First, then, in the material world. Here prediction is on its surest ground, and is, in the first stages, almost a business of mathematics. The physical discoveries of the last twenty-five years must find their application in the world of action - a process which has hardly begun, but the nature of which can easily be seen. So far we have been living on the discoveries of the early and mid-nineteenth century, a macro-mechanical age of power and metal. Essentially it succeeded in substituting mechanism for some of the simpler mechanical movements of the human body, with steam and later electrical power in the place of muscle energy. This was sufficient to revolutionize the whole of human life and to turn the balance definitely for man against the gross natural forces; but the discoveries of the twentieth century, particularly the micro-mechanics of the Quantum Theory which touch on the nature of matter itself, are far more fundamental and must in time produce far more important results. The first step will be the development of new materials and new processes in which physics, chemistry and mechanics will be inextricably fused. The stage should soon be reached when materials can be produced which are not merely modifications of what nature has given us in the way of stones, metals, woods and fibers, but are made to specifications of a molecular architecture. Already we know all the varieties of atoms; we are beginning to know the forces that bind them together; soon we shall be doing this in a way to suit our own purposes. In fact, Professor Goldschmidt of Oslo has already made many model structures in which existing substances are closely copied in different atoms, so as to make new substances, softer or harder, or more or less fusible. Sulpho-nitrdes with silicate structures will be harder and more infusible than anything on earth. A similar substance - carboloy - which is already on the market - combines the strength of steel with the hardness of diamond, and is capable of working glass like a metal. There are similar possible model structures for organic substances; the complexities are greater but the results will be more far-reaching. The linked molecules that make fibers and elastic substances such a rubber or muscle, are already yielding to X-ray investigation; the proteid bodies of living matter must have an analogous but more complex structure. After the analysis will come the synthesis; and for one place in which we can imitate nature we will be able to improve on her in ten, and furnish models of organic materials with more varied properties and capable of withstanding more rigorous conditions. The result - not so very distant - will probably be the passing of the age of metals and all that it implies - mines, furnaces, and engines of massive construction. Instead we should have a world of fabric materials, light and elastic, strong only for the purposes for which they are being used, a world which will imitate the balanced perfection of a living body.
At the same time, much that we require for the purposes of modern life would become no longer necessary. With improved systems of chemical manufacture our food and our clothing will be made with much less expenditure of energy in manufacture and transport. And the development of mechanism will not cease: it should turn into more refined forms - heat-engines capable of working at lower and lower temperature differences, engines of higher and higher speed, electrical machines of high potential and high frequency - and should lead to the solution of two most fundamental problems, the efficient transmission of energy by low frequency (wireless) waves, and the direct utilization of the high frequency (light) waves of the sun. On the chemical side the problem of the production of food under controlled conditions, biochemical and ultimately chemical, should become an accomplished fact. In the new synthetic foods will be combined physiological efficacy and a range of flavor equal to that which nature provides, and exceeding it as taste demands; with a range of texture also, the lack of which so far has been the chief disadvantage of substitute food stuffs. With such a variety of combinations to work on, gastronomy will, for the first time, be able to rank with the other arts.
All these developments would lead to a world incomparably more efficient and richer than the present, capable of supporting a much larger population, secure from want and having ample leisure, but still a world limited in space to the surface of the globe and in time to the caprices of geological epochs. Already ambition is stirring in men to conquer space as they conquered the air, and this ambition - at first fantastic - as time goes on become more and more reinforced by necessity. Ultimately it would seem impossible that it should not be solved. Our opponent is here the simple curvature of space-time - a mere matter of acquiring sufficient acceleration on our own part - which, sooner or later, must be practicable. Even now it is possible to imagine methods of accomplishing it, based on no more knowledge than we already possess. The problem of the conquest of space is one in which all the difficulties are at the beginning. Once the earth's gravitational field is overcome, development must follow with immense rapidity. Without going too closely into the mechanical details, it appears that the most effective method is based on the principle of the rocket, and the difficulty, as it exists, is simply that of projecting the particles, whose recoil is being utilized, with the greatest possible velocity, so at to economize both energy and the amount of matter required for propulsion. Up to the present all forms of rocket depend on the movement of masses of gas in which the individual molecules are moving at high velocities in perfectly random directions, and use is only made of the average velocity in the desired direction. What is wanted in the first place is a form of Maxwell's Demon which will allow only those molecules, whose velocities are high and in the direction opposite to the trajectory of the rocket, to escape. The next difficulty is that to set in motion any large rocket the mass of gas required is of the same order as the weight of the rocket itself, so that it is difficult to imagine how the rocket could contain enough material to maintain its propulsion for any length of time. When the radio-transmission of energy is effected half the difficulty will be removed and the projection may very well ultimately be effected by means of positive rays at high potential. It may be that both the problem of space travel and the ethereal transference of energy have already been solved by Professor Japolsky's magnetofugal waves. These are a type of magnetic vortex ring, propagated through space, which, instead of spreading as ordinary electromagnetic waves, remain concentrated along the axis of propagation. Apart from its mode of projection, the construction of the space vessel offers little difficulty since it is essentially the same problem as that of the submarine. Naturally the first space vessels will be extremely cramped and uncomfortable, but they will be manned only by enthusiasts. The problem of landing on any other plant or of returning to earth is much more difficult, mainly because it requires such a nice control of acceleration. Probably the first journeys will be purely for exploration, without landing, and the travellers, if they return to earth at all, will have to abandon their machine and descend in parachutes.
