From the stars has come the matter of our world and of our bodies, and it is to the stars that we will someday return. These comings and goings are the theme of this book.

Conventional wisdom holds that stars suitable for the origin of life are common, and that planets on which life has arisen are far from rare. This viewpoint is quite in keeping with the past five centuries of Copernicanism in astronomy, which have steadily removed mankind farther and farther from the center of things.

However, in recent years there have been the beginnings of a contrary view. This view holds that far from being commonplace in the Galaxy, life such as ours has resulted from a most improbable concatenation of events. If we then are not at the center of things, at least we may have the pleasure of contemplating that only by rare accident have we been fortunate enough to evolve; that one could search hundreds of thousands of stars without finding our like. Yet life need not be tied to the planets where it arises. Intelligent cultures, by inventing the arts of space colonization and star flight, can make their presence felt on a galactic scale.

We thus are led to think about space colonization. The core of this book is a series of chapters which set forth an agenda and program, a sequence of space projects leading to the building of the largest imaginable space colonies. This sequence is a “sixfold way, ” a group of six major themes or efforts in space. No one of them exists merely to pave the way for greater things; all can be justified and pursued in and of themselves. Yet the sum total of these efforts is to give us true space colonies.

We begin with the space shuttle, which will gain us a routine access to space and allow initial work in space construction, demonstrating anew the promise beyond our Earth.

Next, there is the orbiting construction platform. Supported by the shuttle, it will allow construction of large communications spacecraft. Its most exciting uses, however, lie in experiments that will show the way to the power satellite to gather solar energy. It is the powersat that will stand at the center of a truly large space effort.

The powersat has been conceptualized as a structure as large as Manhattan Island, yet weighing only as much as an aircraft carrier. Such powersats today are receiving increasingly serious attention in Washington, and the first may be built before century’s end. The building of powersats constitutes the third major theme of the six.

The first powersats will be assembled from materials brought from Earth, but they will become more economic if they are built from lunar resources. The use of such lunar resources in powersats will compel us to develop far-ranging paths of space commerce, with over a thousand people living in space. This is theme four.

Next come the first true space colonies. They will be built to serve the powersat project, providing comfortable homes for the space workers and their families. Bit by bit, they will become less dependent on Earth, more self-sufficient.

Finally, when all has been reduced to well-understood practice, these initial colonies will expand, but only when it becomes possible to build new colonies as cities in space, whose land will be available to all.

And when we have gone down this sixfold path, when at last the space colonies have grown and prospered, we will return again to the question of our place in the Galaxy. From a space colony to a starship is but a short step; it is a matter of adding appropriate power supplies and thermonuclear engines. What we may hope to do in the next century or so, perhaps other stellar civilizations have had the opportunity to do for billions of years. On the one hand, locales where intelligent life has arisen are rare. On the other hand, once intelligence arises it may sweep across the Galaxy in an evolutionary moment, and the places of its colonies may be quite widespread. We do not understand at all well our place in the Galaxy, but we may speculate. Among the matters for our speculation is whether after all we may be the only advanced civilization in the Galaxy.

The answer to this question may well lie in the distant future, but space colonization, or at least the major efforts which will point in its direction, are a matter for the next few decades. These colonies are not here yet, but they will come; they have long been foreseen.