The evolutionary universe
Although Vico laid great stress on the need to view man historically, he did not regard man as emerging out of nature, nor did he think that the natural world had a history of its own. During the course of the eighteenth century, however, the belief began to spread that the idea of time is an essential part of the idea of nature. Just as acceptance of the Copernican theory had shattered the tightly knit confines of the world in space, so similarly the tendency to look at things historically led to a correspondingly vast extension of the world in time.
In his revolt against the then prevailing Aristotelian philosophy of nature, Descartes, like Newton half a century later, regarded all matter, both terrestrial and celestial, as subject to the same physical laws. As a mechanical determinist, however, he did not invoke divine intervention to explain the origin of the solar system. In his Principia of 1644 he tried to explain the uniformity of direction of motions in the solar system and their approximation to the plane of the ecliptic by his theory of vortices. He assumed that originally the world was filled with matter distributed as uniformly as possible, and he sketched out qualitatively a theory of successive formation of the sun and planets, including the earth, which he regarded as composed of a series of different layers.
Descartes' idea of the universe evolving by natural processes of separation and combination was the source of a succession of theories of cosmic evolution. Nearly a century later, Swedenborg, in his Principia of 1734, advocated a modified view of the Cartesian cosmogony. He suggested that the planets were ejected from the sun, but his idea of how this may have happened was rejected by Buffon who, in 1745, put forward the first tidal theory of the origin of the solar system. Assuming that comets were far more massive than we believe today, Buffon suggested that a comet colliding with the sun may have torn out sufficient material to form the planets.
Neither Swedenborg nor Buffon applied Newtonian ideas to the problems of cosmogony. The first to do so was Immanuel Kant in his Universal Natural History and Theory of the Heavens, published in 1755. He assumed that initially all matter was in a gaseous state spread more or less uniformly, except for some primeval regions of higher density which acted as centres of condensation under the action of gravitation. One such centre was the origin of the solar system. Kant thought that eventually through collisions coplanar circular orbits with motions all in the same sense about the sun could arise. He was mistaken in thinking that this phenomenon was automatically possible, because it contradicts the dynamical principle of the conservation of angular momentum and hence Newton's laws of motion. (This dynamical principle, however, was not formulated in full generality until 1775, by Euler). Laplace's nebular hypothesis, put forward in 1796, was free from this defect, and his primeval solar nebula was assumed to rotate initially. The idea of cosmical evolution, as distinct from the old idea of cosmical cycles, was also suggested by the great pioneer of modern observational astronomy, William Herschel. In a paper published in 1814 he claimed that 'the state into which the incessant action of clustering power has brought the Milky Way at present is 2 kind of chronometer that may be used to measure the time of its past and future existence'.1
One of the obstacles that the idea of evolution had to contend with was the widespread inherited conviction that the range of past time was severely limited. Bible-based chronology had already become a severe strait-jacket for scientists studying the nature of fossils. In the seventeenth century both Steno and Hooke realized that fossils were the petrified traces of former living organisms. They were led to develop a dynamical theory of geological change but were confronted with the difficulty of fitting this into the accepted time-scale. The naturalist John Ray was at first inclined to accept the views of Steno and Hooke about fossils. He suggested that, if Steno were right in asserting that mountains had not all existed from the beginning, then perhaps 'the world is a great deal older than is imagined or believed'. Eventually, however, under the influence of his theological beliefs he changed his opinion about fossils in favour of an inorganic origin and reverted to the traditional, and then still widely accepted, non-evolutionary concept of the natural world. Arthur Lovejoy has drawn attention to the following forthright statement, made by Ray in 1703: 'Consult the evidence of experience; elements always the same, species that never vary, seeds and germs prepared in advance for the perpetuation of everything . . . so that we can say, Nothing new under the sun, no species which has not been seen since the beginning.'2
During the eighteenth century scientists and others began to discard the Bible-based chronology of nature. In 1721, Montesquieu in his Lettres persanes asked 'Is it possible for those who understand nature and have a reasonable idea of God to believe that matter and created things are only 6,000 years old?' Later that century, Diderot thought in millions of years and Kant suggested that the universe may be hundreds of millions of years old. Buffon, when writing his Époques de la nature, published in 1778, privately estimated that the first stages of the cooling of the earth would have required at least a million years.3 In print he was more cautious and estimated the earth's age as being at least 75,000 years. Some of his ideas were condemned by the faculty of theology of the University of Paris.4
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 hundreds 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 '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 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 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 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 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 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.
