Space colonization is the creation of human settlements beyond the earth. Theorists conceptualize settlements on or below the surfaces of various planets. It is also believed that orbital colonies can be built which will orbit the earth, the moon or other planets.
The idea of space colonization, arrived from the science fiction, is now being advocated as a realistic idea by prominent scientists and politicians. Some companies, like SpaceX and MarsOne are already making serious efforts to bring space colonization into reality. NASA is reported to be planning an orbital space colony that can house several thousand people over a long period of time.
The reasons given for the necessity of space colonization are generally the same as those that have propelled all human colonization efforts, although on a much larger scale. Stephen Hawkins, the noted theoretical physicist, has advocated that the survival of the human species can only be ascertained through a program of active colonization. It is viewed that the pressure of population on an overcrowded earth may eventually threaten the survival of other species.
Another argument generally put up is that space colonization will create a residual pool of human life, enabling the preservation of the species in the event of some global calamity, such as a nuclear holocaust or a strike by an asteroid or comet.
Furthermore, the vast resources of space will open the way for an unprecedented expansion and prosperity of the human race, if properly harnessed.
There are still some technological hurdles that will need to be adequately crossed before widespread space colonization becomes possible. For example, life support facilities for vast numbers of men, protective shields from radiation, transport modes and propulsive mechanisms that will make the traversing of interplanetary and interstellar distances feasible.
However, there is much optimism in this regard and with the current progress, it is very likely that some level of space colonization will be achieved within our lifetime.