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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

#21

Post by abecedarius »

seiferteric wrote: post #9

Wouldn't a counter this argument be biological systems? These are reasonable points as long as we are talking about current methods, but I assume if we were to get to the point of self replicating probes it would be done by something like nanotechnology, synthetic biology like systems.

Yes, I was wondering why the focus on metals. (Admittedly they might be needed in trace amounts for catalysis, or convenient for conductors, etc., or for structural material if you're on a carbon-poor asteroid. Most metals are worse than carbon for the latter if you have reasonably high tech.)

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

#22

Post by mNovak »

jpitz wrote: post #11
in-silico wrote: post #4

One "solution" to these problems is to have the probes land on planets instead of asteroids, and build the necessary infrastructure there.

That solves many of those problems, although it rather introduces a big gravity well to escape from when replication is complete.

Though, by the time we've replicated a complete industrial hinterland (up to and including a semiconductor supply chain) which the author describes, it seems like generating fuel and engines wouldn't be impossible.

Also to the authors last point (extremely long time scales causing degradation), it seems like we'd want high thrust capabilities regardless. i.e. maybe a small gravity well doesn't gain us anything, since we'd need big engines to get up to speed anyway.

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

#23

Post by simiones »

abecedarius wrote: post #21
seiferteric wrote: post #9

Wouldn't a counter this argument be biological systems? These are reasonable points as long as we are talking about current methods, but I assume if we were to get to the point of self replicating probes it would be done by something like nanotechnology, synthetic biology like systems.

Yes, I was wondering why the focus on metals. (Admittedly they might be needed in trace amounts for catalysis, or convenient for conductors, etc., or for structural material if you're on a carbon-poor asteroid. Most metals are worse than carbon for the latter if you have reasonably high tech.)

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 support; whereas metal alone only requires life at a much longer time scale. So, while it may be possible to build a fully inorganic self-replicating fleet, it's certainly impossible to build a fully-organic one with any technology or chemistry we know about today at least.

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

#24

Post by abecedarius »

andrewflnr wrote: post #18

The thermodynamic argument seems much more important to the Fermi Paradox than any difficulties in refining material, but I don't think I understand it.

If physics were to forbid closure at small scale, how could life begin? And how does a micron-scale autotroph reproduce?

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

#25

Post by EA-3167 »

abecedarius wrote: post #21
seiferteric wrote: post #9

Wouldn't a counter this argument be biological systems? These are reasonable points as long as we are talking about current methods, but I assume if we were to get to the point of self replicating probes it would be done by something like nanotechnology, synthetic biology like systems.

Yes, I was wondering why the focus on metals. (Admittedly they might be needed in trace amounts for catalysis, or convenient for conductors, etc., or for structural material if you're on a carbon-poor asteroid. Most metals are worse than carbon for the latter if you have reasonably high tech.)

Life as we know it relies on a complex and interdependent ecosystem, and complex life relies on countless other organisms to support us. Without plants we absolutely couldn’t survive, without microorganisms we can’t survive. Without ample supplies of food, water and oxygen we can’t function.

Generally speaking the pace of biological activity is a lot slower than industrial ones too. We might make up for the pace with scale, but then you’re back to the hard problem of dependencies and “fuel”.

I’m not sure that the problem of beneficiation changes because the system is biological rather than industrial. Edit: Without carrying whole ecosystems with the probe at least.

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

#26

Post by abecedarius »

simiones wrote: post #23
abecedarius wrote: post #21

Earlier quoted context omitted.

Yes, I was wondering why the focus on metals. (Admittedly they might be needed in trace amounts for catalysis, or convenient for conductors, etc., or for structural material if you're on a carbon-poor asteroid. Most metals are worse than carbon for the latter if you have reasonably high tech.)

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.)

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

#27

Post by marcosdumay »

Yes, we don't know how to make a half-ton replicating probe right now.

No, none of the arguments on the article have any implication on the possibility of such a probe. None at all.

There's something to look into at the durability argument. The article has no usable information on it, and it's probably not a showstopper. But again, the only thing on the article is that yes, we don't know how to make one such probe right now.

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

#28

Post by simiones »

marcosdumay wrote: post #27

Yes, we don't know how to make a half-ton replicating probe right now. No, none of the arguments on the article have any implication on the possibility of such a probe. None at all. There's something to look into at the durability argument. The article has no usable information on it, and it's probably not a showstopper. But again, the only thing on the article is that yes, we don't know how to make one such probe ri…

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 theoretically constructible, there is no reason to believe that the way to build it would be found before, say, the sun runs out of hydrogen.

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

#29

Post by marcosdumay »

simiones wrote: post #28
marcosdumay wrote: post #27

Yes, we don't know how to make a half-ton replicating probe right now. No, none of the arguments on the article have any implication on the possibility of such a probe. None at all. There's something to look into at the durability argument. The article has no usable information on it, and it's probably not a showstopper. But again, the only thing on the article is that yes, we don't know how to make one such probe ri…

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…

It's absolutely possible that we'll never be able to build it.

There's absolutely no evidence of that on the article.

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

#30

Post by abecedarius »

EA-3167 wrote: post #25
abecedarius wrote: post #21

Earlier quoted context omitted.

Yes, I was wondering why the focus on metals. (Admittedly they might be needed in trace amounts for catalysis, or convenient for conductors, etc., or for structural material if you're on a carbon-poor asteroid. Most metals are worse than carbon for the latter if you have reasonably high tech.)

Life as we know it relies on a complex and interdependent ecosystem, and complex life relies on countless other organisms to support us. Without plants we absolutely couldn’t survive, without microorganisms we can’t survive. Without ample supplies of food, water and oxygen we can’t function. Generally speaking the pace of biological activity is a lot slower than industrial ones too. We might make up for the pace with…

> complex and interdependent ecosystem

That's why my other comment pointed to the autotrophs with the simplest requirements, and the (unknown but complexity-bounded) origin of life.

> pace of biological activity is a lot slower than industrial ones

Bacterial replication times can be under an hour.

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