Drexler–Smalley debate on molecular nanotechnology
The Drexler–Smalley debate on molecular nanotechnology was a public dispute between K. Eric Drexler, the originator of the conceptual basis of molecular nanotechnology, and Richard Smalley, a recipient of the 1996 Nobel prize in Chemistry for the discovery of the nanomaterial buckminsterfullerene. The dispute was about the feasibility of constructing molecular assemblers, which are molecular machines that could robotically assemble molecular materials and devices by manipulating individual atoms or molecules. The concept of molecular assemblers was central to Drexler's conception of molecular nanotechnology, but Smalley argued that fundamental physical principles would prevent them from ever being possible. The two also traded accusations that the other's conception of nanotechnology was harmful to public perception of the field and threatened continued public support for nanotechnology research.
The debate was carried out from 2001 to 2003 through published articles and open letters. It began with a 2001 article by Smalley in Scientific American, which was followed by a rebuttal published by Drexler and coworkers later that year, and two open letters by Drexler in early 2003. The debate was concluded in late 2003 in a "Point–Counterpoint" feature in Chemical & Engineering News in which both parties participated.
The debate has often been cited in the history of nanotechnology due to the fame of its participants and its commentary on both the technical and social aspects of nanotechnology. It has also been widely criticized for its adversarial tone, with Drexler accusing Smalley of publicly misrepresenting his work, and Smalley accusing Drexler of failing to understand basic science, causing commentators to go so far as to characterize the tone of the debate as similar to "a pissing match" and "reminiscent of Saturday Night Live sketch".
The participants
K. Eric Drexler
K. Eric Drexler is generally considered to have written the first scholarly paper on the topic of nanotechnology, and was a key figure in popularizing these concepts through several publications and advocacy work. Trained as an engineer, Drexler was inspired by a then-obscure 1959 talk by physicist Richard Feynman called There's Plenty of Room at the Bottom, which posited that it should be physically possible to manipulate individual atoms using top-down engineering methodologies. Drexler was also inspired by recent advances in molecular biology, such as recombinant DNA technology. In a 1981 publication in Proceedings of the National Academy of Sciences, considered to be the first journal article on nanotechnology, he argued that biological systems such as the ribosome were already capable of building molecules atom-by-atom, and that artificial machines with this capability could also be constructed. Drexler published two books on nanotechnology: Engines of Creation in 1986, which was intended for the public, and the technical work Nanosystems in 1992. He also co-founded the Foresight Institute, a public interest group devoted to increasing public awareness and information about molecular nanotechnology.Drexler's vision of nanotechnology, now called molecular nanotechnology, is based on the concept of the molecular assembler, a molecular machine that would manufacture molecules and molecular devices atom-by-atom. Drexler drew a distinction between wet nanotechnology based on biological systems, and "second-generation" dry nanotechnology, which would be based on mechanosynthesis, positional control of molecules through principles more related to mechanical engineering. Drexler and his followers have focused almost exclusively on the latter form of molecular nanotechnology, but Drexler has stated that both are valid pathways to creating molecular machine systems.
Richard Smalley
Richard E. Smalley, a chemist at Rice University, was best known as a co-discoverer of the C60 form of carbon known as buckminsterfullerene in 1985, along with Harry Kroto, Robert Curl, James Heath, and Sean O'Brien. Buckminsterfullerene was the first to be discovered of the class of molecules known as fullerenes, which also includes carbon nanotubes. The study and application of fullerenes forms a significant part of the fields of nanomaterials and nanoelectronics, and Smalley, Kroto, and Curl were awarded the 1996 Nobel Prize in Chemistry for their discovery.Smalley had also taken a prominent public policy role on nanotechnology and was an outspoken advocate for using nanotechnology to develop solutions to the world's energy and health problems, for example, raising the possibility of using nanomaterials for efficient energy storage and transmission, and of developing nanomaterial-based drugs for targeted drug delivery. Smalley was also active in commercializing his academic research into carbon nanotubes, having founded Carbon Nanotechnologies Inc., and serving on the scientific advisory board of two other biotechnology and nanotechnology startups. Smalley died of leukemia in October 2005, after the conclusion of his debate with Drexler.
