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A metallurgist's doubts about self-replicating probes

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

#91

Post by EA-3167 »

AlotOfReading wrote: post #73
Diogenesian wrote: post #36

Earlier quoted context omitted.

Why would biological systems be a counterargument? Smelting metals and sustaining life both require an enormous amount of water and about ~1ATM of atmosphere, as far as we know, and there's no plausible known mechanism for sidestepping this requirement. So "magical synthetic biology that can self-replicate in space" is actually a worse solution to the problem than "magical metallurgy that can be done in space" since…

You're making assumptions that the parent isn't necessarily making. Imagine sending humans to other earthlike planets on hypothetical generation ships. Those humans could throw away their technology and rebuild from zero over thousands of years to send more spaceships of humans to yet further planets. Presto, an example of self-replicating biological von Neumann systems.

It's important to say that isn't self-replicating in the von Neumann sense, even setting aside the question of how it's being executed. Humans don't replicate, we reproduce and critically evolve, never more quickly or drastically then when we're introduced to a new environment with new selection pressures. Unless these future humans have the technology to avoid that natural drift then they won't be a probe for the original species in any sense, they will speciate. In fact if you send people on a one-way trip to start over from scratch, I think it's pretty extreme to imagine their nth descendants caring about the goals of the parent civilization. Even if they in turn become spacefaring it's not as though they'll act as "probes" for their ancient and probably forgotten ancestors.

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

#92

Post by AlotOfReading »

EA-3167 wrote: post #91
AlotOfReading wrote: post #73

Earlier quoted context omitted.

You're making assumptions that the parent isn't necessarily making. Imagine sending humans to other earthlike planets on hypothetical generation ships. Those humans could throw away their technology and rebuild from zero over thousands of years to send more spaceships of humans to yet further planets. Presto, an example of self-replicating biological von Neumann systems.

It's important to say that isn't self-replicating in the von Neumann sense, even setting aside the question of how it's being executed. Humans don't replicate, we reproduce and critically evolve, never more quickly or drastically then when we're introduced to a new environment with new selection pressures. Unless these future humans have the technology to avoid that natural drift then they won't be a probe for the or…

There are decades old papers [0] on this subject that explicitly use humans as a analogy and call it "reproduction" because of the need to learn or evolve for local conditions. I don't think using terms in a way they've been used since the first serious analysis of the concept is going to confuse anyone.

    I think it's pretty extreme to imagine their nth descendants caring about the goals of the parent civilization.
It's an example to demonstrate the concept in familiar terms, not a psychohistorical prediction.

[0] https://www.rfreitas.com/Astro/ReproJBISJuly1980.htm

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

#93

Post by saulpw »

asdff wrote: post #89
saulpw wrote: post #80

Earlier quoted context omitted.

That's the source, but for chemical reactions you also need a sink. For instance gasoline is not usable as an energy source without an oxidant. Take away the oxygen in Earth's atmosphere (an asteroid has no atmosphere at all) and now gasoline has no potential energy available. Asteroids have no available oxidants (regolith was already fully oxidized long ago).

If it has been oxidized, there's your oxygen source.

It takes more energy to liberate the oxygen than you could ever get from the fuel. You don't need oxygen atoms, you need the oxidant.

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

#94

Post by SideburnsOfDoom »

neaden wrote: post #66
Animats wrote: post #40

Earlier quoted context omitted.

> Every terrestrial concentration process relies on things an asteroid lacks: gravity-driven sedimentation, water-based flotation, density separation in fluids, atmospheric combustion. That's a good point. Most bulk industrial processes won't work in zero G. This limits asteroid mining. Breaking off pieces of rock and accelerating them to somewhere, maybe. Building a big wheel and spinning it up to get some gravity,…

"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 neighbouring countries.

1) https://en.wikipedia.org/wiki/Juche#Core_principles

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

#95

Post by pfortuny »

asdff wrote: post #69
pfortuny wrote: post #32

Earlier quoted context omitted.

The self-replication assumes also that there is enough energy stored in each planet (or coming from a Sun) to do the work... That is pretty much unlikely.

Any chemical bond is a potential source of energy. Plenty of sources of potential energy too able to be converted to work.

As long as you can get an exogenous reaction from it, which is not guaranteed at all.

