Hi again,

This time I’m starting with a request for you to do some work instead of me 🙂

Luckily this work is not very challenging. I would really appreciate it if you could go to my new website, which is currently at keerlu.github.io, and tell me what’s wrong with it. Please don’t worry about seeming pedantic – I’m actively looking for pedantry! As well as serious cockups, I’m interested in typos, layout bugs, things being two pixels out of place, etc. I won’t necessarily fix the small things any time soon (I’m sick of web design), but I do want to make a list of them to go back to when I can be bothered again.

I’m particularly interested in hearing about what the site looks like on the following browsers and devices, which I haven’t tested:

• Safari
• Any Apple device
• Tablets
• Large monitors

I’m aware there isn’t much content on the site yet! That’s because I’ve spent about a million hours on making the kaleidoscope thingy on the home page instead. This is probably a completely stupid waste of time, but it has taught me a surprising amount about prototyping and designing (will write a post about that soon).

The first thing I want to do is add a bunch more notes in the style of the two pages that are already there (you may recognise the content from previous newsletters if you read those bits). As a lazy first step I may scan in some old printed notes – those might be rather unhelpful to other readers, but first of all I’m making this as a resource for myself, and I think it would be much more useful for me to have these available on the web than sitting in an exercise book I never look at.

Later on I’d like to add some way of tracking the recurring questions I go back to again and again – I’ll probably call it ‘Themes’ or ‘Projects’ or something, but the idea is it would be more a collection of pages than an isolated page of notes. Still working out what I want.

Let me know what you think anyway!

In the rest of this newsletter I will mostly talk about two books, Donald Schön’s The Reflective Practitioner and Huw Price’s Time’s Arrow and Archimedes’ Point. The second of these is mostly preparation for explaining why the hell I keep talking about the van Enk toy model and the Wigner function and so on.

The Reflective Practitioner

This month I read Schön’s The Reflective Practitioner, which is about how people solve problems in professions like architecture, town planning, teaching and management. The problems in these fields are context-dependent and open-ended, resisting any sort of precise theory that applies to all cases. On the other hand, people do manage to solve problems and develop expertise in them anyway.

Schön considers a series of examples to try and understand how this works. The one I find most compelling was a case study of an established architect, Quist, reviewing the work of a student, Petra, who is in the early stages of figuring out a design for an elementary school site. (This is pages 79 to 104 of the book.)

Petra has already made some preliminary sketches and come up with some discoveries of her own. Her first idea was the six classrooms in the top right of the picture below. Playing around, she found that ‘they were too small in scale to do much with’, so she ‘changed them to this much more significant layout’, the L shapes below.

I’m not sure I can fully explain why the L shapes are ‘more significant’, but I do agree with her assessment. There’s more of a feeling of spaciousness than there was with the six cramped little rectangles, and the pattern is more interesting geometrically and suggests more possibilities for interacting with the geography of the site.

At this point, we already get to see a theme that Schön goes back to repeatedly, the idea of a ‘reflective conversation with the materials’. The designer finds that

His materials are continually talking back to him, causing him to apprehend unanticipated problems and potentials.

Petra has already found an example of this. She switched to the L shapes on more-or-less aesthetic grounds, but then she discovers that the new plan ‘relates one to two, three to four, and five to six grades, which is more what I wanted to do educationally anyway.’ The materials have talked back and given her more than she originally put in, which is a sign that she is on to something promising.

After this early success, Petra runs into difficulties. She has learnt the rule that buildings should fit to the contours of the site. Unfortunately the site is really incoherent and nothing she tries will fit into the slope.

Quist advises her to break this rule:

You should begin with a discipline, even if it is arbitrary, because the site is so screwy – you can always break it open later.

Together they work through the implications of the following design:

This kicks off a new round of conversation with the materials.

Quist now proceeds to play out the imposition of the two-dimensional geometry of the L-shaped classrooms upon the “screwy” three-dimensional contours of the slope… The roofs of the classroom will rise five feet above the ground at the next level up, and since five feet is “maximum height for a kid”, kids will be able to be in “nooks”…

A drawing experiment has been conducted and its outcome partially confirms Quist’s way of setting the L-shaped classrooms upon the incoherent slope. Classrooms now flow down the slope in three stages, creating protected spaces “maximum height for a kid” at each level.

