"Asimov: Science fiction always bases its future visions on changes in the levels of science and technology. And the reason for that consistency is simply that—in reality—all other changes throughout history have been irrelevant and trivial. For example, what difference did it make to the people of the ancient world that Alexander the Great conquered the Persian Empire? Obviously, that event made some difference to a lot of individuals. But if you look at humanity in general, you'll see that life went on pretty much as it had before the conquest. On the other hand, consider the changes that were made in people's daily lives by the development of agriculture or the mariner's compass ... and by the invention of gunpowder or printing. Better yet, look at recent history and ask yourself, "What difference would it have made if Hitler had won World War II?" Of course, such a victory would have made a great difference to many people. It would have resulted in much horror, anguish, and pain. I myself would probably not have survived. But Hitler would have died eventually, and the effects of his victory would gradually have washed out and become insignificant—in terms of real change—when compared to such advances as the actual working out of nuclear power, the advent of television, or the invention of the jet plane."