In 1788 the geologist James Hutton in his Theory of the Earth rejected the sudden catastrophic changes that had been previously invoked to explain the stratification of rocks, the deposition of oceans, etc. He realized that the true scientific approach is not to invoke such ad hoc hypotheses but to test whether or not the same agents as are operating now could have operated all through the past. In his view, the world has evolved and is still evolving. In one passage he actually likened it to an organism. He concluded that vast periods of time were required for the earth to have reached its present state, and from his study of sedimentary and igneous rocks he came to his frequently quoted conclusion: 'We find no vestige of a beginning--no prospect of an end.'
The idea of using fossils to establish a chronology of the rocks was first suggested in the seventeenth century by Robert Hooke, but was not acted on for over a hundred years. Towards the end of the eighteenth century, William Smith, an English surveyor who collected fossils, realized that each geological stratum could be recognized by the fossils found in it, and that the same succession of strata occurred wherever the rocks concerned were found. He produced in 1815 the first geological map of a whole country. Meanwhile the science of stratigraphical palaeontology was being founded independently in France by Jean-Louis Giraud Soulavie ( 1752- 1813), who was the first to recognize that the stratigraphical ordering of rocks can be regarded as a chronological ordering.
During the nineteenth century the idea of time as linear advancement finally prevailed through the influence of the biological evolutionists, but the climate of thought that made it possible to contemplate the hun
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dreds of millions of years required for the operation of natural selection to account for the present and past species was prepared primarily by the geologists. It was therefore not surprising that Darwin began his life's work as a geologist, as well as a naturalist. Nevertheless, Darwin's demands on the extent of past time came as a great shock to many, as Sir Archibald Geikie explained some forty years after the publication, in 1859, of The Origin of Species. Geikie wrote:
Until Darwin took up the question, the necessity for vast periods of time, in order to explain the character of the geological record, was very inadequately realized. Of course, in a general sense the great antiquity of the crust of the earth was everywhere admitted. But no one before his day had perceived how enormous must have been the periods required for the deposition of even some thin continuous groups of strata.5
For measurements of geological time, as distinct from guesses, appeal must be made to physics, and here Darwin met what he believed to be one of the gravest objections to his theory. In 1854 the German physicist and physiologist Helmholtz had suggested that the sun maintains its enormous outpouring of radiation by continually shrinking and thereby releasing gravitational energy, which is converted into thermal energy of radiation. He calculated that the current rate of solar radiation could not have been maintained by the sun for more than about twenty million years. This conclusion was supported by the British physicist William Thomson (who became Lord Kelvin in 1892), who thought that at most this estimate could be lengthened to fifty million years.
In confirmation of his view that the hundreds of millions of years demanded by the geologists could not be allowed, Thomson considered the flow of heat through the earth's crust. He argued that this indicated that the earth must be cooling and must therefore have been hotter in the past. He calculated the epoch at which the earth must have been molten and found that this was between twenty million years and an upper limit which he continually reduced from four hundred million to his final estimate, in 1897, of twenty-four million years.
Kelvin was criticized by the geologists but he received public support from the former (and subsequent) prime minister and amateur scientist Lord Salisbury, in his Presidential Address to the British Association at its meeting in Oxford in 1894. Both Kelvin and Huxley were present. Kelvin confined his remarks after the address to a conventional expression of thanks. Huxley's polite and dignified speech of thanks
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'veiled an unmistakable and vigorous protest'.6 The first man who challenged Kelvin on his own ground as a physicist was his former assistant, the mathematician and engineer John Perry ( 1850- 1920). On reading Salisbury's address, he sent a letter to the weekly science journal Nature, where it appeared early the next year.7 He directed attention to Kelvin's simplifying assumption that the earth's thermal conductivity during its cooling was homogeneous, pointing out that, if in fact this conductivity increased towards the centre, Kelvin's estimate of the earth's age would have to be significantly increased. Moreover, if there were some degree of fluidity in the earths' core, thermal conductivity must be supplemented by convection. Perry was attacked arrogantly by the applied mathematician P. G. Tait and in a more moderate tone by Kelvin, who pointed out that, irrespective of his calculations concerning the earth, the sun's heat limited the terrestrial age to a few score million years at most.
