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.
(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
Sweat and Cool offThe 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.
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.
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
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.
A Temperate WorldThe five different thermal properties of water mentioned in Henderson's book The Fitness of Environment also play a key role in bringing about the mild and balanced climate that Earth has.
Water's greater latent heat and thermal capacity as compared with other liquids are the reasons that bodies of water heat up and cool off more slowly than does the land. On land, the difference in temperature between the hottest and coldest places can reach as high as 140°C; at sea, that difference varies at most between 15-20°C. The same situation exists in the difference between daytime and nighttime temperatures: in arid environments on land, the difference in temperature can be as much as 20-30°C; at sea, this is never more than a few degrees. And not only the seas are affected in this way: the water vapor in the atmosphere is also a big balancing agent. One result of this is that in desert regions where there is very little water vapor present, the difference between daytime and nighttime temperatures is extreme while in regions where a maritime climate prevails, the difference is much less.
Thanks to these unique thermal properties of water, the temperature differences between summer and winter or between night and day remain constantly within limits such that human beings and other living things can survive. If the surface of our world had less water than it does land, the temperature differences between night and day would have been much greater, large tracts of land would have been desert, and life might have been impossible or, at the very least, much more difficult. Similarly, if the thermal properties of water had been different from what they are, the result would have been a planet quite unsuitable for life.
Having examined all these thermal properties of water, Henderson concludes:
To sum up, this property appears to possess a threefold importance. First, it operates powerfully to equalise and to moderate the temperature of the earth; secondly, it makes possible very effective regulation of the temperature of the living organism; and thirdly it favours the meteorological cycle. All of these effects are true maxima, for no other substance can in this respect compare with water. 79
The properties of water that we
have considered till now are thermal: that is, they are its heat-related
properties. Water also has a number of physical properties which,
as it turns out, are also extraordinarily fit for life.
Plants are designed to take advantage of water's high surface tension, thanks to which, water can be made to rise many meters up into even the highest leaves of a forest canopy.
The surface tension of water is much higher than that
of any other known liquid. Some of the biological consequences of
this are crucial and this is particularly evident in the case of
Have you ever wondered how plants are able to convey water from the depths of the soil many meters into the air without pumps, muscles, or the like? The answer to this puzzle is surface tension. The channels in the roots and stems of plants are designed to take advantage of water's high surface tension. These channels grow thinner the higher they reach and quite literally cause water to "creep up" on its own.
What makes this excellent design possible is the high
surface tension of water. If water's surface tension were as low
as it is in most other liquids, it would be physiologically impossible
for large plants such as trees to live on dry land.
Another important consequence of water's high surface tension is the fragmentation of rock. Because its surface tension is so high, water is able to penetrate into the deepest recesses of rockthrough the tiniest of cracks where it freezes when the temperature drops below zero. Water, as we have seen, is unusual in that it expands when it freezes. This expansion exerts interior forces upon rock that causes it eventually to break up. This process is vitally important because it releases the minerals trapped in rock into the environment and also contributes to the formation of soil.
A very important consequence of this is that useful minerals and similar substances that are locked up in the land get dissolved in water and transported to the sea by rivers. It is estimated that five billion tons of such matter are carried into the sea every year. These substances are vital for sea-life.
Water also accelerates (catalyzes) nearly all known chemical reactions. Another important chemical property of water is that its chemical reactivity is at an ideal level. Water is neither too reactive and thus potentially destructive (as sulfuric acid for example) nor is it too inert (like argon which takes part in no chemical reactions). To quote Michael Denton: "It seems that, like all other properties, the reactivity of water is ideally fit for both its biological and its geological role."80
Additional details concerning the fitness of the chemical properties of water for life are constantly being revealed as researchers investigate the matter more. Harold Morowitz, a biophysics professor from the University of Yale, makes this comment:
The past few years have witnessed the developing study of a newly understood property of water (i.e., proton conductance) that appears to be almost unique to that substance, is a key element in biological-energy transfer, and was almost certainly of importance to the origin of life. The more we learn the more impressed some of us become with nature's fitness in a very precise sense… 81
Water's low viscosity is vitally important to us. If water were only slightly more viscous, it would be impossible for blood to be transported through the body's capillary system. For example the complex system of veins of our body's liver (shown above) would never have been able to exist.
Does water's low viscosity have any importance for us? Would things be different if this vital liquid were a little more or a little less viscous? Michael Denton answers that question for us:
The fitness of water would in all probability be less if its viscosity were much lower. The structures of living systems would be subject to far more violent movements under shearing forces if the viscosity were as low as liquid hydrogen...If the viscosity of water was much lower, delicate structures would be easily disrupted... and water would be incapable of supporting any permanent intricate microscopic structures. The delicate molecular architecture of the cell would probably not survive.
