Speaker: The Revd Tom Stuckey, Past President of the Methodist Conference (2005)
Theme: The Power of the Cross
Dates: Friday 3 to Sunday 5 November,
How science points to the existence of God - Part 3
Chemistry: It’s elementary
Like the air we breathe, we take so many things about our world for granted. So many things ‘just are’. Yet some things, like air, are essential for our existence, and indeed, for life itself. In this article I’ll be considering how the chemistry of the natural elements is amazingly suitable for providing the necessary basis for biological existence. The chemical elements are utterly basic to the material universe, and to us. Yet the number of chemicals elements, and their properties, are dictated by the nature of the fundamental forces of the universe, which themselves are set by the nature of the Big Bang.
You may remember your school chemistry lessons and wall charts of the periodic table of the elements - 85 stable ones, and 7 radioactive ones that gradually break down into smaller elements. Each chemical element has different properties, though some belong to ‘classes’ that have similar properties, such as the metal elements or the inert gases. Of the 92 elements that occur naturally, 25 are considered essential to life in general, while only 11 are found in every living creature. Among these few, the most important are hydrogen, carbon, nitrogen and oxygen. These are also among the most common elements in the universe, which is providential because the chemical reactivity of each is uniquely suitable for providing the basic biochemistry of life, and not in just one aspect, but in several.
In his book, Nature’s Destiny, Michael Denton argues that everything we see in nature seems to be tailored - designed - towards producing intelligent life. In particular he provides evidence that the chemical elements themselves provide either uniquely suitable or the most optimal characteristics for providing the huge variety of requirements for biochemistry and thus life. What’s so significant is that the biologically useful elements all provide several independent physical or chemical characteristics that are essential or highly beneficial to the biological processes necessary for life. Denton places chemistry alongside cosmology and astrophysics, in providing evidence that the universe is designed for the purpose of fostering life.
Four essential chemicals - hydrogen, carbon, nitrogen and oxygen
Carbon has absolutely no competitor in its ability to react with itself and with many other elements. There are millions of known carbon compounds. Carbon is the basis for all life. Its closest competitor, silicon, cannot provide anywhere near such a range of biologically useful compounds. Carbon is able to react with hydrogen to form an enormous range of hydrocarbons. It reacts with oxygen to form carbon dioxide, an essential for plant life; and with hydrogen and oxygen together, forming the alcohol and the fatty acid groups. These three elements, together with nitrogen, form yet another vital group of compounds, the amino acids, the building blocks of protein.
Between them, H, C, N and O provide the overwhelming bulk of organic compounds, almost infinite in their variety of chemical properties, of physical shape and of biological usefulness. The organic compounds are notably stable at normal temperatures, yet they can be made to react relatively easily without being too energy demanding. Remarkably, the balance between the reactivity and stability of biological compounds is optimum within the very temperature range that’s found over most of the planet. This enables these compounds to be both relatively long-lived yet also easily made to react to form other compounds of every conceivable shape, size and reactivity. Thus they’re astonishingly suitable for the abundant variety of life as we see it.
Atomic carbon and oxygen used to be considered as something of a chemical enigma. All the chemical elements above hydrogen are produced in the nuclear fusion ‘chemical factories’ at the centre of red giant stars. Hydrogen burns to form helium. When two helium nuclei collide they produce beryllium8, a very short-lived radioactive particle. If a third helium nucleus then collides with this atom, atomic carbon is formed. However, the energy levels required for this reaction are not favourable for the production of carbon. Yet carbon is actually found in great abundance. Why? In the 1950’s, astrophysicist Fred Hoyle predicted that carbon must have a nuclear ground state energy ‘resonance’ that enhanced the formation of atomic carbon. This indeed proved to be the case. However, the coincidences don’t stop there. Oxygen is produced by the nuclear interaction of carbon and helium. Energetically, this should be such an easy step that most of the carbon should be used up in the formation of oxygen. However, the absence of a suitable resonance actually inhibits this happening. Thus carbon is preserved. The next step would be for oxygen and helium to combine to form neon. However, this step is similarly hindered, thus preserving oxygen.
When one considers the essential part that these two elements play in the biology of life, it’s an extraordinary coincidence that the creation of carbon and oxygen should be ‘tweaked’ in this way. Certainly, these ‘coincidences’ were sufficient to provoke Hoyle to write, “Would you not say to yourself, ‘Some super-calculating intellect must have designed the properties of the carbon atom, otherwise the chance of my finding such an atom through the blind forces of nature would be utterly minuscule.’ Of course you would ... A common sense interpretation of the facts suggests that a superintellect has monkeyed with physics, as well as with chemistry and biology, and that there are no blind forces worth speaking about in nature. The numbers one calculates from the facts seem to me so overwhelming as to put this conclusion almost beyond question.”
Weight watching and dieting is a multi-million pound industry in this country. Church and community halls abound with organisations promising miracles in weight reduction. All diets are based on manipulating the intake of various forms of hydrogen, carbon, and oxygen, the energy suppliers of metabolism. Atomic oxygen is highly reactive and provides more energy than any other chemical other than the dangerously reactive fluorine. But even in compound form, all three elements can provide energy when reacting with other compounds. Organic compounds of these three, along with nitrogen, are also able to act as stores for energy, which we know commonly as sugars, fats and proteins. They’re very efficient stores, and release large amounts of energy when involved in oxidation reactions.
Is it just fortuitous that these are the very same chemical groups that form the huge variety of the fundamental structures necessary for life? J.L. Henderson noted in his book, The Fitness of the Environment, that “The very chemical changes, which for many other reasons seem to be best fitted to become the processes of physiology, turn out to be the very ones which can divert the greatest flood of energy into the stream of life.”
