Abstract: Mankind's essentially untroubled state of mind in the presence of comets during the last two centuries has been fortified by the overall relative brevity of cometary apparitions and the calculated infrequency of cometary encounters with planets.
During the course of the Space Age, however, the fact of cometary splitting has also become increasingly secure and there is growing appreciation of the fact that mankind's state of mind can never be altogether relaxed. Indeed a watershed in the modern perception of cometary facts has evidently been reached with the most recent and devastating example of cometary splitting, that of the fragmentation of Comet P/Shoemaker-Levy 9 and its subsequent bombardment of planet Jupiter.
Thus there is a recognized tendency now amongst comets, especially those in short-period orbits, due to the occasionally excessive effects of solar irradiation, planetary tides and small body impacts, which gives rise to individual swarms of cometary debris, and it is the resulting repeated penetration of such dispersed swarms by our planet which apparently increases the danger to mankind from time to time.
The danger comprises global coolings, atmospheric pollution and super-Tunguska events, the cometary debris being responsible for both high-level dust insertions and low-level multimegaton explosions in the Earth's atmosphere along with a generally enhanced fireball flux.
Historically, the presence of such danger was drawn to mankind's attention by the observed bombardments over several decades due to "blazing stars threatening the world with famine, plague and war; to princes death; to kingdoms many curses; to all estates many losses; to herdsmen rot; to ploughmen hapless seasons; to sailors storms; to cities civil treasons."
The sense of cosmic destiny aroused by these bombardments evidently involved degrees of fatalism and public anxiety which were deplored by both ecclesiastical authorities and secular administrations with the result that acknowledged dispensers of prognosis and mitigation who endorsed the adverse implications of 'blazing stars' (astrologers, soothsayers etc.) were commonly impugned and censured.
Nowadays, of course, we are able to recognise that the Earth's environment is not only one of essentially uniformitarian calm, as formerly assumed, but one that is also interrupted by 'punctuational crises', each crisis being the sequence of events which arises due to the fragmentation of an individual comet whose orbit intersects the Earth's. That even modest crises can arouse apprehension is known through the circumstances of the nineteenth century break-up of Comet Biela.
Indeed it seems that these crises are rather frequently characterized by relatively violent (paradigm shifting) transmutations of human society such as were originally proposed by Spengler and Toynbee more than sixty years ago on the basis of historical analysis alone.
It would appear, then, that the historical fear of comets which has been with us since the foundation of civilization, far from being the reflection of an astrological perception of the cosmos which was deranged and therefore abandoned, has a perfectly rational basis in occasional cometary fragmentation events. Such events recur and evidently have quite serious implications for society and government today.
Thus when cosmic danger returns and there is growing awareness of the fact, we find that society is capable of becoming uncontrollably convulsed as 'enlightenment' spreads. A revival of millenarian expectations under these circumstances, for example, is not so much an underlying consequence but a deviant manifestation of the violent turmoil into which society falls, often to revolutionary effect.
I. INSPIRATION AND FOREBODING
Today science is more or less unquestioned as the primary body of systematic knowledge reaching us through observation and measurement. However, by making too much of the more passive aspects of this body of knowledge, i.e. its reproducibility through repeated accurate measurement, it is possible to undervalue the significance of its more active aspects, i.e. the inductive insights or connecting links which ultimately give the overall system of knowledge its intrinsic strength.
Scientists, of course, are aware of these countervailing tendencies and while recognising the care, patience and technical skill that are necessary to sustain the reproducibility of systematic knowledge, they do also draw attention to the need for a state of mind in research which brings its practitioners to the point of insight and enlightenment.
Thus a picture for the overall development of knowledge seems now to have emerged in which the network of connections between supposed islands of knowledge may be discontinuously and abruptly rearranged as the islands themselves continuously grow and dissolve. Admittedly any precise description of these discontinuities remains somewhat elusive (Kuhn, 1962 cf. Lindberg, 1992) but there is no lack of archetypes such as Archimedes and his well known cry of Eureka! from the bath as he pondered the problem of the specific gravity of gold.
Our ancestors indeed, who undoubtedly recognised the importance of this not so very subtle aspect of the acquisition of knowledge, would tend to describe an enchanted state of mind which from the very earliest times was believed to have been brought on through the wiles and trickery of a serpent. In fact, a modern dictionary still tells us that to be fascinated, the prerequisite to knowledge, is to be deprived of the power to resist or to escape by the look or presence of a tormentor, possibly a serpent. A mythologist would have little difficulty with such etymology: thus it was the original all-pervading chaos associated with the primeval (cosmic) serpent, whatever this may have been, which served as the principal exemplar down the ages of the turmoil out of which desperate new connections were once forged and which was accepted as naturally illustrating the critical path by which new scientific (mostly astronomical) knowledge was obtained.
In other words, the insights leading to true knowledge have long been thought of as being brought to human attention by some kind of mesmerising process or cunning on the part of nature. That is, we observe natural phenomena as to whose cause we wonder and by whose effect we are astonished. And it is through the perceived enlightenment that comes by joining such cause and effect that a fascination in, say, astronomical phenomena is believed to broaden our cosmic experience and thereby enrich our cultural heritage.
We may be fascinated of course in the sense of being enraptured and heartened, in which case we are in the habit of accepting the cosmic realm as a source of inspiration and our culture as both soothing and ennobling. However, we may also be fascinated in the sense of being agitated and petrified, in which case it can also be that the cosmic realm is a source of foreboding and our culture is both disturbing and intoxicating.
Of the essence here is the injustice to our past if we look back on the sum total of mankind's cosmic experience and fail to recognize how this has ennobled our culture. But equally, there is the unfairness to our future if we look back on this experience and fail to appreciate how it has also overwhelmed our culture from time to time, e.g. through our response to the intermittent incidence of celestial 'signs'. The mistake in fact is to suppose that inspiration and foreboding are uniformitarian and arise in equal measure at all times, rather we should be aware of the possibility of a temporal sequence in the balance of inspiration and foreboding; and of the timescale of variation from one extreme to the other which is tantalizingly beyond the usual reach of direct individual experience. That is, for long periods of time on Earth, generations can follow generations under the impression that our cosmic environment is a continuous source of inspiration only to be succeeded for a while by generations aware of the fact that our cosmic environment can also be an intense source of foreboding.
The point to be noted then is that there are positive and negative, both light and dark, sides to the inspiration provided by astronomical phenomena in the past; and we seriously misunderstand human history if we suppose our celestial environment never impinges adversely upon the Earth.
Quite simply, the enlightened or supposedly uniformitarian view of nature these last two hundred years has diverted attention from adverse celestial inputs and there is now a serious risk, especially from within the fastness of an ivory tower, that inspiration's commonest inducement, the appeal to a sublime principle, will continue to press our cosmic perspective and our cultural endeavour towards some kind of paradisical extreme.
To achieve some kind of balance of course, it is probably necessary to come down from the fastness of the ivory tower and to join the maelstrom in the courtyard below for it is only through grim human contact, it seems, that we are more able to contemplate the punctuational crises which continually threaten and sometimes afflict civilization. There will be optimists, to be sure, who will trivialize such crises and regard such balance as imbalance but, as a well-known yet typical mentor of the last century (Proctor, 1875) once quoted, when troubles were about to befall men, "nation rising against nation, and kingdom against kingdom, with great earthquakes in divers places, and famines, and pestilences, and fearful sights", then "great signs shall there be from heaven".
The point Proctor makes of course is that our cosmic experience has always had both its paradisical and its purgatorial aspects and it is mostly when the latter are in the ascendancy that our cosmic experience rouses us from the opium of culture and plunges us into the politics of despair. Thus it could be a twentieth century indulgence to suppose despondency under uniformitarian conditions cannot be further plumbed for such could be as nothing compared to the depths of despair which have come with the most significant cosmic events during recent millennia.
In this essay, we shall begin with a 'journalistic' perspective on the contemporary politics of punctuational crises and then move on to evaluate the cosmic perspective which now seems to be forced upon us. We shall come to recognize that the great signs from heaven were never primarily the eclipses and random comets which we hang on our supposedly ignorant ancestors, rather they were the fireball flux surges whose nature remains as problematical for us as it was for them.
2. COMETS BY JOVE - A WARNING TO THE PRESIDENT'S MEN?
The unprecedented events on Jupiter during the summer of 1994 served to quicken the pace of developments in space. There was clearly something awesome in those predicted encounters of comet pieces with a planet which, had they occurred on Earth, would have resulted in a mass extinction. Very few could have failed to be moved by the prospect that future comet splittings might suddenly produce a similar impact hazard heading towards the Earth which mankind would be unable to avoid.
Inevitably, so it seemed, there was an added sense of common purpose to mankind's continuing watch on space. Such a sense of purpose in 'spacewatching' has frequently arisen in the past usually in a national context, and can he traced back to the very dawn of civilization: one thinks for example of the Sumerians (e.g. Frankfort et al., 1946), then later the Chinese (e.g. Schafer, 1977) and eventually perhaps the Aztecs (e.g. Sejourne, 1957), all of whom are known to have confronted the cosmos at different epochs for many generations with the same air of realism and foreboding.