However it is effected, the first leaving of the earth will have provided us with the means of travelling through space with considerable acceleration and, therefore, the possibility of obtaining great velocities - even if the acceleration can only be maintained for a short time. If the problem of the utilization of solar energy has by that time been solved, the movement of these space vessels can be maintained indefinitely. Failing this, a form of space sailing might be developed which used the repulsive effect of the sun's rays instead of wind. A space vessel spreading its large, metallic wings, acres in extent, to the full, might be blown to the limit of Neptune's orbit. Then, to increase its speed, it would tack, close-hauled, down the gravitational field, spreading full sail again as it rushed past the sun.
So far, those who have considered spatial navigation have regarded it from the point of view of exploration and planetary visitation, but the vast importance of escaping from the earth's gravitational field has been almost entirely overlooked. On earth, even if we should use all the solar energy which we received, we should still be wasting all but one two-billionths of the energy that the sun gives out. Consequently, when we have learnt to live on this solar energy and also to emancipate ourselves from the earth's surface, the possibilities of the spread of humanity will be multiplied accordingly. We can imagine this occurring in definite stages. When the technicalities of space navigation are fully understood there will, from desire or necessity, come the idea of building a permanent home for men in space. The ease of actual navigation in space together with the difficulties of taking-off from or landing on planets like the earth with considerable gravitational fields will in the first place lead to the necessity for bases for repairs and supplies not involving these difficulties. A damaged space vessel would, for instance, almost be bound to be destroyed in attempting earth landing. At first space navigators, and then scientists whose observations would be best conducted outside the earth, and then finally those who for any reason were dissatisfied with earthly conditions would come to inhabit these bases and found permanent spatial colonies. Even with our present primitive knowledge we can plan out such a celestial station in considerable detail.
Imagine a spherical shell ten miles or so in diameter, made of the lightest materials and mostly hollow; for this purpose the new molecular materials would be admirably suited. Owing to the absence of gravitation its construction would not be an engineering feat of any magnitude. The source of the material out of which this would be made would only be in small part drawn from the earth; for the great bulk of the structure would be made out of the substance of one or more smaller asteroids, rings of Saturn or other planetary detritus. The initial stages of construction are the most difficult to imagine. They will probably consist of attaching an asteroid of some hundred years or so diameter to a space vessel, hollowing it out and using the removed material to build the first protective shell. Afterwards the shell could be re-worked, bit by bit, using elaborated and more suitable substances and at the same time increasing its size by diminishing its thickness. The globe would fulfil all the functions by which our earth manages to support life. In default of a gravitational field it has, perforce, to keep its atmosphere and the greater portion of its life inside; but as all its nourishment comes in the form of energy through its outer surface it would be forced to resemble on the whole an enormously complicated single-celled plant.
