Faster-than-light travel is finally possible

Grab your spacesuit

Most of sci-fi takes place in outer space. It’s part of the DNA of the genre — the wonder of a completely different reality accessible by means of science. Although, to be honest, most of sci-fi doesn’t care about science, it just uses vaguely scientific tropes. I would classify most of sci-fi as cosmic fantasy. Star Wars is a good example.

Real, strict sci-fi cares about science a lot, but it still wants to be in outer space. While there are ways to travel between star systems that we can imagine based on our current technology (like star engines), most of them lack the drama of immediate scenery change. They are just way too slow. A star engine, redirecting the energy of the Sun to move the entire system someplace interesting, would take thousands of years to make any significant progress towards even the closest star. Not an impossible plot for a work of fiction, but in spirit quite different from what sci-fi usually does. Haven’t seen it used anywhere, and very eager to see an example.

So what if you want to depict interstellar travel and stay true to our current knowledge of astrophysics?

Suffer, of course.

The toughest limiting factor is speed of light. The closer you get to that limit, the greater your mass. At exactly speed of light, or c, your current mass becomes infinite. That’s already too much, how does a writer go beyond that? If any body did it, its gravitational pull would become infinite, too, and it would collapse the whole universe onto itself. Again, great plot, not a lot of space travel.

There was a trend of just ignoring the science and going, “We’re moving at 16c? That’s impossible!” but it didn’t stick for too long. I guess the sci-fi crowd is too pedantic to let it. There are some cute and humorous workarounds, like the improbability engine or moving-the-universe engine from Futurama, but they are more provocations than anything else.

Most people just do portals.

I mean, we don’t know they are impossible. Who cares? Just throw that ship into a black hole and take us to the other world. Calabi–Yau manifolds, something-something quantum, fold a piece of paper, punch through it — now you got a wormhole. Multiverse included, by the way, because who says you can’t fold two pieces of paper, catch my drift? This is when any producer starts to salivate, so portals, yes, let’s do portals.

Even The Expanse, which I fell in love with for the scrappy realistic space flight and combat, eventually sinned in the same direction. Initially it only had one technology on top of what we use today, and that is better engines. They made everything work with just that, and space races were pretty dramatic with people accelerating half the trip and decelerating the other half, limited only by how much G-force a human body can sustain. I really respect the efficiency of that one speculation; it fueled the whole world. They didn’t even talk about speed, it is irrelevant in space: only acceleration and time to arrival.

If you try to respect physics, that’s where your limits are. Enjoy asteroid mining in the Outer Belt, interplanetary warfare, nuclear warheads destroying space armadas — you’re stuck in your solar system.

Except things can move faster than light.

I mean, the old train car example still holds. If the car is doing 100, and you shoot from it at 100, the bullet hits a tree at 200. But if you turn on a flashlight, the light doesn’t reach the tree as if it’s moving at c+100, it still moves at c, no matter the speed of the car. That example is true.

However. The elephant in the room is cosmic inflation. It’s a well developed theory which explains, for example, why not every single point in the sky is emanating light towards us, if light doesn’t stop on its own and the universe has a lot of stars. The reason is that the space itself is expanding, meaning the metric of distance between any two points is constantly and exponentially increasing. So if you point at a dark spot in the sky — have no doubt, there is a star there, it’s just moving away from us so fast that you can’t see it. This is getting interesting, right?

Well, the star itself doesn’t move, so the more precise statement is

The distance between you and that star is increasing faster than the speed of light.

And this is why definitions are very important. When we talk about faster-than-light travel, we don’t actually want to move anything — all we want is to get someplace far away quicker than if we moved at the greatest known speed. Portals, yes, I know.

Distance between things is variable. There’s a natural process that modifies it. If we figure out a technology to do it for us, we can just change the distance to any point in the universe and simplify interstellar travel.

This seems so obvious. There have to be some stories based on it, but I haven’t seen any. Have you?