Tuesday, 21 July 2015

Quotes: The Challenge of the Spaceship (1959) by Arthur C. Clarke

Arthur C. Clarke
The Challenge of the Spaceship
First published, 1959.
First Pocket Books printing, June 1980.


The main theme of this book is the impact of the coming Space Age upon our hitherto Earth-bound species. Looking past the immediate present, and ignoring both the occasional triumphs and more frequent failures of today's satellites and rocket probes, it attempts to view the conquest of space as part of a historical process. Except where they are essential to the argument, it is not in the least concerned with technical matters; it assumes that machines are less important than what men do with them – or what they do with men.

Though the various examinations of the Man-Space relationship that follow look at the subject from different angles, some overlapping is inevitable and some is deliberate. I have tried to edit out all unnecessary repetition, but when a thing is really important it is worth saying more than once.

Interleaved between these philosophical and cultural speculations are examples of straight science reporting, most of them from the pages of Holiday magazine. Sometimes, as in the trio of pieces giving helpful advice to interplanetary tourists, the reporting is not so straight. However, anyone who reads that book as a whole will be in little danger of confusing fact with fiction.

The Challenge of the Spaceship[1]

[First lines:]
A historian of the twenty-first century, looking past our age to the beginnings of human civilization, will be conscious of four great turning points which mark the end of one era and the dawn of a new and totally different mode of life. Two of these events are lost, probably forever, in the primeval night before history began. The invention of agriculture led to the founding of settled communities and gave Man the leisure and social intercourse without which progress is impossible. The taming of fire made him virtually independent of climate and, most important of all, led to the working of metals and so set him upon the road of technological development – that road which was to lead, centuries later, to the steam engine, the Industrial Revolution, and the age of steel and gasoline and surface transportation through which we are now passing.

The third revolution began, as all the world knows, in a squash court in Chicago on December 2, 1942, when the first self-sustaining nuclear reaction was started by Man. We are too close to that cataclysmic event to see it in its true perspective, but we know that it will change our world, for better or for worse, almost beyond recognition. And we know too that it is linked with the fourth and in some ways the greatest change of all – the crossing of space and the exploration of the other planets. For though the first space vehicles were chemically fueled, only atomic energy is adequate to lift really large payloads out of Earth’s gravitation field – that invisible maelstrom whose tug can still be felt a million miles away.

Prophesy is a dangerous and thankless business, frequently fatal to those who practice it. We have, however, learned from past experience that even the most extravagant forecast seldom overtakes the truth. H. G. Wells once wrote – and was no doubt laughed to scorn for his folly – that the airplane might have some influence upon warfare by the year 1950. He never dared to imagine that by that date aircraft would not only have become of supreme importance but would have been challenged by still newer weapons.


There are still some scientists who consider that there is no point in sending man into space, even when it becomes technically possible; machines, they argue, can do all that is necessary. Such an outlook is incredibly shortsighted; worse than that, it is stupid, for it completely ignores human nature. Though the specific ideals of astronautics are new, the motives and impulses underlying them are as old as the race – and in the ultimate analysis, they owe as much to emotion as to reason. Even if we could learn nothing in space that our instruments would not already tell us, we should go there just the same.

Some men compose music or spend their lives trying to catch and hold forever the last colors of the dying day, or a pattern of clouds that, through all eternity, will never come again. Others make voyages of exploration across the world, while some make equally momentous journeys in quiet studies with no more equipment than pencil and paper. If you ask these men the purpose of their music, their painting, their exploring, or their mathematics, they would probably say that they hoped to increase the beauty or the knowledge of the world. That answer would be true, and yet misleading. Very few indeed would give the simpler, the more fundamental reason that they had no choice in the matter – that what they did, they did because they had to.


Yet these first direct results of astronautics may be less important, in the long run, than its indirect consequences. This has proved true in the past of most great scientific achievements. Copernican astronomy, Darwin’s theory of evolution, Freudian psychology – these had few immediate practical results, but their effect on human thought was tremendous.

We may expect the same of astronautics. With the expansion of the world’s mental horizons may come one of the greatest outbursts of creative activity ever known. The parallel with the Renaissance, with its great flowering of the arts and sciences, is very suggestive. “In human records,” wrote the anthropologist J. D. Unwin, “there is no trace of any display of productive energy which has not been preceded by a display of expansive energy. Although the two kinds of energy must be carefully distinguished, in the past they have been… united in the sense that one has developed out of the other.” Unwin continues with this quotation from Sir James Frazer: “Intellectual progress, which reveals itself in the growth of art and science… receive an immense impetus from conquest and empire.” Interplanetary travel is now the only form of “conquest and empire” compatible with civilization. Without it, the human mind, compelled to circle forever in its planetary goldfish bowl, must eventually stagnate.

We all know the narrow, limited type of mind that is interested in nothing beyond its town or village and bases its judgments on those parochial standards. We are slowly – perhaps too slowly – evolving from that mentality toward a world outlook. Few things will do more to accelerate that evolution than the conquest of space. It is not easy to see how the more extreme forms of nationalism can long survive when men begin to see the Earth in its true perspective as a single small globe among the stars.

There is, of course, the possibility that as soon as space is crossed all the great powers will join in a race to claim as much territory as their ships can reach. Some American writers have even suggested that for its own protection the United States must occupy the Moon to prevent its being used as a launching site for atomic rockets. Fantastic though such remarks may seem today, they represent a danger which it would be unwise to ignore. The menace of interplanetary imperialism can be overcome only by world-wide technical and political agreements well in advance of the actual event, and these will require continual pressure and guidance from the organizations which have studied the subject.

The Solar System is rather a large place, though whether it will be large enough for so quarrelsome an animal as Homo sapiens remains to be seen. But it is surely reasonable to hope that the crossing of space will have a considerable effect in reducing the psychological pressures and tensions of our present world. Much depends, of course, on the habitability of the other planets. It is not likely that very large populations will, at least for many centuries, be able to subsist outside the Earth. There may be no worlds in the Solar System upon which men can live without mechanical aids, and some of the greatest achievements of future engineering will be concerned with shaping hostile environments to human needs.

