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Anomalous Aspects of Common Water

Evolution News

Michael Denton

The subject of Michael Denton’s new book — water — is ubiquitous, as indeed for living creatures it must be. The Wonder of Water was published this week, and it provides an apt occasion to consider some anomalous aspect of H20.

Our bodies are about 66 percent water. Our brain is some 75 percent water. Our blood is 92 percent water. So it’s no surprise that the earliest civilizations developed near great rivers such as the Nile, the Indus, and the Yangtze. Genesis 2 locates the Garden of Eden near the intersection of four rivers, Pishon, Gihon, Tigris, and Euphrates. The latter two were the lifeblood of the ancient Babylonians and Assyrians.

Perhaps it’s also no surprise that water fills so many creation stories. For the Assyrians and Babylonians, even the gods emerged from a mixture of salt water — Tiamat, and fresh water — Apsu. The Hindu scriptures give water a pre-eminent place. And many of the myths of the Ancient Near East refer to the primordial and chaotic Deep. This strange figure appears in the biblical account of creation. Just after creating the heavens and the earth, God’s spirit hovers over the surface of the waters. Water is here a creature, derivative rather than fundamental; nevertheless, it is, so to speak, present at the creation.

The more philosophically inclined of the ancients tended to invest water with primordial significance. The sixth-century-BC Ionian philosopher Thales saw it as fundamental while philosophers of nature after him often saw water as one of the four elements — water, air, earth, and fire — out of which everything was made.

Interestingly enough, the watershed for modern chemistry was the recognition that water was not elemental, but was itself a compound made up of two gases. The great French chemist Antoine Laurent Lavoisier, guillotined in the aftermath of the French Revolution, was the first to realize this.

One might suppose that this scientific reduction of water to its two constitutive elements would dispel its mystery. No longer was it the ground of being or a source of universal creativity or chaos. But in fact, quite the opposite is true. As wondrous as water may have seemed to be to the ancients, it can hardly compare in the awe elicited by our deeper scientific knowledge of what in the literature are called water’s “anomalies.” Mind you, these are not anomalies because we don’t understand them, but because they put water in a class by itself.

Perhaps the most famous anomalous property of water is its expansion upon freezing. Normally, when things get hot they expand, and when they cool, they contract. Simple physics. Water follows this rule, but only up to a point, that point being 4° C (39.2° F). Then, unlike almost any other substance, water expands as the temperature drops lower.

Thus, water is densest at 4° C. As soon as water at the surface cools to this temperature it sinks to the bottom. A body of water will not cool below 4° C until all its water has first cooled to this temperature. Any subsequent cooling at the surface will then cause the colder water to remain there and eventually freeze solid. Thus, ice floats on liquid water. We observe this phenomenon in the common task of plopping ice cubes into a glass of water.

In his new book, Dr. Denton describes the adverse consequences for life had water lacked this anomalous property:

If water froze (as do nearly all other fluids) from the bottom up, the consequences would be severe in regions that experience persistent temperatures below 0°C (like the higher latitudes on Earth), or in cold eras when temperatures fall below 0°C over much of the globe, even in the equatorial regions (snowball Earth). The ice that formed on the bottom of cold bodies of water of any significant depth would be largely shielded from the warmth of the sun’s rays. Such ice would not easily unfreeze, even on a sunny day. Eventually, virtually all the water on Earth would be frozen solid into vast masses of ice. Ice caps many kilometers deep would form at the poles, and in snowball Earth eras they would stretch right to the equator.

In concert with three of its other anomalous properties — high heat capacity, high latent heat of freezing, and low heat conductivity of ice — water seems engineered for the maintenance of liquid water on the Earth. Again, Denton writes:

[N]o fluid possesses a similar suite of properties that are mutually fit to work together towards the preservation of that fluid in the liquid state.

And this is just a taste from Denton’s book of the many wondrous ways water is unusually suited to support life like our own. Get it here now!