Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!aramis.rutgers.edu!athos.rutgers.edu!nanotech From: landman@sun.com (Howard A. Landman) Newsgroups: sci.nanotech Subject: Re: Why I think Nanotechnology is Bogus Message-ID: Date: 27 Jun 89 06:11:58 GMT Sender: nanotech@athos.rutgers.edu Organization: Sun Microsystems, Mountain View Lines: 73 Approved: nanotech@aramis.rutgers.edu Note: I pulled some of the number below out of my wooly head rather than looking them up, so please feel free to correct them. I don't think any are far enough off to damage the conlusion. In article James.Price.Salsman@cat.cmu.edu writes: >First, I think nanotechnology is bogus, because I think that >information requires finite space. I believe that there is >a fundamental volume that a "bit" must occupy in order for >it to be stable as a memory cell. I think that dreams of >embedding a typical "AI" program in an object the size of a >mitochondria is silly. Well, it's clear that there's a fundamental unit of entropy that corresponds to one bit of information, or more precisely to the loss of one bit of information (information is negative entropy). This gives a lower bound to the amount of entropy that must be generated by any mechanism performing a given computation. However, we are a *LONG* way from running into that limit. We'll probably hit the kT limit first, even with cryonic circuits (liquid nitrogen is still awfully hot). However, in terms of size, it's quite clear that a single atom is enough to store at least one bit of information, perhaps several. There's a tradeoff between density of storage and ease of access, but since you make no claims about ease of access, let me define the storage medium as a modified fatty acid CH3-(CH2)n-COOH. The acid group serves as a handle to identify the start end; after that each carbon bears either hydrogen or deuterium (4 combinations due to stereoisomerism). This give approximately 2 bits of storage for every three atoms (minus a little overhead). Of course if we allow elements like fluorine and chlorine to be used the number of bits goes up and may exceed one bit per atom. In fact, it may not be necessary to stick to linear chains, so that complex data structures may be encoded directly into chemical bonds (gives "tree traversal" a whole new meaning, doesn't it?). As for typical AI programs: you're probably thinking of languages like Lisp or Smalltalk, where the program to print "Hello World!" is about 3 MB in size. It is quite possible to do AI in, say, Forth, where the sizes are orders of magnitude smaller. So, assuming a reasonable program might fit in 30 KB = 240 Kb = ~360 K atoms = 120 K * (atomic weight 12 + 1 + 2) = 1.8 M atomic weights. Now Avogadro's number gives us 1 gram per 6 E 23 atomic weights, so that the matter storing the program might weigh about 3 E -18 grams. That's three billionths of a billionth of a gram. Aw heck, let's be generous and allow 30 MB for the program, that still comes out to 3 E -15 grams. Now I seriously doubt whether that density of storage will be practical because of the difficulty of reading it. It's much easier to read something the size of, say, DNA. But DNA is less than two orders of magnitude larger than the molecule I postulated. Let's call it 1 E -13 grams total. I seem to recall that the human body has about a trillion (1 E 12) cells, and weighs about 250 Kg. So a typical cell weighs something like 2.5 E -7 grams; and our fat, wasteful 30 MB program storage is about a million times smaller. Maybe about the size of a mitochondrion... >Second, I think nanotechnology is bogus, because I think >that energy requires finite space. I believe that there is >a fundimental volume that an "electron volt" must occupy in >order for it to be stable and not dissipate. Darn, JoSH took care of that one already ... just let me add that there's an interesting science fiction study of life built out of nucleons and living on the surface of a neutron star. "Dragon's Egg" and "Starquake" by Robert L. Forward; lot's of good physics, including how to get close to a neutron star without letting the tidal forces get to be a drag. :-) Also ponders the question: How do you relate to a species that thinks and evolves a million times faster than you? Something worth thinking about if we plan on building our own. Howard A. Landman landman@sun.com