Pascal Richet
A NATURAL HISTORY OF TIME
400pp. University of Chicago Press. Paperback, US $29.
978 022671287 1

Flann O’Brien’s fictional scientist and savant De Selby conceived a theory that darkness, far from being the absence of light, is really an accumulation of minutely small black corpuscles. I had attributed this wonderful notion to O’Brien’s joyful surrealism, but I learn from Pascal Richet, in A Natural History of Time, that in 1896 the physicist Gustave Le Bon actually announced to the Academy of Science in Paris the discovery of black light. Maybe the voraciously curious O’Brien had come across this absurdity – a forgotten footnote in scientific history. There was no shortage of similar oddities at the end of the nineteenth century, following the discovery of X-rays – those mysterious entities that could pass through flesh itself. N-rays, “a new type of radiation”, for example, were visible particularly to their discoverer, an otherwise respectable professor from Nancy called René Blondlot. Like radium, they emitted radiant matter. He said of them: “The observer should accustom himself to look at the screen just as a painter, and in particular an ‘impressionist’ painter, would look at a landscape. To attain this requires some practice . . . some people, in fact, never succeed”. Indeed they didn’t, for N-rays were a fiction.

That Blondlot’s observations were taken seriously tells us something about the oddly faltering way in which science advances: a very different tale from one relating scientific history as a journey forwards into the light, guided by a handful of geniuses. To a reader interested in the slow and erratic progress of discovery, the story of how the age of the earth was determined is a marvellous concatenation of red herrings and presuppositions from which the truth eventually emerges, like one of those huge beetles that spend years as a busy, ugly grub before flying perfectly formed out into the world.

In the process of the discovery of temporal history, time itself changed. An eternal world was prevalent in classical times, one governed by cyclical renewal. As things were, so they would remain, more or less at the mercy of the gods. This indefinite time was then replaced by a direct historical narrative, one that began at the Creation. Some such biblical scale dominated Western thought for many centuries. Time was now graspable, since there were only three measures of it: the brief span of human life; the time since the beginning of the world (and its anticipated end); and the infinite – the promise of immortality through salvation. This arrangement was curiously comforting, and one can understand why people might have been reluctant to let it go. A few thousand years since the beginning of things can be understood readily enough; the population of a small town or a flock of starlings is measured in similar magnitude.

Richet points out that for many savants of the Renaissance, and much later, there was simply no questioning the Bible. It was, so they thought, nothing less than a historical document, and one with the special signature of God himself. Leonardo da Vinci had recorded in his notebooks observations of the time needed to form sediments and raise fossils above the present sea level that were, as always, astonishingly prescient – but they were also obscurely concealed in his mirror writing. His insights were mostly ignored. Much more influential was the work of men of unquestionable genius like Isaac Newton. From today’s perspective, it is hard to understand how the prodigy who prised open so many secrets of nature could yet be so blind to the antiquity of the earth. Instead, he devoted much time and effort to his Chronology, the correction of the biblical timescale as recounted by the generations of the Old Testament. He went to endless pains to square his new chronology with recently recognized features of the earth’s rotation. The fact that Newton worked on biblical chronology throughout most of his long life shows that it was a central preoccupation for him. Doubtless, his conviction of God’s order in the universe impelled him in his quest to square the historical scale with the sidereal. We might wonder now at what seems like a waste of that great brain; in fact, he followed a respectable tradition of chronologists, and if they now seem the equivalent of those much-misquoted medieval theologians debating how many angels could dance on the head of a pin, they would not have seemed so piffling to many of their contemporaries. Archbishop Ussher’s date for the Creation, October 23, 4004 BC, just happens to be the one that stuck – and sticks still, to some Creationists.

Not that there weren’t perfectly serious attempts to assess the age of the earth by Newton’s contemporaries. Halley worked out how long it would take for the oceans to attain their saltiness from the input of salt from rivers, but he was – wisely perhaps, given the implications – vague about his inferred long timescale. More than a century later, Joly would use similar evidence to come up with a figure of 80 million years. By the early years of the Enlightenment, as Martin Rudwick has shown in Bursting the Limits of Time, among the aristocratic savants of Europe, speculation about how much time had elapsed since the Creation was far freer than it was among the religious establishment or the laity.