Since the days of Maskelyne all marine chronometers had been tested and checked at the Royal Observatory. In 1833, when John Pond was Astronomer Royal, the Time Ball service was installed there, whereby a ball on the turret of Flamsteed House fell at exactly 1 p.m., so that the time kept by ships on the Thames near Greenwich could be checked thereby. Airy greatly expanded the public service based on GMT by arranging for that time to be distributed throughout the country by means of electric signals. These were transmitted in cables alongside railway tracks, so that for years GMT was called by most people 'railway time'. In his Annual Report of 1853 Airy wrote, 'I cannot but feel satisfaction in thinking that the Royal Observatory is thus quietly contributing to the punctuality of business throughout a large portion of this busy country.'15
The advent of railways greatly influenced the family habit of taking an annual holiday, a custom that had previously been restricted to the wealthy. It was the growth of this habit that led to the development of seaside resorts. Not everyone, however, welcomed the new mode of transport and the changes that it produced. For example, when in 1844 the first excursion train to Cambridge was planned, the prospect of an influx on a Sunday of 'foreigners and other undesirable characters to the University of Cambridge on that sacred day' was so unwelcome to the Vice-Chancellor of the time that he wrote to the Directors of the Eastern Counties Railway to complain that 'such a proceeding would be as displeasing to Almighty God as it is to the Vice-Chancellor of the University of Cambridge.'16
The revolution in transport affected the tempo of many forms of human activity, particularly the dissemination of news. Although the origin of newspapers, in England at least, can be traced back to the pamphleteering of the different factions at the time of the civil war in the 1640s, it was not until the closing years of the eighteenth century, with the introduction of the mail-coach, and the nineteenth century, with railways, that it became possible for the latest news and informed comments on it to be brought rapidly to towns and villages throughout the land. This spreading of fact and comment far and wide was, of course, also greatly facilitated by the abolition, in the middle of the nineteenth century, of that heavy tax on knowledge, stamp duty on newspapers.
The unprecedented speeding-up of communication, both nationally and internationally, following the introduction of telegraphy and the laying of the transatlantic cable in 1858, revolutionized the conduct of government at home and abroad. An ultimatum could be sent off in the heat of the moment demanding an immediate reply, public opinion could be rapidly influenced and armies mobilized overnight. Such was the march of progress that sudden panic on the New York Stock Exchange in the afternoon could lead to a businessman in London shooting himself before breakfast the following morning. With the advent of wireless telegraphy early in the present century, the rate of dissemination of information all over the world became even more rapid and widespread. No major catastrophe, however remote, now fails to produce agonizing all over the world as soon as it has happened and indeed often while it is still going on.
During the nineteenth century people's attitude to time in countries like England was greatly influenced by the Victorian work-ethic, which led to 'spare time', that is, the time when in principle one was free to do as one liked, being regarded as a reward for hard work. This 'spare time' came to be regulated by the day, week, and year. Previously, holidays had been the forty or more holy days that occurred intermittently throughout the calendar. In England the Puritans, who were in power for over a decade in the middle of the seventeenth century, regarded the traditional Christmas festivities as a pagan relic. They tried to abolish them, but they were soon restored after Charles II returned in 1660. On the other hand, in Scotland Puritan influence persisted and Christmas became far less a time for general celebration than the New Year, a tradition that continued into the present century. The industrial revolution led, however, to the general abolition of holidays based on religious festivals because it was uneconomic to have plant that was expensive to maintain frequently lying idle. In place of the former holy days, four compulsory 'bank holidays' were eventually instituted by law, and it gradually became customary for workers to be given annual holidays of a week or more in the summer. Physical recreation, such as football, came to be organized on a weekly basis, usually on Saturday afternoons.