Nowadays, of course, it is the American nation which bears the brunt of this watch and ensures that the responsibility is taken seriously. As recently as 1990 for example, Congress was pressing space agencies for an assessment of the impact risk to civilization. Congress however did not count on inertia within the scientific corpus giving rise to a characteristically sanguine interpretation of the brief. Thus there is a kind of mindset afflicting those who put order into the cosmos which also causes them to resent disorderly intrusions. Disintegrating comets which suddenly appear in the Solar System are of this nature and the reaction which is by way of turning a blind eye to unwelcome visitations can often mean that the common purpose is blunted. Those who would have turned us away from Galileo's telescope so many centuries ago were still able to turn us away from the unprecedented events on Jupiter during the summer of 1994!
Even as the comet pieces arrived though there was movement within the corridors of power to revitalize the body scientific. Thus the US Congress or, more specifically, its House Committee on Science, Space and Technology was evidently impelled to recommend an immediate stepping up of the Spaceguard program - NASA's pipeline project to assess the asteroid and comet threat to civilisation from space.
Reflecting what appeared to be a public pressure on dilatory space guardians the Committee's Chairman Representative George Brown, was to comment to the New York Times (Aug 1, 1994) that "you're going to see this thing take off like a rocket. It's going to be easy to sell in Congress".
Later, of course, the excitement receded and we reached a period of more measured reflection. There was then a question mark over NASA's failure to anticipate cometary splittings and a degree of concern whether this organisation's activities should have been oriented so exclusively to single body events. The latter in fact are rare; and to the extent that the currently nominated space guardians may also have had it in mind to exploit asteroids and comets as the largest accessible resource in space, one could readily suppose that the more frequent hazard due to the more numerous debris from cometary splittings had been seriously overlooked.
However, in making its more measured judgement, it was more or less inevitable that the House Committee would reckon in terms of balancing all of NASA's previously approved and currently perceived requirements. This essentially meant a watering down of the more immediate celestial threat. The question for Congress still remained therefore whether Spaceguard provided everything that the American public expected.
To understand what is going on here, we need to examine some of the Spaceguard programme (Morrison, 1992) details which have been tucked away in the fine print. Thus the Spaceguard Catalogue, when it is completed, will be over 90% asteroids. But some of these asteroids will be dormant or dead comets - and herein lies the catch. For, during the next century, the probability of the pure asteroid threat to civilization being realized is only about one in a thousand. Whereas the probability of the dead, dormant or active comet threat being realized during the same period - due to cometary splitting - is more in the region of certainty.
The asteroid threat by itself therefore is not of the kind that will give Congressmen sleepless nights; the comet threat on the other hand could well be of the kind that is a cause of public concern.
The point is that there are crucial physical differences between pure asteroids and comets which are a significant factor when we calculate their respective threats.
Basically, for the asteroid threat to be realised, we need a direct hit on our planet - truly a rare event. For the comet threat to be realised however, given that these objects break up and the debris sprays out around the parent orbit, we need only a relatively close encounter to have some fraction of the original material impact the Earth - a reduced input of mass evidently but impacts nevertheless which are altogether more frequent and by no means negligible in their effect.
The Catalogue then is not the only problem; we need also to consider when comets are going to fragment. Indeed with the benefit of hindsight on the comets by Jove, the situation for the President is now very clear. He may be provided with a map of the world but that does not tell him where and when the next Rwanda is going to arise. Likewise, he may be provided with a catalogue of asteroids and comets in their various orbits but that does not tell him where and when the next earthbound Shoemaker-Levy is going to arise!
There is a very definite sense therefore in which the current NASA plan is deficient in relation to the civilization hazard from space and lulls the American public into a false sense of security. One has to recognize of course that astronomers are trained not to cry wolf in the night and it is a matter of normal common sense that the paymaster is most comfortable if the catalogue on offer appears to provide enough warning whilst keeping down the cost. Unfortunately, this kind of bashful timidity and mutual backscratching amongst scientists and moneyspinners currently results in our not having a policy to deal with the most probable hazard from space, a situation which seems to provide the American public with rather less than it expects!
For what then should we prepare?
First, of course, there is no point in denying the usefulness of Spaceguard for the ferocity of the asteroid threat, when it is realised, is not in doubt - mankind could well be extinguished. It does not follow however that the more frequent cometary threat can therefore be ignored on account of the greater modesty of its effects - for, in this case, it is also worth noting that mankind could well not be extinguished!
Thus governments are not merely confronted with a general fear of global extinction but with that of localized extinctions, or holocausts, as well. In other words, we really need to know about the troubles that arise during the anticipation and the aftermath of any multimegaton events that occur in the wake of a fractured comet (see Section 3.3). These, as we have noted, occur at intervals of a couple of centuries or so and at the very least now we have to consider the possibility of one or more population wipe-outs or Chernobyl-like disasters on the urban to large nation scale, or a mini-ice age of global proportions.
Less frequently, at intervals of a millennium or so, we can expect the incidence of such disasters to be substantially increased.
Obviously these are tantalizing rates for heads of state who feel that there may be a risk and that to be forewarned is to be forearmed. But invariably, so it appears, the general tendency is to discount the risk with the result that civilization and society are usually unprepared. Thus, just as fifteenth and seventeenth century European society apparently broke down in the presence of newly fragmented comets, so it appears the emerging global village of our present epoch could well break down in the presence of yet another newly fragmented comet.
What matters here is the extent to which society is convinced by contemporary 'experts' that the danger is real.
For example, the breakdowns during the centuries preceding Reformation and Enlightenment occurred as apparent historical certainties concerning the incidence of 'providences' or 'blazing stars' were newly translated into the vernacular (i.e. from the Books of Daniel and Revelation) and propagated uncensored from the pulpit (e.g. Thomas, 1971). In the future, it is more likely to be the deeper historical certainties which are gained from the latest scientific understandings of our astronomical past and which are then propagated uncensored through a modern communications network of even greater power!
The problem always with these hazards, like the occasional snowstorm over England, is their rarity - the fact that pragmatic authorities will at present only handle them in accordance with circumstances, as they arise. This wholly reactive mode means that the comet threat is never going to be taken seriously until such post-detection panic as will occur due to the incoming cometary debris is fully recognized for what it may very well be.
Paradoxically though, the more skilled and informed the civilization, the sooner in general the reality is appreciated and the greater the opportunity there is for the subordinate and more reliant elements of society to become seriously unsettled.
Mankind is not extinguished of course and many parts of the globe may even escape physical blemish, but it is a matter of general experience, overlooked apparently by the American scientific community, that sustained public panic is a very effective leveller of civilizations, even to the extent that many societies are capable of becoming seriously unhinged.
Thus it is not obvious that even the most advanced societies will avoid social chaos without the most careful preparation in advance to counter the illusion of 'last times'.
In the past, it has always fallen to individual nations and their administrations to attempt to deal with the illusion through counter-propaganda. In the future it seems more likely that it will fall to the global village to attempt to deal with the illusion through counter-propaganda and it is by no means clear that any preparations are yet in place.
History is more informative in respect of this problem than many might suppose. Even the word 'revolution' for example, in its more general usage today, seems to have acquired its meaning in the past through the recognized effects of the orbiting debris of a comet! Thus it is generally accepted that its connotation signifying social upheaval was a sixteenth and seventeenth century development arising out of its earlier (Copernican) connotation signifying physical circulation. However it is perhaps not so widely appreciated that the witchhunts and political upheavals of the seventeenth century in England - which modern authorities sometimes look upon as archetypal in respect of the circumstances which generally give rise to revolution - were directly attributed by contemporaries to the unsettling effects of an (observed) celestial circulation: these contemporaries speak of celestial signs which were deliveries of "God's providence" and which were evidently mediated by "God's revolution".
Indeed these types of attribution, once the signs had passed, were very soon to mean that the blazing stars were scorned by the learned: Bishop Sprat (ed. Cope and Jones, 1959) in his History of the Royal Society speaks of a peculiar weakness on the part of his countrymen, to supposed prodigies and providences, which was now no longer to be encouraged. Thus the demise of the London Society of Astrologers broadly coincided with the transition from Interregnum to Restoration and the emergence of the Royal Society of London; and, it is apparent, also to a period of intense scientific censorship (Hill, 1975).
It is well known for example that very few of Newton's historical researches into catastrophism and the role of comets and fireballs were published in his time with the result that astronomical science, and hence natural philosophy, tended thereafter to assume uniformitarian (i.e. non-catastrophic) characteristics.
Nevertheless, we can now tell from past astronomical records when civilization was apparently unhinged by threatening signs in the sky (see Section 4.1) and it is clear that the cometary threat, on the point of being realised, is far from being a trivial occasion - our ancestors were not joking, it seems, when they saw disintegrating comets as "a warning to kings".
Even the President's men therefore may need a degree of authority and understanding in the face of incoming cometary material such as the age of 'enlightenment' has so far failed to provide.