In an echo of Petra’s initial experiment, Quist has got back more than he put in. He hasn’t solved the problem in the clean, definitive way you’d solve a mathematical optimisation problem. Many other designs would probably have worked just as well. But the design has ‘talked back’, and his previous experience of working through problems like this has given him the skills to understand what it is saying.

I find the ‘reflective conversation’ idea quite thought-provoking and appealing. It seems to fit well with my limited experience of design. Unfortunately most of the other examples are not quite as convincing – the practitioners are not as articulate as Quist, and it’s often hard to get a sense of how good their solutions are. I guess Schön was somewhat limited by who he could persuade to be involved.

Along with the examples, there is some discussion of the implications for how these professions are normally taught. Some of this is pretty dry, but there are a few interesting topics. The professions he considers often have something like ‘engineering envy’ or ‘medicine envy’: doctors and engineers can borrow from the hard sciences and get definitive answers to some of their questions, so they don’t always have to do this more nebulous ‘reflective conversation’ thing. It is tempting for experts in the ‘softer’ professions to try and borrow some of this prestige, leading to the introduction of a lot of theory into the curriculum, even if the theory turns out to be pretty bullshit-heavy and less useful than the kind of case-by-case work Quist is doing. Schön advocates for the reintroduction of practice, pointing out that this can never be fully separated from theory anyway:

If we separate thinking from doing, seeing thought only as a preparation for action and action only as an implementation of thought, then it is easy to believe that when we step into the separate domain of thought we will become lost in an infinite regress of thinking about thinking. But in actual reflection-in-action, as we have seen, doing and thinking are complementary. Doing extends thinking in the tests, moves, and probes of experimental action, and reflection feeds on doing and its results. Each feeds the other, and each sets boundaries for the other. It is the surprising result of action that triggers reflection, and it is the production of a satisfactory move that brings reflection temporarily to a close… Continuity of enquiry entails a continual interweaving of thinking and doing. (p.289)

For some reason this book has become really popular with education departments, even though teaching only makes up a tiny part of the book. If you google ‘reflective practitioner’ you find lots of education stuff, most of which looks extremely cargo-culty and uninspired. Schön’s ideas seem to have mostly been routinised into the kind of useless theory he was trying to go beyond, and I haven’t yet found any follow-ups in the spirit of the original. It’s a shame, as there’s a lot more to explore here.

Time’s Arrow, and Archimedes’ Point

This month I thought I’d start giving some background about why I care about phase space and the Wigner function and some random obscure toy model. I sort of just dumped you in the middle of it in my first post without much explanation, so it would be good to go back and start filling this in. It would also be useful for me to regain some perspective after several months in the weeds not really thinking about the wider context.

I’ve sort of rushed this out at the end of the month, and it’s a bit of a complicated story, so unfortunately I haven’t made it to the point where it connects back. I will get there eventually! Even the part I have produced is probably not be very clear – please ask questions if it makes no sense.

For most of what I’m interested in in physics, you can trace a line directly back to one foundational book, Time’s Arrow and Archimedes’ Point by the philosopher Huw Price. This is an unusual book stylistically: he tries to aim it both at philosophers and physicists, and ends up with something that doesn’t quite fit the natural style of either – it’s maybe more like a popular book with some weirdly technical exposition. In the first chapter he says:

Much of the argument is philosophical in character. It deals with live issues in contemporary physics, however… The book thus faces the usual hurdles of an interdisciplinary work, with the additional handicap of a far-reaching and counterintuitive conclusion. There is a danger that specialist readers on both sides will feel that my treatment of their own material is simplistic or simply wrong, and that my account of the other side’s contribution is difficult, obscure and of doubtful relevance.

He is a very clear writer and I actually like this writing style a lot, but probably the style has made it harder to get his view across, particularly to physicists. (It’s more like a philosophy book than a physics book, and I think most physicists would have a strong ‘stop rambling and show me the equations!’ reaction.)

