Physicists in action, latest in an occasional series

we still clearly haven’t conquered the hard-science arrogance problem yet …

You mean the physics arrogance problem, right? As a computer scientist who has occasionally had to deal with physicists, I can assure you that (1) not every “hard science” (if CS can be said to be one) treats other fields as if they don’t exist, and (2) physicists treat us with every bit as much ignorant contempt as they treat you.

I got a nosebleed reading that linked piece so I couldn’t work if they attempted to distingush amongst denominations. And if so, what demominations would be most likely handled by frequent flyers?

I have just overheard–for the fourth time–a respected faculty member in my new department opining that, “What those people on eBay need is a good stochastic-calculus-based insurance scheme to manage the risk that an unscrupulous seller will not send them the thing they bought. See this simple formula, derived from first principles, that captures all the uncertainty about the transaction in this two-variable function of the seller’s feedback rating? There you have it!”

In other words: It ain’t just physicists.

I am preparing a followup paper, building on my work with Dr. Shalizi, with the working title of “A Simple Model of Simple Models: Proof that the upper bound of model utility inversely relates to the spontaneous reinvention rate.”

I have it down to one variable, don’t you see. I am collecting my strength for the last push to reduce the model to zero variables. But I see the light at the end of the tunnel….

…not every “hard science” (if CS can be said to be one)…

It can’t. In fact, it can’t even be called a science. The tip off is when a field finds it necessary to make “science” part of its name because it wouldn’t otherwise be apparent.

Compare:

Physics, Chemistry , Biology – real science

Political Science, Social Science, Library Science, Computer Science – not real science

Not that there’s anything wrong with that. Some of my best friends are computer scientists.

The tip off is when a field finds it necessary to make “science” part of its name

Sociology is coming out well ahead of materials science then. Good news for me, bad news for the buildings I inhabit, I guess.

Sociology is coming out well ahead of materials science then. Good news for me, bad news for the buildings I inhabit, I guess.

You forgot Neuroscience. Bad news for the ol’ noggin’, too.

“Human beings don’t diffuse – they go from one specific place to another. Otoh I seem to remember a lot of quite detailed modelling of SARS which certainly did take airline routes into account so I suspect that the diffusion assumption is really only found in toy models in basic-level textbooks.”

The statement about human beings diffusing is naive-diffusion is a statistical concept. Even specific particles undergoing brownian motion go from one place to another. Also, if this model is so naive and basic so as to be found in basic textbooks, isn’t it a bit surprising that it is not well known to the social scientists here.

Physicists would not be doing this sort of stuff if there were already any social scientists using these approaches in a significant manner.

“If someone was going to quote the existing literature on epidemics, where would you suggest they start?”

The standard text is “Infectious Diseases of Humans: Transmission and Control” co-authored by Robert May, a Theoretical Physicist, the arrogant bastard.

For what it’s worth the paper doesn’t ignore ecology. It starts off by identifying a technique in ecology (the dispersal curve) identifies a problem with a sub-set of curves (the absence of a typical scale length, which means diffusion approximations fail) and adapts an idea from physics to solve it. I’m not sure this isn’t the good kind of cross-disciplinary work.

They’re also quite naive about banknotes. At one point in the paper, they seem to believe that bank notes “exit the money-tracking system for a long time, for instance in banks”. Of course, banks don’t contain large piles of banknotes sitting around for months on end; the only bank notes you will find in a bank are the ones being stored in the ATMs and the tills, and these obviously turn over pretty rapidly.

They don’t appear to assert that notes exit the system–rather, it seems like they’re just considering this as an explanation. I don’t see any reason to believe that many notes don’t sit around in banks for long periods. Notes don’t “spoil”, so banks might just as well use a first-in-first-out inventory, which would result in some notes hanging around for long periods. And god only knows what the Federal Reserve Banks do with theirs (i.e., the ones they don’t destroy).

Furthermore, I would guess that the average human being makes fewer journeys to a banknote sorting centre than the average banknote (I suspect that several of the odd statistical properties that they found relate to the locations of sorting centres in the US).

Probably so, but isn’t this irrelevant? What matters is where the notes appear and where they disappear. Presumably these both happen at local banks (assuming that bank employees are not adding entries to wheresgeorge), and those are presumably distributed more-or-less according to population density.

As for inter-disciplinary respect, it’d be very interesting to see a graph showing what each generally thinks of the other. As a computer science/programmer type, it usually feels like we’re at the very bottom of the heap (perhaps excluding K-12 educators).

Gack, I remember thinking that the most obvious and irrefutable sign of dilletantism was the obvious selection bias in the data set. Can’t imagine people who self-select to participate in this odd endeavor are at all a microcosm of the pool of susceptibles.

I bow to dsquared’s superior dilletantism-radar.

Although I am partial to the inverse square law–I’ve found that it’s a red flag that someone is being clever and not rigorous.