The point here, of course, is that modern society, like its founding fathers, chooses still to ridicule the cometary threat. Ridicule was necessary perhaps as the means to a particular end - the restoration of civil order - in the wake of a previous cometary fracture and its chaotic aftermath. But this end was essentially realized and it may well be now that western civilization requires an attitude to these events in future which is a good deal more subtle than the official American approach currently allows.
There are new understandings of our environment, then, to be taken on board. Thus the last millennium or so tells clearly enough of a Western European civilization which eventually took over the New World but which was also oppressed by cosmic inputs considerably more than most of us have been given to believe.
It also tells of a civilization driven to such extremes by these external pressures that the subordinate and more reliable elements of society could only seek their freedom by aimless uprising while others with the means and some sense of purpose sought their freedom by escaping their environment.
Viewed negatively on the one hand, the cosmic inputs are an unbearable overpressure which society characteristically fails to resist and which has a roughly one in four human lifetime chance of recurring; viewed positively on the other hand, the same inputs are the cause of 'punctuational crises' which are also the principal opportunity for civilization to step out of its mold.
Each new search for civil order in the wake of oppression and chaos has proved to be an added spur to civilization's advance and a likely paradigm shift.
Something of the right note here may be struck by Trevor-Roper (1987) when he tells us, albeit without any reference to an increased fireball flux, how:
... in Germany, the ideas of Paracelsus were combined with [ ] metaphysical speculations: how there too a new era of enlightenment was expected to follow the return of a chemical prophet, 'Elias Artista', who would make all things new; and how the beginnings of the Thirty Years War were seen as the 'shakings' which would precede the fall of Antichrist and, as it were, light the fuse for the great eschatological explosion. That did not work out according to plan; but in 1640, when a new series of 'shakings' began in England, hope was rekindled. The English Puritan Revolution, which we see as a purely national struggle, appeared to many European Protestants as an event of international significance, the second stage of the Bohemian Revolution of 1618. So messianic expectations were renewed and central European enthusiasts looked, and sometimes came, to an England which, they hoped, having reclaimed its historic role, would realise the Bohemian promise of enlightenment as the prelude to the millennium.Trevor-Roper goes on to point out that many of the time were indeed responding to the same intellectual challenge. For at one extreme of the Reformation-Counter Reformation debate we find an anticipated messianic return: that of the likes of 'Elias Artista', essentially the late medieval rendering of neo-Platonism's cosmic demi-urge, for which such as Bruno would go to the stake; whereas at the other extreme of the debate, we find a desire for permanence and stability: an establishment set against any Pyrrhonist (catastrophist) perception and determined at all costs to preserve for Christendom its basic (Aristotelian) cosmic theme. It seems though that "none of them produced a final answer. But in the convulsion of their time the old compromise was destroyed, or at least emptied of its real content, and all of them, out of its relics, incidentally contributed something to the succeeding age..."
In other words, there is a perspective on the historical process which now tells us that the Renaissance needed its Inquisition to preserve the perceived cosmic order and suppress the omens which the astrological view of nature nevertheless allowed.
Likewise the English Enlightenment needed its official ridicule to counter the cometary threat which the scientific view of nature essentially allowed.
But now, with space tentatively explored, the public has learned that neither the Inquisition nor official ridicule will impede future cosmic inputs.
The US Congress no doubt will decide how these inputs will be challenged - but if realism is to prevail, and ridicule no longer works, the new understandings of our cosmic environment will impose their new discipline on society as well!
In short, society still has to come to terms with the seriousness and comparative urgency of the cosmic threat and to recognise the need for an enabling contract between mankind and its leaders which guarantees both the discipline and the challenge.
If history is a guide, the necessity of preventative action will of course be ignored! Thus the situation is by no means new and has occurred many times before (Cohn, 1957; 1993). Recent studies have probably given us a pretty good idea how societies respond in extreme circumstances and, to encapsulate these, we can do worse than go back to the beginnings of western civilization itself. For it is here that we find how the Roman Empire became aware of and confronted the cosmic threat during its fourth and fifth century decline, essentially realising that neither Stoics nor Epicureans had any answer to the intense public anxiety which then emerged.
Thus, it came about, so it now appears, that a whole subjugated people extending from the Eastern Mediterranean to Western Europe rather suddenly succumbed to the blandishments of a Christian community (Brown, 1971) which promulgated the notion that one could escape the torment of "demons" by electing to "belong" to an everlasting (cosmic) community of "saints". By associating these demons and saints with members of the human population as well as with clashing celestial armies and hence with an observed circulation in the sky (Section 3.5), it seems that this Christian notion had its basis in verifiable cosmic facts which had been endorsed by neo-Platonists such as Proclus and Augustine.
The point here is that a basic classical view of the Universe, originating with the pre-Socratics and given its most perfect expression in Plato's Timaeus, reached its zenith with the neo-Platonists. Plato and the neo-Platonists described how a divine agency, the demi-urge, had constructed the main features of the visible heavens: a planetary system in the plane of the ecliptic which probably included the Earth in orbit around the Sun and another divine circulation inclined to the ecliptic which not only intersected the path of the Earth but supposedly reached out beyond the sphere of stars. It was this circulation apparently, with the characteristics of elliptical motion and precessing nodes, which returned to the Earth at long intervals with catastrophic consequences. However the more cultivated and sophisticated elements of Roman society were not at first prepared to go along with this expectation. Rather both secular and ecclesiastical opinion discounted the demi-urge and held to an (Aristotelian) perception of the environment which presupposed some degree of permanence and stability in the cosmos at hand.
Before enduring the Dark Age however, the Roman Empire was to be horrified by the imprint of "deserted areas" which contemporary opinion closely associated with the imminent arrival of world-end (Esmonde Cleary, 1989). Such devastation now seems to have the character of super-Tunguska events; and, indeed, one such putative event in England, as the particular country in question was to become, was subsequently attributed to "the fire of righteous vengeance".
While enlightened scholarship has for long been in the habit of ridiculing the implications of such phraseology, several historians have recently gone out of their way to emphasise the essentially dramatic nature of this event and its consequences. These, realistically interpreted, appear greatly to exceed those expected with a mere exploratory invasion by a boatload of (Anglo)Saxon brigands as enlightened scholarship would normally have it (e.g. Myres, 1986 cf. Clube, 1992).
In other words, the possibility of severe cosmic events is no longer in principle denied and it may therefore be hardly surprising that ideas put about by neo-Platonists during the fourth and fifth centuries should have been in the ascendancy.
During the sixth century Justinian period, indeed, the social upheaval and environmental calamities appeared to be scaling new heights and it is not without significance that a firm administration then closed down the Platonist Academy in Athens and thereby effectively created a subversive undercurrent of astronomical knowledge which was to remain at the heart of Christendom's intellectual discord for at least another fifteen hundred years (e.g. Lindberg, 1992)!
Thus it was in the aftermath of catastrophe, during the latter half of the Justinian administration, that (Byzantine) Christendom securely embraced Aristotelian doctrine for the first time, to be followed a century later along this track by (Muslim, non-Arab) Islam (e.g. Brown, 1971). Subsequently, another five centuries were to pass before Aristotelian doctrine was also embraced by Western European Christendom by which time the latter came to be seen as having experienced an intellectual dark age of some seven or eight centuries.
Now, as we acquire an improved understanding of the relevant cosmic facts (Section 3), it seems that the crucial scientific advances later engineered by Kepler, Bruno, Galileo and Newton provided us with the basic framework which eventually led to the Space Age revelations culminating with the split comet by Jove and which will in due course mark the astronomical notions of the neo-Platonists as ones which should never have been set aside!
3. EVOLUTION, PUNCTUATIONAL CRISES AND THE THREAT TO CIVILIZATION
3.1. Punctuated Equilibrium
The idea that evolution on Earth proceeds at a uniform pace towards some undefined state of perfection in the remote future has given way in recent years to one involving successive states of "punctuated equilibrium" (Gould and Eldredge, 1977). Thus, in keeping with evolution's supposedly progressive nature, it is assumed that both the environment and the distribution of living species remain in successive uniformitarian states for characteristically long periods of time and that these also begin and end with much briefer periods when both the environment and the distribution of species undergo very rapid upheaval.
There is an implicit assumption here, of course, that the upheavals are then necessarily progressive whereas in practice the condition of the environment along with the distribution and character of species, treated broadly as a geophysical/biophysical cum geochemical/biochemical state, is probably most simply perceived as experiencing a catastrophic recession followed by a catastrophic advance. An 'advance' as such does not then have any absolute significance but is merely said to be so on account of its retrospective accord with the direction taken to reach the following equilibrium state.
Under these circumstances, it is to be expected that we are dealing with uniformitarian states which are broadly regressive rather than progressive - that is, tending towards some statistically average state rather than deviating from it - and punctuational states which broadly comprise a recession forced by cometary input and an arguably deterministic advance forced by the random disequilibrium so inflicted.
