Interstellar Travel, but no Interstellar Communication?

So lately I've been trying to flesh out some finer details of a sci-fi setting, and I notice (to my awareness) that while a lot of thought and application of science/scientific-sounding principles is given to faster-than-light/interstellar travel, not quite as much is given to communication across such vast distances. By 'communication' I mean signals, such as radio, phone and internet signals.

So, supposing that interstellar travel is achieved not through faster-than-light speed, but by 'warping', which I believe is the second-most common way to handle it in fiction; how would you get signals to 'warp', as well? Since if they were just broadcasted as-is, it'd take far too long - many, many years - for the recipient to actually receive it.

This got me thinking; what if interstellar travel was possible, but interstellar communication via signals was not? At least not between systems. I figured that transporting just one huge spaceship via warp is already a taxing enterprise^note No pun intended, and so transporting billions upon billions of wireless signals sent every day via warp is either outright impossible or prohibitively expensive, available only to a privileged few. This would lead to the resurgence of physical 'snail-mail' as a method of communication between systems - possibly between planets within these systems, as well - which I think would be a neat application of an old technology to solve a new problem.

Any feedback on this idea? I want to know if there's any 'obvious solutions' I may have overlooked, or if I just don't know how signals even work. :V

edited 7th Jan '18 3:40:43 PM by PresidentStalkeyes

What you describe (FTL transport but not communication) is pretty standard in sci-fi, up until the plot requires that the heroes intercept a distress signal or something. Doing it the other way around is far less common, despite that I feel it would be more realistic that way.

edited 7th Jan '18 4:29:23 PM by DeMarquis

True, but I feel as though that's got more to do with a lack of communication being more convenient to the plot until it's not anymore, similarly to how modern horror movies always contrive a way for the protagonists' mobile phones to break so they can't just call the cops to sort out the whole mess. As opposed to a more conscious worldbuilding choice, I mean.

Just to clarify, I'm not specifically discussing FTL transport/communication/etc, just interstellar transport in general, since FTL is just one type of interstellar transport in fiction and not the one that applies to the setting I'm working with. I'm curious as to what elements you feel would make interstellar signals communications work, though.

I'm getting the impression that interstellar transport is somehow easier to Hand Wave or Technobabble away than interstellar communication is despite being less plausible scientifically (although I know jack-squat about the science behind both, so :V), and so the communication aspect is handled in a much more slapdash manner, with less attention to detail. Either that or they assume that the audience will find it less interesting. I'm probably just generalising, though. I don't have a huge pool of references to work with from the top of my head. :V

edited 7th Jan '18 4:48:54 PM by PresidentStalkeyes

I'd point out that the Dominic Flandry stories are based around exactly this concept.

When you say "warp" are we talking some kind of portal?

If that's the case, depending on the exact details of the technology it could very well be possible. If a portal opens up and a ship passes through, I can't imagine why electromagnetic radiation wouldn't go through too. If it's possible to hole a portal open you could build a device that passes signals through a set of portals.

Of course, then all interstellar traffic would be passing through these bottlenecks, making it vulnerable to sabotage or disruption or what have you.

edited 7th Jan '18 5:39:01 PM by archonspeaks

I was thinking more along the lines of what happens in the Halo games, where ships can 'punch a hole through space-time' into slipspace, which to me suggests some form of Time Travel as well.

It should be noted, though, that I want to avert Casual Interstellar Travel by making it particularly expensive and resource-hungry, and so Interstellar travel is limited mostly to the local Federation and their corporate backers. Interplanetary travel is cheaper and both of them are pretty slow; it takes days to get anywhere, at least.

I like that you mentioned the bottlenecks, though; The Federation in this setting is in many ways a People's Republic of Tyranny and would rather the inhabitants of their system-based colonies be kept in the dark about what is happening elsewhere (primarily to make themselves seem all-powerful and all-knowing when they really aren't); so these communication bottlenecks would make filtering and blocking information trivial for them. It'd also justify why snail-mail made a comeback, since it's likely that passengers on board commercial interstellar passenger vessels would transport mail on the behalf of whoever would pay, perhaps smuggling it past customs if need be.

edited 7th Jan '18 8:01:57 PM by PresidentStalkeyes

Well, as far as the science is concerned, E=MC 2 makes it very unlikely that transporting a multi-ton ship would be easier or cheaper than sending even many millions of electromagnetic signals. I think you are probably right about the lack of communication being necessary to maintain narrative tension.

