So let us presume the sake of plot advancement that Officer Albert (Einstein) is not totally correct about the speed limit. Or maybe his speed limit only applies within town and there is a myriad of super-highways that we just haven’t found the entrance ramp to yet.
There appears to be three major concepts for Faster Than Light (FTL) travel:
Hyperspace
As seen in most fiction hyperspace is most succinctly described as a “somewhere else” within which the laws of general and special relativity decidedly do not apply – especially with respect to the speed of light being the cosmic speed limit. Entering and exiting said “elsewhere” thus directly enables travel near or faster than the speed of light – almost universally with the aid of extremely advanced technology.
https://en.wikipedia.org/wiki/Hyperspace
Is sort of another dimension or layer where the time seems to move at a normal pace but usually there’s a light show out the window (Star Wars, Babylon 5). And when you turn off the light show, you’re a long way from where you started. One interesting variation is how to get to and from, and the implied amount of energy required.
For instance, in Star Wars there doesn’t seem to be much oomph needed to break into hyperspace – even a one-seater Rebellion X-wing can do it, which means it can’t require too horribly much power (or else there is some Source of Power Magic going on – but Star Wars has never been techie about how anything works). Navigation appears to not be an issue – everyone seems to know where they are going.
Contrast to Babylon 5. No special “engine” is required to travel in hyperspace. Larger ships have the ability to “punch” a hole into and out of hyperspace so they come and go as they want. Smaller (and cheaper) ships don’t have jump drives so they have to us a “jump gate” to open a hole between our space-time and hyperspace. Navigation is another thing entirely – ships in hyperspace must follow the beam from the beacon where their destination jump gate is. Lose the beam and you lose your location, and God only knows where you’ll be going.
There are ships which go off the beam deliberately, but those are the deep-space exploration and jump gate builder behemoths. Interstellar travel mainly takes place over well-established pathways.
Another aspect is where can you enter and leave hyperspace. Some authors have put restraints such a depth in gravitational well, not deep within an atmosphere, and so forth. This limit dramatically “makes up” for some of the “get out of jail free”-ness of being able to pop in and out of another dimension at will.
Subspace
What is the difference between “hyper” and “sub” spaces? Besides the terminology? Is “hyperspace” a “higher” dimension and “subspace” a “lower” one?
Perhaps it is that “hyper” space can be seen and “sub” space cannot – like it’s the infrared of space/time and “hyperspace” is the ultraviolet.
In the Star Trek fictional universe, subspace is a feature of space-time that facilitates faster-than-light transit, in the form of interstellar travel or the transmission of information.[3] Faster-than-light warp drive travel via subspace works similarly to the Alcubierre Drive, but obeys different laws of physics.
https://en.wikipedia.org/wiki/Technology_in_Star_Trek
Of course Star Trek is the gold standard for the sciencey part of science fiction – “technobabble” it was called in scripts from ST; TNG and onward. But Roddenberry did ask one interesting “real” question – how much energy might it take to “warp” space time and how would that be generated? A lot – way more than anything we had the vaguest idea how to do. We understood nuclear fission and that could light up a really big bulb. We know how nuclear fusion worked and could see how bright that candle can burn (usually with an awful mess) – and we’ve got a so-so star in terms of energy output.
What was a bigger match than that which lit up the stars? This is this thing called anti-matter, first predicted in 1930 by Paul Dirac and confirmed in 1932 by the discovery of the positron (electron with positive charge). It was not until 1955 that antiprotons were detected. Actual creation of an atom of anti-hydrogen did not occur until 1995!
Anti-matter is not cheap. One estimate is that it would cost $25 billion to make on gram of anti-hydrogen. Then there’s storage and transport. Anti-matter doesn’t like to stick around – the record for keeping anti-matter is 17 minutes, and that requires a lot of equipment to keep it at almost absolute zero and from bumping into the rest of the universe. Not looking good.
When Gene Roddenberry decided that matter – anti-matter annihilation was the only thing powerful enough to move the Enterprise faster than light, the entire notion was still not even slightly hypothetical – it was cut from the cloth of “any sufficiently advanced technology is indistinguishable from magic“.
And so it was done – spoken as if it were the most ordinary thing done every day. Major hand-waving early on, but the itch for having “science” in the science-fiction needed scratching and details began to crop up in the scripts – not always consistent details, mind you – but that provided plenty of fodder for hard core Trekkies to “discuss”.
Following Star Trek series filled in more about the physics of space and warp space travel – mostly pulled out of the heads of the guys in the writer’s room. One can easily find diagrams, charts and ‘equations’ which describe what warp drive is an how it works, how fast is “Warp 5” anyway?
While we’re at it – why are so many anti-matter reactors (i.e “warp cores”) so damn delicate? Those things should be in an enclosed armored chamber wrapped in a dozen force fields and with an unbreakable automatic ejection system.
We don’t know what it is – we just jump through it
The early 2000s reboot of Battlestar Galactica had (unlike the original series) had FTL travel – but none of this hyperspace or subspace or space-time warping. Just spin up the jump engines (which appeared to be driven by a large two-cylinder car engine), push the button and be somewhere else in seconds.