The significance of cometary inputs is that they allow both biophysical and biochemical effects i.e. cosmic insertions reaching different levels in the atmosphere which are capable of generating either catastrophic explosions or catastrophic loading of the atmosphere with particulate material (dust) bearing biologically active chemicals. If this understanding is generally correct then it is clear that the Darwinian perspective on evolution, suggestive of an intrinsic directional quality in natural selection, is no longer supported and that we should look to the random yet (in principle) predictable cosmic inputs and their induced chaos as the fundamental controlling factor determining the course of evolution. Natural selection, on this account, is but a counterbalancing process tending to preserve equilibrium after a disturbance and is essentially mundane!
With the advances during recent years in our knowledge of the astronomical environment, there has been a tendency to suppose these 'punctuations' might reasonably be associated with isolated 'impact crises' due to encounters with single bodies in Earth-crossing orbits. While, as a matter of definition, it might be considered arguable exactly what level of crisis qualifies as a punctuation in the terrestrial record, one can perhaps assume, as a matter of principle, that only those impinging bodies capable of significantly influencing the whole globe for a brief period should be considered.
It is on just such a basis apparently that single near-Earth objects (NEOs) greater than a kilometre or so in size have come to be the new focus of attention so far as terrestrial evolution is concerned. Indeed, through this rather simplistic perception, recognizing also that the human species is a global phenomenon, the notion that km-plus NEOs are the most serious threat to civilization has recently gained some impetus (e.g. Chapman and Morrison, 1994).
Civilization however, is not something that we necessarily associate with mankind as a whole; rather we envisage several different 'civilizations' which occupy different parts of the globe at any one time; and many 'civilizations' during the course of history which have flowered and foundered (e.g. Spengler, 1932; Toynbee 1945).
Civilization, in fact, treated as a modest evolutionary aspect of the human species, not only appears to be associated with distinct ethnographic and demographic qualities of mankind but tends to be regarded as a local rather than a global phenomenon; in which case, the theory of punctuated equilibrium would seem to require that single or multiple sub-km NEOs capable of depositing massive dust veils or inducing super-Tunguska events represent the commonest and hence most likely serious threat to an individual civilization.
At the same time, it may have to be admitted that the modern trend towards the rapid 'globalization' of civilization and its other qualities is perhaps rendering these characteristics more synonymous with mankind as a whole than was formerly accepted. But however globalized and/or superficial the evolutionary characteristics of civilization may be, it is clear that this more qualified understanding of punctuated equilibrium allows the possibility of localized evolution of a dominant strain in association with a localized cosmic input such as a super-Tunguska event and of the global extension of this dominant strain in due course. Such a turn of events is not excluded apparently by the present condition of the human species and its evolution from a single African location during the past million years or so.
It follows from considerations such as these that the evolution of civilization may be no more than a simple extension of the evolution of biological species. Thus we are accustomed to the idea of punctuated equilibrium in biological evolution reflecting isolated encounters with the single km-plus (meteoritic) asteroids which have undergone a prior series of orbital deflections since leaving the asteroid belt. But we are less familiar perhaps with the idea of 'punctuational crises' affecting biological evolution and the advance of civilization, these being due to the more sustained bombardments by fragmentation debris when active, dormant or dead comets which have deviated from the most likely source of comets (the Oort cloud, say) undergo significant splitting in Earth-crossing orbits. Such orbital debris encountering the Earth's atmosphere is evidently capable of introducing both high-level dust and low-level explosions, depending on its mass and cohesive strength, and it follows that punctuational crises are comprised of global coolings and super-Tunguska events together with a generally enhanced fireball flux.
Taken as a whole and in conjunction with a given planetary target (e.g. Jupiter, Earth etc.), the response function to the bombardments is inevitably complex. Nevertheless, we can broadly expect that the strength of a punctuational crisis will vary as the progenitor comet mass, the inverse (velocity) dispersion of its debris and the inverse (time) delay since fragmentation. In which case the encounter between Comet Shoemaker-Levy 9 (P/SL-9) and Jupiter may be taken as representing an extreme punctuational crisis where the dispersion and delay were small.
An extreme punctuational crisis affecting our planet and involving multiple comet fragments may also be envisaged for such evolutionary events as the mass extinction of species, for example the KT event 65 Myr ago. Such rare events however are at one end of the evolutionary scale: at the other end of the scale, we deal with the lesser but more frequent crises affecting the Earth which have disturbed civilization several times during recent millennia - these may have had smaller inverse dispersions and smaller inverse delays but are no less important for that!
Indeed, such crises can now be regarded as the smallest units of our overall catastrophic experience; and to place them in perspective, we need to consider the catastrophic record as a whole. This leads us to recognise the relatively sudden flowering and foundering of civilizations during interglacials as the principal signatures of punctuational crises that arise as the corresponding debris of a giant comet in a short-period, Earth-crossing orbit passes through the final stages (splittings) of its evolution and decline.
Thus we envisage a situation where the particular mass distribution of comets settling in Earth-crossing orbits includes occasional very massive candidates up to a few hundred kilometres in size for it is the evolution of these very massive comets which seems to be dominant in the terrestrial record. For example, the contemporary millennia can now be seen in the context of successive myriads of years (104 - 105 yr) in which the global coolings either persist (a glacial period under the control of a disintegrating giant comet) or remain largely in abeyance (an interglacial period under the control of a largely dispersed giant comet).
The interwoven glacial-interglacial structure which is then imprinted from time to time on the terrestrial record and corresponds to ice ages some - 106 - 108 yr in duration is then readily enough understood in terms of Oort cloud perturbations which characteristically last for such periods of time and of a resulting overall flux of giant comets settling in short-period, Earth-crossing orbits which is apparently not so very different from that currently observed (Bailey et al., 1994).
The evidence, in other words, seems to indicate that it is the cometary flux which dominates the general course of biological evolution, the general course of the global climate and the general course of the civilization to which we belong.
Such pre-eminence in terrestrial affairs accorded to comets remains, of course, a very uncomfortable proposition for much of twentieth century civilization and science.
3.2. Cumulative record of catastrophes
Our knowledge of the impactor flux reflecting the general state of the inner Solar System environment is largely based on the cumulative counts of impact craters formed on lunar mares since the end of the heavy bombardment phase. As a result, the diameter-flux relationship for the largest impactors arriving at the Earth is commonly represented by a simple uniformitarian power law:
Φ(D) = k D -α, 1 <= D <= 102.5 km
Continuity considerations require that this relationship is applicable to the potential impactors in Earth-crossing orbits which are currently observed. Amongst these we must include the Earth-crossers having intermediate and long period orbits which reach out beyond Jupiter towards the Oort cloud. However, their particular direct influence, in comparison with that of the Earth-crossers in sub-Jovian space, which principally derive from short-period asteroidal (mainbelt) and short-period cometary (Jupiter family) reservoirs, is so small that they can reasonably be neglected for the purposes of the present discussion.
It follows that the asteroidal and cometary bodies of interest in Earth-crossing orbits, comprising mostly their sub-asteroidal and sub-cometary fragmentation products which encounter the Earth (meteorites and meteoroids, respectively), are essentially those surviving in two sub-Jovian orbital regimes. These have 'dynamical lifetimes' of ~ 108 yr and ~ 106 yr, respectively, depending on the eccentricity of their progenitor injection orbits - below and above 0.5, say. Thus, so far as these short-period reservoirs dominating the terrestrial influx are concerned, it is basically orbital eccentricity which determines the likelihood of a grazing encounter with a major celestial body such as would tend to remove these smaller bodies from inner Solar System space, and it is now recognized that the terrestrial planets are most likely to play this role when e < 0.5 (Wetherill, 1988; 1991) while the Sun and Jupiter are most likely to play this role when e > 0.5 (Froeschle et al., 1995).
Transitions between these orbital regimes are not of course excluded, so their unique categorization in terms of asteroids and comets, respectively, cannot be absolutely relied upon. Nevertheless it is broadly the case that meteorites and meteoroids have differing (top-heavy) mass distributions and fragmentation spectra as well as differing physical and dynamical lifetimes with the result that cometary-meteoroidal impactors, unlike their asteroidal-meteoritic counterparts, cannot be expected to achieve a fully relaxed spatial distribution with respect to solar ecliptic longitude and latitude. In other words, the minor body flux of cometary origin normally takes a period of time to become fully sporadic which is significantly in excess of its physical survival time. The result, as a consequence of hierarchical disintegration, is that the sporadic distribution is only present at higher (D > 1 km) and lower (D < 10-3km) mass levels while the uniformitarian law undergoes an observed steepening in the intermediate range, such that
Φ(D) = k D -β, 10 -3 <= D <= 1 km
where β > α (Shoemaker, 1983). The relationships (1) and (2) are based on the lunar cratering record but we can also determine the diameter-flux relationship for smaller impactors currently arriving at the Earth, as derived from the bodies in space which are observed either in situ or penetrating the atmosphere (Rabinowitz et at, 1993; Ceplecha, 1992; Tagliaferri et al., 1994), whence it turns out that
Φ(D) = 10 - 100 X Φ(D), D<= 10-2 km
This may evidently be understood as a temporary condition, also in accordance with the observational steepening, and has for some while been attributed, as we have seen, to a still disintegrating, very large comet (Kresak, 1981) of the kind now believed to be present in the inner Solar System from time to time (Δ t ~ 105 yr; Bailey et al., 1994).