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

#96

Post by simiones »

red75prime wrote: post #31
simiones wrote: post #28

Earlier quoted context omitted.

I hate this assumption that many sci-fi enthusiasts seem to make, that as long as something is not ruled out by currently known physics rules, it doesn't matter that we have no idea how it could be built, there will be some way in some plausible future. When we see currently insurmountable problems in creating a piece of technology, it's absolutely possible that we'll never be able to build it. Even if it is theoreti…

> 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 description (though NP-complete would also be enough). That is, if discovering the required technology to build a self-replicating interstellar probe requires solving an instance of an EXP problem that is not ridiculously tiny, then we would likely never be find out how to build this probe. And no amount of AGI would change this, in this case.

I'm not suggesting that I have any reason for this ridiculously precise scenario to be correct. Just that some technology being allowed by the laws of physics should not be taken to mean that it is actually implementable in any imaginable amount of time, even if we were to assume singularity-style AGI.

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

#97

Post by simiones »

torginus wrote: post #58
simiones wrote: post #23

Earlier quoted context omitted.

The thing is, while the universe is full of metals, it's not that full of the materials needed to sustain life (as we know it, at least). You can find metals and other inorganic compounds on virtually every asteroid, moon, and planet, and many comets even. But water and nitrogen and carbon are significantly rarer. Plus, life can't survive more than a few minutes in space without metal encasings and electronic life su…

Actually the other way around: https://en.wikipedia.org/wiki/Abundance_of_the_chemical_elem... There's tons of Carbon, Nitrogen and Oxygen in the universe, but very little metals. Heavier elements are much rarer.

Not in rocky bodies, except maybe for Oxygen (which is commonly found in the form of oxides, very rarely as a gas). Carbon and Nitrogen and Hydrogen and similar elements are mostly found in gas clouds and star that are not really conducive to any form of life or even really fit for extraction by a probe. Maybe some gas giants could be targets for a process of this kind?

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

#98

Post by simiones »

abecedarius wrote: post #26
simiones wrote: post #23

Earlier quoted context omitted.

The thing is, while the universe is full of metals, it's not that full of the materials needed to sustain life (as we know it, at least). You can find metals and other inorganic compounds on virtually every asteroid, moon, and planet, and many comets even. But water and nitrogen and carbon are significantly rarer. Plus, life can't survive more than a few minutes in space without metal encasings and electronic life su…

In the outer solar system organics and water are abundant (and in the inner there are plenty of carbonaceous chondrites, admittedly not the most generic inner-system bodies). Agreed that metals should unlock wider opportunities in the inner system where solar energy is more abundant. I just don't think it matters much, you need a good place to plant your seed; once you've built up to scale you can then build wherever…

> (False that life dies in minutes in space; plus the engineers can invest in even greater error correction than radiodurans.)

What form of life can actually survive (that is, continue living, not just go into some dormant state from which it can later resurrect like a tardigrade) in space for more than a few minutes?

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

#99

Post by simiones »

pushcx wrote: post #46
simiones wrote: post #28

Earlier quoted context omitted.

I hate this assumption that many sci-fi enthusiasts seem to make, that as long as something is not ruled out by currently known physics rules, it doesn't matter that we have no idea how it could be built, there will be some way in some plausible future. When we see currently insurmountable problems in creating a piece of technology, it's absolutely possible that we'll never be able to build it. Even if it is theoreti…

This isn't elaborated on in the piece, but it does mention that it's written in the context of the Fermi paradox. Adding 50,000 years of technological development and a 1,000 year rebooting phase at each star system doesn't meaningfully change how long it would take life to spread when considered against the 13,500,000,000 years since stars developed.

Why 50,000 years of technological development and not 50 billion?

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

#100

Post by pushcx »

simiones wrote: post #99
pushcx wrote: post #46

Earlier quoted context omitted.

This isn't elaborated on in the piece, but it does mention that it's written in the context of the Fermi paradox. Adding 50,000 years of technological development and a 1,000 year rebooting phase at each star system doesn't meaningfully change how long it would take life to spread when considered against the 13,500,000,000 years since stars developed.

Why 50,000 years of technological development and not 50 billion?

I timed it a few times.
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