The outermost layer would have a protective and assimilative character. The presence of meteoric matter in the solar system moving at high speeds in eccentric orbits would be the most formidable danger in space travelling and space inhabitation. Certain meteorite swarms could be avoided altogether by keeping out of their tracks; larger meteorites could be detected at a distance by visual observation or by the effect of their gravitational fields. These might be avoided by changing the course of the globe or deflecting the meteorites by firing high-speed projectiles into them. Smaller meteorites would be impossible to avoid. The shell of the globe would have to be made strong enough not to be penetrated or cracked by them, and would have to possess regenerative mechanisms for repairing superficial damage. Possibly the function which our atmosphere performs for the earth could be imitated by jets of high-speed gas or electrons which, projected at meteorites, would vaporize them and thus prevent them doing any damage. At the same time meteoric matter might be the chief source of the material required for the growth or propulsion of the globe if a method of assimilating it could be found.
The outer shell would be hard, transparent and thin. Its chief function would be to prevent the escape of gases from the interior, to preserve the rigidity of the structure, and to allow the free access of radiant energy. Immediately underneath this epidermis would be the apparatus for utilizing this energy either in the form of a network carrying a chlorophyll-like fluid capable of re-synthesizing carbohydrate bodies from carbon dioxide,. or some purely electrical contrivance for the absorption of radiant energy. In the latter case the globe would almost certainly be supplied with vast, tenuous, membranous wings which would increase its area of utilization of sunlight. The subcutaneous circulation would also have the necessary function of dissipating superfluous heat, in as low temperature radiation as possible. Underneath this layer would probably lie the main stores of the globe in the form of layers of solid oxygen, ice and carbon or hydro-carbons. Inside these layers, which might be a quarter of a mile in thickness, would lie the controlling mechanisms of the globe. These mechanisms would primarily maintain the general metabolism, that is, they would regulate the atmosphere and climate both as to composition and movements. They would elaborate the necessary food products and distribute mechanical energy where it was required. They would also deal with all waste matters, reconverting them with the use of energy into a consumable form; for it must be remembered that the globe takes the place of the whole earth and not of any part of it, and in the earth nothing can afford to be permanently wasted. In this layer, too, would be the workshops and laboratories concerned with the improvement of the globe and arrangements for its growth.
Inside the mechanical layer would be the living region and here imagination has a more difficult task. It would, of course, not be necessary to have either houses or rooms in the same sense in which we have them on the earth. The absence of bad weather and of gravitation makes most of the uses that we have for houses superfluous. Perhaps we can safely assume that a certain number of cells closed by thin, but sound-proof, partitions would be necessary for work requiring special isolation, but the major part of the lives of the inhabitants of the globe would be spent in the free space which would occupy the greater portion of the center of the globe.
This three-dimensional, gravitationless way of living is very difficult for us to imagine, but there is no reason to suppose that we would not ultimately adjust ourselves to it. We should be released from the way we are dragged down on the surface of the earth all our lives: the slightest push against a relatively rigid object would send us yards away; a good jump - and we should be spinning across from one side of the globe to the other. Resistance to the air would, of course, come in, as it does on earth; but this could be turned to advantage by the use of short wings. Objects would become endowed with a peculiar levity. We should have to devise ways of holding them in place other than by putting them down; liquids and powders would at first cause great complications. An attempt to put down a cup of tea would result in the cup descending and the tea remaining as a vibrating globule in the air. Dust would be an unbearable nuisance and would have to be suppressed, because even wetting it would never make it settle. We should find in the end that all these things were great conveniences, but at first they would be extremely awkward. The possibilities of three-dimensional life would make the globes much roomier than their size would suggest. A globe interior eight miles across would contain as much effective space as a countryside one hundred and fifty miles square even if one gave a liberal allowance of air, say fifty feet above the ground.
The activity of the globe is, of course, by no means confined to its interior. In the first place it would necessarily have a number of effective sense and motor organs. Essentially the former would consist of an observatory which continually recorded the position of the globe and at the same time kept a look-out for an meteoric bodies of perceptible size which might damage it. On the whole the globe would not be designed for travel. It would move in an orbit around the sun without any expenditure of energy; but occasionally it might be necessary to shift its orbital position to a more advantageous one, and for this it would require a small motor of a rocket variety.
Yet the globe would be by no means isolated. It would be in continuous communication by wireless with other globes and with the earth, and this communication would include the transmission of every sort of sense message which we have at present acquired as well as those which we may require in the future. Interplanetary vessels would insure the transport of men and materials, and see to it that the colonies were not isolated units.