If, however, you are including STL as the default method of interstellar travel in your universe, then everything is reversed. Interstellar signals would very likely fade away into static by the time they traveled even a couple hundred light-years, but a ship will still be a ship.

One common sci-fi handwave is quantum entangled communicators, though I can't imagine you'd be able to send much data through something like that.

Perhaps the government has access to instantaneous communication that they use for things like running their bureaucracy, coordinating their military and putting down insurrections, and civilians are limited to sending a message pod through their planet/system's portal gate.

I'm imagining each system essentially being its own little "administrative area", and since there's only one way in or out through the gate the central government can control traffic on a interstellar scale without having to have massive fleets.

edited 7th Jan '18 6:54:39 PM by archonspeaks

If I go with the 'somehow create a wormhole in space-time and take a shortcut through there' route, would that technically count as STL? Since they're moving at the same speed the whole time.

Sounds fair to me. I was thinking these 'gates' wouldn't be literal portals or gates floating in space so much as they'd be particular marked points where these 'shortcuts' have been identified, probably from having sent unmanned drones. Funnily enough, though, that's actually pretty close to what I originally had in mind; the central government only administers the Sol System directly, the other systems are considered 'semi-autonomous zones' and have their own local governments that submit to the authority of the main one, since they realised that trying to directly micromanage the affairs of several systems at once was a bureaucratic nightmare waiting to happen.

In short, a literal Federation, which come to think of it, is probably pretty standard, and understandably so. :V

edited 7th Jan '18 8:26:23 PM by PresidentStalkeyes

So the shortcuts are areas where a wormhole can be opened to another system?

Basically, yes.

Andromeda has a setting with relatively casual interstellar travel, but no effective interstellar communication... so long as writers remember it (it's still a fluffy and fun series, so I tend to ignore such occasions). Instead, couriers are sent between systems, and there's an interesting concept of sending messages by semi-interactive holograms pre-loaded with instructions and responses. All in all, it's a functional system you might find useful.

edited 8th Jan '18 4:42:30 AM by indiana404

If you allow FTL travel in your universe at all, you're already messing with established scientific principles of causality, so perfect consistency with known physics is off the table no matter what.

To elaborate a bit: while Alcubierre style warp drives remain a possibility in physics, they don't let you get around the problem that something moving faster than light with respect to the reference frame of another observer can, in certain circumstances, go back in time from the perspective of that observer, something that would break causality. There are other problems, like the idea that you need to somehow generate negative energy to create an Alcubierre warp bubble, and that the edges of the bubble might generate enough Hawking radiation to fry anything inside, but we can stipulate those being solved if we really want FTL in our stories.

As for communication, however, that's a problem. You can transport mass in a warp field because the ship is generating that field, causing the stretching and compression of spacetime behind and ahead of it. But what creates that effect to move pure information, in the form of energy? You need something to create (and maintain) the bubble. It doesn't help that photons always travel at the speed of light in whatever reference frame they are moving, so they'd escape any Alcubierre warp field almost instantly. ^note  But the field would catch up to them as they move out of it due to the change in the velocity of space-time, so the photons might end up "surfing" the front of the wave. Physics is weird and cool at the same time.

Now, certain ideas about warp fields include that we might need to lay down pathways of negative energy by sending something ahead at sub-light speeds, blazing a trail that future ships can travel along at FTL speeds. This suggests the idea of "FTL superhighways" (hyperspace bypasses, anyone?) that could be constantly shuttling things between star systems; signals could possibly travel along such a highway, carried along in the faster-than-light flow of spacetime. How you'd maintain that state is anyone's guess, though.

