Posted by Adam @ 1:39 pm on June 14th 2007

UK physics education: an ex-parrot?

There are many famous stories about Enrico Fermi, who in many ways was the physicist’s physicist. One concerns the Manhattan project:

At Alamogordo, (Fermi’s) determination of the test bomb yield is a classic example of his deep understanding of physics and his simple approach to meaningful experiments. He was about nine miles from the bomb. After the detonation, he began dropping small bits of paper to the ground. When the pressure wave arrived several seconds later, the bits of paper no longer fell directly to the ground, but were displaced. He measured the distance of displacement with a simple ruler and within seconds had calculated the energy released by the bomb. There were, of course, very sophisticated devices to do this with lots of wires and recording instruments that were interpreted later. But Fermi’s measurement was well within the range of those … as he read from a table he had prepared relating displacement to energy released.

This, and the famous ‘Fermi questions’, demonstrate Fermi’s instinct for physics but they also show how a good physicist can use background knowledge, intuition and technique to produce a quick ballpark answer. This is not the genius of the audacious pull of a shortish ball outside off-stump from a world-class bowler, the sort that leads the commentators to cry ‘You just can’t teach that!’; this can be broken down and explained and, sometimes painfully, taught. Of course, having enough knowledge and technique to do this, across a wide group of situations and being able to pick the right route or routes to a solution using that knowledge and technique, is not trivial and it’ll be limited by some measure of brainpower. You can teach it, though, as much as you can teach any technical discipline that needs be applied to varying situations few of which are exactly like the ones described in the textbook. So, in that sense, it’s not so different to, say, learning how to play tennis, although I am not aware that anyone in physics has gone the Kournikova route of making a fortune based on looks whilst being technically pretty crap at the top level.

How to make Fermi types? Well, they’re rare throughout history, so we probably can’t use our ability to produce more of them as a measure of the worth of our education system. As an exemplar, though, Fermi is useful; he was able to bring all his powers and tools to bear on a very wide range of problems, from the spectacular to the apparently mundane, and that is perhaps the best signature of a physicist (as opposed to, say, a mathematician).

The old Nuffield Physics A Level course, which was a physics course that students could take in the last two years of the UK equivalent of highschool (if their school chose to teach the Nuffield course), used very much to test the ability of students to bring their physics knowledge and intuition to bear. There would be a statement and the student, without much direction given, had to apply physics to refute or explain or amplify that statement. An example might be a musing on the ability of a strong, but gusty, wind to knock people over. The good student would know how to calculate the approximate force exerted by a wind of speed v given make ballpark assumptions about the surface area of the person on which the wind was normally incident (about a square meter, is a convenient guess) and the density of air (1 kg per cubic meter is a calculationally handy approximation) and from that, calculate a torque exerted on the person in the wind. The long and short of it is that they would show, in a few lines with a diagram and an assumption, that a person might have to lean forward so far that the center of mass/gravity of the average human was outside the line of their feet and so, in the absence of the wind, isn’t stable. Although it doesn’t deal with the matter of the gust suddenly appearing, it’s suggestive of the problems that hard-gusting winds can present and it requires the application of physics knowledge and understanding to a real-world problem which they wouldn’t have specifically encountered before. Another example of a problem like this was the observation that a metal lid on a pot of boiling water would be periodically displaced by steam and that when the heat was off and the pot and contents cooled, the lid was hard to remove; a quick calculation, with sensible values put in for size and mass of saucepan lid and temperature difference, would show that this was a reasonable statement. In both cases, there were alternate routes to full marks and the mark scheme allowed leeway for the examiner in awarding marks for good physics.

The ability to answer those sorts of questions tends to come later in the course of study; the more you learn, the easier it is to pull together something to work sufficiently well as an answer. This isn’t Fermi-level stuff, but these are 18 year olds being tested and these questions, of all the questions the students had to answer in the course of their physics exams (in which there were, if memory serves, four papers plus an optional Special Paper) tended to differentiate best between the genuinely good physicists and the others. Seeing students ‘get it’ was also a key delight in teaching that particular course, as they jumped the divide between the books and the real world and saw that what they had been learning underpinned, well, just about everything.

