The Faber Book of Science

by John Carey

  Source: Henry David Thoreau, Walden; or, Life in the Woods, Boston, Mass. Ticknor and Fields, 1854.

  On a Candle

  Michael Faraday (1791–1867) was a blacksmith’s son who taught himself science after training as a bookbinder, and was apprenticed, aged 21, to Sir Humphry Davy. A pioneer of electromagnetism, he constructed the first electric motor and the first dynamo. He started the Christmas lectures for children at the Royal Institution in Albemarle Street, and his famous series ‘On the Chemical History of a Candle’ was first given in 1849. A model of lecturing technique, the series included experiments that produced bangs, flashes, soap bubbles filled with hydrogen floating roofwards, and other spectacular effects. To illustrate the expansion of water when frozen, for example, Faraday placed two vessels made of half-inch-thick iron, and filled with water, in a freezing solution, then went on lecturing until the vessels exploded.

  Faraday aimed to show that ‘there is not a law under which any part of this universe is governed’ which the burning of a candle, and the simple experiments leading from it, could not illustrate. Charles Dickens, keen, like Faraday, to bring science to a wider audience, borrowed the notes for the lectures, and in 1850 his family magazine Household Words carried a semi-fictionalized version of them in which a rather priggish nephew, who has attended Faraday’s course, explains the wonders of chemistry to his appreciative uncle.

  This extract represents the climax of the course – the conclusion of the sixth and last lecture.

  Now I must take you to a very interesting part of our subject – to the relation between the combustion of a candle and that living kind of combustion which goes on within us. In every one of us there is a living process of combustion going on very similar to that of a candle, and I must try to make that plain to you. For it is not merely true in a poetical sense – the relation of the life of man to a taper; and if you will follow, I think I can make this clear …

  We consume food: the food goes through that strange set of vessels and organs within us, and is brought into various parts of the system, into the digestive parts especially; and alternately the portion which is so changed is carried through our lungs by one set of vessels, while the air that we inhale and exhale is drawn into and thrown out of the lungs by another set of vessels, so that the air and the food come close together, separated only by an exceedingly thin surface: the air can thus act upon the blood by this process, producing precisely the same results in kind as we have seen in the case of the candle. The candle combines with parts of the air, forming carbonic acid, and evolves heat; so in the lungs there is this curious, wonderful change taking place. The air entering, combines with the carbon (not carbon in a free state, but, as in this case, placed ready for action at the moment), and makes carbonic acid, and is so thrown out into the atmosphere, and thus this singular result takes place; we may thus look upon the food as fuel. Let me take that piece of sugar, which will serve my purpose. It is a compound of carbon, hydrogen, and oxygen, similar to a candle, as containing the same elements, though not in the same proportion; the proportions being as shown in this table:

  This is, indeed, a very curious thing, which you can well remember, for the oxygen and hydrogen are in exactly the proportions which form water, so that sugar may be said to be compounded of 72 parts of carbon and 99 parts of water; and it is the carbon in the sugar that combines with the oxygen carried in by the air in the process of respiration, so making us like candles; producing these actions, warmth, and far more wonderful results besides, for the sustenance of the system, by a most beautiful and simple process. To make this still more striking, I will take a little sugar; or to hasten the experiment I will use some syrup, which contains about three-fourths of sugar and a little water. If I put a little oil of vitriol on it, it takes away the water, and leaves the carbon in a black mass. [The Lecturer mixed the two together.] You see how the carbon is coming out, and before long we shall have a solid mass of charcoal, all of which has come out of sugar. Sugar, as you know, is food, and here we have absolutely a solid lump of carbon where you would not have expected it. And if I make arrangements so as to oxidize the carbon of sugar, we shall have a much more striking result. Here is sugar, and I have here an oxidizer – a quicker one than the atmosphere; and so we shall oxidize this fuel by a process different from respiration in its form, though not different in its kind. It is the combustion of the carbon by the contact of oxygen which the body has supplied to it. If I set this into action at once, you will see combustion produced. Just what occurs in my lungs – taking in oxygen from another source, namely, the atmosphere, takes place here by a more rapid process.