We must not, however, commit the only too common mistake of equating mere physical expansion, or even increasing scientific knowledge, with “progress” – however that may be defined. Only little minds are impressed by sheer size and number. There would be no virtue in possessing the Universe if it brought neither wisdom nor happiness. Yet possess it we must, at least in spirit, if we are ever to answer the questions that men have asked in vain since history began.


Every thoughtful man has often asked himself: Is our race the only intelligence in the Universe, or are there other, perhaps far higher, forms of life elsewhere? There can be few questions more important than this, for upon its outcome may depend all philosophy – yes, and all religion too.


It is true – it is even likely – that we may encounter no other intelligence in the Solar System. That contact may have to wait for the day, perhaps ages hence, when we can reach the stars. But sooner or later it must come.

There have been many portrayals in literature of these fateful meetings. Most science-fiction writers, with characteristic lack of imagination, have used them as an excuse for stories of conflict and violence indistinguishable from those which stain the pages of our own history. Such an attitude shows a complete misunderstanding of the factors involved.

Remember the penny and the postage stamp which Sir James Jeans, in The Mysterious Universe, balanced on Cleopatra’s Needle. The obelisk represented the age of the world, the penny the whole duration of man’s existence, and the stamp the length of time in which he has been slightly civilized. The period during which life will be possible on Earth corresponds to a further column of stamps hundreds of yards – perhaps a mile – in height.

Thinking of this picture, we see how infinitely improbable it is that the question of interplanetary warfare can ever arise. Any races we encounter will almost certainly be superhuman or subhuman – more likely the former, since ours must surely be one of the youngest cultures in the Universe. Only if we score a bull’s-eye on that one stamp in the mile-high column will we meet a race at a level of technical development sufficiently near our own for warfare to be possible. If ships from Earth ever set out to conquer other worlds they may find themselves, at the end of their journeys, in the position of painted war canoes drawing slowly into New York Harbor.

But if the Universe does hold species so greatly in advance of our own, then why have they never visited Earth?[2] There is one very simple answer to this question. Let us suppose that such races exist: let us even suppose that, never having heard of Einstein, they can pass from one end of the Galaxy to the other as quickly as they wish.

That will help them less than one might think. In ten minutes, a man may walk along a beach – but in his whole lifetime he could not examine every grain of sand upon it. For all that we know, there may be fleets of survey ships diligently charting and recharting the Universe. Even making the most optimistic assumptions, they could scarcely have visited our world in the few thousand years of recorded history.

Perhaps, even at this moment, there lies in some rather extensive filling system a complete report on this planet, with maps which to us would look distorted but still recognizable. That report would show that though Earth was teeming with life, it had no dominant species. However, certain social insects showed considerable promise, and the file might end with the note: “Intelligence may be emerging on this planet. Suggest that intervals between surveys be reduced to a million years.”

Very well, you may ask – suppose we encounter beings who judge, condemn and execute us as dispassionately, and with as little effort, as we spray a pool of mosquito larvae with DDT? I must admit that the possibility exists, and the logical answer – that their reasons will no doubt be excellent – is somewhat lacking in appeal. However, this prospect seems remote. I do not believe that any culture can advance, for more than a few centuries at a time, on the technological front alone. Morals and ethics must not lag behind science, otherwise the social system will breed poisons which will cause its certain destruction. I believe therefore that with superhuman knowledge must go equally great compassion and tolerance. In this I may be utterly wrong: the future may yet belong to forces which we should call cruel and evil. Whatever we may hope, we cannot be certain that human aspirations and ideals have universal validity. This we can discover in one way only, and the philosophical mind will be willing to pay the price of knowledge.


The races of other worlds will have senses and philosophies very different from our own. To recall Plato’s famous analogy, we are prisoners in a cave, gathering our impressions of the outside world from shadows thrown upon the walls. We may never escape to reach that outer reality, but one day we may hope to meet other prisoners in adjoining caves, where the shadows may be very different and where we may learn far more than we could ever do by our own unaided efforts.

These are deep waters, and it is time to turn back to the shore, to leave the distant dream for the present reality of fuels and motors, of combustion-chamber pressures and servomechanisms. Yet I make no apology for discussing these remote vistas at some length, if only to show the triviality of the viewpoint which regards interplanetary travel as a schoolboy adventure of no more real value than the scaling of some hitherto inaccessible mountain. The adventure is there, it is true, and that is good in itself – but it is only a small part of a much greater whole.

Not so shortsighted, but equally false, is the view expressed by Professor C. S. Lewis, who has written of would-be astronauts in this unflattering fashion – “The destruction or enslavement of other species in the universe, if such there are, is to these minds a welcome corollary.”[3] In case there are any to whom this prospect still appeals, I would point out that empires, like atomic bombs, are self-liquidating assets. Dominance by force leads to revolution, which in the long run, even if indirectly, must be successful. Humane government leads eventually so self-determination and equality, as the classic case of the British Empire has shown. Commonwealth alone can be stable and enduring, but empires must always contain the seeds of their own dissolution.


Our survey is now finished. We have gone as far as is possible, at this moment of time, in trying to assess the impact of astronautics upon human affairs. I am not unmindful of the fact that fifty years from now, instead of preparing for the conquest of the outer planets, our grandchildren may be dispossessed savages clinging to the fertile oases in a radioactive wilderness. Yet we must keep the problems of today in their true proportions. They are of vital – indeed of supreme – importance, since they can destroy our civilization and slay the future before its birth. But if we survive them, they will pass into history and the time will come when they will be as little remembered as the causes of the Punic Wars. The crossing of space – even the sense of its imminent achievement in the years before it comes – may do much to turn men’s minds outward and away from their present tribal squabbles. In this sense the rocket, far from being one of the destroyers of civilization, may provide the safety valve that is needed to preserve it.

