In a charming letter published in 1774, Benjamin Franklin described an experiment in which he had poured “not more than a teaspoonful” of oil onto a pond, which he found sufficient to calm the water despite a choppy wind. What, you may be wondering, connects Franklin, ponds, tears, and salad dressing? In the last “What … Continue reading How are tears like salad dressing? — What is biophysics? #9
You’re full of amazing liquids. How can a liquid be amazing? One way is to have properties that change depending on how strongly the liquid is pushed. The speed at which a fluid flows depends on the force that’s driving it, and the proportionality between force and flow is known as the viscosity of the … Continue reading How are tears like ketchup? — What is biophysics? #8
No. Nor are atoms, viruses, or grains of sand. It is a fundamental truth that everything is in motion, shaking, twisting, and turning at random with an intensity that depends on temperature, motionless only at the unattainable limit of absolute zero. Though this is a manifestation of physics, its consequences for biology are profound and … Continue reading Are molecules ever still? — What is biophysics? #7
The realization that electromagnetic waves are quantized — that light interacts in discrete packets — marked the beginning of quantum mechanics. Whether this fundamental attribute of the physical world sets the performance limits of human vision is a fascinating biophysical question. It’s so fascinating that Bill Bialek’s excellent graduate-level biophysics textbook begins with it, and … Continue reading Can you see single photons? — What is biophysics? #6
We’ve all seen ants carrying seeds, crumbs, other insects — things whose mass is a good fraction of their own. Most of us couldn’t lift things that are so heavy relative to ourselves, and so ants and many other tiny creatures have reputations for being strong. Is this justified? Answering this question brings up the … Continue reading Are Ants Really So Strong? — What is biophysics? #5
I wrote this essay for the Princeton University Press “Ideas” site as a stand-alone piece connected to my new pop-science biophysics book. It appeared yesterday, and I’m posting it here as well (with permission). DNA is stuff: physical, tangible, material. We all know this; we can even picture in our minds its famous double helical … Continue reading The Physicality of Life
The fourth in a series of biophysical questions (one, two, three). If you put your hand on your chest you’ll probably realize that your heart is a bit left-of-center. Or perhaps not: about one in 10,000 people have their heart on the right. No one’s heart lies exactly on the body’s midline, nor does anyone’s … Continue reading Why is your heart on your left side? (Or is it?) — What is biophysics? #4
The third in a series of biophysical questions (one, two). Finding food is an essential activity for any organism. We and many other animals interpret sights, sounds, and smells to make decisions about where to go or what to do to get things to eat. But what about a bacterium, a single-celled organism just a … Continue reading Can a brainless bacterium navigate? (What is biophysics? #3)
The second in a series of biophysical questions. Proteins are molecules. As is the case for every molecule, the constituent atoms and inter-atomic bonds determine the overall shape. In general, a small or stiff molecule has a well-defined form. In contrast, long, chain-like molecules as found in plastics or the gel-formers of the last post … Continue reading What’s the shape of a protein? (What is biophysics? #2)
An introduction to the series: It’s easy to write that biophysics is the intersection of biology and physics, but this is a minimal and cryptic description. We could elaborate, and describe biophysics as the study of how living things use physical forces to shape themselves, how we can harness physical processes for technological ends, and … Continue reading How can you push DNA through Jello? (What is biophysics? #1)
The Eighteenth Elephant 