Anyhow. Why am I banging on about this lot? Well, a blog post written not long ago by a physics teacher named Wellington Grey has received considerable attention. Grey’s case is that the physics GCSE has become too ‘easy’ in some sense but, more importantly, has veered from what physics is really about. As an aside, the GCSEs are exams that all students in at least England and Wales take at about 16 years of age; at this point, physics is one of the compulsory subjects that all students have to study (and have done pretty much since they started school), although the amount that they take can vary a little from school to school, despite not varying as much in practice as had perhaps originally been envisioned. Grey’s blog post is an open letter to the exam board who produce the syllabus, and accompanying exams, that his students are taking (there is choice amongst syllabi and, therefore, the exams; they are supposed to be standardised so that equivalent performance results in equivalent grades, which is probably roughly true by some measures and not by others).

Now, I haven’t taught formally in the UK for 5 years. I did teach for 7 years prior to that and I also marked A Levels (this is giving the fancy-sounding title of ‘Assistant Examiner’, which is significantly less glamorous even than it sounds), a process where, although I didn’t earn too much money for the amount of effort, I did learn a lot about the examinations process and how the exams are likely to be marked, both of which made me, I think, a significantly better teacher across the board (even though I wasn’t marking GCSEs). My limitations in contributing to this discussion are primarily that I’m five years out of it and that I have not taught the AQA course in question, so bear that in mind. As for why I am no longer a teacher, a number of factors, but most significant by far is that I like physics so much that I went back and did more of it.

My first observation would be that transferring to a new course is difficult, particularly because one of the critical tools in evaluating what to teach is the stock of past papers. One shouldn’t hope to get the same question (the exam boards are supposed to avoid that to a large extent) but it’s not hard to pick out what is, and isn’t, deemed important. When a new course starts, the exam board will produce a set of “past papers” but there won’t be that many of them, certainly not enough to identify areas of interest. This, in itself, makes life hard for the teacher and students.

My second observation is that Wellington Grey is making the change out to be the deathknell for physics, but the fact is that the degradation of the mathematical/technical content of the physics courses has been ongoing since at least 1988, when the National Curriculum was introduced and Science, comprising Physics, Biology and Chemistry, was designated as a ‘Core Subject’; new exams were also introduced for 16 year olds, replacing the old two-tier system of ‘O’ and ‘CSE’ exams with one comprehensive exam, the GCSE. As soon as it became necessary to teach everyone physics to the age of 16, the issue of how to examine the whole range of students became immediately problematic. The old tiering actually reappeared in the GCSEs in any case, but the teaching of physics was changing. Previously, in the ‘O’ level days, physics had been highly technical; in my own experience, understanding the general issues of how physics underpins pretty much everything else was something that was acquired along the way without many attempts to teach it. This certainly worked OK for me and a lot of my classmates (I was at a selective school and, additionally, they didn’t really let you take physics unless you’d done well at it in the 2nd and 3rd form, which is basically Freshman and Sophomore years of Highschool, for the benefit of American readers). Over the time that the GCSEs were in place, it was clear that the style of questioning was changing and the implications being stressed more, at the expense of technical aspects. Anecdotally, as someone who took ‘O’ Level physics as a student and then qualified to teach GCSE physics, it was a huge surprise to me exactly how much things had changed in the meantime.

I am conscious of the fact that Wellington Grey is still in the UK education game, while I am not. Additionally, I am basing what I say next on his ‘open letter’ and not on familiarity with the syllabus and examinations in question. My comments are, therefore, to be taken with a grain of salt.

Wellington Grey’s first specific complaint, about vagueness, is furnished with an example:

Every section starts with either the phrase ‘to evaluate the possible hazards and uses of…’ or ‘to compare the advantages and disadvantages of…’ without listing exactly what hazards, uses, advantages or disadvantages the board actually requires pupils to learn. The amount of knowledge on any given topic, such as the electromagnetic spectrum, could fill an entire year at the university level. But no guidance is given to teachers and, as a result, the exam blindsides pupils with questions like:

Suggest why he [a dark skinned person] can sunbathe with less risk of getting skin cancer than a fair skinned person.

To get the mark, pupils must answer:

  • More UV absorbed by dark skin (more melanin)
  • Less UV penetrates deep to damage living cells / tissue

Nowhere does the specification mention the words sunscreen or melanin. It doesn’t say pupils need to know the difference between surface dead skin and deeper living tissue. There is no reason any physics teacher would cover such material, or why any pupil should expect to be tested on it.

