The answer is, actually, that science-fiction's prophecy is to a large extent phony. It isn't prophecy at all, not in the true sense. It's more like the astronomer's prophecy that there will be an eclipse of the sun visible for so many seconds, on such and such a day, at a specified point. The astronomer's prediction is based on information he has that is not generally recognized--though anyone who wants to get it can go dig it out of the text books. The science-fiction author predicts in the same general way. With the knowledge of what has been accomplished in the laboratories, and a general understanding of what people have wanted in the past, want today, and will probably want in the future, it's not hard to guess how those laboratory facts will be applied. By 1915 it was generally known among scientists that there was an enormous store of energy locked in every pound of matter. Men have, sadly, wanted more deadly killing instruments for all human history--and will pay much more for a means of killing an enemy than they will to save a friend's life. From these facts it's a simple prediction that atomic energy will some day be released--and probably first in the form of a bomb. Science-fiction made such predictions. When the laboratories found U-235 was probably capable of a chain reaction, the science-fictioneer began saying U-235 bombs instead of the more generalized "atomic" bomb. The essentials for good prophetic fiction--and hence good science-fiction--are fairly easily stated. It takes a technically inclined mind. That mind must be intimately acquainted with one or more technologies--and by that I mean both the branch of theoretical science and that branch's engineering applications as of today. Imagination is a third requirement; if imagination is put first, fantasy, not science-fiction, results. An understanding of how political and social set-ups react to technological changes must be added, for the best types of science-fiction. George O. Smith's "Venus Equilateral" series represents an excellent progressive development of a single line of extrapolation. George O. Smith is a radio engineer; at the time the Venus Equilateral series started, he was working on radar equipment and Army communications radio units. It was only natural that he should pick the field of communications engineering as his line for development--he was intimately acquainted with the problems and possibilities of that field, and with the past history of the art.