MIRACULOUS MOLECULE : WATER - 1

This, as most other of the Atheists' Arguments, proceeds from a deep Ignorance of Natural Philosophy; for if there were but half the sea that now is, there would also be but half the Quantity of Vapours, and consequently we could have but half as many Rivers as now there are to supply all the dry land we have at present, and half as much more; for the quantity of Vapours which are raised, as well as to the heat which raised them. The Wise Creator therefore did so prudently order it, that the seas should be large enough to supply Vapours sufficient for all the land.
John Ray, 18th century British Naturalist 1

Most of our planet is covered with water. Oceans and seas make up three fourths of the earth's surface while the land itself contains countless numbers of rivers and lakes. The snow and ice on the summits of lofty mountains is water in its frozen form. A substantial part of the earth's water is in the sky: every cloud contains thousands-–sometimes millions–of tons of water in the form of vapor. From time to time some of this water vapor turns into drops of liquid and falls to the ground: in other words, it rains. Even the air you're breathing now contains a certain amount of water vapor.

In short, no matter where you may look on the surface of the earth, you're certain to see water around somewhere. Indeed, the room you're sitting in at this moment probably contains about forty to fifty liters of water in it. Look around. You can't see it? Look again, more carefully, this time raising your eyes from these words and look at your hands, arms, legs, and body. That 40-50 liter mass of water is you!

It's you because about 70% of the human body is water. Your body's cells contain many things but nothing so much or so important as water. The biggest part of the blood that circulates everywhere in your body is of course water. This is true not just of yourself or of other people however: the bulk of the bodies of all living things is water. Without water it seems, life is impossible.

Water is a substance that was specially designed so as to be the basis of life. Each and every one of its physical and chemical properties was specially created for life.
 

The Fitness of Water

In short, the existence of a liquid environment is essential in order for the processes necessary for life to take place. The most ideal of all liquids–or rather, the only ideal liquid–for this purpose is water.

That water possesses properties that are extraordinarily fit for life is something that drew the attention of scientists long ago. The first attempt to investigate this subject in detail however was Astronomy and General Physics Considered with Reference to Natural Theology, a book by the English naturalist William Whewell that was published in 1832. Whewell had been examining the thermal properties of water and noticed that some of them seemed to violate the accepted rules of natural law. The conclusion he drew from this was that these inconsistencies should be taken as proof that this substance had been specially created in order for life to exist.

The most comprehensive analysis of the suitability of water for life was to come from Lawrence Henderson, a professor in the Department of Biological Chemistry of Harvard University, about a century after Whewell's book. In his book The Fitness of the Environment, which some were later to call "the most important scientific work of the first quarter of the 20th century", Henderson reaches this conclusion concerning the natural environment of our world:

The Extraordinary Thermal Properties of Water

One of the subjects dealt with in Henderson's book is the thermal properties of water. Henderson notes that there are five distinct ways in which the thermal properties of water are unusual:

1) All known solids decrease in size as they grow colder. This is true of all known liquids as well: as their temperatures decrease, they lose volume. As volume decreases, density increases and thus the colder parts of the liquid become heavier. This is why the solid forms of substances weigh more (by volume) than they when they are in liquid form. There is one case where this "law" is violated: water. Like other liquids, water contracts in volume as it grows colder but it only does this down to a certain temperature (4°C) thereafter–unlike all other known liquids–it suddenly begins to expand and when it finally solidifies (freezes) it expands even more. As a result, "solid water" is lighter than "liquid water". According to the normal laws of physics, solid water, which is to say ice, ought to be heavier than liquid water and should sink to the bottom when it forms; instead, it floats.

2) When ice melts or water vaporizes, it absorbs heat from its surroundings. When these transitions are reversed (that is, when water freezes or vapor precipitates) heat is released. In physics the term "latent heat" is used to describe this.3 All liquids have a latent heat of some sort or other but that of water is among the highest known. At "normal" temperatures, the only liquid whose latent heat when freezing is superior to that of water is ammonia. In terms of its latent heat properties at vaporization on the other hand, no other liquid can compare with water.

3) The "thermal capacity" of water, that is, the amount of heat necessary to raise the temperature of water by one degree, is higher than the great majority of other liquids.

4) The thermal conductivity of water, its ability to convey heat, is at least four times higher than any other liquid.

5) The thermal conductivity of ice and snow on the other hand is low.

By now you are probably wondering what importance these seemingly technical five physical properties could possibly have. As it turns out, the significance of each and every one of them is enormous because life in general and our own life in particular is possible in this world just because these five properties are what they are.
Let's now take a look at them one by one.
 

The Effect of "Top-down" Freezing

Let's examine this in detail to see why. There are many places in the world where the temperature falls below 0°C in winter, often considerably below that. Such cold will of course affect the water in seas, lakes, etc. These bodies of water grow colder and colder and parts of them begin to freeze. If ice didn't behave the way it does (if it didn't float in other words) this ice would sink to the bottom while the warmer bits of water would rise to the surface and be exposed to the air. But the temperature of that air is still below freezing so these will freeze too and sink to the bottom. This process would continue until there was no liquid water left at all. But this isn't what happens. What happens instead is this: As it gets colder, water grows heavier until it reaches 4°C at which point everything suddenly changes. After this, the water begins to expand and it becomes lighter as the temperature drops. As a result, the 4°C water remains on the bottom, the 3°C water above it, the 2°C water above that and so on. Only at the surface does the temperature of the water actually reach 0°C and there it freezes. But only the surface has frozen: the 4°C layer of water beneath the ice remains liquid and that is enough for underwater creatures and plants to continue to live.

