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David Griffiths is best known as the author a fantastic series of textbooks. His book on electrodynamics is a classic in North American undergraduate education, although I’ve been disappointed to learn that it’s not as well known in Europe. Since I enjoyed reading his texts so much, it was nice to see that he has an article in the latest edition of Physics World and even nicer to read it. Now that he’s retired, I get the impression that he’s just calling it like he sees it and it makes for a good read.
My parents were professors (history and zoology), and they firmly believed that the purpose of education is to show students “how to think”. When I began teaching, I quickly discovered that many of my students could think much better – or at any rate much faster – than I could. What distinguished me from them was that I knew things that they did not, things they had been led to believe they ought to want to learn. I adopted a less-exalted goal: I think the purpose of education is to pass along to the next generation the accumulated knowledge and wisdom of humankind, and my role as a teacher is to make that process as efficient and palatable as possible.
I have known people who are in some sense too smart to be clear; they cannot remember what it was like not to understand something, because, I suppose, they never had this experience. They may be outstanding physicists, but they do not belong in the classroom. (There are exceptions: the most brilliant physicist I ever encountered, the late Sidney Coleman, was also – by far – the best and clearest teacher.)
Interestingly, another of Sidney Coleman’s graduate students, Phil Nelson, also has a knack for clear and engaging textbook writing and lecturing. Apparently something of Coleman rubbed off on them both.
Read the rest of Griffiths’ polemic for the full story. I can’t resist one more quotation:
I can explain the conservation of momentum in 15 minutes, but three hours in the lab would only convince an honest student that the law is false.
If you could wish for any capabilities in an instrument to help you with your research, what would they be? It might not be hard to come up with a useful super power that’s way out of reach of current or near-future technology, but what about something you might actually have in the next 10 or 20 years?
One of my interests is high resolution imaging, either by scanning probe or fluorescence microscopy, and I’ve seen and taken advantage of some great electron microscopy as well (although I haven’t done any myself). Each of these methods in their current most common form has advantages and disadvantages: scanning probe microscopies tend to be slow but offer high resolution with little sample preparation, fluorescence microscopy suffers from lower resolution but has pretty good acquisition rate and molecular specificity, and electron microscopy involves more complicated sample preparation that can distort the sample and only provides a snapshot, but it can provide truly exquisite images at a range of spatial scales.
These methods are all providing new insights into every area of cell biology and biophysics—fluorescence microscopy especially is now a staple of almost every lab in these fields—but it’s the ways that these methods are being pushed beyond their current limits that are truly exciting. New tools have always provided new insights, but I think cell biology is poised to be completely revolutionized in the next few decades.
Take atomic force microscopy. High resolution in water, but painfully slow. Wouldn’t it be nice if it were faster? It is. The animated gif on the right is an AFM movie taken at 12 frames per second in Toshio Ando’s lab at Kanazawa University in Japan. You’re seeing a single myosin molecule undergo a conformational change in real time. Single molecule fluorescence methods have provided a lot of insight into the mechanism of molecular motor motion (they walk) but there are still finer scales to investigate and high-speed AFM may prove to be the tool of choice in the very near future.
That’s very nice for in vitro work, but ultimately cells are where the action is. I want an instrument that will reduce the vast majority of cell biology to computer science. That will “only” require the convergence of three existing technologies: cryo-electron tomography, environmental scanning electron microscopy, and femtosecond electron diffraction. The ultimate fantasy or course is an atomic scale femtosecond movie of a living cell over hours. That would give you a complete genetic, proteomic, biophysical, and biochemical picture of cell function. You would still need interesting perturbations to ask questions, but all the answers would be provided by a single instrument and clever data mining. Even relaxing the goal by orders of magnitude in every direction to 10 nm spatial resolution and millisecond time resolution in a one minute movie would be radical.
Sounds far-fetched, but don’t forget that we’ve already got Wolfgang Baumeister talking about the molecular sociology of the cell and visual proteomics and people like Philip’s advisor doing femtosecond electron diffraction. Environmental scanning electron microscopy works in water vapour. At a talk at the College of Physicians, Ahmed Zewail spoke about an instrument his group is developing for electron diffraction and imaging. He showed a picture of a cell they took with it and he says their goal is to do a single particle version of electron diffraction in a cell within a few years.
Maybe he wasn’t even exaggerating…
While on the topic of things that might be possible in the future, nanotech enthusiasts might be interested to know that Eric Drexler now has a blog called Metamodern.
Comment [3]
Celebrating 50 years of the journal Physical Review Letters, the editors at PRL have begun collecting hightlights of the past 50 years. They’re only a few years into things, but there’s already a paper that caught my eye: Generation of Optical Harmonics by Franken et al., PRL 7, 118 (1961) (link, seemingly freely accessible).
