# If Drexler Is Wrong, He May as Well Be Right 

I sometimes joke darkly on Discord that the machines will grant us a nice retirement tweaked out on meth working in a robotics factory 18 hours a day. I don't actually believe this because I suspect an indifferent AGI will be able to quickly replace industrial civilization; it will just kill us and eat the world with nanobots. But many don't believe that Drexlerian nanotechnology is possible. 

I am an idiot with little physics knowledge, so possibly this post is only interesting from an amplification via debate frame, but this is why I think something close to Drexlerian nanotechnology (or having similar practical implications to Drexlerian nanotechnology) is likely possible:

The design space is very large. Any proof that Drexlerian nanotechnology is impossible would have to be very robust. And it strikes me that most plausible looking arguments can likely be hacked around given how large the design space is. 

Unless I see a broad consensus from physicists (sorry chemists but I trust physicists way more) that Drexler’s designs, and all things sufficiently similar, are impossible - which in practice means a proof that existing biology is close to optimal in all important dimensions, I am inclined to side with Drexler. I see no such consensus and indeed many people with a physics background think highly of *Nanosystems*. Absent this consensus and given that biology is ignoring large parts of the design space, including many useful elements, it seems plausible to me there are vast gains on the table. 

But let’s assume existing biology is optimal in some sense, and there is some reason I don’t understand why nanoscale machines cannot construct useful things from a wider array of elements than biology on the nanoscale. Well, we know it is possible for nanomachines to construct useful things from this palette at the macro scale. We are such machines! This means we are not even close to the optimal species for scalable power acquisition. DNA can store roughly 215 petabytes per gram. You can fit a lot of schematics for macroscopic machines in DNA. This means you can create a eusocial “species” that has phenotypic traits such as ‘constructs a nuclear power plant’ and ‘bootstraps a lithography fab’. Despite having seen [Friedman's pencil video](https://www.youtube.com/watch?v=67tHtpac5ws), I think it is risible to claim you need a human economy to do such things.  

The design space here is also extremely huge. If you are limited to biological/macro-machine hybrids, your doubling times might not be in the days like in the grey-goo visions, but things would still happen extremely quickly and, provided an AGI is confident in its designs, it can safely dispense with human civilization without worrying about losing long-term industrial capacity. And doubling times of the ‘spores’ for such a life-form could be very fast. So in practice you could get reasonably close to grey-goo-level speeds. 

But let’s go further and pretend ‘biology/macro-machine’ hybrids are too sci-fi for you and you claim nanotechnology is impossible to the point that you think existing life is magic we can’t engineer. Macroscopic self-replicators have very similar practical implications to Drexlerian nanotechnology and the bio/macro hybrid ‘compromise’ solution described above. They, alone, should be sufficient to replace human civilization.

Macroscopic self-replicators are just robotic factories that have the machinery and fidelity to make copies of themselves without any human intervention. This is very obviously physically possible. Anyone who denies this, I just don't know what to tell you at this point. Carl Feynman has a nice post on them [here](https://www.lesswrong.com/posts/rQxrSRPJGmksGjK8z/it-s-time-for-a-self-reproducing-machine). He claims a doubling time of about 5 weeks, which means a few years to get really scary places. But given the nature of exponential growth, the first N seed macroscopic self-replicators could be made in stealth or even in a non-self replicating factory and so things could happen pretty fast once we notice things are happening. 

Non-self-replicating factory? Perhaps there is some room for my retirement after all.