Unlike all other liquids, water expands when it freezes. Because of this, ice floats in water.

(We should note here that the fifth property of water–the low thermal conductivity of ice and snow–is also crucial in this process. Because they are such poor conductors of heat, the layers of ice and snow keep the heat in the water below from escaping into the atmosphere. As a result of all this, even if the air temperature falls to –50°C, the layer of sea ice will never be more than a meter or two thick and there will be many fractures in it. Creatures such as seals and penguins that dwell in polar regions can take advantage of this to reach the water beneath the ice.)

Again let us recall what would happen if water didn't behave this way and acted "normally" instead. Suppose water continued to become denser the lower its temperature became like all other liquids and ice sank to the bottom. What then?

Well in that case, the freezing process in the oceans and seas would start from the bottom and continue all the way to the top because there would be no layer of ice on the surface to prevent the remaining heat from escaping. In other words, most of earth's lakes, seas, and oceans would become solid ice with a layer of water perhaps a few meters deep on top of it. Even when the air temperature increased, the ice at the bottom would never melt completely. In the seas of such a world, no life could exist and in an ecological system with dead seas, life on land would also be impossible. In other words, if water didn't "misbehave" and acted normally, our planet would be a dead world.

Why doesn't water act normally? Why does it suddenly begin to expand at 4°C after having contracted the way it should?

That is a question that nobody has ever been able to answer.
 

Sweat and Cool off

The second and third properties of water mentioned above–high latent heat and thermal capacity greater than other liquids–are also very important for us. These two properties are the keys to an important bodily function whose value we rarely give a thought to. That function is sweating.

Indeed, what good is sweating?

To explain this, we have to take give you a bit of background first. All mammals have bodily temperatures that are fairly close to one another. Although there is some variation, it is not much and mammalian body temperatures range between 35-40°C. In human beings it is about 37°C under normal conditions. This is a very critical temperature and absolutely has to be kept constant. If your body's temperature were to fall just a few degrees, many of its vital functions would fail. If it rises even a few fractions of a degree, as it does when we become ill, the effects can be devastating. A sustained bodily temperature over 40°C is likely to bring on death.

In short, our bodily temperature has a very critical equilibrium in which there is very little room for variation.

However our body has a serious problem here: it is active all the time. All the physical movements, even those of machines, require the production of energy to make them happen. But whenever energy is produced, heat is always generated as a by-product. You can easily see this for yourself. Put this book aside and go take a ten-kilometer run in the blazing sun and see how hot your body gets.

The thermal properties of water enable us to discharge excessive heat from our body through sweating.

But in fact, if you think about it you'll realize that you didn't get nearly as hot as you should have done...

The unit of heat is the calorie. A normal person running 10 kilometers in one hour will generate about 1,000 calories of heat. That heat has to be discharged from the body. If it weren't, you'd collapse into coma before you finished the first kilometer.

That danger however is precluded by the second two properties that water has.

The first of these is the thermal capacity of water. What this means is that in order to increase the temperature of water, a great deal of heat is required. Water makes up about 70% of our body but because of its thermal capacity, that water doesn't get hot very fast. Imagine an action that generates a 10°C increase in bodily heat. If we had alcohol instead of water in our bodies, the same action would lead to a 20°C increase and for other substances with lower thermal capacities the situation would be even worse: increases of 50°C for salt, 100°C for iron, and 300°C for lead. 

The high thermal capacity of water is what prevents such enormous changes in heat from taking place.

But even an increase of 10°C is would be fatal as we mentioned above. To forestall that, the second property of 
water–its high latent heat–comes into play.

To keep itself cool in the face of the heat that is being generated, the body employs the sweating mechanism. When we sweat, water spreads over the surface of the skin and quickly evaporates. But because water's latent heat is 
so great, that evaporation requires large amounts of heat. The heat, of course, is withdrawn from the body and thus we are kept cool. This cooling process is so effective that it can sometimes cause us to experience a chill even when the weather is rather warm.

Because of this, someone who has run ten kilometers will reduce his body temperature by 6°C as a result of the evaporation of just a liter's worth of water. The more energy he expends, the more his body temperature will increase but, at the same time, the more he will sweat and thus cool off. Among the factors that make this magnificent thermostat system of the body possible, foremost are the thermal properties of water. No other liquid would provide for sweating as efficiently as water does. If alcohol were present instead of water for example, the reduction in heat would be only 2.2°C; even in the case of ammonia, it would be only 3.6°C.

There is another important aspect of this matter. If the heat released within the body were not conveyed to the surface, that is to the skin, neither the two properties of water nor the process of sweating would be of any use. Thus the structure of the body must also be highly conductive of heat. It is at this point that another vital property of water appears comes into play: unlike all other known liquids, water has a very high capacity for thermal conductivity, that is, the ability to conduct heat. For this reason, the body conveys the heat generated inside it to the skin. (The blood vessels near the skin expand to achieve this and this is why we become flushed when we're overheated.) If water's thermal conductivity were less by a factor of two or three, the rate of conveyance of heat to the skin would be much slower and this would make it impossible for complex life forms like mammals to live.

What all this shows is that three very different thermal properties of water work together to serve a common purpose: cooling off the bodies of complex life forms such as human beings. Water is a liquid specially designed for this task.