However, the essential positive activity of the globe or colony would be in the development, growth and reproduction of the globe. A globe which was merely a satisfactory way of continuing life indefinitely would barely be more than a reproduction of terrestrial conditions in a more restricted sphere. But the necessity of preserving the outer shell would prevent a continuous alteration of structure, and development would have to proceed either by the crustacean-like development in which a new and better globe could be put together inside the larger one, which could be subsequently broken open and re-absorbed; or, as in the molluscs, by the building out of new sections in a spiral form; or, more probably, by keeping the even simpler form of behavior of the protozoa by the building of a new globe outside the original globe, but in contact with it until it should be in a position to set up an independent existence.
So far we have considered the construction and mechanism of the globe rather than its inhabitants. The inhabitants can be divided into the personnel or the crew, and the citizens or passengers. With the first - except that their tasks would be more complicated and more scientific than those that fall to the officers and crew of a modern ship - we need not be concerned. To the others the globe would appear both as hotels and laboratories. The population of each globe would be by no means fixed; constant interchange would be taking place between them and the earth even when the greater portion of human beings were actually inhabiting globes. There would probably be no more need for government than in a modern hotel: there would be a few restrictions concerned with the safety of the vessel and that would be all.
Criticism might be made on the ground that life in a globe, say of twenty or thirty thousand inhabitants would be extremely dull, and that the diversity of scene, of animals and plants and historical associations which exist even in the smallest and most isolated country on earth would be lacking. This criticism is valid on the initial assumption that men have not in any way changed. Here, to make globe life plausible, we must anticipate the later chapters and assume men's interests and occupations to have altered. Already the scientist is more immersed in his work and concentrates more on relations with his colleagues than in the immediate life of his neighborhood. On the other hand, present æsthetic tendencies verge towards the abstract and do not demand so much inspiration from untouched nature. What has made a small town or a small country seem in the past a narrow sphere of interest has been on the one hand its isolation, and on the other hand the fact that the majority of its inhabitants are at so low a level of culture as to prevent any considerable intellectual interchange within its boundaries. Neither limitation holds for the globes, and the case of ancient Athens is enough to show that small size alone does not prevent cultural activity. Free communications and voluntary associations of interested persons will be the rule, and for those whose primary interest is in primitive nature there will always remain the earth which, free from the economic necessity of producing vast quantities of agricultural products, could be allowed to revert to a very much more natural state.
As the globes multiplied they would undoubtedly develop very differently according to their construction and to the tendencies of their colonists, and at the same time they would compete increasingly both for the sunlight which kept them alive and for the asteroidal and meteoric matter which enabled them to grow. Sooner or later this pressure, or perhaps the knowledge of the imminent failure of the sun, would force some more adventurous colony to set out beyond the bounds of the solar system. The difficulty involved in making this jump is probably as great as that of leaving the earth itself. Interstellar distances are so large that high velocities, approaching those of light, would be necessary; and though high velocities would be easy to attain - it being merely a matter of allowing acceleration to accumulate - they would expose the space vessels to very serious dangers, particularly from dispersed meteoric bodies. A space vessel would, in fact, have to be a comet, ejecting from its anterior end a stream of gas which, meeting and vaporizing any matter in its path, would sweep it to the sides and behind in a luminous trail. Such a method would be very wasteful of matter, and one might perhaps count on some better one having been devised by that time. Even with such velocities journeys would have to last for hundreds and thousands of years, and it would be necessary - if man remains as he is - for colonies of ancestors to start out who might expect the arrival of remote descendants. This would require a self-sacrifice and a perfection of educational method that we could hardly demand at the present. However, once acclimatized to space living, it is unlikely that man will stop until he has roamed over and colonized most of the sidereal universe, or that even this will be the end. Man will not ultimately be content to be parasitic on the stars but will invade them and organize them for his own purposes.
A star is essentially an immense reservoir of energy which is being dissipated as rapidly as its bulk will allow. It may be that, in the future, man will have no use for energy and be indifferent to stars except as spectacles, but if (and this seems more probable) energy is still needed, the stars cannot be allowed to continue to in their old way, but will be turned into efficient heat engines. The second law of thermodynamics, as Jeans delights in pointing out to us, will ultimately bring this universe to an inglorious close, may perhaps always remain the final factor. But by intelligent organization the life of the universe could probably be prolonged to many millions of millions of times what it would be without organization. Besides, we are still too close to the birth of the universe to be certain about its death. In any case, long before these questions become urgent it would seem impossible not to assume that man himself would have changed radically in this environment and the nature of this change we must consider in the next chapter.