The steepening thus straightforwardly implies that the commonest 'evolutionary events' on Earth relating to the low mass end of the Solar System minor body population (i.e. 10-1 < D < 1 km) are due to correlated encounters with the hierarchically disintegrated products of the debris from successive giant comets.
The appeal to a contemporary giant comet does of course represent a general departure from uniformitarianism on timescales 10E4 - 10E6 yr, the typical interval between giant comets settling in sub-Jovian space. The cumulative record of catastrophes thus leaves open the question whether there are additional modulations of the terrestrial record on timescales < and > 10E4 - 10E6 yr which would also be indicative of a predominantly cometary influence on terrestrial evolution.
3.3. Punctuational crises
To many investigators, the idea that isolated impact crises rising above some global threshold are the only astronomical influence we need consider when dealing with evolutionary processes in geology and biology is simply not compatible with the evident complexity of the terrestrial record (Hallam, 1989). Thus it is widely recognized that long-term climatic and other factors must also be involved and it has been known for seventy years that the terrestrial record is marked by periodic and stochastic modulations on timescales between 106 and 109 yr indicative of a Galactic driving force (e.g. Holmes, 1927). Indeed it is for these reasons that many investigators in recent years have given greater credence to a cometary (Oort cloud) rather than a (Mainbelt) asteroidal source of 'punctuational crises' (see Section 3.4).
The role model for punctuations then is not the ostensibly narrow epoch associated with a random (km-plus) asteroid; rather it is the considerably broader epoch associated with the relatively short-lived, orbitally correlated, disintegration products of a not-so-random (km-plus) comet.
There are several points to be made here. First, these considerably broader epochs may be characterized by one or more global coolings and/or super-Tunguska events occurring as a prelude to or in association with an enhanced fireball flux: events of this kind are to be expected as a consequence of high-level dust insertions and low-level multimegaton explosions such as may be produced, depending on their cohesive strength, by sub-cometary masses of about 0.1-1 km in size. Secondly, both the cometary mass function (which is top-heavy) and the tendency of comets to undergo rapid disintegration determine that a high degree of coherence may be present in the incidence of sub-km and km-plus comets on Earth at any one time.
Cometary material in general is capable of being active, dormant or dead and for inner Solar System material of this kind whose distribution does not evolve and which has broadly unchanging orbital and constitutional characteristics, it would certainly be expected that the frequency of punctuational crises (as now defined) at any epoch would also be broadly unchanging and reflective of the integrated "minor body" mass "in residence".
With a variable mass content however, such as arises with the top-heavy mass distribution of comets settling randomly in inner Solar System space, the pattern of punctuational crises may be expected to take on the general character of a glacial-interglacial with both periodic and random groups of events on timescales < 105 - 106 yr reflecting the orbital and fragmentation history of a particular giant comet (e.g. Asher and Clube, 1993).
In other words, as a consequence of the cometary mass distribution, we envisage punctuational crises which are themselves hierarchically nested in the overall manner of glacial-interglacials, each lasting in effect for the duration of ~ 104-10 orbits in accordance with the size of the parent comet within the nested hierarchy i.e. from a few hundred to a few kilometres in size. It is thus in the general nature of the intermittently top-heavy population of comets deposited in inner Solar System space that our planet is bound to experience glacials and interglacials, the latter being themselves interspersed with global coolings of shorter duration which are in association with super-Tunguska events and sustained enhancements of the fireball flux. Several facts then come together to inform us as to the likely nature of the current environment:
a)the disintegration products of comets (meteoroids) currently incident upon the Earth outweigh the disintegration products of asteroids (meteorites) by one or two orders of magnitude (e.g. Tagliaferri et al., loc cit)The evidence indeed points to the contemporary environment having been dominated by an evolved giant comet and it is clear from the dynamical behaviour of other such bodies like Chiron further out in the Solar System (Bailey et al., 1994) that these extended inputs are currently recurring at random intervals ~ 10E5 yr. We may conclude that it is the cometary punctuational crises which are dominant on timescales < 10E6 yr.
b)the sporadic flux of meteoroids in inner Solar System space is dominated by a single, very broad, elliptical torus (e.g. Stohl, 1983) suggestive of a recently disintegrated, very large, Taurid comet (e.g. Clube, 1987; Steel et al., 1994).
c) the current interglacial follows on a recent glacial at ~ 20,000 ± 10,000 BP broadly suggestive of a recently disintegrated, very large comet and is itself interspersed with sustained enhancements of the fireball flux known on several occasions to be correlated with severe global coolings (Asher and Clube, 1993; Clube, 1994; Baillie, 1994).
d) dynamical studies (e.g. Asher et al., 1993) are consistent (within a factor ~2) with a ~ 20,000 yr hierarchically disintegrated Taurid comet characterised by relative speeds of separation ~ 1 kms-1 such as are plausibly associated with differential energetic outflows (jets) from cometary fragments, the fragmentation apparently arising through tidal splitting during close encounters with terrestrial planets, through solar irradiative effects and through intrusive high velocity impacts.
3.4. The Holmes cycle
Unfortunately the cratering record is not yet well enough resolved to describe with certainty any of its possible modulations on timescales ~ 10E6 ~ 10E9 yr (Grieve, 1989). Nevertheless to the extent that geological and biological signatures may be understood as proxy-signatures for punctuational crises, there is good evidence for a late Phanerozoic cycle of 26.3 Myr (Rampino and Caldeira, 1992) broadly confirming previous determinations based on the extinction cycle alone (Raup and Sepkoski, 1984 cf. Holmes, 1927). It also appears that the most recent maximum phase of this cycle coincides with a mid-Miocene peak ~13-14 Myr BP from which the early Pleistocene peak ~ 2 Myr BP introducing the Sun's latest Galactic plane passage is clearly distinguished.
On the assumption that geomagnetic reversal events in particular provide a reasonably undistorted record of the major glacials due to large (inner Solar System) comets, the 26.3 Myr cycle is rather clearly interleaved with another cycle of the same period but lower amplitude; the two together being then uniquely associated with variations of the continuous and stochastic components of the Galactic 'dark matter' gravitational field acting upon the Oort cometary cloud, expected as a consequence of the Sun's vertical oscillation about the Galactic plane (Clube and Napier, 1996 cf. Matese et al., 1995). Quite apart from the not- unimportant implications for dark matter and its nature, these cycles are in fact strong prima facie evidence of a very persistent influence on terrestrial affairs due to very large comets originating from the Oort cloud and we may conclude that cometary punctuational crises are dominant on timescales > as well as < 10E6 yr.
It is perhaps an interesting aside on the theory of punctuational crises that the latest two peaks of the compound Holmes cycle, correlating with two broad spasms of increased terrestrial activity, seem, respectively, to be associated with the first appearance of hominids and with the eventual emergence of homo sapiens while the particular activity that goes with the latest, very large, comet seems remarkably well correlated with mankind's bare survival under stringent circumstances at the end of the Pleistocene during a global climatic recession (i.e. the most recent glacial at ~ 20,000±-10,000 BP) and the subsequent rise of civilization during the Holocene. Civilization in other words is merely the latest random facet of a continuing galacto-terrestrial interaction expressed through the action of comets on the resident gene pool!
3.5. Spenglerian model of civilization
To recapitulate then: by studying the longer term cycles in the terrestrial record and some of the details in civilization's advance, we have now come to recognize the fundamental role of the Galaxy and comets in terrestrial affairs. This role inevitably causes us to give particular attention to very large variations in the impact catastrophe rate. Indeed we can now recognize a broad category of evolutionary events described here as punctuational crises.
Punctuational crises can have an elaborate structure in practice but are no different, in principle, from the recent P/SL-9 encounter with Jupiter. Thus the differences in general are merely those that arise due to the differences in the target, the fragmentation agency and the degree of orbital correlation.
So far as civilization is concerned, the aspect of the matter which gives punctuational crises their special distinction over isolated impact crises is their capacity for inducing social destabilization as a result of fragmentation and the perceived statistical inevitability of encounters with the Earth.
In the case of P/SL-9, since another planetary target was involved, mankind was able to take a detached view of the subsequent proceedings. In the case of an Earth encounter however, since the enhanced fireball flux is indicative of its more massive correlates, the view can never be detached. Such enhancements have in fact occurred frequently in the past - ostensibly in association with the Taurid stream (Clube, 1994: see also Fig. 1) - and the next occurrence, as we have seen, has a roughly one in four human lifetime chance.
Historically, inasmuch as these enhancements have frequently been interpreted as indicating the imminence of 'last times', predisposing even the most advanced societies to break up and lose control, the corrective response has usually depended on the disposition of society as it experienced punctuational crisis.