  You will be astonished when I tell you what this curious play of carbon amounts to. A candle will burn some four, five, six, or seven hours. What then must be the daily amount of carbon going up into the air in the way of carbonic acid! What a quantity of carbon must go from each of us in respiration! What a wonderful change of carbon must take place under these circumstances of combustion or respiration! A man in twenty-four hours converts as much as seven ounces of carbon into carbonic acid; a milch cow will convert seventy ounces, and a horse seventy-nine ounces, solely by the act of respiration. That is, the horse in twenty-four hours burns seventy-nine ounces of charcoal, or carbon, in his organs of respiration to supply his natural warmth in that time. All the warm-blooded animals get their warmth in this way, by the conversion of carbon, not in a free state, but in a state of combustion. And what an extraordinary notion this gives us of the alterations going on in our atmosphere. As much as 5,000,000 pounds, or 548 tons, of carbonic acid is formed by respiration in London alone in twenty-four hours. And where does all this go? Up into the air. If the carbon had been like the lead which I showed you, or the iron which, in burning, produces a solid substance, what would happen? Combustion could not go on. As charcoal burns it becomes a vapour and passes off into the atmosphere, which is the great vehicle, the great carrier for conveying it away to other places. Then what becomes of it? Wonderful is it to find that the change produced by respiration, which seems so injurious to us (for we cannot breathe air twice over), is the very life and support of plants and vegetables that grow upon the surface of the earth. It is the same also under the surface in the great bodies of water; for fishes and other animals respire upon the same principle, though not exactly by contact with the open air.

  Such fish as I have here [pointing to a globe of gold-fish] respire by the oxygen which is dissolved from the air by the water, and from carbonic acid, and they all move about to produce the one great work of making the animal and vegetable kingdoms subservient to each other. And all the plants growing upon the surface of the earth, like that which I have brought here to serve as an illustration, absorb carbon; these leaves are taking up their carbon from the atmosphere to which we have given it in the form of carbonic acid, and they are growing and prospering. Give them a pure air like ours, and they could not live in it; give them carbon with other matters, and they live and rejoice. This piece of wood gets all its carbon, as the trees and plants get theirs, from the atmosphere, which, as we have seen, carries away what is bad for us and at the same time good for them – what is disease to the one being health to the other. So are we made dependent not merely upon our fellow-creatures, but upon our fellow-existers, all Nature being tied together by the laws that make one part conduce to the good of another.

  There is another little point which I must mention before we draw to a close – a point which concerns the whole of these operations, and most curious and beautiful it is to see it clustering upon and associated with the bodies that concern us – oxygen, hydrogen, and carbon, in different states of their existence. I showed you just now some powdered lead, which I set burning; and you saw that the moment the fuel was brought to the air it acted, even before it got out of the bottle – the moment the air crept in it acted. Now, there is a case of chemical affinity by which all our operations proceed. When we breathe, the same operation is going on within us
. When we burn a candle, the attraction of the different parts one to the other is going on. Here it is going on in this case of the lead, and it is a beautiful instance of chemical affinity. If the products of combustion rose off from the surface, the lead would take fire, and go on burning to the end; but you remember that we have this difference between charcoal and lead – that, while the lead can start into action at once if there be access of air to it, the carbon will remain days, weeks, months, or years. The manuscripts of Herculaneum were written with carbonaceous ink, and there they have been for 1,800 years or more, not having been at all changed by the atmosphere, though coming in contact with it under various circumstances. Now, what is the circumstance which makes the lead and carbon differ in this respect? It is a striking thing to see that the matter which is appointed to serve the purpose of fuel waits in its action; it does not start off burning, like the lead and many other things that I could show you, but which I have not encumbered the table with; but it waits for action. This waiting is a curious and wonderful thing. Candles – those Japanese candles, for instance – do not start into action at once like the lead or iron (for iron finely divided does the same thing as lead), but there they wait for years, perhaps for ages, without undergoing any alteration. I have here a supply of coal-gas. The jet is giving forth the gas, but you see it does not take fire – it comes out into the air, but it waits till it is hot enough before it burns. If I make it hot enough, it takes fire. If I blow it out, the gas that is issuing forth waits till the light is applied to it again. It is curious to see how different substances wait – how some will wait till the temperature is raised a little, and others till it is raised a good deal. I have here a little gunpowder and some gun-cotton; even these things differ in the conditions under which they will burn. The gunpowder is composed of carbon and other substances, making it highly combustible; and the gun-cotton is another combustible preparation. They are both waiting, but they will start into activity at different degrees of heat, or under different conditions. By applying a heated wire to them, we shall see which will start first [touching the gun-cotton with the hot iron]. You see the gun-cotton has gone off, but not even the hottest part of the wire is now hot enough to fire the gunpowder. How beautifully that shows you the difference in the degree in which bodies act in this way! In the one case the substance will wait any time until the associated bodies are made active by heat; but, in the other, as in the process of respiration, it waits no time. In the lungs, as soon as the air enters, it unites with the carbon; even in the lowest temperature which the body can bear short of being frozen, the action begins at once, producing the carbonic acid of respiration; and so all things go on fitly and properly. Thus you see the analogy between respiration and combustion is rendered still more beautiful and striking. Indeed, all I can say to you at the end of these lectures (for we must come to an end at one time or other) is to express a wish that you may, in your generation, be fit to compare to a candle; that you may, like it, shine as lights to those about you; that, in all your actions, you may justify the beauty of the taper by making your deeds honourable and effectual in the discharge of your duty to your fellow-men.

