I find this a very interesting topic, even though I do think, unfortunately, than sci-fi style superluminal ships are just not on the cards for us or any other species in this universe. True FTL means causality violations, ie, time travel, which is a whole can of worms that is mostly just ignored in space-opera style flitting around the universe at hundreds or thousands of times light speed. The universe might not actually be causal, of course, but if it isn't, and FTL turns out to be possible, somehow, then basically every spacefaring, superluminally-capable civilization would be immediately engaged in the immense effort of trying to stop people fucking up the timeline so they never even evolved... or something like that. It wouldn't be just cruising over to a pretty star a couple hundred light years away for a day trip and then back again.
That said - on the actual topic - yeah, "Warp Drives" which I think were named after the Star Trek term - although it is quite fitting - are a potential method to travel faster than light, if we just forget about all the causality stuff for a moment. Although firstly - no one is actually studying this. The Alcubierre Warp "theorem" or whatever is not an actual schematic for a superluminal engine. It's a mathematical flight of fancy, that might be theoretically possible but even if it would work as expected, not something that we could ever actually build.
For one - in order to create the warp, at least the back end of the "wave" that you intend to ride through space, you need to create a region of extreme negative energy densities which is something likely not possible on the macroscale. The usual or maybe just the original proposal was to use exotic matter, ie, some kind of material made up of particles that possessed negative mass, which would exert antigravitational effects. This type of exotic matter has never been observed, is not predicted in the standard model, is not permitted by the Higgs field which is what gives particles (positive) mass - and it probably just cannot exist, without delving too deeply into things I don't really understand but do find interesting, there have been some theoretical speculations that allow for exotic particles which do somehow have negative mass values, but when we try to incorporate any of these theories into a functioning universe all sorts of reasons pop up for why they just (probably) cannot exist.
For one - this material would have less energy than empty space (which does have energy) which would mean that vacuum could potentially decay into exotic matter. As there is far more vacuum than there is matter in the universe, this would seem to indicate a high likelihood of runaway vacuum decay just quickly swallowing up the universe. This could actually happen - "vacuum decay" is discussed as one of those outside-context-problems, nothing we could ever do to predict or stop it kind of Cthlulian cosmic horror scenarios, that in actual fact the entire universe exists in a region of the multiverse, or the fabric of space, whatever space actually is, that for some reason is in a temporarily excited state which allows for the configuration of the current laws of physics, but at any moment for reasons that we don't and could never understand, probably, the false vacuum could start to collapse, which would be a phenomenon that expanded from the first pinprick that burst the hypothetical bubble, so to speak, in every direction at the speed of light, ripping out the carpet of the universe on which the laws of physics rest from under everything, immediately cancelling those laws, and just, basically, deleting the universe... it would be like being an ant that built it's colony on one of those unlikely looking feats of erosion on Earth, some kind of precariously balanced rock that looks like it should have fallen over long ago but by some weird quirk is just balancing... you're minding your own business doing ant things and then suddenly one day the rock just tips over into the sea - or maybe more accurately, into an active volcano. Everything is gone.
Heh, sorry, back to Warp Drives... so the basic assumption/theory/working hypothesis is that the universe might be an end state of multiple earlier universes that one day suddenly were gone when their vacuums collapsed. We're talking cosmological timescales and about a place that we don't know anything about and can't even imagine, really (that place in which the universe sits) so a universe could potentially last a long time sitting on a such a false vacuum, like, trillions, quadrillions, heat-death timescales, even... and maybe it's possible that runaway vacuum decay is not an inevitable consequence of high negative energy densities being possible, in which case, if you do have a way to create a deeper vacuum than vacuum, you might have a way to create a warp field.
One counterpoint to the idea that negative energy densities cannot exist is that there
is in fact a force that affects the universe in the same way that negative mass would, if more slowly than the most extreme vacuum decay disaster scenarios - Dark Energy, which is rapidly tearing the universe apart. So it seems that even though we know basically nothing about it, negative energy does exist. Whether it can be manipulated to build a warp bubble is kinda like asking if because wind exists, we could harness it to blow out the sun, but whatever, let's continue this flight of fancy.
Probably actual exotic matter is just going to be a headache if you're a godlike superintelligent being with the ability to move solar masses around and organise them in a way that deforms space just to get somewhere a little faster, you'd probably just want to interact directly with the inverse version of the Higgs field, breed dark energy bosons in accelerators with circumferences somewhere close to that of the Milky Way, and somehow work the end result into your engine... maybe you get a warp bubble. But there are still problems.