This point may be of the utmost importance. By providing an outlet for man’s exuberant and adolescent energies, astronautics may make a truly vital contribution to the problems of the present world. Space flight does not even have to be achieved for this to happen. As soon as there is a general belief in its possibility, that belief will begin to color men’s psychological outlook. In many ways, the very dynamic qualities of astronautics are in tune with the restless, expansive spirit of our age.

In this essay I have tried to show that the future development of mankind, on the spiritual no less than the material plane, is bound up with the conquest of space. To what may be called – using the words in the widest possible sense – the liberal scientific mind, I believe these arguments to be unanswerable. The only real criticism that may be raised against them is the quantitative one that the world is not yet ready for such changes. It is hard not to sympathize with this view, which may be correct, but I have given my reasons for thinking otherwise.

Journey by Earthlight[4]

[First lines:]
Just a hundred years ago, back in 1976[5], the first men landed on the Moon, and the age of space flight began. During the last few years, it must be admitted, the glamor of more romantic places like Mars and Venus has diverted attention from our satellite. Perhaps it’s so close that we tend to take it for granted, just as no New Yorker ever bothers to go to the top of Planet Tower to see what his city looks like from half a mile up. Moreover, until very recently few people went to the Moon unless they were scientists or technicians on official business.

Two things have changed this. Now that the necessary facilities exists, the Lunar Commission is encouraging a limited tourist trade, though for the moment it will be restricted to the Earthward face of the Moon. The second factor, of course, is the establishment of Pasteur City, which is likely to have a profound effect on medical research and even, ultimately, on human society.


However many times you do it, a landing on the Moon is an awe-inspiring experience, totally different from the long glide through the upper atmosphere which brings you down on planets like Earth or Mars. The lunar landing must be made by rockets alone, at the end of an interminable fall which is checked only when you are within a hundred miles of that jagged, pock-marked landscape. Then the silence will be broken as the rockets thunder into life, and your returning weight will force you down into your seat. Through the observation window – if you’re lucky enough to be near one – you’ll see the white-hot pillar of flame which is checking your headlong fall.


Sinus Medii means “Central Bay”; though of course there is no free water on the Moon, such terms as bay, sea, ocean and lake were used by the early astronomers and have stuck so thoroughly that no one can change them now. To make matters more confusing to newcomers, the Latin and English versions are used indiscriminately. It may take you some time to realize, for example, that Palus Somnii is the same place as the Marsh of Sleep. Though there have been several attempts to tidy up lunar nomenclature, nothing has come of them and we’re stuck with the five-hundred-year-old names. Luckily the Moon’s other side – which of course was never seen until the first rockets started to land there – isn’t littered with remnants of medieval astrology. The great formations there have been named after famous men of modern times, so don’t be surprised to encounter Einstein, Churchill, Rutherford, Sibelius, Roosevelt – all of whom have craters more than a hundred miles across.[6]

The Sinus Medii is not only the main spaceport on this side of the Moon, but also the center for surface transport. All long-distance travel is by monorail, for the Moon is an absolutely ideal place for this type of locomotion. There’s no air resistance, so speeds of five hundred miles an hour can be reached with little difficulty. And the low gravity greatly eases the construction problem – the single rail need only be supported at wide intervals, and bridges can have enormous spans.

So come aboard the north-bound track to Pasteur City, in the great walled plain of Plato, and take a ride over the most spectacular scenery on the Moon. We’ll leave in darkness, a few hours after the beginning of the long lunar night.


If you’re lucky, you may see a take-off as you skirt the edge of the spaceport. A night launch from the Moon is an unforgettable sight; its utter soundlessness somehow adds to the effect. The ship will ascend in a cloud of dust blasted up from the plain – a cloud within which the jets will burn like incredibly brilliant suns. As the dust falls behind, the blue-white glare will flood the landscape with a light more fierce even than that of noon. It will ebb away as the ship dwindles against the stars, and suddenly wink out of existence as the departing vessel reaches escape velocity and cuts its drive.

For the first few hundred miles, the monorail runs over relatively flat country as it heads northeast. Though the Sun has set, the landscape will be brilliantly illuminated by the Earth, just passing its first quarter but already giving a dozen times as much light as the full Moon does to the terrestrial scene. It’s a cold light: an arctic radiance that gives not an atom of heat. For it’s tinged with the blues and greens of Earth’s oceans and clouds; it sparkles from the polar caps that even across a quarter of a million miles of space are too dazzling for the unprotected eye. It’s hard to believe that this freezing luminosity really comes from a world of warmth and life.

There’s an observation room at the front of the car, curtained off from the light of the main cabin. Unless you’re a seasoned, blasé traveler, you’ll spend most of your time there, watching the lunar landscape racing past. Ahead of you the single rail, supported by pillars disquietingly far apart, is now running almost due east. Here’s another paradox to bother you: the way directions on the Moon have been chosen, the Sun sets in the east, not the west…


Pasteur City consists of a dozen pressure domes, linked together by air locks, a few miles from the north wall of Plato. One of the domes is transparent, so that the residents can watch the pageant of the changing heavens, can see the long dawn break above the mountains – and can watch the seasons come and go on the world to which they can never return.

Yet it is quite wrong to think of Pasteur City as a home for convalescents, like the space-station hospitals circling Earth. Almost all its twenty thousand inhabitants live normal, unrestricted lives. But they could do so only here, where they weigh no more than thirty pounds and the strain on hearts and muscles is correspondingly reduced.

Like all great advances in medical science, the founding of Pasteur City has opened up new and unsuspected frontiers. If people suffering from chronic heart diseases can live out their normal span under the Moon’s gravity, what will be the expectation of an ordinary, healthy man? No one talks too much about this, but there’s an air of suppressed excitement among the doctors studying the matter. Some of them have been heard to say that old age can now be postponed until far into the second century. If this is true, and the technical problems of supporting a large lunar population can be overcome – well, we can expect some interesting social changes.[7]


In Pasteur City you’ll encounter a practical problem that won’t have bothered you greatly elsewhere. At the spaceport back in the Sinus Medii, and on the monorail trip, you will have been in fairly cramped surroundings, and won’t have been able to perform those athletic feats which the earlier writers about the Moon loved to emphasize. It’s not very practical, for instance, to jump twenty feet high when the ceiling is only a yard above your head. But in Pasteur City, under the domes, you will have your first real opportunity to show off.