The debate
Smalley's ''Scientific American'' article
Smalley wrote an article, "Of Chemistry, Love, and Nanobots", for the September 2001 issue of the popular science magazine Scientific American, which was a special issue on the topic of nanotechnology. Smalley opened by comparing a chemical reaction to an intricate dance of atoms:He referenced the idea of a molecular assembler, a nanorobot capable of manipulating individual atoms to build a desired product, posing how long it would take such an assembler to produce a meaningful amount of material. He estimated that one assembler working alone would take millions of years to produce one mole of material, but self-replicating assemblers could, within a minute, produce a large enough ensemble of assemblers that would then be capable of producing a mole of product in a fraction of a millisecond. Smalley then discussed the fear that the nanorobots could mutate and reproduce indefinitely, causing a grey goo scenario, or, referring to Bill Joy's previous article "Why the future doesn't need us", that the nanorobots could develop swarm intelligence and become alive in some sense.
Smalley then considered how realistic the concept of a self-replicating nanorobot was. He noted that in a chemical reaction, the chemical bonds are all interconnected and that the placement of each atom is sensitive to the position of all the other atoms in the vicinity. He then asserted that a molecular assembler would thus have to control many atoms simultaneously to work, and possess many manipulator arms. This led him to raise two objections to the concept of molecular assembler, which he called the "fat fingers problem" and the "sticky fingers problem":
Smalley closed the article by returning to the analogy of chemistry as a dance of love, remarking that "you don't make a girl and a boy fall in love by pushing them together."
Drexler's response
Drexler responded by publishing a rebuttal later in 2001 through the Institute for Molecular Manufacturing, which was co-authored with others including Robert Freitas, J. Storrs Hall, and Ralph Merkle. The authors first discussed the "fat fingers" argument by attacking Smalley's notion that a chemical reaction must involve five to fifteen atoms, stating that many reactions involve only two reactants, one of which can be immobilized and the other attached to a single "finger". They cited as evidence experimental and theoretical results indicating that using scanning tunneling microscope tips and related technologies could be used as a reactive structure for positional control and for interaction with surface-bound molecules. They also noted that atomically precise final products do not require precise control of all aspects of the chemical reaction. The authors noted that the "sticky fingers" problem is valid in some reactions, but argue that it would be fallacious to conclude that all reactions have this problem.The authors put forth the ribosome as an example of a natural molecular machine; because the ribosome suffers from neither problem, they must not be fundamental, saying:
The authors also questioned Smalley's figures for the replication time of nanomachines. Instead of Smalley's figure of 1 GHz for the atomic placement frequency, they point out that Nanosystems suggested a frequency of 1 MHz, a thousand times slower, and that at Smalley's higher frequency, diamondoid nanomachines would overheat and decompose in milliseconds. The authors called this a straw man argument, writing that "in a serious scientific discussion, a discrepancy of three orders of magnitude between what has been proposed in the literature and what is criticized suggests at best an inadequate grasp of the proposal." The authors closed by stating that the best way to find out whether molecular assemblers are feasible is through experimental and theoretical work, and that "there are many worthy molecular systems engineering challenges to overcome, but thus far, there has been no credible argument that these devices are infeasible."
Drexler followed up with two open letters to Smalley in April and July 2003. The April letter began, "I have written this open letter to correct your public misrepresentation of my work." Drexler accused Smalley of continuing to dismiss his work by publicly describing molecular assemblers as requiring what Drexler now calls "Smalley fingers", which he stated to be unlike the enzyme-like systems he had actually proposed. He asserted:
Drexler compared the nanotechnology debate's importance to that of discussions of spaceflight before Sputnik or to theoretical work on nuclear chemistry before the Manhattan Project. He disputed Smalley's arguments that the fear of a grey goo scenario would hinder continued funding of nanotechnology research, arguing that the potential for long-term risks made research even more important. His conclusion stated, "Your misdirected arguments have needlessly confused public discussion of genuine long-term security concerns."
The July 2003 letter referenced a note from Smalley promising to respond, which had yet gone unfulfilled. Drexler mentions inconsistencies in Smalley's previous public statements on atom-by-atom construction, and ended by stating "I would not ordinarily raise an issue so persistently, but the question of what nanotechnology can ultimately achieve is perhaps the most fundamental issue in the field today—it shapes basic objectives and expectations—and your words have been remarkably effective in changing how this issue is perceived."