The nineteenth century saw a great proliferation of pocket watches, although the most important improvement in their mechanism (apart from the balance spring) had already been introduced the previous century. This was the lever escapement invented by Thomas Mudge ( 1715-94). Later, the mechanism of watches was further improved by Abraham Louis Breguet ( 1747-1823), who also designed, in 1815, an observatory clock to strike each second--the forerunner of the modern time-signal. A prominent early nineteenth-century English horologist who had an important and lasting influence on watchmaking in other countries, notably France and Switzerland, was John Arnold (see p. 146). By the middle of that century Sir John Bennett, whose firm had been founded in 1843, recognized the danger of the growing competition from the Swiss watchmaking industry. He therefore arranged for watch mechanisms to be imported into England so that his firm could put the necessary finishing touches to them and sell them as British. He spent lavishly on advertising his wares at the Great Exhibition of 1851. Later in the nineteenth century the modern mass-production of watches began in USA, but it was taken up and greatly extended by the Swiss, who soon dominated the industry.
One of the most surprising facts in the history of horology is that, long after the invention of more precise devices, makers of domestic clocks and watches continued to make use of the verge escapement. This was because it proved to be particularly well-suited for withstanding the rigours of domestic use and portability, whereas escapements such as the anchor type needed to be kept on level surfaces if they were to function satisfactorily.
Not only do most workers nowadays have to clock in and clock out when they begin and end their working day, but timekeeping applies no less generally to sporting activities. Indeed, anything, however idiotic, can now be regarded as a sport so long as it can be timed and can be used to set up a 'record'. Kevin Sheenan, of Limerick, acquired a kind of fame by talking non-stop for 127 hours, and in the USA a preacher established another record by delivering a sermon that lasted forty-eight hours. (This achievement would not have amused Queen Victoria who is said to have had placed conspicuously in all the pulpits used by her chaplains a sand-clock that ran for only ten minutes!) In these and many other ways most of us have become more and more subservient to the tyranny of time. As Lewis Mumford has so pertinently remarked, 'The clock, not the steam-engine, is the key-machine of the modern industrial age.'17 The popularization of timekeeping that followed the mass production of cheap watches in the nineteenth century accentuated the tendency for even the most basic functions of living to be regulated chronometrically: 'One ate, not upon feeling hungry, but when prompted by the clock; one slept, not when one was tired, but when the clock sanctioned it.'18 A good example of how strange our modern preoccupation with time seemed to someone used to a very different way of life is provided by the diary kept by the Nepalese ruler Jang Bahadur on his visit to Britain in 1850. According to the translation by John Whelpton of a biography of him in Nepali published in Katmandu in 1957 and containing excerpts from this diary, he remarked: 'Getting dressed, eating, keeping appointments, sleeping, getting up--everything is determined by the clock . . . where you look, there you see a clock.'19
Although by 1855 about 98 per cent of the public clocks in Britain were set to GMT, acceptance of this time generally throughout the country encountered difficulties. For example, in the case of Curtis v. March at Dorchester assizes on 25 November 1858, the judge took his seat on the bench at 10 a.m. by the clock in the Court, but as neither the defendant nor his lawyer were present he found for the plaintiff. The defendant's counsel then entered the Court and claimed to have the case tried on the ground that it had been disposed of before ten o'clock by the town clock, whereas the clock in the Court was regulated by Greenwich time, which was some minutes before the time in Dorchester. On appeal, the assize judge's decision was reversed, on the ground that 'ten o'clock is ten o'clock according to the time of the place'. This decision was held to define legal time in Great Britain until 1880.20 In that year The Times published a letter from a 'Clerk to the Justices' pointing out the difficulties of officials conducting parliamentary elections in deciding the correct time to open and close the poll. Later that year an Act of Parliament was passed giving legal sanction throughout Great Britain to Greenwich Mean Time.