While this controversy was raging the concept of evolution was being extended to the history of the earth-moon system. The importance of tidal friction in this context had already been realized in 1754 by Immanuel Kant in the most remarkable of his evolutionary speculations, the short essay that he wrote on the question 'Whether the Earth has Undergone an Alteration of its Axial Rotation'. The frictional resistance of the earths' surface to the tidal currents in the seas and oceans induced primarily by the gravitational action of the moon is very slow in its action, but it is irreversible and over long periods of time could give rise to great changes in the rotation of the earth and the orbit of the moon. Kant's discussion was not quantitatively correct, but it was the first indication that the time of celestial mechanics is not cyclic. Towards the end of the nineteenth century a more thorough and accurate analysis of the dissipative effects of tidal friction on the earth-moon system was made by Charles Darwin's son Sir George Darwin, who tried to fit his results into the time-scale allowed by Helmholtz and Kelvin. He calculated that the minimum time required for the transformation of the moon's orbit from its supposed initial condition to its present form would be fifty to sixty million years. He realized that the actual period was probably a good deal longer. 'Yet I cannot think, he wrote, 'that the applicability of the theory is negatived by the magnitude of the period required.'8
The resolution of these difficulties of time-scale for the age of the earth and of the sun was possible only after the discovery of radioactivity at the end of the nineteenth century and the subsequent investigation of nuclear
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transformations by Rutherford and others early this century. It is now known that there is a sufficient supply of radioactive elements in the crustal rocks to make the net heat loss from the earth extremely small, and Kelvin's estimate for the age of the earth of a few tens of millions of years has been replaced nowadays by about 4,500 million years. Similarly, it is now generally accepted that the sun's heat is maintained by thermonuclear processes in its deep interior that can continue steadily for thousands of millions of years, the age now attributed to the sun being about 4,700 million years.
Radioactivity is an important example of a natural process that is noncyclic and an indicator of 'time's arrow', i.e. of the unidirectional nature of time. Discovered by Becquerel in 1896, it was explained by Rutherford and Soddy in 1902 in terms of the spontaneous transformation of atoms. It is a purely nuclear phenomenon that is independent of external influences, the rate of 'decay' of a given amount of a radioactive element such as uranium being proportional to the number of atoms of the element present. Consequently, radioactivity not only indicates time's arrow but can also be used as a means of measuring time. Besides those radioactive 'clocks' in the crustal rocks that help us to estimate the age of the earth, another well-known example, discovered more recently, is the carbon-14 clock in organic material that has proved so useful for archaeologists.
In the nineteenth century the unidirectional nature
of time in physics was primarily associated with the second law of thermodynamics. This law, originally formulated about 1850 by Rudolf Clausius and William Thomson, was a generalization of the hypothesis that heat cannot of itself pass from a colder to a hotter body. This law determines the direction in which thermodynamic processes occur and expresses the fact that, although energy can never be lost, it may become unavailable for doing mechanical work. Clausius believed that because of this law the universe as a whole is tending towards a state of 'thermal death' in which the temperature and all other physical factors will be everywhere the same and all natural processes will cease. Although this particular application of the law was disputed, and is now no longer accepted because of recent advances in cosmology, it was for a time a powerful influence undermining long-established belief in the idea of a cyclic non-evolutionary physical universe.
