No Faster-Than-Light Travel

[Lago PARANOIA]

So if we can never attain ways of traveling FTL, what does this mean for the future generations? Are they just monkey-fucked to the Solar system?

[Quantumboost]

As long as we can still get gigantic power drives and propel ourselves through space, we can just fly between the stars at sublight (but still ridiculous by our standards) speeds. The nearest few stars are within a single person's lifespan in light-years, as long as the species can keep itself alive aboard ship long enough we'd probably be able to survive the death of our specific sun.

Faster-than-light travel is only a big deal for things like commerce and invidual people's travels between planets, not the continued existence of people as a whole.

Assuming we don't blow ourselves up first, anyway.

[Vebyast]

Nope. It'll just take them a few hundred years.

[edit] Simulpost for the win. [/edit]

[Orca]

Since we can't even send people to Mars in the foreseeable future I can't see this as an issue.

[Juton]

There's also cryosleep, as seen in the movie Aliens. As mentioned above we'll start to see colonization once we have the power needed to go between planets/solar systems and do it for only a few billion dollars. Then you can get a few (very rich) fringe loons who want to live away from 'the man'.

[Crissa]

Well, you could get to Bernard's Star, but who wants to?

-Crissa

[Jacob_Orlove]

I can't imagine that they'd go for cryosleep when they could send embryos instead. Once you give up on sending individual people, you're just transporting genetic data. The most efficient way would be to digitize it and resythesize it on site, but sending a bunch of test tube babies and some robots should be a workable second best.

Actually building a space ship large enough to carry a self sustaining human colony on board for the generations it would take to reach another planet seems like way more effort than it's worth.

[the_taken]

And that's why you need to take short cuts. Grab an asteroid or smallish moon from Jupiter or something, terraform it and slap some rockets on it. Done.

[Vebyast]

And that's why you need to take short cuts. Grab an asteroid or smallish moon from Jupiter or something, terraform it and slap some rockets on it. Done.

You think too small. I'd have preferred a better link, but the scientific note to this comic explains the technique pretty well.

[edit] Schlock Mercenary is a pretty good comic, for those of you into traditional exposition-heavy space opera. [/edit]

[Prak]

This line made me smirk:

think "don't build houses on this side"

Then this one made me giggle out loud:

in which the Earth was moved with the help of giant candle they'd shoved up Uranus.

the english language needs to either choose another term for that particular piece of anatomy, or scientists in general need to choose another name for that particular planet....

[Username17]

Sending information faster than light with quantum entanglement communicators seems to be a done deal. As such, the amount of time it physically takes to get colonies started in another star system or another galaxy is pretty much meaningless. In the long run, we'll be having phone sex with the people in the new colonies with as little lag as dong the same with folks in Korea.

-Username17

[virgil]

I'm reasonably certain that quantum entanglement can't do what you think it does. The current system/understanding is more like a synchronicity generator. The only way it could transmit information through such a channel is by being able to control how a wave form collapses when observed; which I find unbelievable, though I'm outside the field enough to not recall any proofs to push it to impossibility.

However, time dilation has been measured and observed, so FTL communication WILL result in non-causal communication; which is a...troubling scenario.

[Daiba]

As far as I know, quantum entanglement does not enable FTL communication. I'll try to summarize from what I recall from quantum mechanics a few years ago:

The basic premise of quantum entanglement is this: you can have two particles/objects that have their quantum states linked in such a way that when you measure one of them, you can certain of the state of the other one. With spin 1/2 particles, the results are binary: either up or down. When you measure one, you can be certain that the other particle will have the opposite state. Essentially, you have set up a system of two coins where if you flip one and get a result, the other coin, when flipped, will get the opposite result.

Pretty awesome, right? People can totally generate tamper proof encryption keys by physically sending someone else a matching set of particles/coins. When you encrypt your message, you flip all the coins and use the result as your key. When your partner gets the encrypted message, she flips all of her coins and uses the result to infer the encryption key you used.

However, if you try to construct a system of communication using only QE, you run into a problem: nobody knows when the coins were flipped, and there's no way to check it without flipping the coins. You might be able to come up with some sort of arrangement whereby the results from the coin flips would contain information, but you would still have to send your recipient a message (via normal, lightspeed means) indicating that you had flipped your coins.

[Username17]

Quantum Entanglement Communication works oddly, because the information is passed by times of state changes rather than the states that actually are present.

Basically both sides have a deliberate and continuous schedule of flipping the coins and checking their current state. You pass information by reflipping it again before the next scheduled check by the other side. You can't store information that way, but you can send information in that manner.

-Username17

[the_taken]

My dad was looking over my shoulder while I was reading this.

He says he's working on it.

