I'm not physicist, and don't plan on becoming one. I know that right now, it's not a possibility. But what are some ways in which it could theoretically be possible to travel FTL? Don't need anything too complex, but don't want to just dismiss the questions.
I was kinda wanting FTL travel because I want to kinda poke fun at sci-fi tropes involving it. For example, have a scene where the spaceship runs out of fuel, and there's no one near to help (due to the vastness of space), except a interstellar fast-food drive-thru they're able to contact. Another where they have to suddenly halt their FTL travel because they couldn't beat the yellow stoplight before it turned red. Stupid stuff like that. I've heard people mention bending space similar to gravity to make point-to-point travel shorter? Not sure. Doesn't have to be SUPER realistic, but enough to where sci-fi readers will wave it off as no issue.
Yeah, it would be best to make FTL a given if it's comedy. I like the fast food bit. Perhaps missing the wormhole means they have to slog on the long way with only FTL, as if it's not the be-all in space travel. Kind of like getting out to push or missing a turn-off. The kids start whining... LOL
FTL Burgers? That is some bloody fast food! The pizza delivery in a minute or less or it's free (or worse it obliterated a moon or something else).
Three possible FTL options occur to me: wormholes, warping spacetime, and a negative mass drive. Wormholes connecting two distant regions of space through a warped filament of spacetime could shorten the travel between both points at timescales equalling superluminal velocity. Warping spacetime would have the benefit of avoiding the time-dilation problem that might occur with a wormhole because your ship is not really moving at warp; the spacetime around it is moving. A negative mass drive would work by creating a regon of negative mass behind the ship, which would be attracted to the positive mass of the ship. The positive mass, on the other hand, would be repulsed by the negative mass, and the more the negative mass tries to catch the positive mass, the more the positive mass is repulsed, resulting in seemingly endless acceleration. And since the movement between the masses are not due to exerted forces, they could, conceivably, break the cosmic speed-limit without requiring infinite energy. A negative mass drive would not avoid the time-dilation problem, however, so warp drive would be the best solution between the three, even if it's slower than wormholes, and would likely have more energy requirements than a negative mass drive. Those are the only three i can think of at the moment
You misunderstand the idea of negative energy. I assume you are referring to an Alcubierre drive. This is a warp drive, a warp drive and a negative energy drive are the same things. Negative energy is the mechanism that is used it create said warp field. It also doesn't have to be anything like negative mass, the idea is that the drive creates stretching using GR equations, which don't care about mass in the slightest: only energy density. Positive energy densities curve space inwards, which creates gravity wells. Negative energy densities (theoretically) can cause space to warp the other way, pushing it apart. So you'll end up with a gravity well in front of you and an anti-gravity force behind you, the ship then basically surfs along that wave. The thing is it does not get rid of time dilation, it just makes it way more convoluted. We also have no idea how to sustain a negative energy density field. We can create them momentarily at the quantum scale in the lab (it's actually fairly easy) but not at a macro level. The quantum foam will just fill it instantly. Wormholes also have very specific problems. First is obviously, that there are no equations to describe what happens when you tear and recombine space. GR allows for wormholes to exist, but not be created or destroyed. In other words, the universe would have had to form with the at the moment of the big bang. They also produce really strange paradoxes if their ends are causally connected to each other. Imagine if you will one endpoint of a wormhole exists 1 light year away from the other in space and 1 year behind it in time. So you have a photon leaving the end of the wormhole and firing off at the speed of light towards the other end. It arrives at the entrance one year later, which then pops it back out one light year away, one year ago. Now it's back to where it started. It's literally stuck in a temporal loop, which means it's energy was essentially removed from the rest of spacetime, this in itself does not violate any laws, it's just weird.
The three typical types in SF are wormholes, warp and hyperspace. Warp looks like normal space travel but faster (Star Trek), and hyperspace is when you travel in a parallel "dimension" that has different physical laws than ours (Star Wars). Other notions are translating to a different form of matter that already goes FTL (tachyons), or simply jumping to a new place instantaneously without moving or going through a portal. None are particularly scientific.
The maths of quantum mechanics are full of weird looking things like that, we've determined that tachyons do not actually communicate faster than light. It's actually a misnomer because it can mean two different things. In Physics, a tachyon is simply a "particle" in an imaginary mass field, the only one which is known is Higgs.
Hence, "none are particularly scientific". But I wasn't suggesting that tachyons really do one thing or the other - they have just been used in fiction for that in the past. I also don't buy that Albecurie drives are scientific either because they are predicated on a questionable idea - negative energy. All FTL imply time travel. Solve the time travel problem and you can likely go FTL as well.
Yeah, I came up with a convoluted way to deal with that myself that's completely unscientific. I basically state that the time paradoxes exist, but cancel themselves out over a huge number of quantum size corrections. As energy moves around it can be described as a vector in spacetime. This vector is quantized, so if it's stretched beyond it's causal limit, it breaks and becomes two vectors that are disconnected from each other. My future humans figured out how to control how this breaking occurs so that all of the breaking happens in the direction of time. The ship basically sheds it's excess motion through time to the outside space, which causes it to ripple of pure time motion outwards at the speed of light, aging everything around them slightly faster. Total motion through time is conserved, even though the ship made a thousand light-year journey in a week. I do feel blessed to be a sci fi writing enthusiast at a time where we know we're stuck as a species. We know our equations are incomplete, we have lots of mathematical foundations but we have no data to figure out which way to go. I also don't foresee us making a breakthrough any time soon, the amount of energy required to test some of the SUSY models or string theory are far far beyond our capabilities. This is why it really urks me when sci-fi writers use understood concepts incorrectly. I like the picture below: always, always stay inside the chasm of ignorance.
