Why not computer in a can? Michael Nielsen on the varieties of material existence

I have a friend who is prone to thinking that the route from imagination to implementation isn't worth thinking about. I'd tease him with the idea of computer-in-a-can. It's an ordinary aerosol can. You spray computer-in-a-can on a convenient surface and voilà! you have a keyboard and monitor on that surface. You type whatever you need to type and the computer displays your result on the monitor. Just like that.

Michal Nielsen has written an interesting set of notes, The varieties of material existence (title swiped from William James). It's rather more serious and interesting than computer-in-a-can, but who knows? Some passages:

Using electrons, protons, and neutrons, it is possible to build: a waterfall; a superconductor; a living cell; a Bose-Einstein condensate; a conscious mind; a black hole; a tree; an iPhone; a Jupiter Brain; a working economy; a von Neumann replicator; an artificial general intellignece; a Drexlerian universal constructor (maybe); and much, much else. [...]

We usually think of all these things as separate phenomena, and we have separate bodies of knowledge for reasoning about each. Yet all are answers to the question “What can you build with electrons, protons, and neutrons?” [...]

What are the most interesting states of matter which have not yet been imagined? It’s remarkable that human consciousness, universal computing, superconductors, fractional quantum Hall systems (etc) are all pretty recent arrivals on planet Earth. Each is an amazing step, a qualitative change in what is possible with matter. What other states of matter are possible? What qualitatively new types of phenomena are possible, going beyond what we’ve yet conceived? Can we invent new states of matter as different from what came before as something like consciousness is from other states of matter? What states of matter are possible, in principle? In a sense, this is really a question about whether we can develop an overall theory of design? [...]

Much of my confusion is because the standard classification of matter into phases relies on that matter being at (or near) thermodynamic equilibrium. Parts of the human body are near thermodynamic equilibrium. But much is not. The thing that makes it all go, that makes life life – our metabolism – is all about energy flows that keep things away from equilibrium. [...]

I have two broad (and very different) frameworks for thinking about matter.

One of those frameworks is equilibrium statistical mechanics. This is the framework used by physicists to think about the different phases of matter, and (often) by chemists and materials scientists to think about what new materials are possible. It’s a powerful framework, and most stable matter in the world is of this type.

However, many of the most interesting systems – including universal computers, conscious minds, cells, economies, and others – don’t fit well into this framework. Rather, they have the three properties described above: many static components near thermodynamic equilibrium; many energy flows and dynamic components far from equilibrium; and surprising stability and resilience, often with built in self-healing or error-correction mechanisms.