Might I suggest that at least part of the reason is the shocking lack of interest on the part of social scientists in telling the world of what they know?
The world is full of pop physics books, pop astronomy, pop biology, geology, chemistry. These books may not be perfect, but they do at least allow interested outsiders to have some feel for what is known and unknown in the field.

But when it comes to pop sociology and related fields, the cupboard gets bare pretty damn quickly. I can think of Malcolm Gladwell’s Blink and The Tipping Point, at a stretch maybe Freakanomics, and that’s it. This is quite ridiculous.
Sociologists produce plenty of earnest tomes for the public about the plight of some small group of people in some area of the country, but they seem to produce nothing in the way of survey books that are both engaging and that give the public an overview of what is known to be true and known to be false in the field.

“Sebastian and Steve: directed transport isn’t going to be a diffusion phenomenon. More people go from New York to Los Angeles than go from New York to Oklahoma City, which they wouldn’t if the population is diffusing.”

Right, but if you want to track how a disease spread inside Los Angeles from a person who arrived by plane at the airport, diffusion might be an excellent way of doing so.

The methodology provides some insight which gets modified by other insights. This may or may not invalidate the starting model.

But even your mention of New York to LA doesn’t invalidate the diffusion analogy entirely. Fill a maze with water. Introduce a dye at one end of the maze. It will spread by diffusion, but be limited in its direct path by the maze walls. The method of spreading remains diffusion even if it has to go through distance 3X (because of the walls_to get to a location that is only 2X units from the initial starting point (if you measure without the walls).

Yes, simple diffusion can’t cover all the variables possible in a disease outbreak. But it has useful insights inside a local area. It tends not to fully explain the jumps from local area to local area.

Daniel, banks differ.

Some major German banks only use brand-new notes for ATMs and all notes are perfect. I know this to be true. But from one other major bank’s ATMs I received counterfeit DM banknotes (plural) before the DM was phased out. This was quite a shock.

Back in my own increasingly cashless society I watch the money that passes through my own hands. Well over 50% of the €uro banknotes I see does not come from this country.

But coinage does stick around. Before the €uro, we were told that all our coins would disperse through out Europe within a year, and we wouldn’t see them again. But this hasn’t happened. It’s quite rare that I see a foreign coin, and when I checked my coins last night, not a single one out of 24 was foreign.

“More people go from New York to Los Angeles than go from New York to Oklahoma City, which they wouldn’t if the population is diffusing.”

A diffusion process usually considers sub-populations. One chemical will through another . But yes, overall, the population of molcules as a whole is not diffusing. Which is beside the point.

Uh, Maynard Handley, you’re kiddin´, right? Take a look at the shelves at the airport next time you travel, and there you have all the pop psychology and pop sociology you can stomach. It’s all about becoming a better person or manager . Most of it is shite, but I gather that most professional physicist feel the same about pop physics books.

All right.

I enjoy a good piece of academic smack fu as much as the next guy, and the point of the post is very very VERY well taken. In fact, I sent the previous round of the debate to my students: we’re applied math types working in the life sciences, and I’m keenly aware of what we don’t know (which is why we work with experts in the field, and make sure we publish at least some of our work in actual specialty journals, to keep us honest). I keep warning my students about the dangers of falling into the math/physics/engineering arrogance trap.

But…

It would be nice to have another post one of these days on the conjugate outrage: the people in not-quite-yet mathematized fields that take whatever exotic thing they’ve just read about (“chaos theory”, 1/f noise, connectionism, Bell’s theorem, string theory, quantum computing, or the ever-popular “complexity”…) learn to repeat the jargon in knowing, quasi-mystical tones and and then mangle the living shit out of it in order to make a really harebrained, weakly supported model, or worse “theory”.

And then there’s the whole issue of disciplinary possessiveness and turf protection. I’m not saying that Daniel is motivated in this way, but the fact is that often people from the mathematical sciences do indeed have much to offer, but this capacity is viewed (by the paranoid) as a threat and their work dismissed, often using the very same style of argument presented above. The arrogance cuts both ways.

Daniel, reading the paper I don’t think they are arguing for the sort of naive “humans diffuse” model you deplore. My reading of the introductory paragraph is that they are critical of the current situation whereby “the assumption that humans disperse diffusively still prevails in models” despite the lack of quantitative assessment i.e. lack of evidence – something I think you would agree with.

They then go on to develop a mathematical model which they claim produces predictions in good agreement with the empirical evidence of bank note dispersal, which was their intention, and furthermore in good agreement with two sets of data on long distance air travel.

And that, from there point of view, appears to be a step forward in creating models of human dispersal that are testable.

But if you believe that there are alternative distribution models you could put them forward for comparison.

(with “exit the money-tracking system for a long time, for instance in banks”, they are making the point that this does not happen, as you point out).