A study of past civilizations appears to indicate differing responses depending on whether society is subject to theocratic or secular control, the crucial factor being the ability of the administration to maintain basic freedoms whilst avoiding any descent into social chaos.
The situation is not satisfactory for it seems that theocratic states will tend to censor any perceived deviation from the perceived celestial norm (whatever form this takes) while secular states will merely seek to trivialize any threat posed by comets.
As we have already noted, neither censorship nor trivialization is likely to be effective in future and it is not clear therefore that civilization is currently well placed to handle the next punctuational crisis. Indeed, any benefit accruing to civilization through the uncritical endorsement of the Spaceguard programme (Chapman and Morrison, 1994) does little at present to alleviate the pressures due to the next punctuational crisis.
Ultimately, there is a problem here because we still belong to a period of human history in which the Darwinian or progressive view of our past is so securely entrenched that we set aside contemporary and near-contemporary proponents of any alternative view. There is no lack of concern of course as to the fate of civilization but academe still requires a supposedly uniformitarian terrestrial environment and a supposedly innate tendency on the part of the human species to evolve through natural selection towards some perfectly civilized state. It seems in fact that the currently adopted scientific paradigm requires us to take a severely anthropocentric view of the environment, virtually guaranteeing catastrophes will not occur.
Insofar as we pay any respect to the environment, we are encouraged to believe that mankind has it essentially under control. That is, we assume as a matter of principle that the environment can be preserved in a uniformitarian state. Accordingly we no longer pay much attention to any teleological or eschatological view of history (Butterfield, 1981; Bultmann, 1957) and have very little patience with historians such as Spengler (1932) or Toynbee (1945) who have seen in civilization a necessarily ephemeral characteristic of the human species. The former indeed, in his once renowned The Decline of the West, saw only a tendency for the various cultures and their corresponding civilizations to stand alone in space and time in a demonstrably self-contained way. This was not to propose that the principal paradigms of a culture are not part of a longer term evolutionary trend but to indicate that the paradigms which prevail across an interface between successive cultures in time are characterized by a process of random selection and a degree of rapid remoulding. Each such culture-civilization so pre-formed did admittedly evolve but always in a repeated and characteristic manner which depended not so much on the environment or the state of technology but on an inner combination of perceptions borne and successfully conveyed to succeeding generations by a dominant founding group. Thus there would be a frenzied 'spring' and a staid 'autumn', periods of growing dominance and settled equilibrium, respectively, but always such civilizations would begin and end with periods of trauma which marked them off in time. Spengler described these periods of trauma as "psuedomorphic" rather than "punctuational", seeming to imply nevertheless some kind of mainspring which he described as "cosmic". The nature of the cosmic mainspring has not been evaluated, as it happens, but the model was applied to world history, as it was known, with some evident success - albeit with implications which, whilst they were not accepted into the mainstream, have never been precisely refuted.
Foremost amongst these implications was the recognition of a significant pseudomorphosis during the seventh century BC (cf Starr, 1961) associated with the emergence of three major civilizations, those of China, India and the Mediterranean, culturally aligned with Taoism, Buddhism and Stoicism, respectively. Of particular significance to the long term development of these civilizations, so Spengler inferred, was the emergence and decline during the subsequent millennium, of the so-called Magian culture centred on and around Babylon. This he evidently pictured as the main intellectual conduit through which the basic knowledge of an underlying cosmic influence, as it was perceived in earlier neighbouring civilizations such as the Persian, the Mesopotamian, the Egyptian and the Aegean, came to be harmonized and perpetuated. Thus Spengler was able to describe how the domain of Christendom became the principal bearer of an original, predominantly Magian, culture which also underwent significant metamorphosis in the hands of the Greeks. But he also made it clear that this metamorphosis created inherent ambiguities since the modified culture experienced successive schisms at three determining councils (Nicea, Ephesus, Chalcedon) before spreading in its various doctrinal forms broadly along the Eurasian temperate zone.
The significance of the Magian culture, if Spengler is correct, lies then in its cosmic paradigm: the fact of alternative fundamental perceptions of the astronomical environment, both of which came to have very wide, almost global, acceptance by the major civilizations of the world.
Broadly speaking, what we are dealing with here is the (original) pre-Socratic or (later) neo-Platonic version of the Universe and the fact of an intervening unresolved schism which resulted in the Aristotelian version of the Universe eventually being accepted throughout Christendom. We deal in effect with a pre-existing, essentially physical, perception of the astronomical environment which takes the Universe to be infinite in extent, both temporally and spatially; but, inasmuch as the trauma of pseudomorphoses have been moderated by the adoption of a more pragmatic philosophy, we also deal with an imposed, essentially comfortable, perception of the astronomical environment which takes the Universe to be finite in extent, both temporally and spatially, and subject to external, benevolent control. It is the finite version apparently western civilization currently takes the lead in preserving.
It was Aristotle of course who reminded us of a mythical tradition of extreme antiquity in which the stars are gods and in which "the divine embraces the whole of nature". But it was he also who disapproved of the existence of any infinite object or any infinite plurality of objects to explain the Universe, claiming instead that the fixed stars at the same distance from the Earth essentially marked the limit of the world.
Plato, it will be recalled, likewise thought of stars and planets along with the sun and moon as relatively local features of the Universe; but with the important difference in his case that these objects were all temporary products of the recent and even on-going evolution of a former "cosmic egg". Thus Plato and his predecessors quite clearly did not accept the Aristotelian limit and considered the Universe to be infinite. Indeed, the pre-Socratics and the early atomists subscribed to the idea of innumerable worlds or "cosmic eggs" scattered throughout infinite space which passed into and out of existence.
The underlying idea was that of an infinite or 'boundless' Universe whose constituents therefore represented the unlimited 'stuff' of the Universe. Such stuff was of an ungenerated and imperishable nature; it was also in a state of eternal motion, being therefore classified as immortal and divine. In addition though, the pre-Socratics were hylozoists in that they went beyond the mere atomistic conception of dead matter in mechanical motion and the Cartesian dualism of matter and mind supposing that the primary stuff of the Universe carried in some form the essential characteristics of animate, conscious beings (e.g. Cornford, 1952). The soul-stuff of life on Earth, for example, was thus thought of as being in some kind of continuum connecting it with the soul-stuff of a corresponding life-form in the visible, evolved heavens. The living world to which we belong, according to the pre-Socratics and neoPlatonists, was therefore a limited cosmic entity both representing the evolved constituents of a particular cosmic egg and occupying a volume of finite extent in both space and time. It was necessarily part of the Universe but since the latter was of infinite extent in both space and time, it was natural that the immediately visible world was also perceived as the 'world-cavern'.
In effect, the 'world-cavern' was a cosmic setting for the living community, or species, to which we and our basic soul-stuff could be considered to belong. It was a cosmic setting which was also conceived to possess a beginning and an end, both chaotic periods when the relevant cosmic egg was considered to undergo deconstruction and reconstruction, respectively.
But whereas Plato's Universe gave us uniformity beyond the stars - a world of cosmic eggs stretching from here to infinity and from now to eternity - together with an interaction beneath the stars between heaven and Earth, essentially permitting the basic astrological principle; we find that Aristotle's Universe, based on a similar framework of facts- gave us uniform (circular) motion for the planets between the stars and the Earth and thus an absence of any local interaction between heaven and Earth within the world-cavern, essentially discarding the basic astrological principle.
It is the discarded astrological principle of course which removes the theoretical possibility of cosmic terror afflicting civilization and which gives the Aristotelian Universe its particular charm so far as any pragmatic leadership is concerned.
One cannot be surprised therefore that ecclesiastical authorities and secular administrations, anxious to maintain some kind of stability in the face of cosmic stress, should be diverted by the charms of a principle which merely 'saved appearances' and created the illusion of uniformitarian calm in the vicinity of our planet! Astronomers however do not have to be so diverted since the Universe, for them, is not a matter of wishful thinking!
Thus, broadly in line with the Timaeus, before mankind had achieved any kind of measurement which would indicate for certain the sizes and distances of the planets, our 'world-cavern', was thought of as somehow displaying the typical characteristics of an evolving world amongst the plurality of worlds. The general appearance of the celestial sphere seemed to imply a stellar firmament outermost which contained within its space two mutually inclined circulations of material derived originally from the relevant cosmic egg. Plato is known to have ultimately regretted his initial opinion that the Earth lay at the focus of these circulations. This suggests he may have favoured the 'central hearth' or the 'Sun as the centre of the cavern while it was the Earth rather than heaven, of these mutually inclined structures, which comprised the visible bodies we now associate with the ecliptic.
Plato also considered that the original fashioning of this construction was in the hands of the demi-urge, its apparent purpose being to introduce an interaction between heaven and Earth which was to a large extent reflected in the meteoric phenomena which we observe. Thus it was fundamental to the whole perception that the heavenly circulation returned to Earth with apocalyptic force at long intervals of time; indeed, it was a specific and enduring characteristic of the Magian culture, having cosmic significance, that "something was descried in the far future, indefinitely and darkly still, but with a profound certainty that it would come".
