it.

There are many reasons given but the one most relevant to a TFA applicant is of course the quality of teaching. According to the article,
[S]tudents in high-poverty, high-minority schools have less access to highly qualified teachers than do students in low-poverty, low-minority schools. Secondary students in high-poverty schools are twice as likely as those in low-poverty schools to have a teacher who is not certified in the subject he or she teaches. Students in high-poverty, high-minority schools are also more likely to be taught by an inexperienced teacher. Furthermore, teachers in high-poverty schools reported less favorable working conditions than teachers in wealthier schools. Teachers from high-poverty schools were more likely to report that student disrespect and lack of parent involvement were problems.
Makes sense to me. I was very fortunate to attend a nontraditional private school up through 6th grade and then the Manhattan Beach school district after that, both of which encouraged lots of parent involvement, as well as parental financial support. Of course it made a huge noticeable difference to the students, by providing for great art and music programs, relatively happy teachers, etc. Plus parent involvement goes a very long way toward getting students to be engaged with their classes and homework.

I also really like the point about teachers having a credential in the subject they teach. I can't imagine teaching, say, English or History, at any grade level. I suppose I would be capable of doing it if necessary, with the right kind of support. But why would you put me in that position? I don't have much of a passion for history or literature, so I would make an uninspired lesson plan, and then follow it mechanically with far less enthusiasm than someone who majored in that subject, or at least something closely related to it. If a student asked a question that was outside the planned curriculum, I would encourage their curiosity, but I would probably be very little help in answering it myself. It would be very hard for me to show the students the connection between the current lesson and future lessons or careers. (And effective learning is all about students drawing connections between things. That's one of the many things that Carl Wieman talked about when he came to USC -- something else I've been meaning to blog about.) I think people often forget how perceptive students can be. You can bet they know the difference between a historian (or mathematician, or scientist, or musician, or whatever) sharing their love for their chosen field, and someone who is "just" a teacher, plodding through the same old three-ring binder full of lecture notes, year after year.

Okay, you say, you're passionate about Physics. You're really interested in the cutting edge research and string theory and all that. But is it really possible to be that passionate about boring, first semester Newtonian mechanics? Absolutely. I think it's awesome how a few simple equations can describe all kinds of different phenomena in the real world. If you don't buy that, then at the very least, you can remember how interesting it was when you learned it for the first time, and be excited that you have the chance to pique the interest of a whole room full of new students. This is more or less what I said in my TFA application: The achievement gap is depressing, yes. But what disappoints me more (maybe just because I have more first-hand experience with it) is that things I find so intriguing (such as Physics) are so immensely boring for a lot of people. When I tell people I'm a Physics major, they always say things like "Oh God, I hated Physics. I was terrible at it!" This makes me incredibly disappointed, not because the person has "failed" in some way--many of these people are very successful in some other field--but because Physics is really cool and it saddens me to think that people are unable to see how cool it is. I think getting people interested is probably half the battle in getting them to achieve at a higher level. If you truly care about what you're learning, it's easy to be motivated enough to excel at it.

The other article is called Assessment Through the Student's Eyes, and it's all about how assessment affects students' emotions and self-confidence, which of course affects their performance. If they do well on tests and homework, they are pleased and encouraged and tend to keep doing well. If not, they just think "I don't get it" and become less and less motivated, so their scores stay low.

Okay, so what do we do about it? The article is mostly about what it calls "assessment for learning" as opposed to "assessment to verify learning." The assessment methods should be developed by both the students and the teacher, rather than just the teacher. They should be descriptive and contain clear indications about what the student can do to improve. If you're too lazy to read the whole article, I would recommend you skip down to the "scenarios." They show how you can keep students motivated (without just giving everyone an A), and they seem like great examples to follow. I've had a couple of great experiences that follow this philosophy pretty closely.

The private school I went to (then called Via Pacifica, now called Del Sol) didn't have grades, in either sense of the word: No A's, B's, or C's, and also no first grade, second grade, etc. Instead, students were divided into four groups (called "pods" for whatever reason) called the "explorers," "discoverers," "investigators," and "voyagers." People unfamiliar with the school would always ask me, "Well... how do you know if you did well, if you don't have grades?" It seemed like a strange question at the time, because we actually got more feedback than in many public-school classrooms. On writing assignments, we would sit down and go through them, paragraph by paragraph, explaining things that were unclear and figuring out how we could have written them more clearly in the first place. In math, we would identify any mistakes and confusing concepts, and continue to work on them until everything was clear. In fact, the math classes seemed to mimic the article's second scenario pretty closely. Last time you got, say, an 87% on a math test, did you look through it and find all your mistakes, so that you could take it again and do better? Probably not, because there is no incentive to do so in most classes.

The other experience I'm reminded of is last year in Quantum Mechanics with Dr. Richard Thompson. We had homework and tests just like any other Physics class, but after an assignment was returned, we were expected to go back and correct all the mistakes on them. It may sound a little draconian ("Do it again, and don't come back until it's perfect!") but it meant that we would really understand everything in one chapter before diving into the next one. Of course, mistakes ranged from simple sign errors to bigger conceptual misunderstandings, but in each case, we would find the mistake, with the professor's help if necessary, fix it, and then write out the rest of the problem. Once you got used to it, it was a very satisfying system, in which you knew that you really understood everything you'd learned, even though you may have messed it up on an assignment or in the high-pressure environment of an exam.