Quantum entanglement is another beloved sci-fi idea, but sadly we've proven that you can't use it to transmit information faster than light (or backwards in time). The reason is that the interference pattern generated by entangled particle pairs is unreadable unless you know the pattern at both ends. So no Subspace Ansible, sorry.

Wormholes remain a possibility: nothing in relativity says they're absolutely impossible. However, wormholes operate at the quantum level, so you can't send physical objects through them (well, intact anyway — spaghettification would be one potential outcome if you tried). But it might be possible to send information through stable wormholes. Doing so would probably have similar restrictions as the "negative energy pathways" of Alcubierre theory: someone would have to go to the destination physically first — perhaps bringing an entangled particle pair with them — and then create a wormhole to bridge the gap and allow communication.

I've actually contemplated something like this in my own thoughts (which, sadly, I have yet to commit to actual writing). To establish FTL communication, you send someone an entangled quantum particle via Alcubierre drone, then they plug it into their tunneling device which bridges the gap back to the source and lets you transmit information. It's total fantasy in terms of any technology we can currently imagine, but it at least hasn't been absolutely disproven by physics (other than that pesky causality thing).

Then, if you want to get really bizarre, those entangled particle pairs are actually souls, and merge into a universe-spanning supermind...

My personal thoughts on the wormhole ansible idea are that you'd in effect have to create a black hole/white hole pair, and use the event horizons to bridge the gap through spacetime. The problem is that information cannot get through such a system. Whatever passes the event horizon never emerges again in the lifetime of the universe, and whatever emerges on the other side would have no information content that could ever be deciphered. Plus, creating even the tiniest of black holes on a semi-casual basis requires the kind of energy output you'd expect to find in a Type II civilization.

edited 8th Jan '18 11:09:13 AM by Fighteer

All of this only applies if FTL is the method being used, correct? I should probably say that I'm not really aiming for scientific accuracy, more something that doesn't leave any 'obvious solutions' open in terms of plot, and so these 'wormholes' I mention are simply access points to another dimension, let's say one that's unknown to science as we understand it. Objects that travel through this dimension are moving at a 'normal' speed relative to how fast they move in our dimension; so in that event, since they're technically moving slower than light, does that mean signals sent through there would fizzle out as if they had been broadcasted directly from one system to another? Or could they 'leak' through?

No, sorry, wormhole portals are still FTL, even if the ships moving through them are going STL from their own point of view. It's the spatial framework of the beginning and destination points that matter.

I haven't heard that you can't use a wormhole-pair to transmit ships or information before. To the best of my knowledge, the technique would work, provided that we could figure out someway of imparting a stable spin on a torus shaped wormhole (Fighteer is right that someone has to tow one of the two ends of the tunnel out to the destination using STL first).

If that scenario is at least soft-science, then I can't think of any reason why you couldn't transmit radio signals through it. Of course, you could invent a reason—maybe there is too much electro-magnetic interference, and only hardened ships can make it through intact.

In general, I don't think it pays to worry about the scientific plausibility of your story, at least before you have a significant portion of it written. It's much more important to tell your story in an engaging and exciting way, than it is to make it seem scientifically valid.

Do you have the plot outlined yet? If not, I would spend more time doing that than world-building, but that's just my opinion.

Let's be clear. Any travel that bypasses the speed of light, whether it's via a warp field, a wormhole, or an alternate dimension, is still faster than light travel with respect to our universe. If you want it in your story, then you get to decide which known laws of physics you want to break. As the type of travel you're describing — basically, hyperspace — is not real as far as we currently know, you can choose what properties it has free from any constraints of reality.

If it serves the story you want to create to say that physical objects can travel through alternate dimensions but communications cannot, that's up to you, although I have to point out that you need all of our physical laws to keep working in your "hyperspace" dimension for any object brought into it to maintain its integrity and not simply disintegrate or explode. An alternate dimension without an electromagnetic field would cause any matter from our dimension entering into it to fall apart into its constituent atomic nuclei, which would scatter and collide randomly without any electrical force to repel them from other nuclei. Electrons would cease to exist and thus there would be no atoms, and nothing resembling conventional matter could exist. So this dimension would have to have an EM field, and therefore energy would propagate through said field, and thus you could use it to communicate.

