Space can be mapped and crossed and occupied without definable limit; but it can never be conquered. When our race has reached its ultimate achievements, and the stars themselves are scattered no more widely than the seed of Adam, even then we shall still be like ants crawling on the face of the Earth. The ants have covered the world, but have they conquered it — for what do their countless colonies know of it, or of each other?
So it will be with us as we spread out from Earth, loosening the bonds of kinship and understanding, hearing faint and belated rumors at second — or third — or thousandth hand of an ever dwindling fraction of the entire human race. Though the Earth will try to keep in touch with her children, in the end all the efforts of her archivists and historians will be defeated by time and distance, and the sheer bulk of material. For the numbers of distinct human societies or nations, when our race is twice its present age, may be far greater than the total number of all the men who have ever lived up to the present time.
We have left the realm of comprehension in our vain effort to grasp the scale of the universe; so it must ever be, sooner rather than later.