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Light-Speed Spaceships Would Have Trouble Phoning Home
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this post was submitted on 11 Dec 2023
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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.
Then we need the Tim (Allen) Taylor solution.
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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.
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
That's just time travel with extra steps!
It literally is time travel.
We are all currently time-traveling at a ratio of (edit: roughly) 1:1
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.
Quantum entanglement is like ripping a photo in half, putting both halves in seperate envelopes and carrying them to opposite ends of the world.
As soon as you open your envelope, you instantly know which half of the photo is on the other side of the planet - Faster Than Light Information Transfer!
For a variety of reasons, no information is actually transferred. Quantum entanglement can not be used to get around the limits imposed by relativity.
That's what I was trying to illustrate.
Illustrate?? I thought you were talking about photographs
This is a great analogy. Consider it ~~stolen~~ pirated.
So it's not like: when I affect the hue (some attribute) of my half, the other half will change too? That has always been my understanding of it
No, measuring one particle collapses the entanglement and they no longer affect each other. It is a one time thing. You can't modify them after they have been observed.
So at best it can be used for unpredictable coordination between vastly-spaced armies.
Nope. Because you don't know when it will collapse,. Imagine you have 2 balls, a red and a blue. They are both put in boxes and each ship takes 1 box. After you travel a long distance you open your box. You have just collapsed the "superposition" of what color the balls were. You now know what color both balls are, but you don't know if the other person has looked in their box yet.
I think a lot of people get confused by the term "observe" when talking about collapsing quantum uncertainty. Observing requires a photon to interact with the particle which is what caused it to "choose" what state it is in.
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.
You cannot transmit information through entangled particles, so probably not.
Oh, you already know about it. No one else should bother reading then.