  Source: Michael Faraday, A Course of Six Lectures on the Chemical History of a Candle, London, Chatto & Windus, 1861.

  Heat Death

  The concept of entropy (the dissipation of available energy) was the brainchild of the German physicist Rudolf Clausius (1822–88) who, in 1850, formulated the second law of thermodynamics (that heat cannot of itself pass from a colder to a hotter body). In any closed system, Clausius pointed out, there is an inevitable waste or loss of energy (entropy), and the amount of energy available for work will decrease as entropy increases. Regarding the universe as a closed system, he predicted that its entropy would eventually be maximized, i.e. that it would run down, reaching a state of equilibrium and uniform temperature, with no further energy available for doing work – a condition known as ‘the heat death of the universe’. The American novelist and poet John Updike (b.1932) protests against this conclusion in his ‘Ode to Entropy’:

  Some day – can it be believed? –

  in the year 1070 or so,

  single electrons and positrons will orbit

  one another to form atoms bonded

  across regions of space

  greater than the present observable universe.

  ‘Heat death’ will prevail.

  The stars long since will have burnt their hydrogen

  and turned to iron.

  Even the black holes will have decayed.

  Entropy!

  thou seal on extinction,

  thou curse on Creation.

  All change distributes energy,

  spills what cannot be gathered again.

  Each meal, each smile,

  each foot-race to the well by Jack and Jill

  scatters treasure, lets fall

  gold straws once woven from the resurgent dust.

  The night sky blazes with Byzantine waste.

  The bird’s throbbling is expenditure,

  and the tide’s soughing,

  and the tungsten filament illumining my hand.

  A ramp has been built into probability

  the universe cannot re-ascend.

  For our small span,

  the sun has fuel, the moon lifts the lulling sea,

  the highway shudders with stolen hydrocarbons.

  How measure these inequalities

  so massive and luminous

  in which one’s self is secreted

  like a jewel mislaid in mountains of garbage?

  Or like that bright infant Prince William,

  with his whorled nostrils and blank blue eyes,

  to whom empire and all its estates are already assigned.

  Does its final diffusion

  deny a miracle?

  Those future voids are scrims of the mind,

  pedagogic as blackboards.

  Did you know

  that four-fifths of the body’s intake goes merely

  to maintain our temperature of 98.6∘?

  Or that Karl Barth, addressing prisoners, said

  the prayer for stronger faith is the one prayer

  that has never been denied?

  Death exists nowhere in nature, not

  in the minds of birds or the consciousness of flowers,

  not even in the numb brain of the wildebeest calf

  gone under to the grinning crocodile, nowhere

  in the mesh of woods or the tons of sea, only

  in our forebodings, our formulae.

  There is still enough energy in one overlooked star

  to power all the heavens madmen have ever proposed.

  Source: John Updike, Facing Nature: Poems, London, André Deutsch, 1986.

  Adam’s Navel

  Philip Henry Gosse, the man who said God had put fossils in the rocks to deceive geologists, is a laughing stock of popular science. His reputation is defended here by one of the foremost modern science writers, Stephen Jay Gould. A research biologist, Gould has devoted many years to the study of the Bahamian land snail Cerion. ‘I love Cerion’‚ he has declared, ‘with all my heart and intellect.’ However, it is the clarity and originality of his scientific writing that has brought him the widest fame. Four collections of his monthly columns in Natural History magazine have been published. This is from the fourth, Hen’s Teeth and Horse’s Toes (1990).

  The ample fig leaf served our artistic forefathers well as a botanical shield against indecent exposure for Adam and Eve, our naked parents in the primeval bliss and innocence of Eden. Yet, in many ancient paintings, foliage hides more than Adam’s genitalia; a wandering vine covers his navel as well. If modesty enjoined the genital shroud, a very different motive – mystery – placed a plant over his belly. In a theological debate more portentous than the old argument about angels on pinpoints, many earnest people of faith had wondered whether Adam had a navel.

  He was, after all, not b
orn of a woman and required no remnant of his nonexistent umbilical cord. Yet, in creating a prototype, would not God make his first man like all the rest to follow? Would God, in other words, not create with the appearance of preexistence? In the absence of definite guidance to resolve this vexatious issue, and not wishing to incur anyone’s wrath, many painters literally hedged and covered Adam’s belly.

  A few centuries later, as the nascent science of geology gathered evidence for the earth’s enormous antiquity, some advocates of biblical literalism revived this old argument for our entire planet. The strata and their entombed fossils surely seem to represent a sequential record of countless years, but wouldn’t God create his earth with the appearance of preexistence? Why should we not believe that he created strata and fossils to give modern life a harmonious order by granting it a sensible (if illusory) past? As God provided Adam with a navel to stress continuity with future men, so too did he endow a pristine world with the appearance of an ordered history. Thus, the earth might be but a few thousand years old, as Genesis literally affirmed, and still record an apparent tale of untold eons.