Put another way, if there's some barrier between dimensions that's impermeable to electromagnetic radiation, then nothing made of atoms could cross it either, since atomic bonds are formed by electrons exchanging photons with each other. Block that and anything made of matter would simply fall apart. There is no such thing as a material "strong enough" to resist this effect, although you might succeed with really exotic stuff like neutronium — not that you could make anything out of it in the first place.

edited 8th Jan '18 5:29:17 PM by Fighteer

As someone that only knows superficially how time dilation works, why would portals cause it?

Hmm. Wouldn't the ship simply bring it's own "physics" into the other dimension with it? The atoms that make up it's structure needn't give up their photonic bonds, even if there are no such things in hyperspace. That raises interesting possibilities regarding what might come out of such a portal.

However, I would point out that paired wormhole tunnels do not enter a separate "dimension". They warp the three dimensional space through a fourth spatial dimensions, true, but they don't "enter" the 4th dimension in a way that would leave our physics behind. We already exist within that 4th dimension right now, it's just that for topographical reasons we can't see it.

News-note: Apparently scientists have proven that a fourth spatial dimension exists.

By "portals", do you mean portals to an alternate spatial dimension or Einsteinian wormholes? It doesn't really matter for purposes of the question, but it's worth asking because the mechanisms are very different.

Time dilation is caused by two things: relative motion, and acceleration. Something side-stepping normal space and emerging some distance away would stop emitting photons at its previous location and begin emitting them at its new location. To an observer at the old location, the object would cease to exist and then reappear some time later, with zero time having passed on the traveler's clock.

Let's say you instantaneously jump one light-minute away. A minute later, I'd see you suddenly appear at your new location, and you would appear to me exactly as you were when you left. I would observe zero time to have passed for you, while you would have become a minute older in the time it took your light to reach me. Conversely, by jumping that distance, you'd see me as I was one minute previously, and you'd see yourself as well. This is one reason why FTL is weird. From our respective reference frames, both of us just jumped backwards in time one minute.

The problem there is that, by our understanding of how quantum mechanics work, any fields that exist in different states wouldn't retain those states when they collide. This is because one or the other of these universes (ours or the alternate dimension) would have different vacuum energy levels for their various fields, and whichever one is lower would dominate, with the higher-energy field giving up its excess energy in spectacular fashion as it drops down to the new value.

If our hypothetical hyperspace dimension had a lower-energy EM field, then the intrusion of our reality onto it would cause our matter to drop to the lower energy state, releasing a titanic amount of energy in the process, and wiping out the structure of that matter completely, much like formatting a hard drive. Also, we'd have to do something pretty fantastical to keep that collapse of the energy state from propagating back through whatever device we used to cross dimensions, lest our own reality be erased in exactly the same way.

Conversely, if our hypothetical hyperspace dimension had a higher-energy EM field, the intrusion of our matter into it would cause its own energy state to collapse into ours, creating a wave of absolute devastation propagating at its local speed of light, and releasing all of its excess energy in a phenomenal, cataclysmic burst. The wave of energy would utterly annihilate our matter and we'd be awfully lucky if we didn't catch the back-blast through the bridging apparatus. How's it feel to destroy an entire universe, You Monster!?

edited 8th Jan '18 6:55:54 PM by Fighteer

Fascinating. It sounds like heat propagation, although I suspect the effect would diminsh as it propagated.

Incidently, this destroys a head-cannon I had regarding the nature of Godzilla.

In fact, the "reset wave" of the vacuum energy collapse would expand in a bubble at the speed of light throughout whichever universe it happened to. Simple math shows that the energy thus released would grow as the cube of the radius of the bubble. If the collapse happened to our universe's vacuum energy, and we could somehow wall the portal technology off from the effect, then it would merely annihilate whatever matter we transported over to the other universe. If not, it would blast back through the portal apparatus.