The book is about time asymmetry in physics, and where it comes from given that the underlying laws are mostly time symmetric. This is a surprisingly hard topic to think clearly about  – people understand that entropy tends to increase in the future, as systems return to a more probable state, but often fail to notice that their arguments also apply to the past, because of that time symmetry. We have to explain why entropy was low in the past, rather than the current moment just being a weird statistical fluctuation away from equilibrium. (If you have read some garbled pop science thing about ‘Boltzmann brains’ some time in the last decade or so, this is the source. Boltzmann understood the issues pretty clearly in the 1890s.)  Lots of people have fallen into this trap, including Popper and Hawking, and he carefully analyses where they go wrong.

Price points out that our difficulties probably come from our perspective as creatures embedded in time. We have no freedom of movement in time, and so tend to privilege arguments that make sense when played forward in time, and not think so hard about what they look like played backwards. Reading the book is a good exercise in developing an ability to think in terms of what Price calls ‘the view from nowhen’, getting into the habit of replaying arguments backwards or laying them out in an ‘all-at-once’ spatial sort of way. The book is well worth reading for this alone.

Everything I’ve described so far actually seems to have been pretty popular with the few physicists who have read the book. In June I went to a talk by Carlo Rovelli in Vienna, and noticed that Rovelli explained something in a very Price-like way. I got a chance to ask him about this after the lecture, and he got very animated and talked to me for ages. His opinion is something like ‘fantastic book, thinks more clearly about time symmetry than anyone else, shame about the last two chapters’.

The last two chapters are the ‘far-reaching and counterintuitive conclusion’ bit. These are the really interesting ones, from my perspective. In the earlier parts of the books, he’s argued that there must be some condition of low entropy in the past to drive the thermodynamic arrow of time we see today. However, he points out that this is some sort of macroscopic past condition, and there’s no reason to see this in every interaction at the microscale. These microscopic interactions should be time symmetric, with the future measurement condition being just as important as the past preparation condition for the current state of the particle. (Think of this like a spatial system: you would expect the solution for a hanging chain problem to depend on the boundary conditions at both ends, not just one). This turns out to fit very well with what we see in quantum mechanics – for example, the Bell inequality violation is easy to explain if the future measurement condition is also relevant for the particle’s current state.

So to Price, quantum mechanics is more or less just the sort of theory we ought to expect:

… the most promising and well-motivated approach to the peculiar puzzles of quantum mechanics has been almost entirely neglected, in part because the nature and significance of our causal intuitions have not been properly understood. Had these things been understood in advance – and had the real lessons of the nineteenth-century debate about temporal asymmetry been appreciated a century ago – then quantum mechanics is the kind of theory of microphysics that the twentieth century might well have expected.

This is a pretty bold claim! I find his argument for it extraordinarily compelling (the book length version, not my dodgy five paragraph summary) and haven’t been able to stop thinking about it for the last twelve years or so. I will admit that the book is still very disappointing from the ‘show me the equations’ point of view. There’s no mathematical model, not even a toy one. Even Rovelli, who is unusually widely read in philosophy and has more patience with the philosophy style than most, was irritated with this. I find the argument convincing anyway, but it would be a lot more convincing with a model to go with it.

There is one physicist, Ken Wharton, who takes Price’s work very seriously and has put a lot of work into constructing more concrete models. I also recently saw some interest in it from Matt Leifer in quantum foundations. So there is a small amount of mainstream physics interest, and I guess all of this comes under ‘heterodox’, rather than actually ‘crackpot’. (Also, Huw Price is the Bertrand Russell Professor of Philosophy at Cambridge, not some Time Cube guy.) But it’s still a pretty tiny minority position in interpretations of quantum physics, which is quite impressive given how horrible most of the options are.

I’m also interested in the idea of constructing toy models. I have a feeling that there’s something in the area of that van Enk model that’s rich enough to contain what I want and simple enough to be tractable. (The fact it can violate the Bell inequality is a very promising sign. Also the negative probabilities are interesting.) But I’ll have to try and explain that another time.

Next month

I’m probably not going to do a proper newsletter next month. I really like doing these and find them helpful for getting my thoughts out, but it tends to make me produce a lot of half-baked exploratory writing at the expense of actually polishing anything. I’d like to get some finished blog posts out, or get some notes on to my new site, or a mix of both.

(I also discovered while writing the section above that Ken Wharton had a new paper out in May – should probably go and read that!)

I’ll email out a links post or any bits of text I do end up producing at the beginning of September, but it’ll be pretty low effort. Normal ranting will resume in October!

Cheers,

Lucy