If we, as invited, consult the specification, we find on page 50:

  • to evaluate the possible hazards associated with the use of
    different types of electromagnetic radiation
  • to evaluate methods to reduce exposure to different types of
    electromagnetic radiation.

Well, frankly, why aren’t you teaching about melanin and skin cancer? One doesn’t need a great deal of experience as a physics teacher to understand what’s covered by that specification and, furthermore, there is this:

  • Different wavelengths of electromagnetic radiation have different
    effects on living cells. Some radiations mostly pass through soft
    tissue without being absorbed, some produce heat, some may
    cause cancerous changes and some may kill cells. These effects
    depend on the type of radiation and the size of the dose.
  • The uses and the hazards associated with the use of each type of
    radiation in the electromagnetic spectrum

Now, the Head of Department, who ought to be an experienced teacher, should be providing, or at least auditing and approving, the scheme of work; such an individual really should know that the melanin/skin cancer topic is covered (in fact, what else would they say for the hazards of ultraviolet radiation?). I am sure that there are many better examples than this in whatever AQA exam has been set, but I don’t think that this is a good example.

Sometimes, and it’s happened to all of us, we will get situations like this, where a question flies by the majority of our students. It’s not always the fault of the exam board, however (I would add that no one, as a rule, is going to admit fault for it; in teaching, as in many other areas, failure is an orphan).

On the next section, “The Stupid”, I broadly agree. I have no idea why iPods are mentioned (although you can get tuners for them) and resistance to signal degradation would appear to be a better answer for the level required (at A Level, error correction/signal processing would be brought in and then computers could also be mentioned). It may be that Wellington Grey is being rather harsh on the examiners; this is a question from a sample paper, but the final answer scheme for an examined paper will have been modified and isn’t finalised until AFTER the exam has been taken. I remember, myself, examples of allowed answers being added to the markscheme following Examiners or Assistant Examiners finding acceptable answers, often having actually seen them in their allocation of papers, and there can be broad interpretations taken in other cases. I would be surprised if things are done substantially differently for the AQA GCSE, although it’s entirely possible that they are, I guess.

If, however, the sample paper was chock-full of questions like that, it’s a concern; either the Examiner that wrote the paper, or the direction they have been given, has failed. I haven’t the sample paper to judge that, however. As for the reading comprehension question, well, you get a few gimmes; too many reduces the ability of the exam to properly differentiate between students. The business of comprehending the science content of an article isn’t a bad task, but the question about the age clearly isn’t sufficiently testing because just about everyone will get it right, as Grey points out.

On the last two points, I also have some sympathy with Grey. The renewable energy question isn’t entirely political; there is a physical limit to non-renewable energy sources (indeed, the effective meaning of ‘non-renewable’ isn’t far from ‘will run out’). It’s an issue that is quite politically charged, I agree, so the ‘must’ should probably have been qualified, not because logic demands it (indeed, physics demands we develop renewable, or at least approximately renewable, sources of energy) but because many of the students will take the wrong message from the imperative, ie, not the physical one. On the subject of ‘reliability’, I just think that Grey is missing the point; a prerequisite for a ‘reliable experiment’ is that holes can’t be poked in it, or at least that they can be identified and accounted for. The deeper question of what is a ‘reliable experiment’ is a big one; experiments are there to falsify predictions (they can’t prove them, at least for those many of us that are falsificationists). Poking holes is the essential skill and teaches the critical attitude which characterises nearly all good science.

For the issue of why biofuels should be used, Grey again appears to desire specific guidelines that should be in the Scheme of Work provided by his department rather than in the syllabus, which contains (p 49-50) these guidlines:

  • to compare and contrast the particular advantages and
    disadvantages of using different energy sources to generate
    electricity.
  • The advantages and disadvantages of using fossil fuels, nuclear
    fuels and renewable energy sources to generate electricity. These
    include the cost of building power stations, the start-up time of
    power stations, the reliability of the energy source, the relative
    cost of energy generated and the location in which the energy is
    needed.

Now, I can agree that encouragement to teach biofuels in any detail is lacking (although I think that it’d still get covered in nearly any Scheme of Work) — the real point here, however, is that the question is a comprehension. The answers to the questions are there in the text which the students are to read before answering the question (particularly the obvious one about making more money), when combined with a basic understanding of the issues.

