Sacred Cows of the Mysterious West

Phil NelsonUniversity of Pennsylvaniawww.upenn.edu/~biophys

Part 1: Ground rules Let’s not say, “we’re like this and they’re like that.” Actually, let’s not say “we” or “they” at all.

Let’s say, here are some approaches that have worked in the past and may benefit some students not currently getting them.

Maybe if we think carefully about what we want to teach life-science students, and how they’ve been taught so far, we’ll also get some insights into how to teach our own students. Surely we could stand to do a lot more of that.

Interdisciplinarity

“Any course that stays within the confines of one discipline is ipso facto boring and obsolete.”

“(Also my research is better than yours because it’s interdisciplinary.)”

“To be interdisciplinary, a course must be team-taught by members of two or more “disciplines.” And it must be attended by a similarly ecumenical group of students.”

“After all, life science students need to study physical science so that they can learn to model their data.”

“And physical science students will need a job some day, so they need to study life science.”

Here are some things one hears, explicitly or not. Each may contain a grain of truth, but I’m not going to agree with any of them:

Interdisciplinarity, II

“ In fact the lecture course concept itself is dead. Lecture courses are just a lot of dry theory. At the very least, they must be done in PowerPoint.”

“Students don’t need extensive discussion of historical examples of discovery. After all, they’re really not likely to go breaking any big paradigms. They’re more likely to become grunts.”

“As such they need training in how to be good grunts who work effectively in teams … know the ins and outs of grant writing… ethics… animal treatment…”

More propositions one hears:

Part 2: some goals for interdisciplinary education

I do think an interdisciplinary lecture course can be useful if a practitioner of one discipline shows students pursuing a different discipline how his methods have been useful in solving problems of independent interest in the other field.

There are some good reasons to make this an intermediate-level (sophomore+) course, not a tweak of freshman physics-for-premeds.

Here are some details.

So much for what I don’t think are the right goals.

What physics-style courses can give to life-science students

Frame topics around “how could anything like that possibly happen” puzzles. (E.g. the trombone model!)

Stress that understanding is tested by falsifiable quantitative prediction. Shake the hypothesis till it yields up a testable prediction. Push it to a region of parameter space different from the observations that modivated it in the first place.

Consciously teach the art of throwing out details. The theory should not be more elaborate than the data can support. Don’t stop with a successful prediction -- then seek the simplest model that succeeds equally well.

In particular, approximation is not bad. Appropriate approximation -- which is not just sloppiness or laziness -- is essential to understanding.

What physics-style courses can give to life-science students, II

You can be handed a problem you’ve never seen before, even on a timed exam, reach into your toolkit, pull out the right tool without being told, and solve the problem.

In fact your instructor is simulating that process when she stands at the blackboard and invents the subject right before your eyes -- sometimes even making mistakes, finding them and fixing them.

Long chains of logic actually do lead to real conclusions, with the help of mathematical discipline. There’s a nontrivial synthetic step, and suddenly there’s new knowledge that wasn’t there before -- or at least a testable hypothesis, which will turn into new knowledge when an experiment is done.

This by the way is a miracle -- the basic epistemological miracle of physical science. It doesn’t always work, but is has worked in the past.

Specific goals

The reflex to check all results for numerical reasonableness?

The reflex to carry units throughout every calculation?

An intuition of how many significant digits matter?

The concept of dynamical fixed point, and their classification? The limit cycle? Bifurcation? Chaos?

Of the slaving of one variable to another, and the corresponding simplification of theories? Of the simplification that arises when actors living on one length or time scale are viewed on another?

Of basic electrical metaphors like the flipflop? The distributed RC circuit?

Wouldn’t it be great if life science students came (and physical science students too) away with…

Specific goals, II

Historical examples of how the relentless pursuit of an explanation for indirect, physical observations disclosed the existence of a new molecular actor or process?

I’m thinking of Hodgkin, Huxley and Katz... Voltage-gated ion channels.

Or kinetic proofreading…

Or Berg and Anderson… rotary motor.

Or Jacob and Monod… genes

switch genes.

Wouldn’t it be great if life science students came (and physical science students too) away with…

Bacterial growth curves

Specific goals, III

A feeling for numerical data -- you need enough. Some features are real, some fake. You need to show expected trends as an external knob is turned. Some external knobs are much simpler than others (force is simpler than temperature change). You even need to show expected non-trends as external knobs thought to be immaterial are turned!

Seemingly random time series often display crucial information in correlations.

Every state is a dynamical state -- equilibrium is death. Nevertheless, sometimes we can effectively treat a particular substate as equilibrium.

The cell is a very small test tube -- averages are not the full story.

Wouldn’t it be great if life science students came (and physical science students too) away with…

First clean up our own act

Often we just stop after merely showing that physics “works.” We must keep the intrinsic interest of the results and tools front and center.

Usually our textbooks are devoid of real experimental data. Students need to see real data because it’s not as nice as fake data, and yet nevertheless sometimes strong conclusions can be drawn from it.

In our urgent desire to get the basics down, we often forget to put in current discoveries, with appropriate links to the basics.

Too often we overdo the history, and worse, focus on the dead white males whose pictures we see in books.

Turnabout

An understanding of entropy as information?

And all the points on the preceding slides?

Wouldn’t it be great if physical science students (and life science students too) came away with…

Is it hopelessly difficult?Luckily no. All you have to do is a slightly better job than you were doing before, and already you’ll be way ahead of -- say -- other departments’ courses.

Also there are and will soon be books embodying these idea.

Remember to have fun yourself. Students feel it.