This question judges nanotech as if it were a traditional engineering endeavor, but it's not. Nanotech is not a bunch of people working to bring out products next year or even next decade. Some hope for near term diamondoid assemblers, but their false optimism distracts from the real value of Drexler's breakthroughs. Nanotechnologists are rather engaged in theoretical applied science, aka exploratory or speculative engineering, in which the purpose is not to build something, but to determine what can possibly be built, and what can't. Theoretical applied science is quite similar to theoretical computer science, in that it explores broad but firm boundaries of what is easy, hard, and impossible, and leaves the implementation up to others. Theoretical computer science starts from the general mathematical abstract of a computer (the Turing machine); theoretical applied science starts from mature, well verified laws of physics. In fact we could say that theoretical computer science is a special case of, and the first major academic form of, theoretical applied science.
Theoretical applied science's goal is to explore technology that is based on conservative and contemporary scientific knowledge. Two kinds of activities that are _not_ examples of theoretical applied science are: designing wormholes, and postulating dramatic breakthroughs in weather forecasting. Wormholes are based on physical theory too new for theoretical applied science. Good long term weather forecasting is also based on assumption of scientific rather than engineering progress. Scientists didn't have demonstrated predictive theories for long range weather in the 1960s, and they don't now. Predicting a new theory, or predicting the verification of an unproven theory, is a completely different task than theoretical applied science. The latter involves simple engineering designs with conservative design margins based on mature, well demonstrated scientfic facts.
There is a solid scientific basis for nanotechnology. No new scientific discoveries are necessary. Nor would any such discoveries invalidate the designs, because they are based on theories that have long since been thoroughly demonstrated.
The point, again, is not to prognisticate that nanotechnology, reversible comutation, et al. _will_ happen, but to point out that they _can_ happen. They are options to be placed right alongside other options being considering for the future, such as attempts to reduce population growth, prevent or reverse climate alteration, reduce resource usage, etc.
Climate and populations projections and policies are based on theories that are _far_ more dubious than the mature physics on which Drexlerian nanotechnology, reversible computation, and other results of theoretical applied science are based. Soft climate and social theories are, like theories about weather, much more likely to change than the theories underlying theoretical applied science -- mature physics and chemistry.
If long range projections (>50 years) don't consider the results of theoretical applied science, they, and the policies they imply, are at best complete nonsense, and more likely destructive and dangerous mythologies.
There are at least two important reasons for determining what is possible. The first is that long-range forecasts play an important role in our culture and politics. I'd trace the origin of the nanotech meme to the Club of Rome doom&gloom projections, and the space colonization meme which rose in reaction to it. Out of that Drexler matured into studying the bounds of technological possibility in general, and developed the nanotech meme.
Such exploratory engineering is distinct from both traditional science and engineering, and as such has had a hard time catching on. It is held in low repute in many circles, mainly due to its resemblence to science fiction. On the other hand, nanotech is much less of a fiction than the naive economic/ecology projections that dominate the public discourse, eg our beloved Vice President's _Earth in the Balance_.
The good news is that with computer simulation we can now design machines, and demonstrate with reasonable confidence that they will work, even if we are far from having the capital needed to actually build them. Thus designs for molecular gears, motors, ratchets, and computation elements, enclosed biosphere cities, ocean and space colonies, etc. which are all highly impractical to today's engineering (and rightly scoffed at when it is suggested to engineers or investors that these things should be built now), but are very important for the public discourse and long-range planning of our own lives.
To this mix I hope we will add back in economic projections, but from a business finance point of view as well as the traditional economimc/ecological point of view. One problem Tim May has pointed out is the desirability of finding paths across the "product desert" from here to nanotech. That is a task both for theoretical applied science and what I call "exploratory business plans", or "biz plan strawmen", which are basically cost projections and cash flow spreadsheets based on the theoretical applied science. I've developed several of these myself, including one for Mars gold mining (which assumes we discover gold in ores of a quality similar to those of prehistoric Earth), comet mining/ice rockets, etc. Normally people who make business plans are looking for investors, and indeed I get people saying things to me like "good luck finding investors!", even though that is totally beside the point. There are a bunch of (usually conservative ) assumptions and "what-ifs" about technology and economic trends built into these plans which are not true today, but might come to pass a few or many decades from now. The point is to find out what is possible, and with the exploratory business plans to get a sense of what is most economically likely, to get a sense of which parts of "tooling ecology space" are fertile valleys and which are the deserts.
The second reason to study theoretical applied science is our personal stake in the future -- a quite new and important element of futurism that is unique to Extropianism. The most personally important need for long-range planning is probably the decision to sign up for cryonics. Projecting what is possible after a couple hundred years of suspension, the understanding of how the brain works and what technology is possible that might repair ischemic and freeze damage, is quite important even if we can't build cell repair machines today or within the next few decades. Pascal's wager would look much better if I could read the blueprints and spreadsheets for Heaven, instead of just poetry some imaginative folks have written about it. So the synergy between nanotech and cryonics is not surprising, and theoretical applied science is an important endeavour that should take its place beside traditional science and engineering, but not be confused with them.
Theoretical applied science is thus important both for judging the possibilities for both personal futures, and the possibilities for the the future of society, a concern which plays an increasingly large role in our culture, politics in particular. For more information on both theoretical applied science and K. Eric Drexler's nanotechnology, I heartily recommend his _Nanosystems_ (1992, John Wiley & Sons).
Nick Szabo firstname.lastname@example.org