Extraterrestrial Civilizations - Isaac Asimov [107]
Lagrange discovered five such points altogether, but three of them are of no practical importance because they represent an unstable condition. An object would have to remain exactly at those points to remain at rest with respect to the Moon. Once pushed out of place, however slightly, the object would continue to drift away and would never return. The two points in which an object remains stably in place (except for libration) are those points that form equilateral triangles with the Moon and the Earth. The one that lies toward the eastern horizon is L4 and the one toward the western is L5.
O’Neill suggested that advantage be taken of that gravitational lock and that space settlements be built in the regions around the two libration points, settlements that would become permanent parts of the Earth-Moon system. The settlements themselves could consist of spheres, cylinders, or doughnut-shaped objects that would be large enough to hold 10,000 to 10 million people.
Human beings could live on the inner surface of such objects, which would be set to spinning at a rate that would produce a centrifugal effect that would hold everything and everyone to that inner surface with a force equivalent to Earth’s surface gravity. The inner surface could then be designed and contoured into a familiar world. It could be spread with soil, which could be used for agriculture and, eventually, animal husbandry. All the artificial works of man—his buildings and machines—would be there, too.
The material forming the hull of the settlement would be composed of alternations of metal and glass. Sunshine, reflected by large mirrors that would accompany the settlement into orbit, would enter and illuminate the settlement, turning what would otherwise be a cave into a sunlit world. The entry of light could be controlled by louvers over the windows to allow for alternating day and night and to keep the temperature of the settlement equable.
It is from the Sun that the colony would obtain its energy—a copious, easily handled, nonpolluting form of energy.
The larger settlements would have a content of air thick enough to allow a blue sky and to support clouds. Parts of the inner surface of large settlements could be modeled into mountainous territory—full-sized mountains and not just bas-reliefs.
It would be expensive to build such settlements, but the expense would be far less than the world now spends on its various military machines. Since Earth, if it is to survive, will have to practice increasing international cooperation, those military machines will have to wither, and the effort to build settlements in space may well offer us a constructive way to make use of the money and people that are now engaged in war and its preparations.
Besides, the expense of building settlements will decrease as the techniques for the purpose are improved and as the space settlers themselves, in the natural urge to expand their range, take over the building of further settlements.
But where are we to get all the material for the construction of these space settlements? Our groaning planet, sagging under its weight of humanity, with its supply of key resources sputtering and giving out, couldn’t possibly afford to give up the colossal quantities of supplies needed for it all. Millions to hundreds of millions of tons of construction material would be needed for each settlement.
Fortunately we have the Moon, a completely dead world with no native life, however simple, whose “rights” need trouble our sense of ethics.
Lunar material would yield the aluminum, iron, titanium, glass, concrete, and other substances needed for constructing the colony. Lunar soil would be spread over the interior surface. Not only is all that material present in the Moon in huge quantities, but lifting it off the Moon against that body’s weak gravity would require only 1/20 the effort necessary for lifting it off Earth. All the smelting and other chemical work would