If the viscosity was higher, the controlled
movement of large macromolecules and particularly structures such
as mitochondria and small organelles would be impossible, as would
processes like cell division. All the vital activities of the cell
would be effectively frozen, and cellular life of any sort remotely
resembling that with which we are familiar would be impossible.
The development of higher organisms, which is critically dependent
on the ability of cells to move and crawl around during embryogenesis,
would certainly be impossible if the viscosity of water was even
slightly greater than it is. 82
Water's low viscosity is essential not only for cellular motion but also for the circulatory system.
Water's low viscosity is essential for all living things, even plants. The tiny veins in the leaf seen at the left are able to transport water because it is so fluid.
All living creatures with a body size of more than a quarter of a millimeter have a centralized circulatory system. The reason is that beyond that size, it is not possible for nutriments and oxygen to be diffused throughout the organism. That is, they can no longer be taken directly into the cell nor can their by-products be discharged. There are many cells in an organism's body and thus it is necessary for the oxygen and energy taken into the body to be distributed (pumped) to them through "ducts" of some sort; similarly, other channels are necessary to carry away the waste. These "ducts" are the veins and arteries of the circulatory system. The heart is the pump that keeps this system moving while the substance carried through the "ducts" is the liquid we call "blood", which is mostly water. (95% of blood plasma–the material remaining after blood cells, proteins, and hormones have been removed, is water.)
This is why the viscosity of water is so important for the efficient functioning of the circulatory system. If water had the viscosity of tar for example, certainly no organic heart could pump it. If water had the viscosity even of olive oil, which is a hundred million times less viscous than tar, the heart might be able to pump it, but it would be extremely difficult and blood would never be able to reach all the billions of capillaries that wend their ways through our bodies.
Let's take a closer look at those capillaries. Their purpose is to carry the oxygen, nourishment, hormones, etc that are necessary for life to every cell everywhere in the body. If a cell is more than 50 microns (a micron is a thousandth of a millimeter) away from a capillary it cannot take advantage of the capillary's "services". Cells more than 50 microns from a capillary will starve to death.
This is why the human body was so created that the capillaries form a network that pervades it completely. A normal human body has about 5 billion capillaries whose total length, if stretched out, is about 950 kilometers. In some mammals, there are as many as 3,000 capillaries in a single square centimeter of muscle tissue. If you were to gather ten thousand of the tiniest capillaries in the human body together, the resulting bundle might be as thick as the lead of a pencil. The diameters of these capillaries varies between 3-5 microns: that's three to five thousandths of a millimeter.
If blood is going to penetrate passages that narrow without blocking them or slowing down, it certainly needs to be fluid and, thanks to water's low viscosity, it is. According to Michael Denton, if water's viscosity were just a bit more than what it is, the blood circulatory system would be completely useless:
A capillary system will work only if the fluid being pumped through its constituent tubes has a very low viscosity. A low viscosity is essential because flow is inversely proportional to the viscosity... From this it is easy to see that if the viscosity of water had a value only a few times greater than it is, pumping blood through a capillary bed would require enormous pressure and almost any sort of circulatory system would be unworkable... If the viscosity of water had been slightly greater and the smallest functional capillaries had been 10 microns in diameter instead of 3, then the capillaries would have to occupy virtually all of the muscle tissue to provide an effective supply of oxygen and glucose. Obviously the design of macroscopic life forms would be impossible or enormously constrained... It seems, then, the viscosity of water must be very close to what it is if water is to be a fit medium for life.83In other words, like all its other properties, the viscosity of water is also "tailor-made" for life. Looking at the viscosities of different liquids, we see that they differ by factors of many billions. Among all those billions there is one liquid whose viscosity has been created to be exactly what it needs to be: water.
Water is "just right" for life to a degree that cannot be compared with any other liquid. The larger part of this planet, a world whose other attributes (temperature, light, electromagnetic spectrum, atmosphere, surface, etc) are all suitable for life, has been filled with just the right amount of water necessary for life. It should be obvious that this cannot all be accidental and that there must instead be intentional design.
To put it another way, all the physical and chemical properties of water show us that it is created especially for life. The earth, purposefully created for mankind to live in, was brought to life with this water that was specially created to form the basis of human life. In water, Allah has given us life and with it He causes the food by which we are nourished to spring from the soil.
But the most important aspect of all this is that this truth, which has been discovered by modern science, was revealed in the Qur'an, bestowed upon humanity as a guide fourteen centuries ago. Concerning water and mankind, Allah's word is revealed in the Qur'an thus:
It is He who sends down water from the sky. From it you drink and from it come the shrubs among which you graze your herds. And by it He makes crops grow for you and olives and dates and grapes and fruit of every kind. There is certainly a Sign in that for people who reflect. (Surat an-Nahl: 10-11)
Allah is Known Through Reason
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