For one - it's hard to see how the bubble could be controlled - if you can manipulate the fabric of space with the absolutely enormous energies required - even allowing for later extrapolations of the theory which reduced the energy requirements significantly (from hundreds of suns to maybe just a couple of Jupiters, off the top of my head - so, maybe more convenient) it seems like this would be something you'd build in a dedicated facility - even if that facility was an array of dysoned supermassive black holes somewhere near the one at the center of our own galaxy... it would be like a shaped gravity wave, essentially, you just set it off with it's payload inside (or sitting inside it, perhaps) but then... how to steer? Or slow down?
It would be like a fly somehow ending up in a soap bubble and then trying to steer it without just destroying the bubble. You can't put machinery outside the bubble because then it wouldn't be englobed by the physics-defying structure and there'd be no point having it in the first place, and without being able to exert any influence on the outer edges of the field, poking the inside in any way is liable to just make it burst, and because of the energies involved this kind of collapse could be like a small supernova and would probably destroy everything inside the bubble as well.
There's also the problem that although theoretically it could move faster than light, and carry something inside it, practically as soon as you passed the lightspeed barrier all radiation impacting on the forward surface of the bubble (and this is just gonna be cosmic microwave background at best, but it doesn't matter, you can't avoid it) is gonna blueshift to infinity, either destabilizing the bubble explosively, or simply frying everything inside it which would rapidly become an oven turned up to the high end of the Planck temperature and probably eventually - again - explosively pop the bubble. And this blueshift problem would actually start before you even hit lightspeed.
But... we're thinking speculatively, I guess. If you can manipulate space to make a bubble in the first place, perhaps you can engineer some extra layers to guide the influx of radiation around a central cocoon. There's yet more fancy maths that proposes shrinking the bubble's exterior while expanding the inner volume, like a Tardis, in which case some of your blueshift problems are solved, I think, if the outer bubble is smaller than the wavelength of a gamma ray. But, you STILL might not be able to go faster than light because, fuck, I can't remember, there's some ideas about Chronology Protection Conjectures that basically means once you open the door to creating a Closed Timelike Curve (time machine), some weird shit happens with virtual particles that has essentially the same effect as the blueshift-to-infinity problem we had earlier, rapidly building up around all the spacetime distortions you need to create this thing until they just break apart... probably explosively.
So, maybe maybe maybe not completely impossible but probably completely impossible to build a warp drive that can actually go faster than light.
Slower than light warps while they still seem like immensely pointless and probably still impossible endeavors do not have all of the same problems that the superluminal versions do, so maybe someone could make one of those one day.
An alternative to an actual ship that goes faster than light, assuming you have the means to create massive negative energy densities, is to simply (lol, "simply") build a traversable wormhole that you set up and then leave wherever is convenient, which would enable faster than light travel effectively but only between 2 fixed points. If you get good at it though, start building a network and then who needs warp ships? You do have to be careful how you arrange them though because they do still open the door to possible causality violations, so if that virtual particle flux shit I can't recall the details of is true then if you make a mistake setting up the network then one or several will explosively collapse, and these things are also massive and dangerous to have around if they're liable to explode, so you're still gonna have some slower than light journey time to and from the wormhole mouths.
However! You can simulate a kind of faster than light travel using ships if you get good at subluminal spaceflight and building wormholes. Here are the steps, let's say you want to go a 1000 lightyears or so a bit more quickly.
- Create the wormhole - or wormholes, perhaps, because even though this is technically just 1 tunnel through space, it has 2 "mouths" which will appear to be separate things.
- Keep one wormhole at home, put the other on the most advanced, fastest, just state-of-the-art ship you can find, and accelerate it to your destination 1000 light years away as hard as possible, get as close to c as the ship can bear - relativistic time dilation will occur for the wormhole mouth that you loaded onto the ship, so that ~1000 year journey (probably a bit more but we're being pretty loose with the numbers) to anyone onboard the ship will only experience, say, 1 year of travel time!
- You can enter the wormhole mouth you kept at home whenever you want, and will essentially be travelling into the future, but after 1 year you'll have a bridge between regions of space 1000 light years apart, potentially, with no superluminal travel needed.
You're welcome, lol. In case it isn't obvious I've read quite a bit of the speculative fiction on
orionsarm.com, and this is basically how they get around the FTL problem to still claim some kind of "hard science" and vast interstellar empires. It's scifi of course and very speculative, but if you're into that shit I'd recommend reading.
dude... see that's exactly what I was talking about when I said: