Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The Challenge of Relativistic Spaceflight

icarusinterstellar.org

Post reply on HN
Print view View original

81–89 of 89 posts

Re: The Challenge of Relativistic Spaceflight

#81

Post by snowwrestler »

fooqux wrote: post #45
mitchty wrote: post #39

Earlier quoted context omitted.

I guess I disagree that uploading minds is more feasible. One is more of an engineering/physics challenge, and uploading minds is dependent upon a vast set of unknown unknowns. We aren't even out of the door on the idea of biological computing let alone at the mailbox.

One key difference is that we know brains can exist. We might not know the entirety of how they work, but the important thing is we already know they can be reproduced in some fashion. Hyperdrive or any other form of FTL travel is purely in our thoughts. Nothing currently exists that even proves it is possible in our current reality. For all we know we could spend an infinite time attempting it and never achieve it.

We have no evidence at all that a given brain can be reproduced. We know that new brains can be made and developed (i.e. procreation), and even then we don't really know how that works.

But the post above said "mind" not "brain" which typically signifies that the author draws some sort of distinction between the two. I'm just saying: I don't know of any physical evidence for that distinction.

Re: The Challenge of Relativistic Spaceflight

#82

Post by icambron »

kjs3 wrote: post #70
ForHackernews wrote: post #57

Earlier quoted context omitted.

\ shrug\ It's all sci-fi tech anyway. Artificial wombs probably aren't that far off: http://www.popsci.com/scitech/article/2005-08/artificial-wom... There's a clear demand for advanced reproductive technology, and it would offer the secondary advantage of neatly sidestepping the current abortion debate.

You're missing my point (which I suppose I really didn't make, so my bad). A child raise by machines is likely to be one seriously emotionally messed up child.

Well, all kids are raised by machines, just usually machines called Mom and Dad. The question is whether the machines we could make to replace us as parents are better or worse. It's hard for us now to imagine artificial machines being better at it than we are, but, you know, so is relativistic spaceflight.

Re: The Challenge of Relativistic Spaceflight

#83

Post by rm445 »

GFK_of_xmaspast wrote: post #80
Tloewald wrote: post #69

Earlier quoted context omitted.

There are plenty of simple, well-made machines designed to work indefinitely -- e.g. doorknobs, window assemblies. Even simple, robust, well-maintained machinery tends not to last a very long time. There's a stone bench somewhere that Thomas Jefferson supposedly used to sit on that has become curved over time.

Are you seriously going with "a stone bench" as your example of the durability of "robust well-maintained machinery".

I'm pretty sure he's taking the opposite view, that (a) building elements have indefinite design lives but don't last that long, and (b) Even stonework doesn't endure indefinitely.

I'm not sure I really agree with the second point in this context - stonework tends to endure. We have Norman cathedrals that are looking good at nearly a thousand years old, comparable to the timescales under discussion to spaceflight. More to the point, there's no reason to believe that the basic structural elements of, say, a hollowed nickel-iron asteroid wouldn't be durable enough for spaceflight.

Re: The Challenge of Relativistic Spaceflight

#84

Post by rm445 »

Tloewald wrote: post #33
ryandrake wrote: post #24

TL;DR: Chemical propulsion is a dead end. But, the alternatives require matter/energy of ridiculous scale (hundreds of times the power output of human civilization, launching hundreds of millions of tons of matter into orbit). We're not going anywhere, any time soon.

Not just magnitude but duration. Name one machine that works without major overhaul for more than 100 years. For bonus points, name a machine that's significantly more complex than a clock.

What sort of major overhaul do you have in mind? A spacecraft on a multi-century flight would presumably have continuous ongoing maintenance and repair, but would need to function without a spell in space-dry-dock halfway through its journey.

So to answer your question, what about the London Underground? It's a pretty complex machine that has been running for 120 years, with various overhauls, but of the frequent short shutdown type rather than total closure and redevelopment.

The challenge for a spacecraft is being a closed system, but it's just an engineering problem.

Re: The Challenge of Relativistic Spaceflight

#85

Post by Tloewald »

snowwrestler wrote: post #78
Tloewald wrote: post #36

Earlier quoted context omitted.

Uploaded minds is hardly an argument depending on cartesian duality. Arguing that there's something irreproducible about the human brain is quite close to cartesian duality. I am not arguing that uploading minds is any more feasible than a generation ship, but it is at least more plausible than hyperdrive -- based on what we think we know right now.

Human brains are no more difficult to exactly reproduce than any other piece of matter: extremely difficult. The best we've done to date is a few previously entangled particles. Edit to add: what I'm talking about here is quantum teleportation of the matter of the brain. Typically when people talk about "uploading a mind" they mean that the mind is software running on the hardware of the brain--like Windows running o…

The question comes down to "could you run a sufficiently accurate simulation of a brain on a sufficiently powerful computer that it could pass for the mind of the person whose brain was being simulated"? I'd say the belief that the belief this is impossible is a variant of the cartesian duality.

