Comment by jordwest | Hacker News Reader

Comment by jordwest | Hacker News Reader

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> even for a civilization at the end of the technology development tree.

How do we know what the end of the technology development tree looks like? There are just so many mysteries that remain within our current understanding of science, we can’t say for sure that it’s not easy (for example) to bend space time or some other possibility that makes faster than light travel possible. Quantum entanglement, for example, breaks many of our assumptions about the impossibility of FTL travel.

> When aliens visit, everyone will know.

Maybe, but perhaps a civilisation that has survived the great filter would look differently at civilisations they stumble upon. Maybe, like we do when searching for microbes on Mars, they would try not to disturb the life they discover.

This is all just speculation of course, but I think when looking at this topic it’s all too easy to apply a human centric view on what’s possible and what’s not, and the truth is we just know so very little. Or, we know a lot, but there are so many more mysteries than solved problems.

While I would also not presume to know how different our understanding of the universe may look in hundreds (or thousands!) of years, I do draw some exception to the following comment:

>Quantum entanglement, for example, breaks many of our assumptions about the impossibility of FTL travel.

Quantum entanglement can produce correlated measurements between systems, even when the entangled systems are separated by large distances. In a sense, this can be used to measure the state of an entangled system at great displacement "faster" than it would take light to travel from that distant system to the observer. However, the state of the entangled systems is prepared before the systems are separated from one another (at much less than the speed of light.) Any attempt to change the state of one of the entangled systems (at a distance) breaks the entanglement. Entanglement cannot be used to communicate information from one point to another faster than the speed of light. It certainly doesn't allow FTL transfer of matter/energy.

> However, the state of the entangled systems is prepared before the systems are separated from one another

Isn’t the state still a probabilistic one at that point though? As in it’s not until it’s observed later that both particles instantaneously collapse into a correlated state. But the precise outcome of the observation isn’t determined before they’re separated.

My understanding of quantum mechanics is far too limited to really dive into this, but my point isn’t that it enables FTL communication or travel directly.

Rather my understanding is that it appears to break our previous assumptions - physicists haven’t yet settled on a way to unify relativity and quantum physics [1] which leaves many possibilities open. We still just don’t know enough to say it’s definitely impossible.

[1] https://en.m.wikipedia.org/wiki/Problem_of_time

>Isn’t the state still a probabilistic one at that point though? As in it’s not until it’s observed later that both particles instantaneously collapse into a correlated state. But the precise outcome of the observation isn’t determined before they’re separated. This is correct.

I’ve never looked too deeply into this, but why can’t someone use something like Morse Code to communicate? Say you had 50 buckets of entangled entities, that would get you 50 dots and dashes.

Because if you attempt to influence the state of the entangled bits--say, to set a bit to up/down (dot/dash or zero/one) state to form your message--you will break the entanglement. You can measure the states of the unperturbed entangled bits, and therefore know about the states of their distant entangled partners, but the message will be random. You could also influence the states of the bits while you create the entangled pairs, but then you have to carry them far away from one another (at less than the speed of light), so you won't be able to communicate FTL; you would just have a pair of messages in a bottle, so to speak.

There’s no way breaking one entanglement breaks all others across the universe, right? So what I was saying is, just have 50 different pairs of entangled bits. You could only send a 50 bit message once, but bam, you have FTL communication.

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