Well, take it easy. Don’t go up until you are sure you know how come down. It’s all too simple to turn over in flight and land on your head – which will damage you just as much as it would on Earth. Should you wear one of those lead belts which are recommended for visitors during their first few days on the Moon? That’s up to you; try one, by all means – it may save you from injury through carelessness. But there’s a snag, which many people don’t realize, about loading yourself down with lead. Whereas weight on the Moon is reduced to a sixth, inertia is exactly the same. Your hundred pounds of lead will help keep you on the ground and will be no burden when you are standing still. But as soon as you start or stop, or try to change direction, it will feel exactly what it is – a hundred pounds of lead!

Personally, I think the best thing to do is to accept your weight for what it is, and learn to reduce muscular effort accordingly. Your first attempts to take strides of normal length will look somewhat prissy and mincing, but you’ll soon get used to it.


From the region round Pasteur City, the Earth hangs low in the southern sky, its continents clearly visible and its blanket of atmosphere forming a luminous haze around its edge. It is so near the mountains that you expect it to set at any moment, and it will be a long time before you get used to the idea that it will always be there, fixed in the lunar sky. The Sun and stars rise and set, taking two weeks of Earth time to cross from horizon to horizon; but Earth remains forever motionless, apart from a slight swaying back and forth caused by the fact that the Moon’s orbital motion is not perfectly regular. The only change that Earth shows is that of phase, as it waxes to full and wanes to a threadlike crescent. After a while, you will be able to tell the time by the great clock hanging there against the stars….

The stars – yes, they will give you another surprise. Even today, people will tell you that on the Moon you can see Sun and stars in the sky at once. It’s a statement which is both true and false. If you look directly at the Sun, you won’t see anything else for a long time, and you’ll be lucky not to damage your eyes. During daytime on the Moon, if you are out in the open, the glare from the rocks demands the use of sun filters and your pupils will be fully contracted. Consequently, though the stars are shining up there in the sky, you won’t be able to see them and it will be perfectly black overhead. If you want to look at the stars, step into the shadow of a convenient rock and shield your eyes from all the glare around you.

Then, as your vision adapts itself and your pupils enlarge, you'll see the stars come out. First there will be the bright, familiar constellations, then the legions of their faint companions, until at last the whole sky seems packed with glowing dust. All those countless points of light will be shining with a steady, unvarying radiance: none will twinkle or scintillate as they do in the clearest nights on Earth. Now you will understand why all great observatories are on the Moon: you will realize that, until he had climbed above the atmosphere of his own planet, no man had ever really seen the stars….


The Moon has already turned out to be a much more valuable and interesting place than the first pioneers expected. The millions that have been sunk into it are beginning to pay off in terms of knowledge – from the observatories and vacuum labs; of raw materials – from the mines and refueling stations; and of human happiness – from Pasteur City. There were some who feared that when we reached the Queen of Night, her romance and mystery would be destroyed. They need not have worried. We may roof the lunar craters, spread our cities across the dusty seas, build our farms on the Sunward-facing slopes of the mountains. We will not change the essential nature of the Moon. She watched life emerge from the steaming oceans of the dawn; she saw Man embark on the conquest of his own world – and, a little later, the conquest of space itself.

She will still be watching, drawing the tides beneath her, when our descendants have spread so far from home that few could say in what region of the sky lies the ancestral planet Earth….

What Can We Do About the Weather

During the Second World War, the Royal Air Force made a rather determined effort to Do Something About the Weather, if only on a local basis. All too often, a bomber squadron would take off to Germany only to discover, when it had completed its mission and returned to England, that its base had been closed down by fog. Many planes and crews were lost for this reason, and the “boffins” – as the R.A.F. affectionately christened its civilian scientists – were called upon to produce an answer.

That answer was FIDO (Fog, Intense, Dispersal Of), one of the war’s most spectacular yet least publicized secret weapons. I was fortunate to be associated with the tests of the biggest FIDO installation ever built, on a large airfield in Cornwall, not far from Land’s End. The runway was lined on either side with a double row of pipes – four or five miles of them in all – which convey gasoline to long rows of burners. When they were in action, they consumed fuel at the awesome rate of 100,000 gallons an hour (I trust that this figure is no longer a well-kept secret from the British taxpayer) and formed multiple walls of flame the full length of the runway.

At night, with the fog rolling in from the Atlantic, a FIDO operation was like a scene from Dante's Inferno. The roar of the flames filled the air and made speech difficult; they created such an updraft that small stones on the edge of the runway were picked up and tossed around by the air currents. As far as the eye could see, the yellow walls of fire, taller than a man, stretched away into the foggy night. The miles of burners were pumping heat into the air at the rate of 10,000,000 horsepower, cutting a long, narrow trench through the fog, down which the returning bombers could find their way to the ground.

I have known nights when the fog was so thick that visibility was less than ten feet – but standing in the middle of the runway, with the flames roaring on either side, one could see the stars shining overhead. FIDO worked by brute force, and the development of radar made it obsolete; but it did show what could be done when incentive was sufficiently great – and expense was no object.

Where’s Everybody?

Yet even if life is common throughout the Universe, intelligence may still be rare. There are millions of different types of living creature on this Earth, but only one with the power of abstract thought – and he hasn’t been round for very long. Just how late Man has appeared on the cosmic stage can best be realized by this analogy borrowed, with improvements, from Sir James Jeans.

Let the height of the Empire State Building represent the age of Earth; on this scale, a foot is about two million years. Now (if the wind will let you) stand an average-sized book upright on the TV tower. It won’t look very conspicuous from ground level – but its few inches of height correspond roughly to the entire existence of Homo sapiens.

However, we haven’t finished yet. Now place a slightly worn dime on the top of the book. The thickness of the coin corresponds to the whole of man’s civilization, right back to the building of the pyramids. And if you want to represent the era of modern science and technology – that is about as thick as a postage stamp.

