A metallurgist's doubts about self-replicating probes • Hacker News Board

Re: A metallurgist's doubts about self-replicating probes

#101

Post by red75prime » Wed, Jul 15, 2026, 6:09 PM UTC

simiones wrote: post #96

red75prime wrote: post #31

Earlier quoted context omitted.

> there is no reason to believe that the way to build it would be found before, say, the sun runs out of hydrogen. A lot of computational power can be thrown at the problem in this time. So, the problem should admits no shortcuts, no decomposition into simpler problems, no alternative ways to get similar functionality that allow shotrcuts or decomposition. The result should look like a jumble of atoms that somehow pr…

> A lot of computational power can be thrown at the problem in this time. We know plenty of actually very simple problems that we would not be able to solve from now till the Sun explodes even if we all of the computers on earth were only doing this. Say, solving a worse case instance of the Knapsack problem for n > 250 items easily fits into this. If you want to be precise, the complexity class EXP best fits my desc…

> if discovering the required technology to build a self-replicating interstellar probe requires solving an instance of an EXP problem[...]

Ah, I think I know why I felt it was very unlikely. Engineering constraints should be very "unlucky" so that only the solution works. That is, there's no wiggle room that allows an approximate solution (which is usually simpler to find) to work, even if it would be slightly heavier, costlier, or something of the sort.

For such a tight constraint not to be a coincidence, nature itself would have to be able to solve EXP problems. Which might mean that not all is lost.

ETA: ChatGPT has pointed out that many interesting instances of computationally hard problems are still solvable. For example, see SAT-solvers (SAT is NP-complete).

That is in addition to tight constraints the problem instance should have no exploitable structure.

Re: A metallurgist's doubts about self-replicating probes

#102

Post by neaden » Wed, Jul 15, 2026, 6:34 PM UTC

SideburnsOfDoom wrote: post #94

neaden wrote: post #66

Earlier quoted context omitted.

"Israel or North Korea, both of which try to be self-sufficient" - Neither of them do any such thing though. From a quick search Israel imports about 80% of their calories though they also export some food they are heavily reliant on imported grains and meat. North Korea is obviously harder to get information on but it imports large amounts of food from China.

North Korea has an official ideology of "Juche", and "The goal of Juche is to establish a self-reliant state" (1) It may not be like that in practice. But nevertheless, self-reliance is in their stated goals, and North Korea is one of the least "open" states in the world. I think you can make the case that they "try to be self-sufficient". They do try . As for Israel, eh, it depends. They certainly don't rely on neig…

Sure North Korea tries, but they don't succeed so it's not really helpful as an example of a self sufficient society to base a space colony off of. As for Israel yeah, they mostly don't import food from their neighbors (most of whom also import the majority of their food calories) but I don't see what that has to do with anything, as I said they import 80% of their calories which is certainly not tenable for a space colony to do.

Re: A metallurgist's doubts about self-replicating probes

#103

Post by Windchaser » Tue, Jul 28, 2026, 3:54 PM UTC

andrewflnr wrote: post #88

Windchaser wrote: post #39

Earlier quoted context omitted.

So that adds some extra "benefits" (mutation and natural selection improves the probes over time) along with some extra difficulties - how do you keep the self-reproducing probes "on-task" from one generation to the next? How do you instill "explore and report home" as an innate goal to a mutating system?

> how do you keep the self-reproducing probes "on-task" from one generation to the next? This is, indeed, the exact question one must ask before attempting to build and launch biological Von Neumann probes.

I think it applies to non-biological Von Neumann probes as well. It'll apply to any system that can mutate, even if that mutation is just cosmic rays flipping the bits on a hard drive.