Soon afterwards steps were taken to standardize timekeeping throughout the world. In 1882 the United States passed an Act of Congress authorizing the President to call an international conference to decide on a common prime meridian for time and longitude, and in October 1884 delegates from twenty-five countries assembled in Washington for the International Meridian Conference. With only one country ( San Domingo) voting against and two others ( France and Brazil) abstaining, it was agreed to recommend that the Prime Meridian of the world should pass through the centre of the instrument at the Observatory at Greenwich known as the Airy Transit Circle and that the Universal Time should be GMT. This was not surprising, since the invention of the marine chronometer by John Harrison and the introduction of the Nautical Almanac in 1766 by the Astronomer Royal Nevil Maskelyne had already led many mariners of all nations to use Greenwich time and the Greenwich meridian. By the early 1880s nearly three- quarters of the ships throughout the world used charts based on the Greenwich meridian. Until 1925, however, as mentioned on p. 15, astronomers continued to begin their day at noon, because it meant that the date did not change in the middle of a night's observing. Another important consequence, although not specifically recommended by the Conference, was the setting-up of a time-zone system throughout the world as had originally been suggested by an American professor, Charles Dowd, in a pamphlet published in 1870. The need to co-ordinate timekeeping was much greater in a large country such as the United States than in Great Britain, but the crucial factor that influenced Dowd was the different times kept by the many railway companies that sprang up after the Civil War and the great inconvenience that they caused to the travelling public. For example, at Pittsburgh, Pennsylvania, there were six different time-standards for the arrival and departure of trains. Dowd's proposal was a scheme identical in principle with the standard time system used throughout the world today.
As long ago as 1881 an American, G. Beard, wrote a book called American Nervousness to point out that the widespread and increasing emphasis on punctuality was causing men to worry that 'a delay of a few moments might destroy the hopes of a lifetime'. Among those in Europe who were anxious for time to be standardized was Count Helmuth von Moltke, who pleaded with the German Reichstag in 1891 for the abolition of the five different time-zones in Germany because they severely impeded the co-ordination of military planning.21 The resulting adoption of a single standard time greatly facilitated German mobilization in 1914. On the other hand, in France, where the lack of time-standardization was much worse than in Germany, a journalist, L. Houllevigue, writing in La Revue de Paris in July 1913, admitted that the delay in correcting this until 1911 was primarily due to Anglophobia. Indeed, the law that came into force defined legal time in France as nine minutes and twenty seconds later than Mean Paris Time. 'By a pardonable reticence, the law abstained from saying that the time so defined is that of Greenwich, and our self-respect can pretend that we have adopted the time of Argentan, which happens to be almost exactly on the same meridian as the English observatory.'
One of the main reasons for the catastrophic failure of diplomacy to prevent the outbreak of the First World War in August 1914 was the inability of diplomats to cope with the enormous volume and unprecedented speed of telegraphic communication in the last days of July. The rate at which messages could be sent from one capital to another necessitated rapid and often ill-considered responses. Ironically, the main reason for the failure of the Schlieffen plan for attacking France through Belgium was the unprecedented success of German mobilization, with thousands of trains ferrying troops to the front so rapidly that they outran their own timetable and consequently the supplies they needed failed to keep pace with them.
The decisive weapon in that war was the machine-gun with its rapid firing. On the Western front it has been estimated that it caused four- fifths of the casualties. Of the 60,000 casualties that the British army suffered on the first day of the battle of the Somme, 1 July 1916, most occurred in the first hour--probably in the first few minutes. One of the social consequences of the First World War was the increased use of wrist-watches. Many men had considered them unmanly until they became standard military equipment. The battle of the Somme began when hundreds of platoon leaders blew their whistles as soon as their synchronized wrist-watches showed that it was 7.30 a.m. Thus, whereas Einstein had shown ten years before that in the physical world simultaneity was a 'private' concept rather than a 'public' one (see ch. 11), in the world of human action it had become far more important than it had ever been.
The introduction of the radio time-signal early this century for the dissemination of time for navigational purposes led to the final abandonment of the lunar-distance method of determining longitude at sea, since it now became possible to check a ship's chronometers directly. (The lunar-distance method had been used occasionally to check chronometers at sea when no other method was available.) Since the First World War radio, and later television, and the ever-increasing speed of the new modes of transport made possible by the invention of the internal combustion engine have led to our dependence on the clock becoming ever greater. In recent years the most spectacular example of this has been provided by space vehicles and the associated requirement of ultra-precise timekeeping.