The science of geology was entirely post-Newtonian. Strata yielded up much of the evidence for the earth’s antiquity in the heroic days of the new science: not for nothing is the earthly scale known as “geological time”. By the early eighteenth century, it was already recognized that the temperature in mines was elevated: indeed, geology had begun as a practical adjunct to the extraction of ores. An ensuing speculation about the origin of the earth from a molten state reduced time to a calculation based on the physical processes of a cooling sphere – leaving behind as a memory of primeval days the heat that still bothered silver miners delving deeply in the mines of Bohemia. Georges-Louis Leclerc, later Comte de Buffon, performed a series of experiments by heating up and then cooling steel balls of various sizes. He then scaled up the results to account for the conditions remaining on earth today, assuming a molten origin for the planet – and came up with an age for the earth of slightly less than 200,000 years. The importance of the result lies not in its accuracy – it is wildly incorrect – but in the application of reasoning and experiment to the problem, and the abandonment of the old methods of chronology. Buffon’s reputation could scarcely have been more stellar during his lifetime, and many a rue Buffon in France still attests to his fame. Even so, he failed to convince: “As for the cosmogonical romances of Buffon, they have been destroyed by others who will soon suffer the same destiny”, wrote one cynical naturalist only a few years after Buffon died in 1788.

The evidence of the stratigraphic succession of rocks was piled ever higher. Fossils had once been accounted “sports of nature” – allegedly grown from “seeds” within the rock. But by the end of the eighteenth century their organic nature was beginning to be accepted, and what Leonardo had seen as obvious was at last getting close scrutiny from a new generation of men of science. As a result, the utility of fossils in mapping rock strata soon became patent. William Smith’s geological map can be inspected today by any interested visitor to the Geological Society’s premises in Piccadilly in London. It was not only a practical guide to strata, it was also a narrative of geological time. Similar maps of France provided ample testament to the succession of life forms, and the recognition followed that many of the species in the rocks were extinct. The age of trilobites was followed by the age of dinosaurs, and then of mammals, and – finally – mankind. Revolutions were not confined to France; they were evidently part of time itself. In Britain, the grasp of the Church was stronger than it was in post-Revolutionary France, but even there a diversion recognizing fossils as evidence of the Great Flood was not long-lived. It seemed inevitable that time in good measure was needed for the accumulation of all those strata – now recognized as having been laid down in seas long vanished. But how much time?

Organic evolution certainly required time, and lashings of it. So the age of the earth inevitably became entwined with the greatest scientific controversy of the nineteenth century. Charles Darwin and T. H. Huxley and their many supporters needed plentiful time to achieve the gradual transformation of life – and their reckoning ran to hundreds of millions of years. However, Lord Kelvin, a physicist with the authority of a minor god, had other ideas. Using a more sophisticated version of Buffon’s terrestrial cooling model, by the late nineteenth century Kelvin had settled on no more than a few tens of millions of years for the age of the earth, and he didn’t budge from his conclusion. Huxley, “Darwin’s bulldog”, demanded a dozen times the span. Even estimates based on the time taken to accumulate the thickness of sedimentary rocks then known – the whole pile added together – yielded figures of an order of magnitude higher than Kelvin’s. An impasse had been reached.

The deadlock was broken by the discovery of radioactivity. The story of the age of the earth now became part of the tale of understanding the constitution of matter itself. Michael Faraday had remarked in 1866 that “to discover a new element is a very fine thing, but if you could decompose an element and tell us what it is made of – that would be a discovery indeed worth making”. The time for dissection of matter had arrived. N-rays and radiations allegedly emitted by psychics were perhaps the last of the distractions from that denouement. The production of energy from radioactive decay rewrote all the equations that Lord Kelvin had used for his estimates. The earth was a boiler, not a cooling potato. The instincts of the geologists and the palaeontologists had been correct after all; and the apparent certainties of physics had been revealed as inadequate. The earth could, after all, be very old. When it was realized that many chemical elements could exist as different isotopes, it became clear that radioactive decay converted one form of uranium into another of lead at a predictable rate. Here, at last, was the objective “clock” that had been sought since the time of Buffon. Decay of elements ticked off geological time in millions of years. Different decay routes provided a double check on any results. Margins of error tumbled as one piece of “kit” was replaced by yet another, still more sophisticated, and eventually capable of counting the very atoms themselves. Through shared technical advances, the story of the age of the earth then became entangled with the tragedy of Hiroshima.

