Water, Ice & Stone. Bill Green
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And yet something endures in all of this. Something is merely changing form. And Thales answered, “It is water.”
Philosophers say that Thales posed one of the truly great questions ever about the world. It was the question that began the quest—the quest whose conduct has affected us all, whose revelations and outcomes we still await. It is worth considering for a moment. Already in the sixth century B.C., a mind was driven to find unity in the “manifold of phenomena.” As a start, Thales proposed a kind of “primary matter” whose permutations and combinations, whose rearrangements in space, could account for all that we see. That he should have chosen water seems a triumph of observation. For it appears for all the world that water, when it freezes, can become stone; and when it vaporizes, rises into steam-white clouds, can become air; and when it flows to the sea, can yield up earth in trellises of dark loam as deltas; and when it appears as storm, can give rise to the skittering fire of lightning. So many forms and so many names.
Water is everywhere, so we take it happily for granted, think it somehow usual that rivers should drain the planet’s skin, that seas should lie in its basins and folds. That rain should come from the skies along with snow and mist and dew. But we know thousands of liquids. Tens of thousands. Among all of these, water is singular, almost preternaturally strange.
At what temperature, for example, should water boil? If we knew only the molecular siblings of water—hydrogen sulfide, hydrogen selenide, hydrogen telluride, all of which look like water when you write their formulas down—then we would expect water to boil near minus eighty degrees Celsius. The kettle would sing in the dark, frozen night of the world. If water behaved like its siblings, it would be a gas at Earth temperatures and the atmosphere would roll with its troubled cloud banks and the sea would be a hovering fog.
Even as a staid and proper solid, water is no more predictable. On a winter lake, ice and zero-degree Celsius water move atop the denser liquid below. There is nothing dramatic in this, or so it seems, until you think just how absolutely strange it is that solid ice should float. The way of the world is for solids to sink in their own liquids; for cooling lead or mercury or methanol to settle out of their own fluids and crystallize. Thus things freeze from the bottom up, the molecules of the solid becoming neatly packed, as dense as cannonballs on a town green. But ice is different. As it forms from the surrounding water, the molecules open outward, link in delicate lattices and structures, geodesic domes buoyant on the water below. Because of this simple, immensely complex fact, the winter lake lies protected by the solid phase of its own self, its heat sealed and safe from the chilling air above. Because of this fact, fish inhabit northern lakes.
The buoyancy of ice is borne of its expansion. Other substances, regardless of their state, shrink as they cool, and for the most part, it is true of water too. But below about four degrees Celsius, something quite unexpected happens. As the temperature edges further downward toward freezing, liquid water begins, almost incredibly, to distend. If we were to view its cooling in a fine tube, as the Florentine scholars of the seventeenth century did, we would be amazed to see the shrinking column reverse its travel and begin to move steadily upward. This expansion of water continues as the temperature is lowered to zero. Finally, as water freezes into solid ice, its volume increases even more. The increase is dramatic—a full nine percent over the volume of the liquid. I have seen water, frozen in a confined space, shatter steel, embed shards of metal in laboratory walls. And the very same thing happens when drops of water freeze in winter stone. The water expands, the stone breaks, and slowly the entire mountain falls.
So, if water behaved like a normal liquid, there would be no lakes in the Antarctic Dry Valleys, only blocks of ice. Water would solidify first at the bottom, along the sediments, as needles and fingers of ice. Every living cell would be gradually locked into stillness, into an eternity of cold. But as it happens, ice freezes and floats on the surface. The waters below are protected from the fierce winter night as though they were cosseted in wool. And beneath this ice, in the liquid water that moves below, things can live and much can happen.
Yet the anomalies of water are not limited to cold temperatures. With the exception of ammonia, water has the highest heat capacity of any liquid or solid on Earth. This means that it has a kind of thermal inertia—its temperature is not easily moved by heat. “A watched pot never boils,” we mutter impatiently. And from childhood we remember that the sidewalk puddle is always deliciously cooler than the scorched summer pavement on which it sits. Because water is so slow to warm (and to cool), it has a moderating effect on climate. Cities on the ocean enjoy cool summer breezes from the sea and mild, snowless winters. Surrounded on three sides by water, San Francisco has one of the most equable climates on the continent. In fact, from this single phenomenon comes the relative mildness and uniformity of much of our planet. The oceans store and distribute vast quantities of heat, shift it from the dazzling latitudes of the equator, move it north and south against the rims of continents; an ocean current a hundred miles wide can transport as much heat in a single hour as can be gotten from nearly 200 million tons of coal.
There are other properties of water with Earth-wide consequences. Unlike gases, which have a certain “springiness” to them, liquids can be compressed only with great difficulty. But of all liquids, water is the most compressible, its volume the most responsive to high pressure. And while this effect is slight and is difficult to measure with any but the finest laboratory instruments, its significance on a global scale is considerable. If the volume of water did not shrink at all under pressure, if water were truly incompressible, sea level would be sixty meters higher than it is today, and the land area of the Earth would be reduced by a full five percent. The Netherlands, the towers of Manhattan, all of Bangladesh, and the Maldives would be gone.
Even the very surface of water is unusual. It is the wet, stretched skin of a drum, and the evidence is all around us: A water strider darts across the silver-satin finish of a pond, creating only dimples on the unbroken fabric as it goes. A steel needle, gently placed, floats in a cup of afternoon tea and the higher density of steel is defied. The inept diver breaks the surface of a lake and for a split second there is a lash across the belly, a fierce sting, a redness that will not abate. It is this tautness, this same surface tension that coaxes water into droplets and spheres. The shape of falling rain, the shape of rain on windows, the shape of dew on a blade of grass, on a spear of barley—these roundnesses go back to that surface.
So too does water’s power to erode. A drop of water is a bullet fired at the Earth. It is a hard pellet with a hard skin. It can blast tiny fragments from the most solid rock. Rain breaks on the face of the mountain, shatters microlayers of stone, craters the stone with its force, carries it away as sand and silt. All night long the rain falls as hard as sand against the stone, and the stone, in time, disappears.
But among the extraordinary properties of water, perhaps none is more important than its power to dissolve whatever it touches. As if in answer to the alchemist’s prayer, water is indeed the universal solvent. It takes everything, to some smaller or larger extent, into its bulk and substance. Oxygen, nitrogen, and carbon dioxide from the air; calcium, magnesium, sodium, and potassium from the stone. The entire periodic table runs with water in every river and rill. The atmosphere lives in it as in a mirror. For these elements, water is the gathering place, the medium of their collusion, their joining and condensation, their prebiotic building into amino acids and proteins, into sacks of living matter. Because it can dissolve, it is the font of life. Because it can dissolve, it can move mountains.
A drop of water touches a crystal of salt. How common a thing this is. For a split second nothing happens: the crystal is sturdy and built to last. To melt table salt, to rattle the cubic cages its ions form, requires high temperatures, foundry temperatures, eight hundred degrees Celsius. Then, before you realize it, the salt is gone. Dissolved. Become part of a solution, no longer visible as a translucent cube. How, in contact with water, does sodium chloride glide into seeming non-being so offhandedly, with such insouciance and at such modest temperatures that the whole vanishing act appears to be pure presto-chango, solid substance one moment, then gone the next? Change of this order should require extremes: large objects dropping from the sky; blaring trumpets; blast furnaces. Grinning devils with pitchforks, at least. Surely something more respectably intense than cold water.
But there is this trembling at the heart of matter. It goes on and