Eventually, as the perceived awesome nature of the forthcoming event became even more intense, there was increased speculation as to the character of the world-cavern and its association with a succession of demi-urges (or 'craftsmen' - 'sons of God'). The latter supposedly fashioned the successive ages of mankind, each new beginning being marked by the return of the everlasting fire and by the occurrence of a portentous cosmic birth, conceivably a cometary splitting and hence a recognizable 'messianic' sign (see Section 4.1).
In due course, the Magian culture would undergo transformation during the fourth and second centuries BC and then again during the first and third centuries AD before experiencing yet another profound pseudomorphosis during the Dark Age period 400-600 AD. By then, the belief in the apocalypse had intensified to the extent that it penetrated the doctrine of European Christendom where it was to remain for at least another millennium undergoing yet further transformation and revival during yet further pseudomorphoses around 1100 AD, 1500 AD, 1650 AD and 1790 AD, each time in association with enhancements of the fireball flux (Fig. 1).
At each of these epochs, the Platonist tradition is evidently restored, most intensely perhaps during the Dark Age and the Reformation, but each time only to be countered by revival of the Aristotelian tradition. In fact, the fear of "last times" has never entirely disappeared from western culture, notwithstanding Comet Biela and the Darwinian Enlightenment, and perhaps there is now an increased suspicion, arising through the line of historical development which Spengler perceived, that the modern influence of a Taurid progenitor and the ancient perception of a cosmic egg, both of which are believed to have fragmented and dispersed, have a great deal in common.
We might well suppose in fact that our Space Age findings in relation to the Taurid/Encke stream are in close accordance with the pre-Socratic cosmic perception. In other words, the Space Age like a typical fireball flux enhancement, by arousing an intense awareness of the probable nature of our astronomical environment, can ultimately be seen as providing us with a cosmic perception equivalent to that of the Platonist tradition; and it is natural that this should already have been countered (unsuccessfully!) by an entrenched Aristotelianism opposed to the implications of the Taurid-Encke stream!
4. CELESTIAL INFLUENCE OF THE TAURID-ENCKE STREAM
The air we breathe can be remotely or locally sensed, e.g. through our eyes and nose, respectively. Likewise, to the extent that it may continuously penetrate the Earth's atmosphere and produce condensation nuclei in sufficient numbers to constitute recognizable atmospheric features e.g. noctilucent clouds, the material content of the interplanetary environment is also capable in principle of being remotely or locally sensed.
In most instances however, it appears that the air we breathe and the material content of the interplanetary environment we are able to detect remain below the threshold of everyday experience. Thus the action of the interplanetary environment tends to be substantially unmonitored and we can only build up our general picture of what is going on largely through a process of irregular sampling as and when the development of new technology unexpectedly provides us with a new capacity to detect one of this environment's effects. The pace of technological progress has certainly advanced this process significantly during the Space Age but we cannot presume that this period will necessarily have coincided with the interplanetary environment's most dramatic effects.
4.1. Chinese astrological records
The basic perception now arrived at, as described in this article, is that of an extraterrestrial input which transfers to our planet from the sub-Jovian interplanetary environment and which in former times was regarded as transferring from within the perceived 'world-cavern'. Included from within this region at the few percent level is the asteroidal-meteoritic material diverted from the main asteroid belt but the dominant contribution by far from within this region, as we have seen, is evidently the ecliptic-wide distribution of cometary-meteoroidal material arriving at the Earth from the broadly elliptical (i.e. helion/antihelion) circulation in sub-Jovian space whose main concentration intersects the Earth's orbit in late June and early November (Stohl, 1986). The dominant component, being of comparatively recent origin, does indeed have a non-uniform -distribution in solar ecliptic longitude reflecting its continued concentration close to the orbit of the circulation's source; whence it follows that this main concentration is also the likely most significant target for intrusive hypervelocity impacts giving rise to intermittent disintegration events in sub-Jovian space.
The most prominent of these events resulting in significant dust signatures, i.e. the so-called cometary trails, are then naturally associated with the largest bodies in inner Solar system space capable of rapidly undergoing hierarchical disintegration. Such bodies are likely to be choked off and rendered inert by their dust-laden environments; likewise they may be naturally associated with the release of substantial daughter bodies, even as large as small comets, which separate only slowly from the parent source; and also with relatively short-lived meteoroidal swarms in neighbouring orbits, which may retain their coherence long enough to be repeatedly penetrated by our planet.
The picture arrived at is evidently one which allows us to bring together such prominent interplanetary features as the well known helion/antihelion flux, the conspicuous Encke trail, the major meteoroidal concentration which has been found near the core of the helion/antihelion flux and the huge intermittent enhancements of the meteoroid flux known to us through Chinese astrological records maintained during the two most recent millennia (cf. Fig. 1).
In fact, these records of fireballs are now rather firmly indicative of the Taurid-Encke stream harbouring the bulk of the disintegrating meteoroidal material in inner Solar System space and of successive major disintegration events every other century or so afflicting the Earth: the most recent of which probably gave rise to Comet P/Encke some short interval of time prior to its discovery in 1786 (e.g. Asher and Clube, 1993).
Thus, while the sizes in general of prominent daughter bodies cannot be readily predicted and while the absolute calibration of the Chinese records is uncertain due to unknown variations in the monitoring process and the detection threshold, these records do nevertheless reliably suggest a stochastic Taurid source function which has given rise to possible cometary apparitions and fireball flux enhancements (x 10-100) around AD 0-100, 400-600, 1040-1100, 1400-1460, 1500-1540, 1640-1680, and 1760-1800, the last of these active periods apparently bracketing the supposed formation epoch of Comet P/Encke and the current Encke trail. It is perhaps surprising to note on this account that Comet Encke could be merely the latest in a succession of demi-urges while the Encke trail harbours the principal (inert) remnant of the original giant comet which gave rise to the Taurid Complex (cf. Section 3.5)!
With regard to the observation of fireballs, it is worth noting that a distinction can be drawn between the fluctuations detected since the 18th century and those detected prior to this period. Thus the former reflect as much the increased scientific activity in which we currently participate while the latter reflect a moderately uniform, slowly extending, observational regime in China and the Orient, particularly Japan and Korea.
For the duration of this regime, the astronomical interests of the Orient, like those of Europe, lay with portentous rather than with astrophysical phenomena, the maintenance of suitable records being to a large extent professionally organised only in China (Schafer, loc cit). Given the presumed nature of this observational material, whatever the astrophysical reality giving rise to the recorded meteoroid flux and its correlates (e.g. high level dust insertions, super-Tunguska events), we can be confident that the phenomena, especially during the periods of their dominance lasting for several decades at a time, would most probably have been understood in both China and Europe as divine revelations or rather fearsome exemplars of a natural (presumed astrological) process in which the cosmos necessarily interferes with terrestrial affairs.
Indeed, these enhancements of the meteoroid flux which, as we have seen, are likely to be broadly associated with the most recent giant comet to have settled in inner Solar System space, are of particular interest in their European context since the periods of their principal activity happen also to coincide with periods of pronounced social and intellectual upheaval when it is clear that the normal ascendancy of secular over fundamentalist modes of thought, affecting the general view of the cosmos, experiences a sharp reverse. It is reasonable, in other words, to suppose these were the periods when cosmic agencies were expected to interfere in terrestrial affairs, when the inspiration due to the cosmos gave way to foreboding.
We note, for example, corresponding to these particular epochs: the time of Christ, the Dark Age foundation of the Holy Roman Empire, the initiation of the Crusades against Islam, the Great Schism, the Reformation, the English Revolution and the American War of Independence allied with the French Revolution. The activities during all these periods point to a much closer link between political, religious and cosmic affairs during the ancien regime than historians normally countenance. In fact, the political consequences of revived fundamentalism and the renewed interest in demonic agencies during these periods, especially their destructive tendencies, often perceived as a millenarian threat (Cohn, 1957), no longer appear to be without an identified material cause of external origin.
The prevailing tendency nonetheless, since the 12th century, has increasingly been to regard demonic agencies as a heresy (Thomas, 1971), not only distorting our view of the cosmos but raising unwarranted doubts as to the reality of the likely eschatological associations at these and earlier epochs.
4.2. Eschatology displaced
Eschatology is a relatively long-established if now somewhat obscure branch of learning currently stranded somewhere in the hinterland between history and theology where it remains comparatively untouched by scientists and by historians of science. Its concern is with the doctrine of so-called 'last times' or, more precisely, with the perceived occurrences which, as a matter of historical record, were thought of as bringing the known world to its final destruction.