The answer finally came fifty years ago, with the dating of meteorites that had formed at the same time as our nascent earth: creation was 4.55 billion years old. The dates were consistent from several samples, the techniques as good as could be managed. The beginnings of bacteria were probably at about 3.5 billion years, so the start of life was calibrated, too. Oddly enough, finally arriving at the “answer” carries a slight whiff of disappointment. Does the scientist simply pack up and go home once the answer is reached? After all, there is nothing intrinsically scientific about the answer itself. But think of the changes wrought to time: from the domestic scale of medieval days to a number so vast that we can utter it, but not really comprehend it. Our own brief human occupation of the earth points up our vulnerability. God has been shuffled progressively away from the centre of the narrative. The expansion of time has been accompanied by a diminution in our own stature. If we are the children of time, our inheritance has been anxiety and a sense of insignificance.

Pascal Richet is a geophysicist, and well able to explain the complexities of the discoveries that led from Crooke’s tube through to those of Pierre and Marie Curie, and on to the discovery of isotopes of lead and uranium. Richet never short-changes the reader on the science, and his grasp of more than a thousand years of speculation about our origins is unfailingly impressive. Some of the scientists are well known from many other contexts – do we really need a thumbnail sketch of the Darwin– Wallace years when they have been anatomized so many times? My own pleasure, and this may be perverse, was in discovering some of the forgotten figures, like M Le Bon and his black light, or Joseph Pitton de Tournefort, who thought that “there was nothing strange in assuming that rocks had semen”. In a curious way, the doomed aberrations of science mark out the changes in zeitgeist more effectively than the triumphs of the famous names. Newton’s obsession with chronology is as informative of the times in which he lived as his triumphs in mathematical physics.

Richet’s view of science is very much ad hominem. His attempt to include almost every figure of note is at times exhausting – I counted twenty different figures (with their dates) introduced in one chapter alone. There is not so much a sense of Thomas Kuhn’s shifting paradigms as an impression of relentless struggle and disagreement between individual scientists. However, Richet does observe how history – the French Revolution par excellence – has poked its grubby finger into the lives of even the unworldliest scientists. He is also admirably even-handed and unchauvinistic – how good to find Britain’s own Arthur Holmes recognized by a Frenchman, and, conversely, it is surely correct to point up the weighty contributions of Buffon and Cuvier to making geology a science. Unscrambling the timescale seems to have involved almost every nation on earth. A book of this scope is bound to draw from the works of scholars and historians of science rather than mine original material. No doubt those scholars will have nits to pick, but I cannot imagine a better attempt at such a broad sweep through science and history.

Richet has been generally well served by his translator, though a few phrases will leave the reader stranded: “X-rays had just come out of limbo, while the electron still took its delight there”. Technical jargon is always a problem: too little of it and the more geeky reader feels cheated; too much and the layperson begins to suffer. Richet usually gets it about right.

Problems with time have not gone away. “Creation science” still plays games with it. Those who cling to the comfort of a short timescale for the earth probably do not realize where they belong in intellectual history: imagine their astonishment if they were offered medical treatment appropriate to the same era. Contemplating the magnitude of time is discombobulating; we might prefer to think of something else, something less cruelly vast. It is a service to have an explanation of time and where it came from. Richet’s natural history is – dare I say it? – timely.

Richard A. Fortey is a senior research scientist at the Natural History Museum. His new book, Dry Store Room No. 1: The secret life of the Natural HIstory Museum, is published this month. The Earth: An intimate history appeared in 2006.

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