The postage stamp on the top of the Empire State Building is a picture we should bear in mind; it shows how extremely unlikely it is that, on any particular world, intelligence should exist at our own level of development. Even assuming that evolution takes similar roads on all suitable planets, only upon one world in millions could we expect to find a civilization that had discovered steam power a couple of centuries ago, and which now dreams of the conquest of space as it passes into its Atomic Age.

No – it is far more likely that if other intelligent races exist, the vast majority of them will be at stages of development corresponding to points millions of years in our past – or in our future. The latter, indeed, seems more likely, for our own history is so short that we must surely be among the youngest peoples in the Universe.

This leads to an inescapable conclusion. Scattered around us in space, at distances which cannot be more than a few scores of light-years, there must be not a few civilizations far in advance of ours – and there may be dozens of them. Which brings us back to our opening question: If they are so advanced, why haven’t they come here?


It may well be argued (and indeed has been by many eminent scientists) that our apparent isolation can be explained very simply. Travel from planet to planet inside the Solar System may be possible in the relatively near future, so that we shall visit neighboring worlds such as Mars and Venus. But travel to the planets of other suns – interstellar travel – may be totally impossible because of the sheer distances involved. On this theory, the Universe may be full of intelligent races, but they must forever exist in total ignorance of each other, quarantined by space itself.

This is a serious and plausible argument, and must be dealt with before we proceed any further.


The velocity of light, therefore, appears to set a limit to the speed with which any object can move through space. That speed may be approached more and more closely as propulsion systems improve, but it can never be reached, still less exceeded. If this is the case, time of travel between even the closest star systems can never be less than four or five years; between inhabited star systems, in our fairly crowded corner of the Galaxy, we might not be far out if we fix the lower limit of travel time as ten years.

This is a good deal longer than we would like, especially as the return trip still has to be considered. But can anyone seriously argue that it is an absolutely insuperable objection to interstellar flight?


Visitors from space may have landed on our planet dozens – hundreds – of times during the long, empty ages while Man was still a dream of the distant future. Indeed, they could have landed on 90 per cent of the Earth as recently as two or three hundred years ago – and we would never have heard of it. If one searches through old newspapers and local records, one can find large numbers of curious incidents that could be interpreted as visitations from space. That stimulating if eccentric writer Charles Fort made a collection of such occurrences in his book Lo! and one is inclined to give them more weight than any comparable modern reports, for the simple reason that they happened long before anyone had ever thought of space travel. Yet at the same time one cannot take them too seriously, because before scientific education was widespread even the commonest celestial phenomena – meteors, comets, auroras and so on – gave rise to the most incredible stories. As they still do, in fact.

Going further back in time, it has been suggested that some of the legends and myths of prehistory, perhaps even the weird entities of many pagan religions, may have been inspired by glimpses of beings from other worlds. But this is pure and unprofitable speculation – unprofitable for the reason that it can never be proved of disproved, but only argued endlessly.

Do we have to wait ten years or a thousand years before the next ship calls? Or if none has ever called before, when will our Earth’s billions of years of isolation be ended? It may be that our first meeting with alien intelligences is already far nearer to us in time than Columbus’ landing in the New World.

One would like to think that we will be the discoverers, not the discovered. Yet perhaps when we leave the snug little confines of the Solar System, we may meet a bored reception committee which greets us with the words: “Taken your time, haven’t you? Welcome to the Galactic Federation; here’s the book of rules.”

Or – and this is the most depressing thought of all – perhaps we have already been blacklisted. It provides a very simple, and horribly plausible, explanation for our apparent lack of visitors to date.

The neighbors may already know everything about us; who can blame them, therefore, if they’ve kept a few light-years away?

The Sun

[First lines:]
If Dr. Gallup were to ask a fair sample of the public the straightforward question: “What is the nearest star?” the replies would probably be something like this:

95% – “How’s that again?”
3% – “Alpha Centauri”
2% – “Proxima Centauri”

They would all be wrong, even the erudite 2% who knew that Proxima was a fraction of a light-year closer to Earth than its companion, Alpha. For the nearest star is – the Sun.


As soon as fairly accurate measurements of the Sun's distance and size (diameter 864,000 miles – or a hundred times that of Earth) became available about three centuries ago, astronomers had a major problem on their hands, though just how major it was they didn't realize for another century. The amount of energy that Earth receives from the Sun is enormous; it is roughly equivalent to a one-kilowatt electric heater on every square yard of our planet's surface. But Earth itself intercepts only a minute fraction of the Sun's rays; most of the energy goes rushing past into space and is, from our admittedly self-centered point of view, completely wasted.

Where does all that energy come from?


In the history of the world, there has been no more momentous quest than the search for that secret – uncannily foreshadowed in the legend of Prometheus, who brought fire from heaven to earth at the price of having his own body continually devoured.


We now know that helium is the ash which is left when hydrogen is burnt in the atomic furnace of the Sun. But the type of “burning” that takes place in the Sun is as much fiercer than ordinary combustion as the flame of a blowtorch is warmer than the pale glow of a firefly. It is an atomic, not chemical, process, and takes place at temperatures of millions instead of thousands of degrees. The Sun's interior, in fact, is far too hot for fire, as we know it, to exist.

The solar transmutation of hydrogen to helium, with its accompanying enormous release of energy, is a complex process involving several intermediate stages, and is quite different in detail from the reactions which take place in the H-bomb – though the final result is the same. The Sun also operates on a slightly larger scale; every second of time, some four million tons of matter are converted into raw energy. As the Department of Defense has unaccountably failed to answer my courteous letter asking for precise details of the H-bomb's composition, the following figure is only approximate, but will not be more than a zero astray in either direction. We would have to explode ten billion H-bombs every second if we wanted to equal the energy output of the Sun.

Of Mind and Matter

[First lines.]
For thousands of years the human race has debated, with singular lack of agreement, such questions as the existence of the soul, the meaning of personality, the relationship between the mind and the body and – above all – the possibility of survival after death. The fact that the debate is still just as heated as when it began in the Late Neolithic Period strongly suggests that the wrong questions have been asked, and certain spectacular developments of the last decade indicate, with equal force, that now is a good time to recast them into a form that makes sense.

