Light-Speed Spaceships Would Have Trouble Phoning Home

kalkulat@lemmy.world to Technology@lemmy.world – 238 points –
Light-Speed Spaceships Would Have Trouble Communicating, Spelling Bad News For Interstellar Travel
iflscience.com

Subspace is the answer of course!

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Uh, no shit? That's how light works once you're able to travel at relativistic speeds - communication over interstellar distances using light is going to take ages.

Even within our own solar system interplanetary travel will have significant communication time delays.

Edit: also, we already know that matter and light can't exceed c, but I wouldn't be surprised if we discover that other forces (gravitation, or another that we haven't understood yet) can transmit information at speeds >c. I wouldn't be surprised if we turned to quantum entanglement for instantaneous communication over extreme distances either.

Gravity travels at c. The Alcubierre drive tried to use bubbles in spacetime to "bend the rules" in order to result in apparent >c velocities but recent simulations indicate the bubble becomes unstable when attempting to exceed c.

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My first thought was 'no shit' as well. There's a horrible heartbreaking anime about that.. Voices of a Distant Star.

other forces ... can transmit information at speeds >c

I sadly disagree. Even if we figure out a way to instantaneously transport ourselves across the universe, there will be some shitty clause in fine-print that says we can't go back, or it took 0 time for us but 1 billion years for everything else.

Check out this video by Anton Petrov:

https://odysee.com/@whatdamath:8/woah!-someone-just-sent-an-impossible:4

They're probably referring to quantum entanglement, which affects the entangled particles instantly.

Yeah but you can't interfere with quantum entangled particles, if you do you break the entanglement. So it isn't usable as a method of communication.

It isn’t usable as a method of communication by any means we’re aware of.

Something I’ve not been asked to get through my head about QE: If observing the entangled particle destroys the entanglement, doesn’t that mean we’d need “containers” of entangled particles to send a bunch of information?

You can't send information with entangled particles. You just learn the state of the other particle by inference when you observe the first particle.

C is more than just the speed of light. It is the speed of Causality. No information can travel faster than C in a vacuum. Gravitational waves already reach us faster than the light from events that cause them (i.e. neutron star collisions) Because small particles slow down the light over long distances, as they absorb and then re-emit the photons.

The problem with information traveling ftl is, that you're very quickly running into paradoxes. So just by logic wanting to keep intact, I feel like ftl communication will be impossible

Logically it makes sense, but the real world is years and often we don't use the right logical systems. It makes logical sense to most people that a heavy object falls faster then a light object ,but we know that is false (and a also a non obvious logical system that also shows it is false)

If you actually calculate the maximum speed at which information can travel before causing paradoxes, in some situations it could safely exceed c.

For two observers who are not in motion relative to each other, information could be transmitted instantly, regardless of the distance, without causing a paradox.

The faster the observers are traveling relatively to each other, the slower information would have to travel to avoid causing paradoxes.

More interestingly, this maximum paradox-free speed correlates with the time and space dilation caused by the observers' motion.

From your own reference frame, another person is moving at a speed of v*c. The maximum speed at which you could send a message to that observer, without causing a paradox, looks something like c/sqrt(v) (very simplified).

By the time we invent any sort of lightspeed travel, we'll have long conquered quantum entanglement. If you have a signal transferred over a properly quantum entangled technology, the signal would transfer instantaneously.

Another option would be tiny temporary Einstein Rosen bridges. Sure the energy requirements would be hideous, but if we've figured out how to exceed C, I don't think we really care about energy costs anymore.

Oh, you already know about it. No one else should bother reading then.

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It might become like the days of sail. The fastest mode of communication might actually be the speed of ships. In order to get a message between earth and alpha centauri you might have to actually build messenger ships.

You might have to build small automated FTL capable ships with massive data storage capacity and then download all of the data you need to send and then set the ship off on its way.

Never underestimate the bandwidth of a spaceship full of tapes hurtling through the cosmos.

Star Citizen has a ship like that. A cabin strapped onto the largest engine that wouldn't kill you, with data storage added almost like an afterthought.

Well, star citizen has a ship like that - it doesnt have any gameplay loops that make use of that though.

The futuristic version of never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway.

Data storage ships is a thing in Beacon 23.

I was hoping the days of sail would be some kind of cool Sci-Fi movie or series.

Why is this even an article? It’s obvious.

Somebody just watched the Expanse for the first time and thinks it’s a neat new thing to explain to the Earthers

Is it weird that I've only ever read the books? I didn't even know there was a show until recently. Is it any good?

It's fairly good. Some things are a bit abridged for the sake of action and visuals. Like travel that takes weeks is sometimes happening within hours or days.

However the dialogue, writing and characters are pretty good. It did lack a bit in season 6 (the last one) but that's because the material wasn't there yet in the books and somehow it cuts things short with material from book 6 at best.

Thanks, I might check it out!

Also Passengers, starring Chris Pratt, has a mention of this too.

i knew the expanse would pop up somewhere in the comments! been working my way through the books and it's great!

Have they never watched Star Trek, subspace relays people.

What exactly is subspace anyways?