In the early 1920s the accuracy of civil timekeeping was significantly improved by W.H. Shortt, a railway engineer, who in association with the horologist F. Hope-Jones and the Synchronome Company perfected what came to be known as the Shortt free-pendulum clock. The material used for the pendulum was a virtually temperature-independent alloy of steel and nickel called 'invar', first produced some years before in France. Any interference with the free motion of the pendulum was reduced to a minimum by the ingenious use of a subsidiary 'slave dock'. Shortt clocks were the standard timekeepers at the Royal Observatory, Greenwich, from 1925 to 1942. Previously, the best clock-accuracy was about one- tenth of a second (100 milliseconds) a day, but Shortt clocks were accurate to about 10 seconds a year, that is, about 30 milliseconds a day. In the 1930s still greater accuracy was obtained by utilizing the mechanical vibrations of the crystalline mineral quartz, instead of the vibrations of a pendulum in the earth's gravitational field. The quartz crystal clocks which replaced the Shortt clocks as the standard timekeepers at the Royal Observatory in 1942 were accurate to about two milliseconds a day.
For centuries the time kept by our clocks and watches was controlled by the rate of rotation of our planet, but with the invention of more accurate clocks it was found that the rotating earth is not a sufficiently accurate timekeeper for modern needs, because it is subject to small variations. The earth is a solid body surrounded by water and air, and seasonal changes in these, for example the melting and freezing of the polar ice-caps, affect the earth's rate of rotation so that the length of the day fluctuates during the year by just over a millisecond (thousandth of a second). There are also small irregular changes attributed to processes in the earth's deep interior. Besides these changes there is a progressive slowing down of the earth's rate of rotation caused by tidal friction in shallow seas that produces an increase in the length of the day of about 1.5 milliseconds a century. As a result in 1952 the rotating earth was displaced as the fundamental timekeeper by Ephemeris Time, based on the length of the year, which is decreasing by about 0.5 seconds a century but can be predicted. However, even this did not prove entirely satisfactory and because of the increasing demand for high-precision time- measurement it has become essential to have some more fundamental standard of time than any that can be derived from astronomical observations. Such a standard is given by the frequency of a particular spectral line of an atomic or molecular vibration. The most successful method of this type has been developed by Dr L. Essen of the National Physical Laboratory.22 Consequently, in 1967 a new definition of the second was made in terms of the electromagnetic radiation generated by a particular transition in the ground state of the caesium atom. It is called the 'SI second' (Système Internationale). It is formally defined as the duration of 9,192,631,770 periods of radiation corresponding to the transition between two hyperfine levels of the caesium-133 atom. In this transition the spin of the outermost electron of the atom 'flips over' with respect to the spin of the nucleus. (A quartz crystal oscillator is controlled by means of a known relationship between its frequency and that of the radiation generated by this transition.) The caesium atom was chosen because the frequencies concerned are in the radio range and can be measured by standard techniques. In recent years there has been much technical discussion concerning the relation between TAI ('International Atomic Time'), obtained by the continuous summation of time-intervals deduced from these measures of frequency, and the time-scales used by astronomers. The accuracy of astronomical time, which is still required for practical purposes, is checked by means of the frequency of this radiation. This atomic frequency standard is now so precisely determined that in individual cases its accuracy can be as high as one part in 1014, which is equivalent to an error of only one second in three million years.
The world's time signals are now co-ordinated by the Bureau International de l'Heure (BIH) based on a world 'mean clock' that is the average of some eighty atomic clocks in twenty-four countries. It provides direct synchronization to within about a millisecond. Although this 'Co-ordinated Universal Time' (UTC), which has replaced GMT as the basis of civil time throughout the world, is now controlled from Paris, the world's prime meridian for longitude and time still passes through the old Observatory at Greenwich. In practice, the zero meridian is now defined by the adopted longitudes of the instruments that contribute to the determination of UTC. Since 1985 the contribution of the Royal Greenwich Observatory to the international determination of UTC and longitude has been through its observations of the artificial satellite Lageos by a laser-ranging system in use at Herstmonceux since the autumn of 1983. As from 1 January 1972 time signals have radiated atomic seconds, but just as there is not a whole number of days in a year, so there is not a whole number of atomic seconds in a solar day. This has led to the adoption of corrections, either positive or negative, of exactly one second. They are called 'leap seconds' and when required are on the last day of a calendar month, preferably on 31 December or 30 June.