Those developments are purely scientific – a fact which will upset a great many people with vested interests in some of the pseudo-answers now current. They lie almost entirely in the fields of biophysics, neurology and electronics, and at first sight it may seem improbable that such areas of modern technology could have any conceivable relation to the great questions of philosophy and religion.

But four centuries ago, it would have seemed equally unlikely that several thousand years of cosmological speculation, culminating in the poetic fantasies of Paradise Lost, could have been swept away in a few decades by a couple of lenses in a tube. Today, we are witnessing another scientific breakthrough, in an area that affects us much more personally than any astronomical discovery could possibly do.


Many details of the fantastically complex electro-chemistry of life will elude us for generations yet, but it cannot be doubted now that there is nothing inherently mysterious, or fundamentally unknowable, in the processes that build and power our bodies. That makes them none the less marvellous; real knowledge, when it dispels superstition, seldom diminishes awe. (For can the petty cosmos of Milton compare with the grandeur of the Universe we know today?)


A good many people find it somehow degrading to realize that the human brain, like the human body, is “only” an electrochemical machine and flatly refuse to admit it. This attitude is completely absurd. The Taj Mahal is “only” a mass of stones; the roof of the Sistine Chapel is only plaster and paint. The material is unimportant; the pattern is all that matters. Should an athlete feel that sport is worthless because of the undeniable fact that his body is an elaborate artifice of pumps, levers and elastic fibers? Of course not; indeed, it adds zest and interest to his performance. (It is no coincidence that the first man to run a mile in four minutes was a doctor.) It may well be that we will learn to think properly and effectively only when we know how we think.

We must not commit the elementary error of supposing that the mechanism of the human brain is necessarily similar in detail to that of today’s (or tomorrow’s) electronic computers. It is certainly not so, if only because of the different structural elements involved. This, however, is quite unimportant; what matters is that memory, personality – all the components which make up every human being and distinguish him from all other men who have ever lived – are (    ) the by-product of data storage and processing in an extremely complex computer of some kind. (That blank parenthesis, by the way, is to allow you to insert the word “merely” if it helps your feelings. It will affect the situation just about as much as the actions of Kipling’s “Village That Voted the Earth Was Flat.”)


Even those readers who have found nothing surprising or controversial in what has gone before had better fasten their seat belts at this point.

One characteristic of a pattern is that it can be reproduced; a good example is the way in which endless indistinguishable copies of a symphony can be stamped out from a master recording. (Indistinguishable? Not strictly speaking, but the differences can be made so small that they are of no practical importance.) Now the duplication of a human personality would be an immensely more difficult problem – but it is not a fundamentally different one. We cannot at this primitive stage of our technology begin to guess how it could be achieved, any more than Beethoven could have imagined how a performance of the Ninth Symphony could be snatched out of time and saved for eternity.

The basic problem is that of recording and playing back – using those terms in a general sense – the vast quantity of information involved in defining personality and memory. Yet the actual storage space required is quite small. If Nature manages to compress the pattern of a human body into a couple of cells invisible to the eye, and the memories of a lifetime into a lump of jelly six inches across, is it expecting too much to suppose that Man may one day perform the same feat with a few cubic yards of electronics? After all, we could now pack the Library of Congress into a show box if we had to, and the amount of information there must be comparable with that defining an individual human being.

It therefore follows that, in a strictly scientific sense, reincarnation is theoretically possible.


If you think that this is absurd fantasy, of no practical importance, you have a surprise coming. For it happened to you during the last few months; it will have happened to me by the time you read these words. This is a simple statement of fact – though a fact that could never have been imagined before the tools of modern science were turned upon the mechanism of life.

The atoms in our bodies are in a state of constant flux, being replaced so rapidly by others from the food we eat that we are completely rebuilt every few weeks. Even the bones are involved in this ceaseless ebb and flow of matter. Every one of us moves through the world like a flame, seeking fuel from his environment, assembling it into a momentary pattern, then rejecting the smoke and ash. Only the flame is – relatively – unchanging, until it gutters to extinction at the end of life.

It has been said that no man ever steps twice in the same river; it is almost equally true that no man ever looks at his face twice in the mirror. The flow of flesh may be slower than the movement of water to the sea, but it is no less inexorable.

We are involved, therefore, in a kind of continuous reincarnation almost as marvelous as any other type that has ever been postulated. At the same time, we can see that another popular idea of the mystics – transmigration through lower animals – can have no logical basis. The personality and memory of a human being could no more be squeezed into the limited storage capacity of any other vertebrate (still less invertebrate) than could the entire musical heritage of mankind be recorded on a six-inch disk.


I have little doubt that a great many people will consider these speculations naïvely mechanistic, because they cannot reconcile such imponderables as personality, intelligence – even the soul, if one cares to use the word – with the concepts of electronics or information theory. Such an attitude is a hangover from nineteenth-century materialism – though this charge will make many critics doubly indignant. By the word “machine,” far too many otherwise educated people still envisage a contraption of cogs and cranks and levers; they are still mentally in the steam-engine era. They cannot imagine the subtlety and sophistication of the great computers which are now leaving the laboratory, some of which may comprise a million circuit elements and be as large as a house – yet contain practically no moving parts, though they may carry out a hundred thousand operations a second. The machines we are building now differ in kind as well as degree from all that mankind has ever seen before – and their evolution is barely beginning.

No one can say where it will lead, but glimpsed vaguely in the mists of the future is a dream – I will not say a possibility – which has long been hinted at in most of the religions of the world. Since pattern alone is important, can mind and intelligence exist without matter?


And thus, intelligence, which arose from the interactions of matter and has used it as a vehicle for so many ages, may at last break loose from its origin, as a butterfly from the prison of its chrysalis. And like the butterfly climbing into the summer sky, it may go on to orders of experience completely beyond the reach of its earlier metamorphoses.

