Brad Ideas - On the need for self-replicating nanotech assemblers - Comments

This has been considered elsewhere...

Anonymous — Wed, 07 Dec 2005 07:57:50 -0800

The idea that a nano replicator will be under the control of a larger system has other interesting facets.

To be useful, we effectively need a nano replicator to be both a "universal constructor" (capable of making any molecule with its appendages) and a "universal computer" (capable of doing the thinking necessary to build something).

Unfortunately it's very difficult to build something so small which can think as well as do tasks!

Some models call for the thinking part to be a single separate macroscopic computer which sends commands to the machines which are slaved to it. Eventually the computer would need to control a very large number of replicators indeed, but by then a new control centre could possibly be build. Humans would be in control of the control centres.

This avoids the problem of the "stray infecting pathogen" because such a machine would be helpless without the control centre. Of course, replicators such as viruses do exist, so we can't rule out an entirely self contained machine, but I suspect it would be a lot less versatile, larger, bulkier, and slower to replicate than machines which don't need to think for themselves. The smaller, faster dumb robots would probably wipe them out.

Safety is still the main reason to avoid self-replication

Peter McCluskey — Wed, 28 Sep 2005 16:14:10 -0700

This is probably true for the first few generations of nanotechnology, but for mature nanotechnology (which is primarily what Kurzweil is talking about), I suspect it will become more like software. Is a version of Linux that can't replicate itself much faster to mass produce? I don't expect this analogy to be perfect (especially for very small machines), but it's close enough that I don't want to rely on efficiency arguments.
Kurzweil's arguments seem faulty because he ignores the possibility that a responsible AI or enhanced human would be fast enough to oversee the replication. Kurzweil says we won't need quickly replicating machines until we have strong AI. It seems improbable that strong AI would react too slowly, so as long as we trust the AI we don't have much reason to take the risks involved with self-replicating unintelligent machines. And if we don't trust the AI, I expect rules against self-replication won't be enough to save us.

space, not time, is the problem

Alex Goldman — Tue, 27 Sep 2005 09:32:46 -0700

Actually, I think that a more compelling argument against nanoreplicators (I'm no expert) is space, not time. If you build a billion, you overcome the time problem, but you replicate the factory one billion times.

A separate factory should allow a more efficient nanobot.

Furthermore, a separate factory should enable a better (and larger) factory that is also easier to design, given today's technology.

So I agree that there are good reasons to avoid nanoreplication, but argue that the problem is ease of design second, and wasted resources through unnecessary duplication first.

OTOH, you could design different generations of nanobots, with the early versions containing factories, and later generations containing purely the lean mean efficient machines.

On the need for self-replicating nanotech assemblers

brad — Sun, 25 Sep 2005 12:05:56 -0700

In recent times, I and my colleagues at the Foresight Nanotech Institute have moved towards discouraging the idea of self-replicating machines as part of molecular nanotech. Eric Drexler, founder of the institute, described these machines in his seminal work “Engines of Creation,” while also warning about the major dangers that could result from that approach.

Recently, dining with Ray Kurzweil on the release of his new book The Singularity Is Near : When Humans Transcend Biology, he expressed the concern that the move away from self-replicating assemblers was largely political, and they would still be needed as a defence against malevolent self-replicating nanopathogens.

I understand the cynicism here, because the political case is compelling. Self-replicators are frightening, especially to people who get their introduction to them via fiction like Michael Chrichton’s “Prey.” But in fact we were frightened of the risks from the start. Self replication is an obvious model to present, both when first thinking about nanomachines, and in showing the parallels between them and living cells, which are of course self-replicating nanomachines.

The movement away from them however, has solid engineering reasons behind it, as well as safety reasons. Life has not always picked the most efficient path to a result, just the one that is sufficient to outcompete the others. In fact, red blood cells are not self-replicating. Instead, the marrow contains the engines that make red blood cells and send them out into the body to do their simple job.

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