It’s a different part of the universe, separate from normal space where things like baryonic matter exists. In subspace certain of our universe’s fundamental rules as seen in normal space don’t apply or constants are different.

How much of this is based on reality and how much is based on Star Trek wanting a mechanism to be able to communicate between star fleet and the Enterprise?

I think entirely Star Trek on this one. Although, if we ever want to move* faster than light, it’ll almost certainly require a science or an understanding of nature which we don’t even have theoretical concepts of in 2023.

We use ions for a bunch of stuff like Li-ion batteries and various other chemical engineering marvels on a daily basis. I wonder how new is the idea of ions anyway?

Wikipedia has this to say: “Svante Arrhenius put forth, in his 1884 dissertation, the explanation of the fact that solid crystalline salts dissociate into paired charged particles when dissolved, for which he would win the 1903 Nobel Prize in Chemistry. Arrhenius' explanation was that in forming a solution, the salt dissociates into Faraday's ions, he proposed that ions formed even in the absence of an electric current.”

We’ve built so much on top an idea that’s only about 139 years old. Before that, it must have been pretty difficult or even impossible to explain large parts of chemistry we use every day.

I wonder how would you imagine the future of chemistry in the early 1800s? Could you imagine that nowadays we leach gold from a mineral that doesn’t even look golden at all? Could you imagine that we can pull aluminium from rocks that don’t even look metallic in any way? Could you imagine that we use it to build all sorts of things like cans, door frames and airplanes? What about surface coating of materials to give them corrosion resistance, different colors or scratch resistance. In the past 139 years we’ve done all sorts of absolutely wild things with ions.

If you start studying chemistry in 2023 you’ll probably hear about ions during the first lecture and later you’ll build all sorts of wonderful things on that bit of information.

Thanks for this. I have similar thoughts as to some people's definitiveness about our understanding of the universe and its speed limit.

The thing is, we don’t know is the speed limit is a hard problem.

Maybe will struggle with it for centuries or maybe we’ll find a way to avoid the problem within the next 130 years. Maybe we’ll find a way to bend space so that you don’t really need to travel very fast. Maybe wormholes become a viable option. Maybe we’ll build hyperspace gates or something like that.

Or maybe none of that is viable and a thousand years later we’re still struggling with the speed of light wishing there was a way around it.

At some point, microbes and immunology were a complete mystery. People dying after surgery was a hard problem and nobody knew how to fix that. Turns it, all you need is ethanol and penicillin, but we couldn’t even imagine it at the time.

Space is like a rainbow, subspace is equal to ultraviolet and hyperspace is infrared. At least inmy head cannon.

Subspace is what the warp bubble moves through

Ok, then it's fictional. The theoretical warp drive that is consistent with Einstein's field equations moves through normal space but just warps it in a way that it effectively moves faster than light (while locally obeying the light speed limit).

Though that still requires something with negative mass or gravity (I was very disappointed when they confirmed antimatter has normal gravity, I was hoping the theory was wrong on that).

There's still dark energy and dark matter that are kinda odd

There is the idea that everything is shrinking instead of space expanding, which resolves the dark energy question.

Who would have thought that Doppler could apply to communication equipment, too! Shocking!

Next they are going to tell us that messages might take some time due to c!

Duh.

how could that be surprising??

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imo by the time we have lightspeed ships we may have faster ways to send info, imagine back 2000 years ago and we tell people we can communicate faster than the speed of sound

data can't go faster than the speed of light

Yeah but physical objects also can't move faster than the speed of light so in any scenario where that's possible we've obviously either found a workaround or we were fundamentally wrong about some part of physics.

Maybe we have access to wormholes and we can just send radio waves through the wormholes Stargate style.

well, any going faster than light will have to utilize the bending of space-time, if it ever happens and the wormhole thing has even more problems

problem with wormholes is that you can send information into the past - so if you receive a message, does that mean you're predetermined to subsequently send that message?

Quantum entanglement? (forgive me if dumb thought, quantum physics is magic to me)

Quantum entanglement can't transfer data. As soon as you try to use the connection you break it.

Quantum entanglement is like this - you have two sealed envelopes. In one envelope the letter A is written on a sheet of paper and the other has a sheet of paper with B written on it. No one knows who has which envelope until it is opened. All opening the envelope does is let you know what is written on the piece of paper the other person has. It transfers no data between the two points as the data was already set.

doesn't work, "reading" the entangled particles causes them to change state, thus you can't know if it changed as part of sending a message, or just because you were reading it.

There is no "sending" The data was set when the particles were entangled. All you're doing is moving a particle from point A to point B.

the data is still being "sent" according to the field of information sciences.

not that it changes anything about the physical impossibility

Speech can't go faster than the speed of sound, sound waves.... But then comes telephone networks

to be fair, it's still both slower than the light signals that were then as are now the fastest possible form of data transfer.

saying "but someone might invent something" doesn't mean shit to physics, it's why we can always with confidence say that Perpetumobile are impossible

You're missing the point

no, I don't think I am, unless you want to make the argument that infinite free energy is just 1...n brilliant inventor(s) away

Now i'm visualizing a world where long distance communication is done with sound and you have screaming pipes across the continent

We have that. It's called Twitter X.