Re: The Challenge of Relativistic Spaceflight

#86

Post by userulluipeste »

cousin_it wrote: post #25

What's the point of these huge generation ships? It's not like there's not enough atoms on other planets. You should send a tiny fast robotic ship, maybe with an uploaded mind if your AI tech isn't good enough. It will mine materials at the destination and build a receiver antenna. Then you can send more uploaded minds by radio, which will arrive at the speed of light with low energy cost. Another reason why you shou…

I heard about this interstellar communication silver-bullet before. You're just taking communications on earth for granted - need more bandwidth between points A and B? Just throw in another independent physical communication channel between them! Well, that's fine here but it doesn't work the same way at creating data links between Earth and another celestial body inside our solar system and definitely not between the solar system and another star system. Think how much info can we theoretically send at a time to another star and how much time will it take to send a brain of knowledge! I think it will be more feasible to send those brains of knowledge in some physical form (and guess what the most intuitive way for doing that would be).

Re: The Challenge of Relativistic Spaceflight

#87

Post by userulluipeste »

kjs3 wrote: post #52
ackydoodles wrote: post #16

The numbers only become science-fictiony large if you want to go fast. Why not go slowly? The only reason humanity is obsessed with speed is because of our short life spans, but that is a solvable problem. All we have to do is to eliminate aging and it's associated diseases, and then we can take our time going to the stars. The most difficult part may be accepting limits upon our appetites, so that we are not driven…

Ignoring the whole "we'll just cure mortality...how hard can it be?", people tend to go batshit crazy after spending a couple of months in confined conditions looking at the same faces day after day. Think they're going to do better mentally when they look forward to the same for a 100 years.

Then we have to address this newly pinpointed problem - to somehow make people not „go batshit crazy”. Maybe practicing some kind of meditation? I admit that it's not as exciting as some technical overhaul we all expect, but still...

Re: The Challenge of Relativistic Spaceflight

#88

Post by cousin_it »

userulluipeste wrote: post #86
cousin_it wrote: post #25

What's the point of these huge generation ships? It's not like there's not enough atoms on other planets. You should send a tiny fast robotic ship, maybe with an uploaded mind if your AI tech isn't good enough. It will mine materials at the destination and build a receiver antenna. Then you can send more uploaded minds by radio, which will arrive at the speed of light with low energy cost. Another reason why you shou…

I heard about this interstellar communication silver-bullet before. You're just taking communications on earth for granted - need more bandwidth between points A and B? Just throw in another independent physical communication channel between them! Well, that's fine here but it doesn't work the same way at creating data links between Earth and another celestial body inside our solar system and definitely not between t…

Hmm. Theoretically it seems like lasers should support speeds of terabytes per second, so you should be able to transmit a human mind in minutes to hours (maybe faster with compression), and that should take less energy than sending an actual brain at reasonable speed (rocket equation). If you want more bandwidth, use multiple lasers located close to the solar system, but still far enough that they can be distinguished from another star. At longer distances, use multiple intermediate stars in parallel, like the internet. Or is there some theoretical limit that I'm missing?

Re: The Challenge of Relativistic Spaceflight

#89

Post by userulluipeste »

cousin_it wrote: post #88
userulluipeste wrote: post #86

Earlier quoted context omitted.

I heard about this interstellar communication silver-bullet before. You're just taking communications on earth for granted - need more bandwidth between points A and B? Just throw in another independent physical communication channel between them! Well, that's fine here but it doesn't work the same way at creating data links between Earth and another celestial body inside our solar system and definitely not between t…

Hmm. Theoretically it seems like lasers should support speeds of terabytes per second, so you should be able to transmit a human mind in minutes to hours (maybe faster with compression), and that should take less energy than sending an actual brain at reasonable speed (rocket equation). If you want more bandwidth, use multiple lasers located close to the solar system, but still far enough that they can be distinguish…

"is there some theoretical limit that I'm missing?"

Well, considering that the closest star (Alpha Centauri) is 4.367 light-years away, that only means that if something's wrong with the transmission itself, we can figure it out only after almost nine years. Other than that, I don't really imagine any feasible solution for communication on interstellar scale other than laser-based one, so my initial point was put forward exactly in that use-case. If there ever will (and I hope it will) be a galactic-scale communication system, humanity will have to:

- Improve the current laser technology to the point of sending laser beams without much dispersion over light-years distances.

- Improve the optical sensor technology in order to receive (and distinguish) from (multiple) artificial sources of light orbiting close to a noisy star.

- Set up the laser system(s) taking in account: the time-frame of the moving celestial bodies - both stars and the orbiting emitter(s)/receiver(s), the gravitational time dilation factor, other currently known factors that I don't know of (I'm not a professional physicist), and whatever any other new additional subtle effect that may be still discovered in such setting! I think this fine calibration will be the cake's top-cherry, BTW.

So yes, theoretically all is just an engineering problem. The development speed cycles of such systems though, are already dictated by the laws of physics - years (and in human time - generations). The mere reliable communication on such scale will be a great success, but I don't dare to hope of sending brains of knowledge['] in mere hours.

['] http://www.scientificamerican.com/article/what-is-the-memory...

Post reply on HN