[angelfromanotherpin]

in which the Earth was moved with the help of giant candle they'd shoved up Uranus.

the english language needs to either choose another term for that particular piece of anatomy, or scientists in general need to choose another name for that particular planet....

I choose invisible option C: Pronounce the name correctly.

[Parthenon]

Yes, but doesn't that still means quantum entanglement is effectively useless? Surely the most important information is not at scheduled times? And if spaceships are going at like more than 0.7c and accelerating or decelerating then the rate of flipping coins will have to change at a non-predictable rate.

And I'm probably a complete idiot who has forgotten most of his physics and mangling what I can recall, but with the universe expanding and different planets and suns moving at different speeds won't different planets have slightly different time flow due to relativity so realtime connections will behave really weirdly?

[Username17]

Yes, but doesn't that still means quantum entanglement is effectively useless?

No. It's a persistent connection. Every single scheduled shift you either send a zero (by not doing an extra shift) or a 1 (by doing an extra shift). It's not a radio where you send information or not. You have no choice but to fill every single allowed bit. With either a zero, or a one.

Surely the most important information is not at scheduled times? And if spaceships are going at like more than 0.7c and accelerating or decelerating then the rate of flipping coins will have to change at a non-predictable rate.

Why? These journeys don't involve people pressing the space gas pedal and swerving around, they don't really have a pilot at all. Any changes in acceleration would be scheduled years in advance. Calculating the schedule would be a very difficult math problem, but compared to determining where a twinned quantum state had been lasered once or twice since your last laser pulse, it's no big deal.

And I'm probably a complete idiot who has forgotten most of his physics and mangling what I can recall, but with the universe expanding and different planets and suns moving at different speeds won't different planets have slightly different time flow due to relativity so realtime connections will behave really weirdly?

It's real time relative to the schedule of the quantum exchanges. Which means that you'd have to calculate all those accelerations. But again, you'd have to do that anyway.

-Username17

[NineInchNall]

It's fundamentally the same concept behind any sort of asynchronous communication model. Anyone who's had to do network programming has had to deal with data streams that have to be checked repeatedly to see whether new data has been sent/received.

[Nihlin]

However, time dilation has been measured and observed, so FTL communication WILL result in non-causal communication; which is a...troubling scenario.

Actually, you can still have causality, what you lack is locality. Remember that Bell's Theorem lets you have locality or causality, but not both. The probabilistic interpretation of quantum mechanics keeps locality at the cost of microscopic causality. But many other interpretations keep microscopic causality at the cost of locality. At present, no experimental data exists to clearly favor one over the other, but quantum communication someday might provide such insight.

[virgil]

Yes, Bell's Theorem says you have locality or causality, but not both. However, that leads to the same statement of "you have causality breaking FTL communication, or you don't". This is countered by the no-communication theorem.

Everything I've seen of quantum entanglement makes it look more like a shared viewing experience; and attempts to schedule viewing in a manner that could infer information would result in the receiver's observation retroactively influencing the sender's message, resulting in no information being sent.

[Prak]

in which the Earth was moved with the help of giant candle they'd shoved up Uranus.

the english language needs to either choose another term for that particular piece of anatomy, or scientists in general need to choose another name for that particular planet....

I choose invisible option C: Pronounce the name correctly.

The joke/innuendo is still there, though, especially in written form when it seems to be implied.

[virgil]

Aha! I finally found the best example I know to explain why FTL anything gives time travel

[Ganbare Gincun]

in which the Earth was moved with the help of giant candle they'd shoved up Uranus.

the english language needs to either choose another term for that particular piece of anatomy, or scientists in general need to choose another name for that particular planet....

I choose invisible option C: Pronounce the name correctly.

What? And miss out on comedy like this?

Oh, and the Normandy uses quantum entanglement to communicate with the Illusive Man. Go figure, eh?

[Lago PARANOIA]

Any time where you can know the spin of a particle, the entanglement is destroyed. The only time entanglement exists is when two particles are in a superposition - they're really the same thing, a superposition exists because you don't know the states of the entangled particles. In order to send information via spin-coupling, you need to know what the spin is at your end much in the same way you need to know, at your end, if you've just made a dot or a dash when sending morse code, otherwise you're sending information free noise - and to do that means pulling it out of a superposition, which means the entanglement is destroyed. Removing the entanglement just gives you a probabilistic collapse from a superposition to a known state, meaning you get random noise at both ends which no information can be encoded in. It's effectively identical at both ends, but there's no information transmitted because it's randomised. There is absolutely no way to get around this. Any time you want to manipulate a particle, you remove the entanglement and such manipulation is what is needed for meaningful information to be encoded. Indeed, if you assume the hidden variables interpretation the appearance of entanglement and action-at-a-distance is just an illusion anyway.

So... thoughts?