This is part of IEEE Spectrum's SPECIAL REPORT: THE SINGULARITY
How to usher humanity into an era of transhumanist bliss: first, end scarcity. Second, eradicate death. Third, eliminate the bungled mechanisms that introduce imperfections into the human body. The vehicle for accomplishing all three? Molecular nanotechnology--in essence, the reduction of all material things to the status of software.
To reduce the splendid complexity of our world to a list of instructions, a mere recipe, would involve harnessing the most basic components of life. Start with Earth's supply of atoms. Evolution, the laws of physics, and a big dose of chance have arranged those atoms into the objects and life-forms around us. If we could map the position and type of every atom in an object and also place atoms in specific positions, then in principle we could reproduce with absolute fidelity any material thing from its constituent parts. At a stroke, any material or artifact--a Stradivarius or a steak--could be available in abundance. We could build replacement body parts with capabilities that would hugely exceed their natural analogues. The economy, the environment, even what it means to be human, would be utterly transformed.
This vision holds wide currency among those anticipating a singularity, in which the creation of hyperintelligent, self-replicating machines triggers runaway technological advancement and economic growth, transforming human beings into cyborgs that are superhuman and maybe even immortal. Some of these futurists are convinced that this renaissance is just a few decades away. But in academia and industry, nanotechnologists are working on a very different set of technologies. Many of these projects will almost certainly prove to be useful, lucrative, or even transformative, but none of them are likely to bring about the transhumanist rapture foreseen by singularitarians. Not in the next century, anyway.
It's not that the singularity vision is completely unrecognizable in today's work. It's just that the gulf between the two is a bit like the gap between traveling by horse and buggy and by interplanetary transport. The birth of nanotechnology is popularly taken to be 1989, when IBM Fellow Don Eigler used a scanning tunneling microscope to create the company's logo out of xenon atoms. Since then a whole field has emerged, based mainly on custom-engineered molecules that have gone into such consumer items as wrinkle-free clothes, more-effective sunscreens, and sturdier sports rackets.
However, it is a very long way indeed from a top-notch tennis racket to smart nanoscale robots capable of swarming in our bodies like infinitesimal guardian angels, recognizing and fixing damaged cells or DNA, and detecting, chasing, and destroying harmful viruses and bacteria. But the transhumanists underestimate the magnitude of that leap. They look beyond the manipulation of an atom or molecule with a scanning tunneling microscope and see swarms of manipulators that are themselves nanoscale. Under software control, these ”nanofactories” would be able to arrange atoms in any pattern consistent with the laws of physics.
Rather than simply copying existing materials, the transhumanists dream of integrating into those materials almost unlimited functionality: state-of-the-art sensing and information processing could be built into the very fabric of our existence, accompanied by motors with astounding power density. Singularitarians anticipate that Moore's Law will run on indefinitely, giving us the immense computing power in tiny packages needed to control these nanofactories. These minuscule robots, or nanobots, need not be confined to protecting our bodies, either: if they can fix and purify, why not extend and enhance? Neural nanobots could allow a direct interface between our biological wetware and powerful computers with vast databases.
Maybe we could leave our bodies entirely. Only the need to preserve the contents of our memories and consciousness, our mental identities, ties us to them. Perhaps those nanobots will even be able to swim through our brains to read and upload our thoughts and memories, indeed entire personalities, to a powerful computer.
This expansive view of molecular nanotechnology owes as much to K. Eric Drexler as to anyone else. An MIT graduate and student of Marvin Minsky [see table, ”Who's Who in the Singularity,” in this issue], Drexler laid out his vision in the 1992 book Nanosystems (John Wiley & Sons). Those ideas have been picked up and expanded by other futurists over the past 16 years.
In his book, Drexler envisaged nanostructures built from the strongest and stiffest materials available, using the rational design principles of mechanical engineering. The fundamental building blocks of this paradigm are tiny, rigid cogs and gears, analogous to the plastic pieces of a Lego set. The gears would distribute power from nanoscale electric motors and be small enough to assist in the task of attaching molecules to one another. They would also process information. Drexler drew inspiration from a previous generation of computing devices, which used levers and gears rather than transistors, for his vision of ultrasmall mechanical computers.
Assuming that an object's structure could easily be reduced to its molecular blueprint, the first order of business is figuring out how to translate macroscale manufacturing methods into nanoscale manipulations. For example, let's say you wanted a new pancreas. Your first major challenge stems from the fact that a single human cell is composed of about 1014 atoms, and the pancreas you want has at least 80 billion cells, probably more. We could use a scanning tunneling microscope to position individual atoms with some precision, but to make a macroscopic object with it would take a very long time.
The theoretical solution, initially, was an idea known as exponential manufacturing. In its simplest form, this refers to a hypothetical nanoscale ”assembler” that could construct objects on its own scale. For instance, it could make another assembler, and each assembler could go on to make more assemblers, resulting in a suite of assemblers that would combine forces to make a macroscopic object.
Setting aside the enormous challenges of creating and coordinating these nanoassemblers, some theorists have worried about a doomsday scenario known as the ”gray goo” problem. Runaway replicators could voraciously consume resources to produce ever more stuff, a futuristic take on the old story of the sorcerer's apprentice. Not to worry, say Drexler and colleagues. In the latest vision of the nanofactory, the reproducing replicators give way to Henry Ford–style mass production, with endlessly repeated elementary operations on countless tiny production lines.
It's a seductive idea, seemingly validated by the workings of the cells of our own bodies. We're full of sophisticated nanoassemblers: delve into the inner workings of a typical cell and you'll find molecular motors that convert chemical energy into mechanical energy and membranes with active ion channels that sort molecules--two key tasks needed for basic nanoscale assembly. ATP synthase, for example, is an intricate cluster of proteins constituting a mechanism that makes adenosine triphosphate, the molecule that fuels the contraction of muscle cells and countless other cellular processes. Cell biology also exhibits software-controlled manufacturing, in the form of protein synthesis. The process starts with the ribosome, a remarkable molecular machine that can read information from a strand of messenger RNA and convert the code into a sequence of amino acids. The amino-acid sequence in turn defines the three-dimensional structure of a protein and its function. The ribosome fulfils the functions expected of an artificial assembler--proof that complex nanoassembly is possible.