Fourth-day Universe is a site dedicated to promoting individual achievement in the areas of science fiction, fantasy, and the paranormal, what were once collectively called "speculative fiction". Unlike regular fiction, speculative fiction places the reader or audience in a world that operates by different rules. It always asks the question, what if "the way things are" changed? What if a boy in England woke up one day and discovered he was actually a wizard? What if the North had lost to the South in the American Civil War, or if the Colonies had lost to the British in the Revolution? What if we made contact with an alien race in outer space? What if we made contact right here on Earth?
Such questions require a great imagination even to ask; hence Philip K. Dick's assertion that such writing requires us to create a universe "that won't fall apart two days later." He would know; his short stories and novels (and the worlds he created for them) have lasted far longer than three days.
The task, then, is to create a world, even a universe sometimes, with its own people and geography, history and religions, politics and economics, and much, much more. It must serve the needs of the characters while at times being familiar enough or even invisible enough that the readers never question that it exists. Some speculative fictionists short circuit this process by setting their fantasies in "our" world, with a few adaptations such as the existence of vampires or wizards, mutants or robots. Others go the extra mile (or light-year) and then some by taking us to alien worlds or to galaxies far, far away.
Just because this extra leap is taken, though, doesn't make sci-fi any better or worse than regular fiction; it merely makes them different. The same themes can be explored in both: love and hate, justice and mercy, good and evil. The advantage sci-fi has, I feel, is the ability to explore these issues in new and, dare I say, fantastical ways.
Before you can begin to explore those themes, though, either on paper or on the screen, you need your "world" to be stable. You need it to hold together for those first crucial "days". If you've constructed it well, if everything (including whatever magic or fictional science you've included) works the way it "should", if it's still there on the fourth day, then you can tell us what happens next.