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Creation's Story (14)

R W Cargill, St Monans


We have already noticed that Earth is a unique planet having the correct surface temperature for life to exist, the heat from the sun being balanced by its distance from us. This distance in turn depends upon the mass of the planet, which, if heavier would be nearer and hotter; if lighter would be farther away and colder. This surface temperature allows water to exist as a liquid, the only form which can support life. Freezing solid ice or scalding gaseous steam would not do.

Of all the substances we find on earth, by far the most common one is water, most of it in large quantities. Although we take it for granted, it is a remarkable substance, uniquely designed and essential to sustain life. Those who (vainly) search for the existence of life elsewhere, e.g. on other planets, look for water as their first clue. Without water, there can be no life. Most of the matter in the universe consists of very hot gases (in the stars), or as deeply frozen solids (in the outer planets). Although so common on earth, water is extremely scarce in the universe. Earth is often described as "the watery planet". Just over 70% of its surface is covered by water. In vapour form it also pervades the atmosphere. Even those areas which we call dry or arid still contain significant amounts of water.

There are several special properties of water which make it truly unique and necessary for natural life. Before we look at these, remember how in Scripture water often represents what is necessary for spiritual life. Water is a figure of the Holy Spirit without whom no spiritual life is possible (Jn 3.5; 4.14; 7.38-39). The "washing of water by the word" (Eph 5.26) is necessary for the maintenance of spiritual life and the fulfilment of God's purpose for us. The last invitation in the Bible is, "Whosoever will, let him take of the water of life freely" (Rev 22.17). Even in the spiritual deserts of this world, the soul of the believer can be like "a watered garden" (Is 58.11; Jer 31.12). We must constantly be nourished by the "upper and nether springs" of the Spirit and the Word.

Properties of Water

Each of the chemical and physical properties of water makes it a key substance to the support of life at every level. The tiny single microscopic cell cannot function without it, nor can the large animals on land and in the sea. All types of vegetation need it too, from the scrub of the deserts to the luxuriant growth of the tropical rain forests. It is required for the obvious necessities of drinking and irrigation, and for diffusion and distribution of nutrients and energy. It also very efficiently controls the temperature on earth and in all living things which can only survive if temperatures do not vary greatly. The special molecular structure of water gives it critical thermal properties.

Thermal Properties

Liquid water is able to absorb heat without a large increase in its own temperature, and this heat is retained efficiently. It can also release heat in large amounts without a large fall in its temperature. Water is better at doing this than any other common substance  it is said to have a high heat capacity. Life benefits from this in two ways.

First, the large oceans keep temperatures on earth steady, not rising or falling too much. Oceans are also enormous reservoirs and conductors of heat. Great ocean currents like the Gulf Stream transfer vast amounts of heat from the equator to the cooler latitudes, so that the climate of countries like the UK is moderated.

Second, when we are exposed to heat or cold, the temperature of our bodies is kept fairly steady because they are made up of about 70% water (as are those of many animals). This effect due to the high heat capacity of water is, however, further assisted by another of its properties - its heat of vaporisation is also high. This means that when liquid water is changed into vapour a lot of heat is used up. Thus when our bodies need to lose heat quickly, water is evaporated in our breath and through our skin  as heavy perspiration in extreme cases - allowing our bodies to maintain their stable temperature. A lot of heat can be removed with the loss of only a small amount of water. It is the only substance which can do this so well.

Properties of Ice

It is commonplace to notice how water forms ice when it freezes, and to see the ice floating on top of the water. But it is most unusual for the solid form of any substance to float on top of its liquid at the freezing point - most solids sink to the bottom because they are more dense ("heavier") than the liquid. But not ice  it is less dense than water at 0 degrees C where it freezes, so that, unlike almost every other substance, ice floats on the surface of water.

This unusual behaviour is extremely important for all types of aquatic life. If ice did sink to the bottom when it formed, the body of water would freeze from the bottom upwards until it all became solid and every living thing in the water would be pushed to the top where it would freeze to death. As it is, ice forming on the top layer acts as an insulator to prevent the colder air from affecting the underlying water which remains above freezing point, at around 4 degrees C where water has its greatest density.

It is an amazing thing that ice, solid water, is such a good insulator, because liquid water is actually a very good conductor of heat, four times better than any other common liquid. This high conductivity is another factor which further helps water to regulate and distribute heat in the oceans and in our bodies as described above. Its properties all work together for the benefit of life.

Solvent and Diffusion Properties

A vast range of different substances can dissolve in water, although to different extents. Water has been called the universal solvent. Therefore water can dissolve many substances and take them from one place to another, for example to provide nutrients and remove wastes efficiently in all types of living systems and in the larger environment. This is another of the key reasons why living systems need water.

Water can dissolve large amounts of salt and sugar. It can also dissolve a lot of carbon dioxide, and this helps to remove this gas from our bodies and controls the acidity of our fluids. It also dissolves oxygen, another substance critical for life. Our lungs absorb oxygen gas directly from the air. There it dissolves in the blood in a specially efficient way to transfer it quickly to where it is needed by cells and muscles. Life in the waters requires dissolved oxygen for breathing through gills. Dissolved oxygen is also critical for water purification  to oxidise contaminants into relatively harmless substances so that the water is freed from pollutants and can be reused. The truly versatile nature of water enables each form of life to thrive in its own habitat.

Some of the other properties of water show how uniquely and ideally suited it is for life support. Its viscosity is low enough (not like treacle or oil) to enable it to pass easily through very small tubes such as blood capillaries; diffusion through it is fast enough for essential materials to reach the required sites (for example oxygen goes through a body cell in one hundredth of a second); its surface tension allows it to spread on certain types of surfaces but not others. You could not get a better substance than water to support life. Indeed water incorporated into the design for life is an eloquent testimony to the Creator's wisdom.

The Water Cycle

Water on earth is constantly being cycled and recycled as the heat of the sun evaporates surface water into the atmosphere from which it falls again in the form of rain, snow, or dew, eventually to return to the sea. Solomon observed this long ago (see Eccl 1.7). The cycle desalinates, purifies, and distributes the water for the use of all living things. It has been calculated that the atmospheric water is changed and recycled about 40 times per year. While it is in the atmosphere it assists global warming, without which surface temperatures on earth would be below freezing, and nothing could live.

This special substance called water uniquely supports life here and now. But it will also do so in the millennial earth as "living waters" go out from Jerusalem (Zech 14.8). And, flowing from the throne of God, the "pure river of water of life" will ensure the eternal freshness of the new Jerusalem above (Rev 22.1). 

To be continued.


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