How did this supposedly work? Not one techie word spoken during four seasons and 76 episodes did anyone try to ‘techsplain’ how much of anything worked – it just did or it didn’t. A lot like how might look at our car – get in, start up and drive. Don’t need to care about what’s under the hood. (OK, there was an episode where someone gets into the guts of the jump drive and disables it – but it was all mechanical and nary a rainbow touch screen to be seen).
So other than knowing that jumps required calculations – of energy use and vectors I would assume – not much else was discussed. But its pretty much ‘were are here, then we are there and we hope that there isn’t in the cronosphere of a star or inside a random asteroid – that would cause a real mess.
OK, so what?
The real reason that faster than light travel exists in science fiction is the need to make the story move. In an episodic series, something new has to come along every time.
If the show is centered on a space ship the characters will go hither and yon, encountering new adventures and peril. If the show is centered on something stationary, the adventures must come to you (i.e. Star Trek Deep Space Nine and Babylon 5). The latter can more challenging because you have to make your location important enough to have all these other characters go there. (Or, as in Battlestar Galactia, have a solar system with a dozen planets all within a reasonable sub-light travel radius.
In any case, the story has to move and that means characters have to move, and that requires hand-waving your way around the laws of Officer Albert.
The Enterprise needs to be somewhere new every week, otherwise where is the story coming from? Sure there were some ‘bottle’ episodes (which means using only the standing sets). Some of these were quite good, but were often born of financial issues – building another set just for that episode or a location shot costs money – the one single factor dictating what what you see on the screen.
Is it possible to have an interstellar story without sneaking around Officer Albert? Yes, but it takes a lot of time compression, waving a hand and saying “fifteen years later” before the next scene.
Larry Niven did this well in his “Known Space” series, but again the timelines were a bit compressed. Years passed between chapters, and the crew were in some sort of hibernation so not to die of old age or boredom. Of course that expects that an interstellar spacecraft can operate for years (if not decades) without things wearing out or being hit by a random piece of space debris (as in the movie Passengers ).
Sometimes these “other spaces” are characters in the story themselves. As noted previously, the hyperspace of Babylon 5 was not a place to just wander around in. If you don’t follow the navigation beams linking jump gates, you can quickly found yourself lost. Hyperspace is not a place for ship-to-ship battle either. Exit portals can be opened anywhere, including deep inside an atmosphere. Entry portals however, should not be done in the atmosphere of a gas giant (you know, the ones mostly made of hydrogen) unless you want a big boom (and yes, both of these were done in the series).
Subspace can be a tricky place also – it can be bent and twisted. Do it wrong and you can get lost there also. And there are even more subspace levels (I suppose that what they are) – the kind which allows you to cross the galaxy in a reasonable length of time (this is how the Borg get from their side of the galaxy to ours).
I get it already!
Would it be great to travel close to or more than ‘C’? Yeah, the entire Solar System would be reachable within less than half a day (Pluto on the other side of the Sun for instance). But Officer Albert spoils the whole thing with Special Relativity. The faster you go, the slower time moves. OK, that’s a good thing – right? And you get squashed flatter and flatter but you don’t notice it – you being the fast moving thing doesn’t know any of this is happening.
The ball-buster is the faster you move the greater your mass, thus requiring more energy to continue increasing your speed. The speed / mass curve gets really steep really fast.
It ain’t gonna happen, right? Back to Star Trek – eventually every worthwhile civilization gets far enough with its physics to find the path to subspace and therefore warp drive. The “Prime Directive” (which Kirk wasn’t quite always loyal to) says “if a civilization hasn’t discovered warp drive yet, no first contact – if they cannot travel among the stars themselves, then they probably aren’t to take well to meeting folks which do”.
Maybe that is the case – we need to keep smashing particles in super-colliders and filling chalkboards with equations until we find that Officer Albert doesn’t preside over everything. For centuries, the gravitational math of Issac Newton was sufficient for astronomy and interplanetary flight. But Issac’s math broke down for Mercury – it was just a bit off and there was no explanation for it.
But dear Mr. Einstein gave us another theory – general relativity. Gravity bends spacetime. In particular it slows time down. Take two identical atomic clocks which have been in sync for years – put one at sea level, and the other on a mountain and they will eventually drift apart, the mountain-top one clicking faster than at sea level. The difference in gravity pulling on the two clocks.
Back to Newton and planets. General Relativity says that things orbiting close to a large gravity source – in our the The Sun (think about it – it’s gravity holds on to things many billions of miles away from it) – will have its perihelion shifted by the bending of spacetime. Those equations, when applied to observations of the orbit of Mercury, explained everything.
To go to planets in our neck of the woods and farther, Newton will pretty much work. Going inwards – close to that heavy ball of hydrogen fusion – you use Albert’s road maps.
So what does this have to do with “warp drive” or “hyperspace”? Simple – Newton was not wrong. His equations work for most of the Solar System. But Officer Albert gave us the improved version which is right for everywhere.
Somebody may find a way around his speed limit. That would not mean that Einstein is/was wrong – it means his work is just not complete. There is more to discover and calculate and test and examine and theorize and dream.
If this does happen, it will probably be from something that we don’t even have the slightest clue about today.
Know what that is called?
It is called “science”.
Shouter to Dead Parrots 