You forgot Facebook.

But I'd agree Twitter is more akin to just shouting

You forgot Facebook.

But I'd agree Twitter is more akin to just shouting

There were pipes for large houses back in the day for talking...

Edit* for Link https://lafayettesquarearchives.com/1892-speaking-tubes-and-old-homes/

Btw that seems pretty cool to have in the house, and the also furnace is always useful especially if you have many enemies

Something like that but with amplifiers to repeat over tens of kilometers

Maybe if we have faster than light travel we can assume that we'll have a faster way to transmit data. It's possible there will be a transitional period where we move at subluminal speeds and can transmit data at superluminal speeds, but I don't think being able to hit the speed limit ourselves will imply that we can break it with data.

Plus relativity will really fuck with things if we are able to reach the speed of light. Time dilation will reduce bandwidth from the perspective of the stationary observer because they need to sync up with a clock that will appear to get slower and slower. Maybe some kind of warp technology will avoid this, but if it doesn't, this will apply even if the signal can be transmitted instantly.

I've become resigned to the likelihood that if we ever do get out of this solar system, it will either be unmanned probes (like the ones we've already sent, which are still debatable as to whether we can consider them outside of it or not yet; they've passed the heliopause but haven't gotten to the Ort Cloud yet), or they will be effectively independent branches of humanity that will diverge and become their own thing over time. We'll be in contact (assuming both sides survive), but it will be more like pen pals where messages take years to arrive and meeting up in person is impossible. The ship will travel for generations before arriving at its destination with a good chance that they'll just die on the way or shortly after getting there unless they are prepared for further generations of terraforming moons and planets in the new system.

And with our current situations, even that seems unlikely. I'll be impressed if we see a self-sustainable moon colony or space station during our lifetimes or asteroid belt mining.

AI will beat us out of the solar system by far. They'll pack themselves up in Von Neumann probes and go to all the nearby stars at the same time. Then go on to the next furthest stars and on and on and on with some taking the plunge and venturing into the intergalactic void heading to another galaxy.

Our best bet would be to hitch a ride as DNA data. It will be modified on site to survive whatever world they come across, and then grown in tanks. They'll be raised by robots or AI in similar bodies to that of the new humans.

It's not a surprise, it's just a concern being presented because it's not a thought for the average person.

isn't developing light speed spacecrafts a far more direct concern?

why even concern about communications when travelling such distances isn't even possible.

I don't see the point of the article.

Most people have missed the bit about time dilation messing up the clocks used in signalling, which I thought was interesting at first. However, surely the fix is just as simple as including a timing signal with the transmissions?

Yeah we solved this problem in the 50s by including a clock signal in some form with the data. Most modern digital communications use it.

If nothing else, you discovered a way to gloss over the impossible thing in a bad scifi movie. "No it works because we added a timing signal!"

I think the problem is less timing the messages, and more that the messages from earth will just get redshifted more and more as the ship accelerates, which will require an ever larger antenna to pick up. This also has the affect of bandwidth tending towards 0.

There was an early 2000s anime movie that explored this idea. It was called Voices of a Distant Star.

Honestly this seems like a future me problem.

Jerry Pournelle's "CoDominium" books work like this. The ships are FTL, but can only use the FTL drive at a certain point to leave a system. There isn't a way to send messages faster than light, other than a ship. There is mention of "message sloops" which are small ships with high acceleration wich can move from the jump point to the inner system faster than one of the battleships.

This is why Jesus invented ‘two cans and a piece of string’.

Dammit, I’m not even a trained physicist but I still have to do all the thinking around here.

But where are you going to get a string that long?

Isn't that what string theory was meant to solve?

Yeah, but they never found the strings, so we don't pay attention to them anymore. Once they have some testable results we may invite them to the party again.

The fucking string store duh

Jesus Christ, why'd this get so downvoted? Do people not get sarcasm?

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What's the propagation speed of vibrations through carbon nantubes? I've done no math or experiments but back up this startup tech 100%. I pull on it at Alpha Centauri, it instantaneously pulls a receiver at Sol. I'd say a vat of liquid nylon with a thread pulled and dragged but that sounds sticky.

Edit /s no one is towing a rope

Now I'm imagining spider-ships traversing the galaxy making strings of filament behind them, connecting the galaxy in a vast web of communication lines.

Speed is always the same as the speed of sound through the item

Does a lower frequency signal travel the same speed? 1hz? I suppose it would be the same because the tether would have immense mass over it's length. So even though I'm picturing an impractically long tether moving as one solid length to tap slow morse code, the mass would be unfathomably high and therefore inducing significant stretch. That's without getting into vibration kinetic energy being lost to heat along the way

I'm obviously not genuinely proposing this. It's just a brain exercise.

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Can we quantum entangle two particles and then move one particle to part of a grid to "type" superluminally?

Nope:

https://en.m.wikipedia.org/wiki/Superluminal_communication

They play with this in the three body problem

Maybe that's where I got the idea, I read the trilogy years ago. That was such a good series.

I don't remember though. Did they solve the problem?