These two experiences reinforce what the article said: Assessment can and should be used, not just to evaluate the performance of students and teachers but to provide useful feedback to the students that will help them understand what to do as they move forward, and motivate them to do it.

Again, comments are welcome. Wish me luck on the interview!

1.05.2008

Portal Physics

I really want to post with some consistency, even if I'm just rambling. So tonight, I will be rambling about the physics of the popular video game Portal. In case you're unfamiliar, you can read about it online, but basically, you're in an enclosed room, armed with nothing but a special portal gun. Shoot it at a wall to create a bluish portal, and at another wall to create an orangish portal. As if by magic, the two portals will be connected, so that you can send any object, including light, or yourself, through one portal, and it will come out the other. You use this to transport yourself or other objects to places that would otherwise be unreachable. It looks kind of like an FPS, but it's actually more of a puzzle game, which is why I like it. Of course, teleportation in video games isn't new, but what's unique about Portal is that the momentum of objects is also transferred through the portal, which leads to some very interesting solving techniques. For example, if you're on a high "cliff" next to a wide, deep chasm, and you need to get across the chasm, but can't create a portal on the other side (some walls resist the portal gun), you can shoot one portal in the wall next to you, so that it faces across the chasm, then shoot another on the ground of the chasm, way below you. Then jump into the lower portal, and you will soon find yourself shooting out of the wall portal, across the chasm. Of course, almost as much fun as actually completing the game is running through some interesting hypothetical scenarios. I really am just rambling here.

Put one portal on the ceiling, and another on the floor, directly below it. Jump into the floor one, and you'll fall out of the ceiling and into the floor, infinitely many times, moving faster and faster each time. (You can actually do this in the game, and there is apparently some kind of randomization built in that causes you to slightly miss the floor portal after a few iterations. Suppose that didn't happen though.) Suppose you keep your body oriented the normal way. If you look up or down, you see an infinite tunnel of portals, similar to the infinite "hall of mirrors" effect if you stand between two parallel mirrors. Clearly, each time you go through the portal, your kinetic energy is unchanged, but your potential energy increases by your weight times the height of the ceiling. So yes, conservation of energy is being violated, but don't worry about that for now.

As the person goes faster and faster, they measure the distance between the floor and the ceiling to be shrinking, according to special relativity. Eventually, this effect should be so pronounced that, according to the person, two or more parts of the body are at the same place relative to "the" floor. For example, suppose the room has contracted enough that its height is half that of the person. Just as the person's feet are entering the floor portal, his waist is also entering the "previous" floor portal. The person might cite this as evidence that there truly are an infinite number of portals. Meanwhile, an observer sitting quietly in the room would see the portal traveller shrunk to about half his normal height.

I can see that having a basic understanding of special relativity, and almost no understanding of general relativity, is going to be a problem. Still, let's go on. What if the falling portal traveller starts feeling sick, and shoots a portal onto the floor nearby, with the same color as the current floor portal, so they will instantly stop? Putting aside the broken bones and bruises that will likely result, we now have a paradox. If the portal traveller and the stationary observer were both wearing watches, each would have said the other's was running slow. Now that both are in the same frame of reference, which watch has the earlier time, assuming the traveller's watch miraculously didn't break upon impact? Admittedly, no real physical theory should be required to answer this question, as we've already violated conservation of energy, but it's still an interesting thought.

One thing that is completely absent in the game (and probably for good reason) is any significant quantity of liquid. Suppose you have two large tanks. Tank A is full of water, and sits on the ground. Tank B is elevated somewhat, and initially empty. A portal is created that connects the bottom of both tanks. What happens? My first thought is that it works like a siphon, with water "seeking its own level" -- that is, water will flow through the portal, filling tank B, until both tanks have exactly the same water level, relative to the ground. By this logic, if tank A is lifted up after equilibrium is reached, water will again flow from A to B. I can't see why this would happen, so I think a new hypothesis is needed.

One of the first things we learned in PHYS 162 last semester is that electric field lines always diverge from positive charges and converge to negative charges. They never form closed loops, and can only start and end on charges or go out to infinity. Suppose a room contains a single positive charge. If you can trace a field line through a portal, it should come out the corresponding portal, potentially at a different angle. Assume the portals are as in the first situation: one on the ceiling, one on the floor. It seems to me the only way to draw the field lines accurately would have to be by modeling the setup as an infinite set of rooms, stacked one on top of the other, each containing a single positive charge. Further evidence that the portals really do create "copies" of the room, rather than simply connecting two parts of the room which are normally separate.

What if you dropped the positive charge into the portal, the same way we dropped a person through it originally? You would have a moving positive charge, i.e. a current. I suppose this would set up a magnetic field in the room, which would be constantly increasing. If you used two floor portals, instead of a floor and ceiling portal, you would effectively have two nearby AC currents, thus instead of infinite kinetic energy, you could create infinite electromagnetic energy.

I think that's enough for now.