My arm-chair physicist opinion is that faster than light travel is impossible. That is to say going FTL through the intervening space between two distant objects is impossible as there seems to be a maximum rate of change related to matter. Photons being the smallest theoretical particle "of matter" (might very well not be) the speed of light would seem to be a limiting factor. That is, that's as fast as something will go through space (maybe.) not necessarily arrive at its destination. God, do I need a beer! (Not cursing, praying.)
Not all FTL travel violates causality. There is a type of wormhole that allows for FTL but due to how its nature preserves causality. Time travel is in a sense possible but you'd never be able to create a paradox with it. I don't remember the details of how it works, and it's apparently remarkably hard to look it up online (causality preservation and wormholes gives mostly explanations of how traditional wormholes violate causality, go figure). As for the original question: with the known laws of our universe's physics, wormholes and spacial warping are the most "realistic" methods, with space warping generally being considered the more plausible. And finally, addressing something else said earlier: a negative mass/positive mass pairing would not be able to accelerate past the speed of light. It would produce infinite energy (hypothetically), but infinite energy is required for anything with mass to reach the speed of light, and as such would not be able surpass it. It isn't a matter of whether or not the forces are external, the mass-speed limit is with respect to an object's movement through space, and so while such a pairing could certainly be used for infinite fuel (attach the +/- mass pair to some rods that spin to power a generator), it wouldn't break the cosmic speed limit on its own.
I the chasm of ignorance then, I borrow from something I picked up. It was half of a sentence about something to do with the information of matter. The other was a (likely more philosophical) theory that matter was the only thing that truly or reliably existed - making science (measuring) the artificial limit of itself. The conclusion was that because there was no space, time or matter at some point before the universe expanded, an accessable steady-state simply exists. When you access it, the information of matter can be projected to anywhere inside the universe, out of space and time, then 'manifest' at whatever place and time is projected - just don't 'miss'. Clean your brain off the floor and walls, and have fun with that! Read Dune (Herbert), and Anvil of Stars (Bear)
@Some Guy I kinda don't like the idea of "instant" FTL, but that's more because I like the idea of a journey, exploring. So I kind of limited FTL to around fifteen-times lightspeed under most circumstances--there are other kinds but that's the most common.
Most FTL science fiction is just because the author wants to use planets that aren't in our solar system and wants the journey to resemble the kind we are used to from human history. It is a hang up we have because adventure means a reasonable level of inconvenience coupled with a timescale that matches the emotional relationships we are used to. What's funny about all that is that sub-light travel with high enough acceleration to near light speeds is extremely swift for the traveler. At 100 Gs, a 1000 light year journey takes 80 days for the astronaut. But that means 1000 years for everyone back home.
Which is why space travel is impractical in any lifetime, unless instantaneous and out of time. It's never about getting there, it's about what you come back to. Get in any FTL, and you are essentially gone from origin, in human terms. But hey, who cares? It's all about the journey! It's just for fun. If what you're doing requires leaving the planet, it's obviously more important than what you leave behind. Just sayin.
Alastair Reynolds certainly makes it seem practical. And there is no reason that the a lifetime should be a century in SF.
The brain liquifier is: that would still be something around 30-50(?-math sucks) generations, so you may as well be a visitor on your own planet. Here's another meltifier - you're in a galaxy, moving at some cosmic speed already in itself, then the rotation of it is a factor. Whatever your headed for is more of a chase than a destination. And, traveling cosmic distances makes anticipating the position of your destination more of a prophesy than a navigation. Your travel would never be a straight line, thus added distance. A course correction at FTL would destroy the craft, and generate a 'wake' effect in space. It's all for fun. FTL is 'the box' we as writers need to think outside of. FTL is the handwave. The chasm is the solution, ironically.
If people were living for thousands of years, what is considered a generation might be a lot different. With extremely long lives society might not change very much, allowing a 300 year absence like people currently tolerate a 9 month military deployment.
Honestly we have no idea if FTL is possible or not. We assume it's not because today we lack the knowledge to make it work, but a century ago people lacked the knowledge to build a nuke and now they're a stock weapon in First World nations' arsenals. In 1903, the idea of any kind of practical powered flight was seen as a distant dream...then in 1912 there were flocks of biplanes dogfighting over Europe in WWI, and a few decades later we were walking on the moon. Hell if you want to really reach back, if somehow I went back in time to ancient Rome and showed them an assault rifle rifle they would think I was some kind of war god with magical bang-bang powers. If I went back in time to 1990 and tried to explain the smart phone to people they would think I was insane, and yet here we are in a world where everyone is carrying the HAL 9000 in their pocket. Realistically, what we define as the "laws" of physics are what we know about it now, because let's all be clear this stuff changes DRAMATICALLY over the course of generations. So I have no reason to believe that a century from now people may have actual faster-than-light warp drives like in Star Trek...hopefully, they don't all become soyboys like in Star Trek too.
