[extropy-chat] Smalley, Drexler and the monster in Lake Michigan

[Hal Finney]

Unfortunately I don't have time to write about all the issues that
I see regarding the nanotech debate, or to organize my thoughts as
well as I should.  It's disappointing that the recent nanotech bill
has explicitly removed funding for Drexlerian nanotech.  But this just
reinforces that Brett is right: at least in practice, given the current
political situation, the burden is on the pro nanotech camp to produce
a more convincing case for the technology.

But I don't see that happening, at least not yet.  The initial response
seems to be to try to "spin" the debate into a huge victory for the
home team.  Contrast that with some of the comments in the article
I pointed to last week on the economics of nanotech by Brad DeLong,
http://www.j-bradford-delong.net/movable_type/2003_archives/002838.html.
Some quotes:

> Brad -- if you pursue this, I strongly recommend you leave out the
> Drexler stuff. The man is, IMHO, a snake oil salesman who doesn't know
> his stuff. The Chemical and Engineering News debate pointed to by drk
> above, at http://pubs.acs.org/cen/coverstory/8148/8148counterpoint.html,
> shows the difference between someone who actually knows his chemistry
> (Richard Smalley) and someone who doesn't.

> Apropos "Drexlerian" nanotechnology:
> http://pubs.acs.org/cen/coverstory/8148/8148counterpoint.html
> I saw Drexler speak over a decade ago in front of a group of physicists
> at Stanford. I remember thinking at the time that did not stand up well
> to questioning by hard scientists. I'd put my money on Smalley.

I think the perception by those who are not already nanotech proponents
is that Smalley won the debate.

And I also object to some of the tactics being used in this spin
doctoring.  Smalley is being misrepresented and taken out of context.
>From the Foresight press release: "In the current C&E News exchange,
Smalley now agrees that assemblers (without impossible "magic fingers")
could use something like enzymes or ribosomes as tools for doing precise
chemistry."  This makes it sound like Smalley has conceded that Drexler's
ideas for nanotech could work.  But in fact, Smalley was attempting
to show that to the extent that nanotech needs to rely on things like
enzymes and ribosomes, it will share the limitations of those systems,
such as reliance on water and the inability to make strong objects,
hence that nanotech could not meet its claimed goals.

And about this water business, which has also been trumpeted as showing
that Smalley is ignorant of chemistry (a claim which sounds absurdly
arrogant to the unbiased spectator).  Maybe there are some enzymes
which can work in polar solvents or even in gas or vacuum.  But ribosomes
don't, and so Smalley's overall point still holds.  The chemistry of water
dominates virtually everything about proteins, enzymes (which are a subset
of proteins), and ribosomes (which are built equally of RNA and protein).

So what does Drexler really mean when he says that nanotech will work
like enzymes?  As Smalley asks, "do you think it is really possible to
do enzymelike chemistry of arbitrary complexity with only dry surfaces
and a vacuum?"  I think the answer Drexler would give is basically yes,
albeit not of "arbitrary" complexity (no system could achieve that goal).
He does believe that he can achieve and surpass the power of enzyme-like
systems using dry surfaces and a vacuum.  He refers to this somewhat
obliquely in his reply: "Bound groups adjacent to reactive groups can
provide tailored environments that reproduce familiar effects of solvation
and catalysis."

I've read Nanosystems, and it's always bothered me that the technology
described there is so different from what most nanotech fans are
familiar with.  Drexler describes the famous robot arm; you can see a
picture here, http://www.zyvex.com/nanotech/images/fig13.14left.jpg.
He goes into a lot of detail about how it would work and how strong it
would be for mechanosynthesis.

But he doesn't use it!  The proposed manufacturing system that he
describes in some detail only uses giant robot arms in a final assembly
stage, to manipulate relatively large, pre-built blocks that are a
cubic micron in size, far larger than the arm above (which is only 0.1
micron long).  Instead, the actual molecular manipulation and assembly
is done by means of a "mill".

This is a system which holds molecular fragments on miniature pallets
attached to 4 nm wide assembly belts. The belts run past each other such
that the pallets are pressed together, and possibly rotated or manipulated
in some way, so that the payload molecules react, transferring one or
more atoms from one pallet's payload to the other.

