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« Refining the Work Ethic | Main | The difficulties of security »

April 15, 2004

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Matthias Sohr

Chris, are the statements in the wiki article, as quoted in my e-mail to you, correct?

Chris Phoenix, CRN


I sent you email yesterday; did it fall in the bit bucket? (I'm switching ISPs soon; I've been very unhappy with Verio/NTT's reliability.)

Anyway...
"no tools that allow us to place a particular molecule in a particular place"

Mostly true. Mechanochemistry has been demonstrated, but it's not useful yet for fabrication.

Nanosystems "failed to address issues related to the massive numbers and atoms needed to create even primitive molecular machines"

False. Nanosystems did detailed calculations of throughput.

"no computational methods exist to determine the reaction coordinates and other information needed for the mechanochemistry proposed"

Mostly false. Freitas has found one candidate reaction already and analyzed it in detail.

Matthias Sohr

> did it fall in the bit bucket?

I always check all filtered email before permanently removing it; I´m experimenting with the Pegasus mail client though, and it might as well have eaten your email. I guess it´s back to Outlook Express, after all. OE may be susceptible to catching viri, but at least it´s reliable at that.

> Mostly false. Freitas has found one
> candidate reaction already and analyzed it
> in detail.

So would you say it is safe to remove the statement in question? In particular I was wondering about the computational methods. Freitas has one of the tools, but his paper, although I really loved the expected lifetime of the dimer tool (10^90s), isn´t about determining reaction coordinates, so has work been done in this respect, and if: got a URL?

> False. Nanosystems did detailed calculations of
> throughput.

Thanks for the correction, I strongly suspected anyway (Note! Prediction about the past!) that such a basic issue could not possibly have been omitted in Nanosystems and NOT be picked at by the real nay-sayers. On the other hand, many of these (like a certain Noble laureate) seem to never even have read Nanosystems or much of the technical literature anyway. Or, worse, they just keep ignoring it. Also, scaring our children by telling them today´s basic problems (distribution of wealth, diseases, environment et al.) might virtually never be solved doesn´t help either.

May I quote you when correcting the Wikipedia entry?

Brett Bellmore

You ought to read Nanosystems; Drexler did a great job of writing it in such a way that you could get the gist of it without having to delve too deeply into the math.

Chris Phoenix, CRN


The simulation of the reaction includes the position/trajectory of the atoms. Is that not a useful set of reaction coordinates?

I should perhaps qualify my statement about throughput. Nanosystems includes calculations for the time a mill takes to process its mass, 13.3.5.d: 3 seconds. And a manipulator arm: 13.4.1.f: 5 seconds for the mass of the arm itself (~5 million atoms), not counting the base, control computer, or power supply. In these cases, the geometry is known well enough to get an order-of-magnitude estimate of the atom count for each piece of machinery. I'd consider this a detailed calculation.

Table 14.1 has an estimate of the total mass of the fabrication and assembly mechanisms of a nanofactory at various scales. The accompanying text handwaves somewhat about the other systems, asserting (reasonably, I think) that they won't weigh more than seven times as much as the production mechanisms, so the whole thing should come in under a kg and should process a gram per second. So this doesn't count as a detailed calculation.

My nanofactory paper gives detailed calculations for everything I could think of: computers, walls, robotics, etc., all with geometry and physical layout.
http://www.jetpress.org/volume13/Nanofactory.htm#s8.3
I calculated that a 9.4 kg nanofactory, using much more primitive technology than Drexler's design (Stewart platforms rather than mills), would be able to produce 4 kg every 3 hours or so.

About scientists ignoring Nanosystems and not reading it: I'm told by a student at Mark Ratner's university, Northwestern, that scientists are even telling their students not to read it.

Yes, you may quote me in the Wikipedia entry.

Chris

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