Perhaps when blowing your nose, or the nose of a sick child, you’ve wondered where all this stuff comes from. How can one nose make so much mucus? The answer involves electrical forces and the physical character of mucus. Mucus, the gooey liquid secreted by your nose as well as by the linings of other body parts, is made of polymers — long, string-like molecules. The polymer molecules are negatively charged; imagine lots of speckles each with one electron’s worth of negative charge along each string: For every negative charge, there’s a positive charge somewhere, an ion floating around in th ..read more

Viruses encode their genomes in RNA or DNA, which they pack into a tiny space. For example, Varicella zoster, the virus that causes chickenpox and shingles, stuffs a double-stranded DNA molecule about 40,000 nm in length into a shell about 200 nm in diameter. This is even more impressive than it may seem because DNA and RNA are rather stiff molecules, and so resist being bent, and are highly charged, and so repel themselves strongly if confined. As a result of the viral packaging, the genomic contents are highly pressurized. We might suspect that, like a champagne bottle with the cork lopped ..read more

There’s a lot of advice out there for prospective applicants for academic faculty positions [1], so you don’t really need mine. However, some advice is outdated and some is incomplete, so I thought it would be worthwhile to add a small bit of information based on experiences from my department’s search last year (Physics, University of Oregon, U.S.A.). There are details regarding how applicants are evaluated that are not widely known, even by existing faculty, involving for example Zoom interviews and DEI statements; perhaps cataloging this will be of use to people on the U.S. STEM academic j ..read more

Last Spring, I taught the second term of University of Oregon’s statistical mechanics / thermodynamics for physics majors course (syllabus). I might at some point describe how the course went and what lessons might be drawn, beyond the key lesson that statistical mechanics is a wonderful subject. For now, something far less substantial: I often play music before the start of classes I teach, usually something instrumental. For this course, however, I thought I’d play songs that have some (perhaps tenuous) connection to the subject of statistical mechanics and thermodynamics. It was a lot of f ..read more

What makes one microscope better than another? A few weeks ago I co-ran a week-long Physics and Human Physiology day camp for high school students, part of the University of Oregon’s “SAIL” program that especially targets low-income students. I’ve written about SAIL before (2019, 2017, 2014) — this was our 14th Physics + Human Physiology camp, and the 16th time I’ve run a SAIL camp of any sort! I bent my policy of “if it ain’t broke don’t fix it” and designed two new activities, running them along with a piece on surface tension that I’ve done many times. The new activities involved microscop ..read more

Biophysics is full of deep puzzles that are surprisingly simple to state. Imagine a pill shaped bacterium. (Your body is home to trillions.) It grows and then cleaves itself into two equally sized progeny. How does it know where its middle is? For us, looking at the bacterium, finding the middle is an easy task. We can imagine holding a ruler to the cell or (more realistically) counting pixels in a microscope image, finding the point halfway between the ends. The bacterium, though, lacks a perspective external to itself, not to mention eyes or rulers. You might like to ponder possible strateg ..read more

The last seven books I read were all published in 1965. I decided on this literary time travel after noticing that I unintentionally read two books in a row from 1965. I thought: Why not continue? Would I get a deep sense of the mid-1960s zeitgeist? I don’t think so, but I did find two of the best books I’ve read in several years: Manchild in the Promised Land by Claude Brown and The Magus by John Fowles. I thought I’d write about these seven books now rather than waiting until my usual end-of-year book recap, in part because I’ll probably have other books to write about by then, and in part ..read more

Suppose someone told you that they were deeply concerned about environmental issues, the consequences of fossil fuel use in particular, and that they would therefore take concrete action to reduce their energy footprint. The action: driving one mile per hour more slowly than usual — 54 rather than 55 mph. You would probably be unimpressed. I was at a presentation recently, at a university but not mine, and from a staff member but not a scientist, at which the speaker told us that to reduce her environmental impact, she intends to grow more food in her garden. I was floored. Growing food is wo ..read more

I’ve taught several times a graduate course on biophysics, the first instance of which I blogged about here. I love teaching this class, and students seem fond of it as well. I’m teaching it again next Fall (2023) but with a twist: it will now be a combined undergraduate / graduate course. The motivations are twofold: At the University of Oregon, as at many universities, there isn’t sufficient demand to sustain distinct undergraduate and graduate biological physics classes, and the unfamiliarity of most physics students with the wonders of biophysics means that an introduction to the topic ca ..read more

How many books are published each year? I’ll provide some numbers that were a surprise to me when I learned them a few years ago. First, some context. At the American Physical Society “March Meeting” two months ago, I was part of a workshop on Communicating Biological Physics. Four of us gave presentations and led discussions on various aspects of this topic. Here’s a link to the poster I made, which lists the presenters and presentation titles. I focused on communication with non-scientists, part of which involved describing the motivations and the process of writing a book. If you’re read a ..read more