Writing popular fiction

is actually best suited to the short story, unless the problem the characters must solve is so complex, with so many ramifications, that the novel length is justified. In this form, the author confronts his hero with a seemingly insoluble scientific problem and forces him to use his wits to overcome staggering odds.
    A typical sort of problem story might be this: The hero has landed his spaceship on an uninhabited, lifeless world, without benefit of his rockets which are out of order. As he fixes the engines, he discovers the planet's atmosphere is combustible, of a gasoline-like vapor. If he had landed with the rockets blazing, the entire kaboodle would have exploded; he was lucky. But, now that he's down, how in the devil can he take off again? Even if the engines are repaired, can they lift off without igniting the atmosphere around them and completely destroying themselves in the resultant explosion? One answer is this: Since the atmosphere is composed of gasoline-like vapor, and is not pure oxygen, it cannot explode; there is simply nowhere for the expanding vapor to explode
to
. All it can do is burn, and that cannot harm them at all as long as they remain inside their escaping, steel ship.
    Unfortunately, the problem story leaves room for little more than adequate characterization, and the plot is severely constricted by the necessity to solve the main, center-stage problem which usually concerns, not people, but a scientific phenomenon. Many well-known science fiction writers began with problem stories, but Hal Clement (
Mission of Gravity, Star Light)
is the only writer to have made a solid career from them.

ALTERED PAST STORY
    Sixth, we have the
altered past story
. These tales are based on the notion that the world would have been substantially different than it is, if some ma/or historical event had not happened, or if it had been reversed. For example, Philip K. Dick wrote a masterful Hugo Award-winning novel (The Hugo is the science fiction world's equivalent of the Oscar)
The Man in the High Castle
, which dealt with a world in which Germany and Japan won World War II and split the United States between them. That idea, clearly, is staggering. Keith Roberts'
Pavanne
tells the story of a world in which England did not defeat the Spanish Armada, Spain Catholicized England, and the Middle Ages, when science was considered necromancy and was banned, have never ended.
    The wealth of story ideas is obvious. What if the South had won the Civil War? What if America had lost the Revolutionary War? What if a nuclear war had been fought in 1958? What if Lincoln had not been assassinated?
    The new science fiction writer should be warned that the research required to write such a "period" science fiction novel is intense indeed. Before you can project how things would have developed since the historical event was rewritten, you must know how things really were back then, what forces would have filled the vacuum, what philosophy would have replaced the dead ones, what persons would have replaced the assassinated greats.

ALTERNATE WORLDS STORY
    Akin to the sixth type is the seventh type of science fiction story: the
alternate worlds story
. Imagine that, in the beginning, there was only one Earth but that different
possible
Earths branched off from ours at various points in time. Let's say that every time something could have happened two different ways, another possibility world came into being. On our world, there was a World War I which the Allies won; in another world, the Allies lost; in our world, we did not avoid the Second World War; in a third world, they did; in a fourth world, the U.S. got into World War II, and lost to the Germans who took possession of America, giving the course of history yet another turn. So on, and on, and on. The result is a vast, indeed an infinite number of possible Earths existing side-by-side, each invisible to the other but nonetheless real. This is, basically, the theory of other dimensions beyond our own, dimensions in a romantic sense rather than the mathematical. Specific science fiction novels that deal with alternate worlds include: my own
Hell's Gate; Worlds of the Imperium, The Time Benders
, and
The Other Side of Time
by Keith Laumer;
The Gate of Time
by Philip Jose Farmer; and
The Wrecks of Time
by Michael Moorcock.
    While the alternate worlds and the altered past stories are similar in essence, the alternate world background allows a hero from our own Earth and