The role of time in modern industrial society
Since the origin of modern industrial society in the eighteenth century
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time has come to exercise an ever-growing influence on human life generally and even on the way most of us tend to think. For example, consider the concept of 'anachronism'. In antiquity only the Romans seem to have had any idea of it. In ancient Israel the linear concept of history as the fulfilment of a promise made by God involved no such sense; and among the Greeks few writers, apart from Herodotus, showed any awareness of historical development. Turning to the Romans, we and that Virgil's characters, unlike Homer's, have a sense of past and future, and that Horace, in the Art of Poetry, pointed out that both costume and language change in the course of time. As regards the evolution of language, Horace influenced Chaucer in Troilus and Criseyde (c. 1386): 'Ye knowe eek that in forme of speche is chaunge / Withine a thousand year.' Thus, as P. Burke has remarked, with reference to this passage, 'The sense of history in one age stimulated the sense of history in another.'9 Although the idea of anachronism appears to have influenced some people in the Renaissance period, it only came to be widely appreciated in the course of the eighteenth century. In particular, before the end of that century it led to the introduction of period costume in the theatre.
Perhaps the most striking effect of the growing importance of time on the way people lived was the introduction of an unprecedented countrywide system of organizing transport. The idea of an omnibus service appears to have been first suggested in the middle of the seventeenth century by Pascal, but the first great advance beyond traditional methods did not occur until more than a hundred years later. Indeed in England as late as the reign of George II ( 1727-60) the customary speed of land travel was no faster than in the first century BC, when it took Julius Caesar, travelling in the comparative comfort of a litter, eight days to cover a distance of 730 statute miles from Rome to Rhodamus. In 1639 Charles I took four days to ride from Berwick to London, a distance of about 300 miles. Owing to the deplorable state of the English roads, which had been greatly neglected since the Roman occupation ended more than a thousand years before, wheeled traffic almost ceased in winter and most people were marooned in their towns and villages for at least half the year. In the seventeenth century some towns near London had a carrier service to and from the capital, but since the roads tended to be appallingly bad, travelling on them in unsprung coaches must have been quite an ordeal even for the hardiest of travellers!
The introduction of tarred roads and the turnpike system in the course of the eighteenth century certainly made for faster going, but the decisive breakthrough came in 1784 when almost within twelve months a unified
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network of public transport based on strict timekeeping was introduced throughout the length and breadth of England, the mail-coach system. It was founded by John Palmer, MP for Bath. His coach left Bristol at 4 p.m., drove through the night at the standard speed of ten miles an hour, and arrived--strictly on schedule--at the London General Post Office in Lombard Street at 8 a.m. the following morning. Thomas De Quincey, in his well-known essay on 'The English Mail-coach', refers to Palmer as being responsible for 'the conscious presence of a central intellect, that, in the midst of vast distances--of storms, of darkness, of danger--over-ruled all obstacles into one steady co-operation to a national result,' and in a footnote to 'vast distances' he mentions the case 'where two mail-coaches starting at the same minute from points six hundred miles apart, met almost constantly at a particular bridge which bisected the total distance'. He goes on to inform us that it was the mailcoach that distributed over the land 'the heart-shaking news of Trafalgar, of Salamanca, of Vittoria, of Waterloo'. Foreigners often complained of the English mania for saving time. An American Quaker, John Woolman, wrote that 'Stage-coaches frequently go upwards of one hundred miles in twenty-four hours and I have heard Friends say in several places that it is common for horses to be killed with hard driving.'10
The introduction of the mail-coach led to a novel problem of time- keeping that was to affect travellers and others for the next 100 years. All towns went by local or 'sun' time, but in the west of England this could be up to twenty minutes behind London's and in the east up to seven minutes ahead. As might be expected, countrymen objected to having London time imposed upon them. The solution that Palmer's Superintendent Hasker adopted was to provide each coach with a timepiece that could be pre-set to lose or gain as required, constant checks being made at certain Post Offices en route. The sound of the posthorn was an audible reminder to all inhabitants of the towns and villages through which the mail-coach passed of the importance of time and punctuality. Moreover, the regular sight of the mail-coach must have been a constant reminder to many a countryman of the possibility of seeking his fortune in the town. At the beginning of the nineteenth century four out of every five people in England and Wales were country folk, but by mid-century this was true of only about half.
