It’s late May, almost June, but the shady valleys a few hours from Berkeley still contain a few slushy snow banks. The Sierras, of course, will be dappled with white year-round. In the spring the abundant snowmelt makes for waist-high river crossings and trails that can look more like Venetian canals.
Water, water, everywhere. The triatomic molecule, seemingly so simple, occupies whole academic clans of physical chemists. One might choose to study interface properties, solvated electrons, solvent reorganization energies, molecular cluster structures, evaporation mechanisms, exotic ice phases—the list is exhaustive. Or one might choose only to contemplate the smooth surface of an alpine lake.
The triple point of water—the temperature and pressure at which vapor, liquid, and solid are at equilibrium—is 273.16 K, just over the standard freezing point, and 612 Pascals, or 0.6% of atmospheric pressure. Because conditions on earth are relatively close to these, H2O regularly cycles through its phases, even if temperatures don’t vary all that much. If planetary scientists get really excited about liquid water, it’s because it’s so hard to imagine life arising without solution-phase chemistry. Solvation and diffusion allows substances to mix thoroughly and react quickly. Strong solvent interactions stabilize reactive intermediates until products form. Though some organisms exhibit “desiccation tolerance”, no life has ever been found in the complete absence of liquid water. Consequently, in a world where weather stood still and water sat around in the same stagnant pool millennium after millennium, any life would surely be confined to the oceans. I’m surprised that Captain Kirk didn’t redesign his ship to spend more time underwater.
Spending time away from the tap sure reminds us of the human body’s need for water. The total weight a backpacker carries is highly dependent on the contents of her bottle. Most swear by 1-2 L per day, but some won’t leave home without six. Some Central Valley watersheds are mercury-contaminated, and hiking there makes one acutely aware of water’s pound-per-pint weight. However, if a flourishing microbial biome is the only concern, we purify stream water with little brown tablets kept in an opaque, cotton-plugged bottle. Each tablet contains 20 mg of tetraglycine hydroperiodide (the chemical determined “least pleasant” in a blinded palatability study of water disinfectants). The aqueous hydroperiodide ion decomposes to release a mixture of hydrated iodine species, including I2 and HIO. I2 is a powerful and indiscriminate oxidizing agent. Over the course of 30 minutes, it quickly diffuses through microbial cell walls and begins to displace hydrogen in amino and thiol groups, disrupting the shape of nucleic acids and proteins. Furthermore, iodine adds across double bonds in the unsaturated fatty acids that form cell membranes, raising their melting point and essentially freezing their once-fluid folds. In short, if I were the size of a protozoan, iodine would kill me too.
Picking my way from stone to stone across a swollen creek, I think about how the far-behind urban world is a place where layers and layers of human design are all stacked up over each other. Back home, I am never so aware that the water I drink rushes through my veins in much the same way as it gurgles through this streambed. In the field, someone has arranged it all for me, and my overwhelming concern is with being a productive graduate student. In places where every examinable surface has been socially and technologically organized and molded into tools for designated activities, where do we find the imperative to understand the workings of starkly basic systems—physical, geological, and biological?
It is true that we study medicine and seismology in order to avert disaster, but in the Sierras my safety is not my only reason for wondering at the natural world.
Both the clouds, stained by sunrise a pale and succulent pink, and the fluids cradling the proteins in my tired limbs, are completely agnostic about my or anyone’s existence. These natural systems are beautiful in part because, in thinking about their structure and function, I feel I explore a meaningful context for that existence.
In a 2005 commencement address, David Foster Wallace told an intentionally cliché parable about a fish who suddenly asks, “What the hell is water?”. An education, he concludes,
“has almost nothing to do with knowledge, and everything to do with simple awareness; awareness of what is so real and essential, so hidden in plain sight all around us, all the time, that we have to keep reminding ourselves over and over: This is water.”
Understanding the microscopic complexity of “plain sight” reality doesn’t always make a person more aware of the water in which she’s swimming, perhaps because it’s rare to truly intuit the connection between scales of atoms and scales of goldfish. What chemistry can do is remind us the “real and essential” always goes beyond our immediate impressions. Those who explore structures and processes beyond the visible can’t ignore that we have immense power over how we see, think about, and experience reality.
Grads, how has your research changed how you see this stuff we’re swimming in? And does it feel more or less “real”?