Grey’s point about physics being about big ideas is also a misleading one, I think; it’s not as damaging as the Cult of Genius but the fact is that physics is about explaining what goes on, using falsifiable theories — sometimes, this falls under ‘big ideas’, but most professional physicists, even, aren’t engaged in the ‘big ideas’, even though selective media coverage might lead one to believe otherwise. Ever since Newton showed us that the same rules that govern our immediate surroundings govern the heavenly bodies, the universality of physics has been one of it’s big selling points, sure, but the big fact to take from that, as from the later example of Fermi, is that physics is real. That students should appreciate how physics interacts with the everyday world is essential; whether or not they need to be examined on it as much as they are is an entirely different matter, but there has to be some place for it, particularly if we are going to make physics study compulsory for all British schoolchildren up to the age of 16. As most of them will not continue their studies, we should focus on the benefits that they will leave with; general scientific comprehension is a pretty big one, if it can be taught (and one that we’d all agree, I think, benefits society as a whole).

My personal opinion is that the school physics of yesteryear probably is dead, but it’s been dead for a while. Firstly, the decision to make it compulsory was the beginning of the end; as soon as all abilities, particularly mathematical abilities, have to be covered, it becomes more difficult to teach the technical aspects of physics. In some schools (such as two of the ones at which I taught), that’s not such a big deal, either because there were sufficient pupils and school funding to have a large number of sets sorted by ability to ensure relative homogeneity within a set, or else because the whole cohort was sufficiently homogeneous itself, so that a smaller number of sets would suffice (this was the case in the selective school at which I taught). This is important because the more homogeneous a group of given size is, the easier it is to teach the technical aspects (there are many arguments in favour of teaching a mixed-ability class, but that class should be smaller, as a rule, because teaching such a class is more demanding). In a lot of other schools, however, this won’t be the case. The decision to make physics compulsory also leads, indirectly, to the second problem; more physics teachers are required with so many more students taking it, yet the number of people with the skills to teach the more technical physics is limited; furthermore, industry values those skills sufficiently that physics teachers’ wages look somewhat paltry by comparison. For as long as it is difficult to really bust the payscale wide open and pay physics teachers significantly more than teachers in other, more easily filled, positions, having a physics course that’s heavy on the technical material is going to result in insufficient teachers who are really able to teach it. As the course degrades and is less well-taught (often by people who are really non-specialists, because of the problems in recruitment of specialists), it seems logical that less students will follow physics to degree level which will increase the problems in recruiting good new physics teachers (in whose reducing numbers Wellington Grey appears to be). It’s not a new problem, however, and Grey is just seeing another, most recent, part of a long, sad, story.

I agree with Grey’s general complaint, but I don’t agree with all of his examples and I don’t agree that just now has some critical turning point been achieved. I am conscious that people with more experience than I might point to changes further back than I have and grumble about my whippersnapperish whining although, having worked with people of significantly more experience than I, I can anecdotally report that most of them also identified the 1988 change as key (and it was the biggest change in education in the UK for many years).

4 Comments »

  1. although I am not aware that anyone in physics has gone the Kournikova route of making a fortune based on looks whilst being technically pretty crap at the top level

    Hawking, maybe?

    Comment by Rojas — 6/14/2007 @ 1:43 pm

  2. The part I’m having the hardest time comprehending is the idea that Physics isn’t just compulsory in British schools, but THREE YEARS OF IT are compulsory. In most states of the US, Physics is a one-year elective course, as are Biology and Chemistry. Most American HS students will graduate with a year of each, or two of the three; I myself never took Physics, and the world is better for that fact.

    Three hours of science for each year of high school? It’s impressively rigorous, but what time is left for students to take Maths, English, History and the like?

    Comment by Rojas — 6/14/2007 @ 1:51 pm

  3. More than three years. Kids start learning it when they start school (although ‘which one sank’ is about where it starts).

    Science can take a lot of timetable time, particularly at the later stages (the last two years before GCSEs, for example, where it might be not far from 25% if you add all three sciences together).

    Comment by Adam — 6/14/2007 @ 1:56 pm

  4. I begin to understand Thomas Dolby’s complaint.

    Comment by Rojas — 6/14/2007 @ 1:59 pm

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