Either way, whichever universe gets "reset" would see a wave of absolute destruction expanding from the intersection, and whichever universe caused the reset would see the backwash of the energy thus released, making things rather unpleasant for all involved. In fact, this has been hypothesized to be one possible cause of the Big Bang, or at least Big Bang-like phenomena in the multiverse. Either bubble universes intersect and trigger vacuum energy collapses, or an existing (likely, dead) universe undergoes spontaneous vacuum decay over a time scale of googols of years.

For more on the concept of vacuum energy collapse, see this video. For more on the concept of bubble universe collisions, see this video.

All of this is a long way of saying that we'd better hope that our hyperspace dimension has compatible physical laws.

edited 9th Jan '18 6:26:17 AM by Fighteer

@Fighteer: I think I understand. All matter falling apart without electromagnetism... not a pretty sight. :V Of course, archon has already suggested a decent in-universe explanation as to why comms can't get through; the government is actively blocking them. Perhaps making up a faux-scientific reason as to why they're not getting through to save face, which anyone with any knowledge in the subject knows is a lie.

@DeMarquis: Makes sense. And yes, I agree; I'll admit that I find worldbuilding a bit easier than actually making plots, so more than a few story ideas of mine have arisen from worldbuilding exercises rather than the reverse, but that's just me. With regards to how this affects the plot here, I know the entire story takes place on a single spaceship that's making a jump from one system to another; a process that takes even longer than usual as the ship in question is quite old.

Disregarding all the wordbuilding fluff to emphasize how cut-off the systems are from one another, this serves to fulfil the aforementioned 'cut off all outside contact to maintain narrative tension' trope; the plot would be resolved instantly if they could just send out a distress signal when the inevitable crisis happens, and I felt like making it a 'universal' thing rather than just having their communications inexplicably break would be more interesting.

I may as well mention that I was also considering having their journey within a single system rather than between systems; in which event, interplanetary communications would be of little help to them, as messages sent between planets can take hours or even days to reach their recipient. IIRC, it takes about that long for someone on Earth to receive a hypothetical message from Mars.

edited 8th Jan '18 7:05:29 PM by PresidentStalkeyes

At its closest possible approach, Mars is 3 light-minutes from Earth, which is still semi-reasonable as far as receiving and acting on a distress signal is concerned. At their farthest possible distance, light would take 22 minutes to travel between the two planets.

I'm assuming that your spacefarers will be stuck in normal space, possibly exiting their hyperspace trip earlier than intended. If they're stuck in hyperspace, then you can make up whatever rules you want. But if they're in normal space, can't get back into hyperspace, and can't send messages through hyperspace, then they are really stuck. That's about as dead as you can get, since presumably a ship designed to move around FTL isn't going to be equipped for years-long STL journeys. ^note The Millennium Falcon has a "backup hyperdrive" by Word of God; it didn't travel from Hoth to Bespin at STL.

Thus, you can have them stranded at any distance from a source of help that serves the plot. If they'll run out of air, water, or power in six days, then put them seven light-days from the nearest communications facility. Or maybe someone can receive their FTL transmission, but is censoring or jamming it for some nefarious reason. It's up to you.

On the other thing, it's even more dramatic than just falling apart if you think about it enough. A universe with no EM field would have no energy, period, since energy is transmitted via photons, which are fluctuations in that field. No photons equals ... nothing. Eternal darkness, atoms would never form, stars and planets couldn't exist. Time wouldn't even really happen since there would be nothing to transmit causality. An eternal, featureless, dead void.

edited 8th Jan '18 8:09:26 PM by Fighteer

It might still have fluctuations in the underlying quantum foam, although I suppose that phenomenon in our universe ultimately explains where our energy comes from. And such a universe would still be a dead void: no discernable time or spatial dimensions would exist there. It might actually be impossible for an object in our universe to cross over there. No sensor of ours (including eyes) would even so much as detect the presence of the "dead zone" on the other side of the portal.

Frankly, it's difficult to mentally picture a coherent universe that simply lacks one of the quantum fields. Each one contributes a necessary component of reality, and omitting it would result in a universe unlike anything we can imagine.

edited 9th Jan '18 6:22:59 AM by Fighteer