Wherefore FTL?
Much of the science fiction genre known as Space Opera uses locations in the galaxy far from Earth. That is many lightyears distant. Generally, for a satisfying read, the story’s characters need to get to or move around in these locations with the same ease and timeliness that they would on Earth. Hence, the familiar trope: FTL. Faster than light travel. Authors of these stories vary widely in how they treat the ability to exceed the speed of light.
How much help does the writer give to their readers to support the needed suspension of disbelief? Because, FTL within a normal galaxy such as ours is impossible. Not just because it violates the Einstein theory of Special Relativity. FTL violates logic. For example, suppose a new type of baseball bat makes a ball travel faster than light. Fans in the bleachers would see the outfielder catch the ball before the batter hit it. Or fumble it. In either case, effect before cause. Travel to the past would also be possible with embarrassing or even disastrous consequences. Remember the familiar Grandfather Paradox. You could go back to the past and change something that would result in you not being born.
Even if technology someday overcomes Einstein and we can, in fact, achieve FTL, how do we deal with the illogic of FTL? There are some creative solutions that are believable. One is to use parallel universes with alternate timelines. The characters or events exist in both with little or no interaction. Another is to posit a dimension in which time does not exist but which is accessible to the protagonists. I have used both techniques in my stories.
Of course, many sci-fi stories simply ignore the logical implications. Other writers treat readers with mind-bending logical paradoxes as if they were obvious to anyone with a high school education. More recent episodes of Star Trek are especially guilty of this. I wonder what Gene Roddenberry would think?
How about the science of FTL? Here, science fiction stories vary from simply assuming FTL to be possible without further explanation to rather creative, and in some cases, nearly believable machines and theories. Take your pick—there are great stories out there all over that spectrum. And there are some that aren’t so great. These are often written by authors who do not have a science background or have failed to get expert help. They just wing it with facile references to or complex descriptions of FTL that get in the way of our ability to enjoy the story. A story does not have to either explain or justify FTL in order to be good. But if an explanation is attempted there should be something about it that appeals to our imagination, whether or not we are scientifically inclined.
One of the best explanations of how spacecraft achieve FTL use the theories propounded by the astrophysicist Miguel Alcubierre. By assuming the existence of negative mass (not that remarkable) Alcubierre showed that a ship could warp space in such a way that it could get to distant reaches of space without moving at all in its own spacetime location. Make distant space locations come to you more or less instantly instead going there at impossible speeds. That’s not really FTL but the effect is the same. And there is no violation of the Einsteinian dictum. A similar mechanism is the use of wormholes, which may be found to exist in our universe someday. Except that current physics suggests that the only way to keep a wormhole open is to salt it with Alcubierre’s negative mass. So travel through a wormhole is not much different than using a warp drive.