Where are we today in the hierarchy which, ages hence, may culminate into something which only the word “spirit” can describe? Are we the chrysalis, the larva – or merely the unhatched egg?

Of Space and the Spirit

That both planets and living creatures are common throughout the Universe must, therefore, now be taken as highly probable, though it cannot yet be proved beyond doubt. We may be hopelessly conservative if we guess that life may be associated with one star in every hundred. Dr. Harlow Shapley, in his book Of Stars and Men, reduces the figure to one in a trillion by being deliberately ultrapessimistic; he considers a more reasonable estimate to be one in a million. But every figure is, at the present state of our semi-ignorance, pure guesswork; let us for the sake of argument settle on that one in a hundred, and see where it leads us.

It implies the existence of a billion life-bearing worlds in our single Galaxy – the whirlpool of stars of which our Sun is an undistinguished out-of-town member, lying in one of the remoter spiral arms. And within the range of our telescopes there are approximately a billion other galaxies.

Now a billion is a number all too familiar in today’s budgets and military estimates, but that does not mean that anyone could visualize it. Should you feel like trying, I recommend this simple and highly instructive experiment.

Go down to the nearest beach and collect a bucketful of sand; then bring it home and empty it on the table. You now have in front of you – assuming that the sand is of reasonable fineness – something like a billion separate particles. Sift them through your fingers; each is a distinct entity, different from all its companions. How long would it take you to examine every clearly visible individual in the small pile before you? Devoting one minute to each, and working eight hours a day, it would keep you busy for almost six thousand years – the whole span of human history.

That is what a billion means; and now try to imagine that every one of those grains of sand is itself a world, perhaps teeming with life, and perhaps bearing rational creatures who measure their histories not in thousands but in millions of years. If you succeed, you have a faint mental picture of our Galaxy; if you wish to visualize the whole observed Universe, however, the operation must be repeated with each grain of sand now representing an entire galaxy.


The discovery of any form of life, however humble, on the planets would greatly affect our outlook upon the Universe by changing what is now a surmise into a certainty. Even a few lichens on Mars or a few amoebae in the (still hypothetical) seas of Venus would prove that life is not a rare disease that happens to have attacked the planet Earth. And with that settled, it would be illogical to deny the existence of higher forms elsewhere.


With today’s electronic techniques stretched to the utmost, we could just about get a readable Morse signal to the nearest star. It might therefore be worth while, as soon as we can establish satellite listening posts well away from the radio racket and electrical interference of Earth, to begin a search for intelligently modulated signals from space. If we can tackle interstellar communication only sixty years after we have invented the radio, it is not unreasonable to assume that there may be transmitters within a few light-years of us far more powerful than any we have yet built. Even today, many of our radars must far outrange the Solar System – though we can be thankful that our commercial radio programs will have faded far below the level of cosmic noise before they can affront any stellar neighbors.

By one means or another, therefore, we may hope to establish the existence of extraterrestrial intelligences before many more decades – or at most centuries – have passed. If anyone still feels doubtful of this, I would remind him of the unfortunate error of August Comte [1798-1857], who rashly proclaimed our eternal ignorance concerning the composition of the stars. The speed and thoroughness with which the spectroscope refuted him is a good reminder that there are no apparently fundamental limits to knowledge which may not be transcended by new techniques or inventions.

Keeping this in mind, it is not premature, and it is certainly stimulating, to consider what effect these undoubted but still unknown revelations will have upon the minds of men. They will certainly accelerate a process which has been gaining momentum since Copernicus dethroned Earth from the center of creation and started it upon its still-continuing journey to the periphery of the Universe. Today, it is difficult for us to believe that as recently as the time of Shakespeare no one knew that other worlds existed; though the Greeks had surmised it, there was no direct proof until the invention of the telescope circa 1608, and so to almost all educated men up to a dozen generations ago, our planet was the Universe. One might even say that this was still true, for 90 per cent of the human race, until the morning of October 4, 1957.


As mankind’s modest place in the scheme of the Universe is more and more widely recognized – on the emotional as well as the intellectual level – the effects on our racial pride will certainly be profound. To the Psalmist’s question, “What is Man, that Thou are mindful of him?” the future may well give the ironic answer, “What, indeed?” Our species has come into existence in the last five-thousandth of the Earth’s history, and the entire span of human civilization extends for barely a millionth of that time. Unless we exhibit a conceit which can be aptly termed astronomical, we must assume that there are many, many races in the Universe far more advanced than ours intellectually as well as spiritually. Indeed, the extreme youth of Homo sapiens on any cosmic time scale makes it likely that the vast majority of rational extraterrestrial creatures may be superior to us by millions of years of development.

This prospect has been viewed with some alarm by many Christians, who find it hard to reconcile the existence of other intelligent races with the doctrines of Incarnation and Redemption. If God made Man in His own image, what of all other creatures who must be made in different images, if they are to survive on alien worlds? And if Christ has saved us alone, what have we done to merit such special treatment?


Undoubtedly the most stimulating writer on these matters is C. S. Lewis, professor of literature at Magdalene College, Cambridge University. In two famous novels, Out of the Silent Planet and Voyage to Venus (Perelandra), Lewis has developed the theme that only humanity has fallen, and that the creatures on other planets are free from the guilt which requires our redemption. This view of mankind’s peculiar depravity, well justified by a glance at the daily papers, implies that our planet is under quarantine; in a recent issue of Christian Herald (April, 1958) Professor Lewis makes it clear that he regards with some disfavor our current attempts to evade this quarantine. “Let us,” he remarks, “thank God that we are still very far from travel to other worlds.” Unless one considers twenty-five years a very long time, this statement must now be modified to mean “travel to other worlds inhabited by intelligent beings.”

Another possibility, but one so flattering to our racial pride that it is hard to believe it can be true, is that the redemption of other races will proceed through us – that we, in fact, may one day take salvation to the stars. Remembering how “gun and gospel” have been combined in the past, and the manner in which so many missionaries have attempted to “civilize the natives,” Lewis is not at all happy about this prospect. “Would our missionaries,” he asks, “recognise an unfallen race if they met it? Would they continue to press upon creatures that did not need to be saved that plan of Salvation which God has appointed to Man? Would they denounce as sins mere differences of behavior which the spiritual and biological history of these strange creatures fully justified?