The most recent authoritative account of eschatological theory by Bultmann (1957) in his Gifford Lectures at Edinburgh indicates that this subject, which was of decisive importance for the long history of the West, developed in association with the ancient concept of a periodicity in the course of world events. This idea originating with the earliest known astronomical traditions based on the ancient Near East, most probably involving a Zoroastrian tradition from Persia (Cohn, 1995), was later developed in Greek and Roman philosophy chiefly by the Stoic thinkers and is perhaps best known today through the reference in Plato's Timaeus to bodies from space which return at great intervals to cause a serious conflagration on Earth: the general concept is indeed that of a universal catastrophe deriving from the cosmic Zeus from whom also radiated a new world. Thus the astrological literature countenances a periodically moribund world-civilization in need of revival and restoration and the periodic emergence of a new star at the end of an aeon, or world-year, to mark the occasion.
Bultmann emphasises however that, in addition to this over-arching perception applicable to the known natural world, we must recognise in the earliest historical narrative an account of normal human welfare characterised by occasional catastrophes, mostly cosmic, which are typical acts of divine chastisement.
The point here is that the catastrophes of divine origin were once a common enough perception to imply relatively frequent occurrence and it is against this background that ancient authors considered the more serious effects of periodic universal catastrophes. Thus the Old and New Testaments were fundamentally distinguished by the latter's added anticipation of a forthcoming new aeon freed from Satan's (catastrophic) rule. The picture to be envisaged therefore was that of a new 'world catastrophe' which would bring to an end both the lesser catastrophes and the sequence of past 'world catastrophes'. In practice, the precise start of the new aeon was subject to a good deal of chronological reckoning based on the apocalyptic scheme due to Daniel and there was growing agreement during the period of the 'Pax Romana', even amongst secular historians, that the new order would be introduced around 500 AD.
Historians of course are in dispute over the precise nature of the Dark Age. The fact of major reverses in civilization in some parts of Europe during the fifth and sixth centuries has to be set against survival, often in reduced circumstances, in other parts. A decline in the level of civilization in Britain, for example, which is said not to have been restored for upward of twelve or thirteen centuries, is perhaps material enough evidence of the deprivation involved. Thus, in the face of this kind of reality, whatever physical hardships were endured, one can hardly be over-critical of survivors of a predicted world-catastrophe who then appear somewhat casual about the shortcomings of a failed astronomical theory i.e. it can certainly be assumed that survivors would have recognized that the 'last times' did not in fact arrive. It is perhaps but a short step therefore from Plato's soul-stuff continuously emanating from the world-cavern to the perception of a versatile if somewhat magical 'divine providence' through which such effects as a partial conflagration might be judiciously realized.
During a subsequent era, then when the possibility of a universal conflagration no longer appeared probable, one can perhaps understand that a continuing cosmic struggle might be envisaged between the dark powers of nature and unreasonableness on the one hand and divine providence on the other hand, the latter now losing its material attributes and becoming primarily the source of free will and enlightened reason!
Thus, as Bultmann supposes, "the idea of the eschatological consummation would later be interpreted as the victory of reason, regarded as the necessary end of the historical development". Indeed, by subsequently placing such an interpretation on the fifth century writings of Augustine, the Church can now be seen to move away from a purely naturalistic interpretation of the celestial influence. However we should not overlook the fact that the general period corresponding to the decline of the Roman Empire (400-600 AD) was in association with circumstances which were widely seen as predictably marking a world-end of cosmic provenance (Barb, 1963).
In fact, such anomalies of the period as the desertion of major tracts of land and the forced migration of whole peoples (Esmonde-Cleary, 1989) point to an underlying cause of the Dark Age which enveloped at least the whole of Europe and which could well have been be due to a succession of localized catastrophes involving super-Tunguska bodies as implied now by the formation epoch of Comet P/Encke and by the 1760-1800 and 400-600 AD enhancements of the fireball flux (Asher and Clube /oc cit). Thus a cometary progenitor for the Taurid meteoroidal concentration is also implied and it is the coincidence of the latter's orbital nodes with the Earth's orbit around 400-600 AD which would now lead us to envisage a wholly material cause for the Dark Age.
The evident fact of a new aeon which was not freed from Satan's rule can of course be eventually seen as a fairly pressing problem for the leaders of the subsequent Holy Roman Empire and there would have been a natural tendency for later scholars to defer the arrival of 'last times'. Indeed it was to be a feature of historiography, then in the future, that the apocalyptic tradition with its scheme of the four world empires of Daniel and the idea of an eschatological end to history were gradually reinstated as part of the protestant tradition.
4.3. Paradigm shifts
In fact, the protestant tendency, which was most seriously aroused on the occasions of an enhanced fireball flux, was generally intent on maintaining the apocalyptic tradition. The resulting debate was of course a critical factor determining the pattern of social upheaval and revolution throughout Europe until the end of the eighteenth century.
Indeed it is only since Hegel specifically pronounced against the role of "divine providence" in secular and philosophical affairs (e.g. Lewis, 1954) that the crises and catastrophes comprising the main national and world events have come to be seen as motivated by non-cosmic disputes between oppressors and oppressed. In view of the likelihood now of a straightforwardly natural (cosmic) explanation of the apocalyptic tradition, we have to face the possibility that Hegel and his successors were mistaken as to the true nature of providence as well as to the prime cause of revolutions!
Amongst the twentieth century historians, both Spengler (1932) and Toynbee (1945) have argued for the origin, growth and decay of civilizations, effectively in the tradition of eschatological history, each new growth emerging from a preceding period of chaos so that the movement of history is brought about by an unpredictable factor, namely, the behaviour of a nation in a critical situation. Spengler indeed perceived such situations as a quite natural extension of biological evolution as a whole. Thus he anticipated the theory of punctuated equilibrium with the following perceptive commentary:
"The picture that we possess of the history of the Earth's crust and of life is at present still dominated by the ideas which civilized English thought has developed, since the Age of Enlightenment, out of the English habit of life, [thus] Lye11's 'phlegmatic' theory of the formation of the geological strata, and Darwin's of the origin of species, are actually but derivatives of the development of England herself. In place of the incalculable catastrophes and metamorphoses such as von Buch and Cuvier admitted, they put a methodical evolution over very long periods of time and recognize as causes only scientifically calculable and indeed mechanical utility-causes".To Spengler therefore, civilization is no more than the fullest development of a culture or a paradigmatic view whose principal characteristics are essentially dictated from the cosmically induced chaos through which they emerge.
Rather "all that we see about us impels us to the conviction that again and again profound and very sudden changes take place in the being of plants and animals, changes which are of a cosmic kind and nowise restricted to the Earth's surface, which are beyond the ken of human sense and understanding in respect of causes, if not indeed in all respects. So, too, we observe that swift and deep changes assert themselves in the history of the great Cultures, without assignable causes, inferences or purposes of any kind".
Accordingly, for example, we now see the fireball flux enhancement of 1640-1680 initiating the predictions of world end in England at this time, based on the latest analyses of the Book of Daniel by scholars such as Alsted, Brightman and Mede (Trevor-Roper, 1987). Received into popular currency alongside a breakdown in official censorship, these predictions were to precipitate social upheaval and intellectual chaos, as well as civil war and interregnum in the aftermath of which those affecting to make something of a principle out of pragmatic protestantism selected to discount providential fireballs (Sprat loc cit) and restore scientific censorship. Thus was silenced the recently aroused Pyrrhonist (neo-Platonist) wing within the broad protestant tradition, tipping the balance once again towards its more catholic (Aristotelian) wing. These were the ambiguous conditions under which Newton was able to make public his science and yet keep private his eschatological speculations.
Likewise, while we may now see such understandings of the stellar, galactic and cosmological environments which have emerged during the nineteenth and twentieth centuries as enriching our understanding of an earlier, neo-Platonist perception of the boundless Universe, it seems that some of the perhaps less well known astronomical findings of the Space Age now also provide us with an understanding of the Sun and its planetary and cometary environments which enriches our understanding of the Magian world-cavern!
To be precise, it now seems that the latter is neither altogether imperishable nor is it altogether temporary. Rather the Sun, its planetary system and life on Earth are comparatively ancient constructions from the boundless while it is the latest giant comet, also a product of the boundless, which we should now identify in particular with the most recent evolution of the human species and upheavals on Earth. As such, this giant comet is merely the latest in a continuing series, the overall picture being that of punctuational crises which extend over a wide range of intensities and which transform our understanding of biological and social history. The overall picture, furthermore, is one that necessarily provides divine revelation and cosmic myth with a natural material content, now essentially removing such entities from the realm of fantasy.
Indeed, it seems that the secular eschatological component of theological debate throughout history can also no longer be denied. In short, there is inspiration and foreboding generated by a giant comet which has masqueraded as both a cosmic egg and a cosmic serpent. There is also a watershed in the modern perception of cometary facts marked by the fragmentation of Comet P/SL-9 which society and government would be unwise to ignore.
A substantial section of this article is reproduced from two of the author's earlier papers, one of which was composed in collaboration with Dr D. J. Asher. The author would like to thank the organisers of the 'Inspirations' conference for their patience during the preparation of this article. The author also wishes to acknowledge and express his appreciation of the very material assistance, while this patience was being exercised, provided by Dr. W. M. Napier and, through the good offices of Dr S. P. Worden and Dr. S. Nozette, by the USAF (EOARD SPC-93-4076).
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