It has always been recognised that water is life-giving and refreshing in a way that no other liquid can be. It is also regarded as sacred by holy men of various faiths and Christ Himself used it as a metaphor when talking to the Samaritan woman at the well: ‘…whoever drinks the water I give them will never thirst. Indeed, the water I give them will become in them a spring of water welling up to eternal life.’ John chapter 4, verse 14.
Blood also has been regarded with awe since the dawn of consciousness and considered sacred, as has the heart by which it is pumped around the body. And blood is over 80% water.
Water pervades our bodies not only as blood. It constitutes 90% of the lungs and over 70% of the brain, washes out waste in the kidney and liver and moistens mucous membranes. It regulates the body temperature of mammals and moves nutrients at the cellular level throughout the entire spectrum of the animal and plant kingdoms.
Water has also proved indispensable for civilisation. It permits hygiene (e.g. disinfectants) and waste disposal (e.g. sewage systems), commerce by ocean-going vessels as well as river transport, steam engines, steam turbines and water mills. It is used in innumerable manufacturing processes and the generation of electricity (e.g. hydroelectric power and cooling of nuclear reactors). Even the internal combustion engine depends on petroleum formed from organisms living in and depending on water 300 million years ago. Plate tectonics, a phenomenon apparently unique to Earth, depends on a water-related composition (OH) deep in the crust to help reduce friction between the crustal plates as they slide over each other.
Apart from its astonishing utilitarian value water enhances life in an aesthetic way. In oceans and the atmosphere it forms spectacular phenomenon such as violently churning seas, strange marine lighting effects, rainbows, billowing cumulonimbus clouds, breathtaking sunsets, sparkling dew, patterns in frost, geometric perfection in ice crystals and undulating, pure white landscapes of snow. All for the pleasure, inspiration and fear of conscious beings.
Today the power of science is progressively revealing just how astonishing is this substance. When it was formulated – in some non-temporal, non-spatial but mindful way, before our universe of space, time and energy came into being, the water molecule was given a particular structure using particular atoms (two hydrogen and one oxygen) forming bonds of a particular strength at a particular angle to each other, with electrical charge distributed within the molecule in a particular way and with charges attracting each other with a particular strength. A miniscule departure would have meant no water and no living systems.
This configuration of atoms and their properties is further dependent on a host of very finely tuned fundamental physical constants: for example, the electromagnetic force constant which determines the strength of attraction between electrical charges inside and between water molecules has to be right to within 40 decimal places. See also A universe built for life; but how much life?
The fundamental nature of the hydrogen and oxygen atoms in the water molecule and the interaction between these molecules leads to a remarkable set of properties. Had any one of these properties been very slightly out there would be no life on this planet.
Dissolving power: greater than for any other liquid. This, for example, allows it to carry a rich diversity of nutrients around the body and transport minerals and salts using oceans, lakes, rivers, rain, sleet, snow, fog, mist and cloud. No other liquid would do.
Viscosity: a measure of how thick and treacle-like is a liquid. If water was more viscous it would be too difficult to pump round the circulatory system of a mammal, while sub-cellular and inter-cellular transport would have been impossible. Aquatic creatures would have found it difficult to swim and diffusion of dissolved oxygen into cells would be too slow. If it was too thin there would be profuse bleeding upon injury and cells would not have been able to retain their shape and structure.
Surface tension: this governs the tendency of a liquid to assemble itself into a droplet or a bubble. Had this been lower there would be no rain, or dew or fog or mist or cloud – all essential to the operation of the life- sustaining global water cycle and planet-wide transport of elements crucial to life as well as of bacteria and viruses, which are themselves essential for the functioning of plants and animals.
Adhesion: this is the ability of a liquid to stick to a surface. Combined with surface tension it determines capillarity. Without this property water would not be soaked up by wet paper, for instance. It is a measure of how easily a liquid rises up a microscopic tube. microtubes are ubiquitous in the plant world, allowing water to be imbibed by roots and distributed throughout the plant. No other liquid has such a high capillarity.
Density: water is unique in having a maximum density above its freezing point, i.e. at 4 deg C. When the temperature falls below this level there is expansion. Water is also alone in being more dense as a solid (i.e. ice) than as a liquid. Overall, the result is that instead of seas, lakes and rivers freezing solid from the bottom upwards a thin thermally insulating layer of ice forms on the surface.
Thermal conductivity: a measure of how well heat is transmitted through a medium. Water has the highest thermal conductivity of any substance and this is just as well since it means that, combined with water’s high specific heat, the sea temperature evens itself out over the planet. Large temperature differences would result in a severely chaotic climate hostile to life. The high thermal conductivity is equally crucial in allowing cells to dissipate heat and so avoid destruction through overheating.
Specific heat: this is the amount of heat needed to warm up a given volume of a substance. This is very high for water so that a mass of water holds a lot of heat and cools only slowly. As stated above it means large temperature differences between bodies of water are avoided.
Latent heat of evaporation: this is the heat needed to turn a liquid into a vapour. For water it is extremely high and this is fortunate since otherwise there would be no water left on earth. Neither would organisms be able to shed heat through evaporation.
Vapour pressure: water has a high vapour pressure and this means that the air above it can hold a lot of moisture, thus enabling rain to form. Since water has the largest heat of evaporation, its vapour pressure increases more rapidly with increasing temperature than for other liquids.
Boiling point and melting point: these are anomalously high. Because they are both high the water remains in liquid form at normal atmospheric pressure and so able to perform its miraculous life giving functions. Its role in the biosphere largely depends on water being able to exist in the liquid state for 4 billion years and to assume a variety of forms of precipitation (snow, hail, rain, fog, mist, dew). This planet is the only one we know of which allows this.
I can’t begin to do justice to this subject so if you want to look further I recommend a seven part series, starting with this one, from the RTB website.
Does all this mean that life appears wherever there is water? If that were so living planets would abound. Unfortunately, this looks increasingly unlikely since water, though crucial, is only a necessary condition for life, not a sufficient one. Numerous conditions (e.g. stable environment and protection from harmful radiation), too many to mention here (see Our precious planet), appear to be needed and we still have not much idea how it got started or what it really is.
Our perception of reality, ancient and modern
Our perception of reality, ancient and modern
Author, 2077: Knights of Peace
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