These mills would gradually build up larger and larger pieces, which
would eventually be transferred to appropriately scaled-up mill systems.
These would use the same principles, now working with pieces with
perhaps thousands of atoms, attaching them together in various ways.
Eventuallly we get up to the micron size, which will have billions of
atoms, and at that point he uses almost-macro-scale robot arms to start
attaching these "bricks" together.

This molecular mill system provides a possible context to understand
Drexler's comparison of nanotech assembly to enzymes.  Enzymes bring
reactants together in a carefully controlled environment.  The active
site is surrounded by atoms which provide the exact pattern of positive
and negative charge, hydrophobic and hydrophilic regions, acidic or base
pH, necessary to promote the desired reaction.  This is what Smalley
means when he talks about biologically catalyzed chemistry occuring
as the interaction of a dozen or more atoms, which would seemingly be
impossible using robot arms.

But it is conceivable that a mill could provide a similar degree of
control over the external environment as what we get in an enzymatic
active site.  The pallets that hold the reactants can be designed
to have desired patterns of charge, ionization and electron binding.
When we bring the reactants together, surrounded by the two pallets that
held them, the environment surrounding the reactants can therefore be
controlled to a considerable degree.  The reactants can even be held
in pouches or grooves within the pallets to provide for full 360 degree
control over the local environment.

This is what I think Drexler means in the quote above, "Bound groups
adjacent to reactive groups can provide tailored environments that
reproduce familiar effects of solvation and catalysis."  The bound groups
are part of the pallets that hold the reactants; solvation, that is,
the effects of water molecules, can be mimicked by means of patterns of
charge; and catalysis achieved by carefully adjusting the properties of
the atoms lining the pallets so as to provide the necessary lowering of
energy barriers.

I think it is rather difficult to interpret Drexler's comment in terms
of robot arms.  They have a limited flexibility in terms of tailoring
the environment in the near vicinity of the reaction.  It would be
extremely complicated to recreate the effects of solvation (the widespread
presence of water molecules shielding and modifying electrical effects)
and catalysis using robot arms, raising fat-finger problems.

The point of this rather lengthy digression is that Drexler and other
nanotech proponents are not doing a good job of explaining their design
concepts.  This is in part why they are so commonly misunderstood.
And it seems almost willful.  Drexler is trying to explain exactly
how his system will work: "In machine-phase chemistry, conveyors and
positioners (not solvents and thermal motion) bring reactants together."
But this terminology is complete generic and unspecific: conveyors and
positioners.  It applies to mills, but could also apply to robot arms,
where reactants are conveyed to the tip and then positioned to be applied
to the work piece.

Didn't anyone reading this exchange wonder about Drexler's insistence
that "fingers" are not needed for his assembly process?  What is a robot
arm if not a finger, in this context?  Do people realize that Drexler
has moved away from arm-based assembly, perhaps due to some of the very
objections that Smalley has (re-) discovered?

Of course, I'm not even 100% sure that my interpretation is right, either.
I've explained above how I think his comments relate to the designs
in Nanosystems.  But maybe I'm wrong, maybe he does still plan to use
robot arms.

Why should I have to guess?  And why should Smalley?  This continued
evasiveness and refusal to plainly specify a design strategy
forces nanotech critics to extrapolate their own understanding and
interpretations.  And once this happens, the nanotech proponents sit back
and smugly call "strawman".  Drexler and Smalley are talking past each
other, because Drexler refuses to plainly state how his manufacturing
system will work, contenting himself with telling Smalley that all his
guesses are wrong.

This isn't a game of 20 Questions.  If nanotech were the dominant
paradigm, this lack of specificity might be acceptable.  But when you
are on the outside looking in, it will not succeed.  All you're going
to do is make people confused and angry.

I share Smalley's frustration when he writes, "it would be helpful to
all of us who take the nanobot assembler idea of 'Engines of Creation'
seriously if you would tell us more about this nonaqueous enzymelike
chemistry."  Rather than lobbying and spinning the debate, I'd suggest
that nanotech proponents work harder at fleshing out and clearly
describing their proposals.  Give your critics something to criticize, and
at least the debates won't be as empty as the Smalley-Drexler exchange.

Hal