Anyone who has read accounts of past mission activities (Bradford Smith’s Yankees in Paradise is an excellent example) will appreciate the force of these questions, and Lewis argues nobly: “We must stand firm against all exploitation and all theological imperialism…. Our loyalty is due not to our species but to God. Those who are, or can become, His sons, are our real brothers even if they have shells and tusks. It is spiritual, not biological, kinship that counts.” In applauding these sentiments, one can also wish that they were better applied on Earth.


At this moment in time, at the very beginning of the centuries-long gold rush into ever richer, ever expanding fields of knowledge, we must realize that there is no hope of understanding our Universe until we have examined a fairly large sample of it – certainly a good deal more than one small planet out of billions. Though this cautious attitude may disappoint many who are hot for certainties, any other policy would be utterly naïve. It would put us in the same position as Pacific islanders who have never yet had any contact with the world beyond their coral reef, yet who attempt to construct a picture of the whole Earth and its peoples from the view they get from the top of their highest palm tree.

Harlow Shapley, in the already-mentioned Of Stars and Men, looks forward to our present “anthropomorphic religions and philosophies, which have so often been conspicuously earth-bound and much tangled up with the human mind and human behavior” expanding to embrace these new revelations of science, adding that “a one-planet deity has for me little appeal.” The British astronomer Fred Hoyle, in the controversial series of radio talks which later became the well-known book The Nature of the Universe, took an uncompromisingly materialist view which caused much heart-burning and ink-slinging among his listeners. He concluded that there is no evidence for the existence of God in the Universe around us, religion presumably being an illusion of the human mind.

On this view, it must be assumed that when we contact superior extraterrestrial intelligences we shall find that belief in a supernatural order of things marks an early stage of development amongst most rational creatures, and perishes with the rise of science. Most disconcerting of all would be the discovery that Man alone is a myth-making animal, forever impelled to fill the gaps in his knowledge by fantasies. (Yet if this be the price we have had to pay for the whole realm of art, which is always an attempt to create the non-existent, we need not be ashamed. We will be better off than beings who possess all knowledge, but know nothing of poetry and music.)

Whatever the outcome of our discoveries and adventures in space, the fact will remain that the real Universe is more miraculous than any miracle. And even if every man now alive, seen from a century hence, appears no more than “a savage suckled in an outworn creed,” that will leave God precisely where He has always been, if He is anywhere – back at the beginning of creation, X billion years ago. (As of today, X = 5. But remember Archbishop Ussher.) Perhaps when God reached zero of the cosmic countdown, He turned His attention elsewhere, knowing that His work with us was done. It will certainly not diminish His glory – rather the reverse – if we discover that, in all ages since time began, He has never tinkered with the mechanism of the Universe. Only an unskilled craftsman is forced to make perpetual adjustments to his handiwork; the real expert packs his tools and walks away when the job is done….

Let us, therefore, wait in a spirit of expectant humility for whatever light the future may throw upon these great questions, remembering that our intellectual sincerity may well be judged by our lack of apprehension. No honest man was ever afraid of the truth.

Faiths come and go, but Truth abides. Out there among the stars lie such truths as we may understand, whether we learn them by our own efforts, or from the strange teachers who are waiting for us along the infinite road on which our feet are now irrevocably set.

[1] “The Challenge of the Spaceship” is a much revised and updated version of a talk delivered to the British Interplanetary Society in 1946, during my first term as a chairman. Despite the obvious derivation of the title, it should not be assumed that I now owe any particular allegiance to Professor Toynbee, though at the time of writing I was much taken by a lecture I had just heard him deliver on “The Unification of the World”.
One other historical note: I am still rather proud of the fact that when I sent the first printed version of this paper to George Bernard Shaw (then in his ninety-first year), he promptly joined the British Interplanetary Society, and remained a member until his death.
[Arthur’s original note.]
[2] For a more detailed discussion of this problem, and an updated version of Jeans’ analogy, see “Where’s Everybody?” [Arthur’s original note.]
[3] Perelandra (Voyage to Venus). Professor Lewis’s more recent views are discussed in “Of Space and the Sprit”. [Arthur’s original note.]
[4] This essay, together with “So You’re Going to Mars?” and “Vacation in Vacuum”, all written for the Holiday magazine in the early 1950s, constitute Arthur’s interplanetary Baedeker. All three were first published in book form in The Challenge of the Spaceship (1959), but only “Journey by Earthlight” was not reprinted in Report on Planet Three and Other Speculations (1972). Selections from the other two essays can be found in the post about the later volume where they benefit from the addition of prefatory notes. In the end of “The Challenge of the Spaceship” in this book, there is another prefatory note worth quoting:
In the following three pieces I have attempted to bring home the realities of space travel by considering what the tourists of the twenty-first century will meet when vacationing on the Moon, Mars or a satellite hotel. These articles were commissioned, with considerable foresight, by Holiday Magazine almost five years before the launching of the first Sputnik, and I have reproduced them here with only one alteration – the addition of the letters U.S.S.R….
In attempting to give close-ups of the Moon and Mars I have, obviously, had to go beyond the limits of known facts; the best telescopes cannot bring us to within less than 50,000 miles of Mars, or 250 miles of the Moon. My comments on extraterrestrial life forms are therefore purely speculative, but I have been careful not to let them conflict with present-day knowledge.
Much of the material in these three articles has been used to provide the background of Islands in the Sky [1952], Earthlight [1955] and The Sands of Mars [1951].
[5] This seemed wildly optimistic in the early 1950’s. Today, 1970 would be a safer guess. [Arthur’s original note.]
[6] See “The Men on the Moon” for a fuller account of lunar nomenclature. [Arthur’s original note.]
[7] Cf. Arthur’s story “The Secret” (1963), reprinted in the collection The Wind from the Sun (1972).

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