For most people, travel around the country, either to visit relatives or to go on holiday, had to wait for the advent of railways in the second quarter of the nineteenth century. The effect of steam power on people's
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way of life and sense of time was not, however, due only to the invention of the locomotive. Steam power was the driving force of the industrial revolution. Although the old cottage-based handloom weavers often had to work very hard for a living, they could at least work when they liked, but factory workers had to work whenever the steam power was on. This compelled people to be punctual, not just to the hour but to the minute. As a result, unlike their ancestors, they tended to become slaves of the clock. The vice of 'wasting time' had already been castigated by Puritan writers, for example by Richard Baxter who, in his Christian Directory of 1664, wrote:
To Redeem Time is to see that we cast none of it away in vain, but use every minute of it as a most precious thing. . . . Consider also how unrecoverable Time is when it's past. Take it now or it's lost for ever. All the men on earth, with all their power, and all their wit, are not able to recall one minute that is gone.11
In the nineteenth century this point of view became increasingly widespread, so that even one so remote from manufacturing industry as the poet Wordsworth was criticized by William Hazlitt because he had 'made an attack on a set of gypsies for having done nothing for twenty- four hours'.12
Although steam had been used as a source of power for some years, it was not until the Rainhill trials of 1829 with Stephenson's 'Rocket' that it was at last clear that a machine had been produced which was capable of much higher speed than a horse. As Jack Simmons has pointed out, 'the world at large . . . became aware of the railway at a single moment of time'.13 The same point was emphasized by C. F. Adams, jun. in the 1886 edition of his book on Railroads: the locomotive and the railroad 'burst rather than stole or crept upon the world. Its advent was in the highest degree dramatic. It was even more so than the discovery of America.
At first railways tended to be run in a rather happy-go-lucky manner, timekeeping being the sole responsibility of the engine driver
. In 1839, when George Bradshaw was compiling his first railway timetables, one director refused to supply him with the times of arrival of trains, because he believed that 'it would tend to make punctuality a sort of obligation',14 but the obligation had to be accepted when mail began to be carried. Each town still kept local time, but owing to the greater speed of railway trains than that of the mail-coach the situation became more
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difficult to control. In Paris clocks outside railway stations were kept five minutes ahead of those inside, not just to ensure that passengers boarded trains in good time but because railway time was Rouen time. In The Times of 11 July 1972 there appeared a letter in which the writer said that her late husband, Sir Shane Leslie, had told her that when the famous Provost of Trinity College, Dublin, Professor Mahaffy, once missed a train at a country station in Ireland he observed that the time on the clock outside the station differed from that on the clock inside. When he tackled an elderly porter about this inefficiency, which had caused him to lose his train, the old man scratched his head and replied, 'If they told the same time, there'd be no need to have two clocks!'
In England a uniform railway time was adopted by the middle of the nineteenth century. This was based on Greenwich Mean Time, that is, the time on the meridian of the Royal Observatory at Greenwich, usually denoted by the letters GMT. The Astronomer Royal of the day, Sir George Airy ( 1801-92), who was the prototype of the modern government scientist, wished to change the attitude of the public to accurate timekeeping. In the late 1840s he was consulted in connection with the design of Big Ben, the huge clock that was to be installed in the tower of the new Palace of Westminster. (It was not named after the Chief Lord of Works, Sir Benjamin Hall, but after the prize-fighter Benjamin Caunt, who in his last fight weighed 238 lb. The term 'Big Ben' was often used for an object that was the heaviest of its kind.) Airy insisted that the new clock be regulated by Greenwich time and that the first stroke of the hour should be correct to within one second, an accuracy previously unheard of in a turret clock.
Time in History: Views of Time From Prehistory to the Present Day Page 21