Shortly after the invention of the ruby laser (and before that the maser), it was discovered that a harmonic of the laser’s natural frequency was being emitted from dielectrics when incident beam was sufficiently intense. This has become a commonly used property, in that many of the lasers today (particularly emitting in the green, like YAG lasers) all use frequency doubling to produce visible output, as the diodes naturally output in the near IR.
To find out how it works, I recommend reading the paper, but I suspect you might not be convinced. Here’s why:
No doubled light as far as I can tell! Maybe they didn’t have peer review back in those days.
(I actually suspect it is the manner in which the digital copies were created. I’m going to check the library’s paper copy tomorrow.)
Comment [5]
Just before the new year, Rosie Redfield (at RRTeaching) blogged about biology being more difficult than physics. Why?
Biological processes of course are consequences of physics and chemistry, which is why we require our biology students to study the physical sciences. But organisms are also historical entities, and that’s where the complexities arise. The facts of physics and chemistry are constant across time and space. Any one carbon atom is the same as any other, and today’s carbon atoms are the same as those of a billion years ago. But each organism is different. That’s not just a statement that fruit flies are different from house flies. Rather, each fruit fly is different from every other fruit fly alive today, and from every other fruit fly that ever lived, and it’s the differences that make biology both thrilling and hard.
No disagreements from me here. The laws which govern physics and chemistry are contant across the universe (though there is some debate as to their constancy in time). Without the strict adherence to the laws we observe, physics and chemistry would be near impossible to understand. It is lucky for biology that this is how the world works, because, as Rosie notes, biology depends on it!
Skipping ahead, here’s where I get confused:
Even genetically identical cells are not functionally identical. When a cell divides its molecules are randomly distributed between the two daughters; because ‘randomly’ does not mean ‘evenly’, these daughters will have inherited different sets of the proteins and RNAs that carry out their functions. And even if the two cells had identical contents, these contents would still have different interactions – repressors bump into cofactors at different times, DNA polymerase slips or doesn’t slip at different points in its progress along a chromosome. Understanding the how and why of biological phenomena thus requires us to consider historical and ecological factors that are many orders of magnitude more complex than those of physical systems.
When trying to understand biological systems (nay, any kind of system, be it a crystal or a batch of cells), much ultimately depends on the type of measurement. Every measurement does not need to take into account the histories and ecological factors that make up every individual cell – it is impossible to know them to the required resolution that such data would be useful. When and where a DNA polymerase may stall on the chromosome in a particular cell of a mL culture containing billions upon billions of cells is effectively irrelevant for a huge number of interesting experiments I might want to do with those cells — say, the study of expression of a particular gene with a gene chip.
Continuing,
The critical word is probably ‘population’. Biologists rarely try to define it, but they use the term everywhere to refer to similar but not identical organisms or cells (or even molecules) that interact in some way. ‘Population thinking’, the realization that species are populations, not pure types, is said to have been key to Darwin’s insight that members of a species undergo natural selection. And population thinking is probably what makes biology so much more complex than the physical sciences.
Here’s where I think my ultimate displeasure with the post lies. That biology is more complex than physics (though what exactly is limited to the realm of physics is now very much in question) is a reasonable statement: the most common biological molecules are much too complicated to apply something like the Schroedinger Equation and expect to understand anything about them, but “complex” and “difficult” are not the same thing. That physics has traditionally been confined to the well-defined and “simple” systems like infinite lattices of identical carbon atoms, doesn’t make it “easier” to study than biology. I don’t even know what it could mean for one field of science to be “easier” than another, given that everyone studying a science is different, like, as Rosie mentions above, how each fruit fly is different from every other fruit fly. Some people find the mathematics required to understand physical systems extremely difficult, while others don’t have the required attention to detail to perform a successful experiment in a biology lab. To do any kind of science, however, it is the same: you require critical thinking and quantitative analysis of experiments to make any sense of your results. This is true from particle physics all the way up to ecology.
Rosie’s opening paragraph ends with the following:
[I]n reality biology is much more complex than the physical sciences, and understanding it requires more, not less, brain work.
I hope someone in the social sciences gets wind of this and belittles biologists. Sociology is obviously more complex than biology, so it cleary requires more brainpower to be a social scientist than a biologist, right? Rutherford’s famous statement that all science save physics is mere stamp collecting wasn’t a useful thing to say, and this isn’t much better.
Comment [9]
Biocurious is written by Andre Brown and Philip Johnson, since 2005. Content of the weblog is licensed under a Creative Commons Attribution-Share Alike 3.0 License.
