[extropy-chat] To: Hal Finney Re: Nano-assembler feasibility

[Chris Phoenix]

 > I agree with much of Brett's skepticism on this issue.  Given the fact
 > that so many prominent scientists continue to maintain that assemblers
 > are impossible, supporters of the concept need to take on the burden
 > of proof.  It's not enough any more to say, tell us why it won't work.

We're not saying "Tell us why it won't work."  We're saying "Tell us 
where is the error in our work."  There's lots of work out there, 
including a decade-old 500 page technical book, that no one is 
reviewing--or they are reviewing, but are not publishing the fact that 
they haven't found any errors.

 > In the case of assemblers, we're missing the most important pieces:
 > .... I mean specifically what tool-tips will be used, how they will
 > be swapped out, and what construction sequences will be used to
 > build the components.

What do you think of the one Freitas and Merkle found recently?  Does it 
count as a piece?  Does it indicate to you that the rest of the pieces 
are likely to be findable?
http://www.rfreitas.com/Nano/DimerTool.htm

 > Now, there are two parts to this question.  The first is, how can an
 > assembler self-replicate; how can it build its own parts.

Agreed, this is a question we don't have a full answer to.  Further 
studies are needed.

 > The second,
 > even more difficult, is how can we bootstrap into an assembler from
 > today's technology; how can we build its parts without already having
 > an assembler.

Not sure this requires much more than knocking together a scanning probe 
that can duplicate the motions of the assembler's tip.  I wouldn't have 
sounded so blase about this a year ago, but there are now multiple 
techniques for making 3D structures down to 20 nm.  And multiple 
actuation techniques.  I no longer expect this to be especially challenging.

 > I'm really just asking the first question, the easier one.  If you
 > could show an assembler design that was complete enough to give
 > confidence that the answer to the first question was positive, it
 > would eliminate many of the objections of the skeptics.

This is one stage of many.  It's easy to pick a stage and say "This will 
satisfy the skeptics."  But I don't think this would satisfy Brett that 
it's worth looking at further.  And it's more than should be needed to 
inspire further research.  I would've thought that finding the first 
tool tip, out of maybe six to ten total (Freitas' estimate), would pique 
the interest of anyone who wasn't biased against the idea.

 > No longer would you have to use shaky
 > biological analogies or vague and confusing jargon to address
 > Smalley's fat-finger and sticky-finger issues.

What shaky biological analogies were made to address Smalley?  Drexler's 
talk of enzymes was not analogical.
Where did you find vague and confusing jargon?

 > [qualifiers].... it looks to me
 > that tool tips have been designed which could plausibly work
 > to produce large pieces of diamond. The problem is that this is
 > not enough to produce all possible parts, even among those that
 > are composed solely of carbon and hydrogen.

All possible?  Of course not.  But a large number of parts of the family 
"bulk diamond with voids" can probably be produced.  At what point does 
it make sense to say, "OK, we've got enough functionality to start 
looking at the design of kinematic systems with parts of this class"?

 > Different strategies for construction are necessary for different
 > surfaces.  But these techniques will not be applicable to a small
 > part, because it does not have consistent surfaces with uniform
 > atomic spacing. Each atom in the small part is going to be a
 > unique challenge and require a customized assembly procedure.

If that customized procedure required building new hardware, I'd be 
worried.  But if it merely requires changing the parameters in the 
manipulator-driving software, I'm not very worried.  I can't prove 
that's all it requires.  But the atoms aren't going to be *that* far out 
of register.  You might need one tool for surfaces, one for edges, and 
one for corners.

 > Then there are the problems in gripping the parts, ....
 > These are where I think Smalley's finger problems are most likely to be
 > an issue.

Wait... gripping a part doesn't require careful control of a chemical 
reaction, does it?  How are the "fingers" relevant for part-gripping? 
Especially since the parts can, in this case, be bigger than the fingers.

 > and in putting the
 > first two pieces together at the beginning of constructing a part.
 > .... I'd like to see a synthesis for diamond that didn't already
 > start with a big slab of diamond.

Merkle has proposed (in conversation) starting with a big slab of 
diamond, then cleaving the part loose when it's finished.

 > The other direction towards answering my question comes from one paper
 > by Merkle from 1997(!),
 > http://www.zyvex.com/nanotech/hydroCarbonMetabolism.html.  This is the
 > only paper I am familiar with that makes a real attempt to close the
 > loop and show how an assembler can construct its own parts.  This is
 > the kind of work I'd like to see expanded, but as far as I know no one
 > has developed it any further.

The NNI says there's no point in studying it.

 > The reasons why this does not fully answer my questions are, first, that
 > the assembler being described is a very simplified and schematic one;

You're not going to get a full answer until we build the thing.  We 
could model the reactions (as I assume Merkle did), but someone can 
always say the models aren't trustworthy.

 > and
 > second, that the reactions seem to have potential fat-finger problems.
 > They require four assembler arms (or equivalent) to come together in a
 > tiny space.

This seems unlikely to be the only reaction set.  It's the first 
attempt, not the last hope.

 >  Yet you've never seen a diagram of an assembler from Drexler
 > which required four arms, have you?  If assemblers are going to require
 > this many arms, wouldn't it be nice to find out ahead of time?

Yes, of course it would.  (Note that Merkle said two arms plus fixtures 
would probably be sufficient, and it might be done with one.)  Obviously 
what we need is more study.

 > So we are back
 > to the chicken and the egg, that we can't get started on a large project
 > until we know we will succeed, and we can't know we will succeed until
 > we get a detailed design, and we can't get a detailed design without
 > getting started on a large project.

And it doesn't help when certain people keep asserting that there can be 
no basis for guesstimating likelihood of success until the thing is 
fully done.  There are, in fact, non-large projects proposed that may go 
a long way toward answering these questions.  But "We shouldn't do 
anything till we see it working" guarantees that even these won't be 
tried.  Bleah.

 > This is why the alternative strategy is being tried, of claims that we
 > already have enough data to know that we will succeed.

Who's claiming that?  I'm not.  I'm claiming that we have enough data to 
be legitimately worried, and that the appropriate response to that worry 
is to start studying.  Since, after all, we can learn a lot more about 
the difficulty of development without solving the whole problem.

 > But I think the
 > political reality today is that this strategy is not working.  The only
 > alternative is to take many years of time and effort to tackle these
 > problems one at a time, until we do get to the point where we have a
 > design that answers all the questions and eliminates the objections,
 > by construction.

What do you think of the alternative I described just above?  More 
formally, it goes like this:
1) Note that there's some risk of badness due to ignorance about 
molecular manufacturing.
2) Put some effort toward trying to disprove molecular manufacturing.
3) Note that continued failure of step 2 increases the risk, and 
justifies increased effort.  Iterate.

This does not require trying to develop molecular manufacturing.  It 
only requires playing it safe--something that bureaucracies and 
governments ought to be good at.  The trouble with that algorithm is the 
temptation to deny molecular manufacturing, rather than admitting you 
can't disprove it yet.  Especially when the NanoBusiness Alliance is 
lobbying for it not to be studied at all.

It might be argued that the initial risk is so low that there's no point 
in starting the process.  But the appropriate initial effort can be 
calibrated by noting that if there is no hole in Nanosystems, a powerful 
form of molecular manufacturing can and will be developed.  An 
appropriate effort for the initial step 2 would be comparable to the 
attention that has been paid to the book already... over the last 12 
years.  History says that if there's a problem, it probably won't be 
easy to find.

Chris

-- 
Chris Phoenix                                  cphoenix at CRNano.org
Director of Research
Center for Responsible Nanotechnology          http://CRNano.org