The water of life
We’re so familiar with water that we can easily overlook its very remarkable properties. At the temperature range found across the planet earth, water exists in all three phases - solid, liquid and gas. In its liquid phase, it provides the fluid matrix in which life’s chemical reactions can occur. Although it’s not quite a universal solvent, water is outstanding in the range of compounds that can be dissolved in it to at least some extent. We should be grateful for this remarkable property, particularly when wanting the loo! Water’s solid phase, ice, provides thermal stability to the climate, as well as grinding rock into small particles, forming a matrix for soil and releasing minerals into it. In its gaseous phase, it provides a mechanism for transferring water from the oceans to the land.
the range of chemical elements and their derivatives seem tailored to provide all the necessities for life and for the emergence of intelligent life.
Water also has several unique thermal properties that are essential for a life-permitting environment. Like all liquids, water contracts when it cools. But anomalously, at 40ºC it begins to expand again. Thus the oceans’ depths rarely reach a temperature below this. Further, at freezing point, there’s another sudden expansion on the formation of the solid phase. This means that ice floats. If it didn’t, it would sink to the depths where it would be insulated from the warming effects of the sun and atmosphere, with the result that the earth would have quickly become an ice planet, and hostile to life.
Denton points to other seemingly fortuitous characteristics of water. It has a high surface tension exceeded by very few other liquids, as anyone who has seen water boatmen insects skipping across ponds will have noted. This high surface tension facilitates the capillary action of water in soil and in drawing water through the roots and xylem of plants and trees.
The viscosity of water is also important. It is very low, which means dissolved molecules can easily diffuse through water. Further, blood (which is largely a suspension of red blood cells in water) acts as a non-Newtonian fluid, which means that when it flows through a narrow tube, if the pressure is increased the viscosity decreases and the flow increases. The benefit of this to complex animal life is incalculable. For example, without this character mammalian muscles undergoing exertion would be unable to receive extra blood flow, and thus oxygen. We’d be couch potatoes by necessity!
In yet another beneficial characteristic, the thermal capacity of water is higher than most other liquids. This means that a relatively large amount of heat is required to raise its temperature. This characteristic buffers the extremes of temperature of summer and winter, it stabilises weather patterns, and it also enables relatively small bodies of water to remain in the liquid phase in winter, which is of clear benefit to aquatic life. High thermal capacity, together with water’s high thermal conductivity, enables heat to be evenly distributed in the cells of multicellular organisms.
Denton concludes, “water is uniquely and ideally adapted to serve as the fluid medium for life on earth in not just one, or many, but in every single one of its known physical and chemical characteristics ... There is indeed no other candidate fluid which is remotely competitive with water as the medium for carbon-based life. If water did not exist, it would have to be invented.” (Italics original.)
The air we breath
The nature of the atmosphere is similarly optimised in providing the conditions for life. Firstly, the viscosity and density of air is within that very small range which is biologically useful. If air was denser and more viscous, animals would need to use much more of their energy just breathing. Secondly, the oxygen content of air, at about 21%, is near the maximum before it becomes dangerously reactive. If it were around 30%, runaway combustion would become the commonplace result of lightning strikes. Thirdly, above this same level, oxygen is so dangerously reactive it becomes toxic to life.
The atmosphere is remarkable in yet another independent but essential way. The gases of our atmosphere are transparent to precisely that range of the electromagnetic radiation spectrum that is useful to life. Most of the radiation spectrum is either too energetic and harmful to biological molecules, or else is below their activation energy levels. It’s only the infrared and visible wavelengths that provide the right amounts of energy required to provoke biochemical photo-reactions. Remarkably, the electromagnetic output of the sun is almost entirely restricted to this narrow range, which is useful to photochemistry. If this weren’t so, there could be no life, since there are no alternatives. Even so, for life to be possible, the atmosphere must be such that it allows this useful part of the solar spectrum to penetrate to the planet’s surface. It’s a remarkable providence that the main gases of the earth’s atmosphere, oxygen, nitrogen, carbon dioxide and water vapour, are all transparent to this part of the spectrum, and allow about 80% of the sun’s radiation to reach the planet’s surface. Yet radiation either side of this range is strongly absorbed. It is as though there’s a ‘window’ in the electromagnetic absorption range of the atmospheric gases designed to allow the sun’s light to penetrate.
There are many other examples which could have been given, too many to enumerate here, all showing how the range of chemical elements and their derivatives seem tailored to provide all the necessities for life and for the emergence of intelligent life. Denton comments, “And so the coincidences lengthen further. In case after case, the constituents of life - water, the carbon atom, the oxygen atom, carbon dioxide gas, the bicarbonate base - turn out to be uniquely and ideally fit in so many diverse and complex ways for their biological roles.” There’s no prior reason why this should be so. It just is, it’s a given, a gift from the nature of the universe, yet an utterly necessary one.
What conclusion, then, should we draw from the remarkable nature of the chemical elements and their compounds? Chance? Necessity? Or design? We’ve already seen how cosmology and astrophysics appear to be designed to facilitate the emergence of life. Here, we’ve seen the same principle extended into chemistry. In the next article, we’ll be discerning design in biology - by far the most controversial area in the interface between science and faith.
Michael J. Denton (1998) Nature’s Destiny – how the laws of biology reveal purpose in the universe
A detailed analysis of how chemical elements are uniquely or optimally suited to biological function. Denton appears to have a deistic view of purpose, arguing that life anywhere in the universe will follow the same overall direction as life on earth, since the characteristics of the chemicals necessarily set both limits and optima to biological function, and therefore to the range of possibilities of how life can develop.