If I have seen further it is by standing on the shoulders of giants.

Saturday, November 26, 2011

There’s Plenty More Room at the Bottom: Beyond Nanotech to Femtotech

Not long ago nanotechnology was a fringe topic; now it’s a flourishing engineering field, and fairly mainstream. For example, while writing this article, I happened to receive an email advertisement for the “Second World Conference on Nanomedicine and Drug Delivery,” in Kerala, India. It wasn’t so long ago that nanomedicine seemed merely a flicker in the eyes of Robert Freitas and a few other visionaries!

But nano is not as small as the world goes. A nanometer is 10−9 meters – the scale of atoms and molecules. A water molecule is a bit less than one nanometer long, and a germ is around a thousand nanometers across. On the other hand, a proton has a diameter of a couple femtometers – where a femtometer, at 10−15 meters, makes a nanometer seem positively gargantuan. Now that the viability of nanotech is widely accepted (in spite of some ongoing heated debates about the details), it’s time to ask: what about femtotech? Picotech or other technologies at the scales between nano and femto seem relatively uninteresting, because we don’t know any basic constituents of matter that exist at those scales. But femtotech, based on engineering structures from subatomic particles, makes perfect conceptual sense, though it’s certainly difficult given current technology.

The nanotech field was arguably launched by Richard Feynman’s 1959 talk “There’s Plenty of Room at the Bottom.” As Feynman wrote there,

"It is a staggeringly small world that is below. In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began seriously to move in this direction.

Why cannot we write the entire 24 volumes of the Encyclopedia Brittanica on the head of a pin?

The next big step toward nanotech was Eric Drexler’s classic 1992 book Nanosystems, which laid out conceptual designs for a host of nanomachines, including nanocomputer switches, general-purpose molecular assemblers, and an amazing variety of other fun stuff. Drexler’s 1987 book Engines of Creation also played a large role, bringing the notion of nanotech to the masses. Contemporary nanotech mostly focuses on narrower nano-engineering than what Drexler envisioned, but arguably it’s building tools and understanding that will ultimately be useful for realizing Feynman’s and Drexler’s vision. For instance, a lot of work is now going into the manufacture and utilization of carbon nanotubes, which have a variety of applications, from the relatively mundane (e.g. super-strong fabrics and fibers) to potential roles as components of more transformative nanosystems like nanocomputers or molecular assemblers. And there are also a few labs such as Zyvex that are currently working directly in a Drexlerian direction.

But Feynman’s original vision, while it was focused on the nano-scale, wasn’t restricted to this level. There’s plenty of room at the bottom, as he said – and the nano-scale is not the bottom! Theres’s plenty more room down there to explore.

One might argue that, since practical nanotech is still at such an early stage, it’s not quite the time to be thinking about femtotech. But technology is advancing faster and faster each year, so it makes sense to think a bit further ahead than contemporary hands-on engineering efforts. My friend and colleague Hugo de Garis has been talking to me about femtotech for a while, and has touched on the topic in various lectures and interviews; he convinced me that the topic is worth looking at in spite of our current lack of knowledge regarding its practical realization. After all, when Feynman gave his “Plenty of Room at the Bottom” lecture, nanotech also appeared radically pie-in-the-sky. Hugo’s personal take on femtotech is presented in an essay he wrote recently, which is presented here as a companion piece to this article; the two articles are intended to be read together.

There are many possible routes to femtotech, and Hugo notes a number of them in his article, including some topics I won’t touch here at all like micro black holes and Bose-Einstein condensation of squarks. I’ll focus here largely on a particular class of approaches to femtotech based on the engineering of stable degenerate matter – not because I think this is the only interesting way to think about femtotech, but merely because one has to choose some definite direction to explore if one wants to go into any detail at all.

Physics at the Femto Scale

To understand the issues involved in creating femtotech, you’ll first need to recall a few basics about particle physics.

In the picture painted by contemporary physics, everyday objects like houses and people and water are made of molecules, which are made of atoms, which in turn are made of subatomic particles. There are also various subatomic particles that don’t form parts of atoms (such as photons, the particles of light, and many others). The behavior of these particles is extremely weird by the standards of everyday life – with phenomena like non-local correlations between distant phenomena, observer-dependence of reality, quantum teleportation and lots of other good stuff. But I won’t take time here to review quantum mechanics and its associated peculiarities, just to run through a few facts about subatomic particles needed to explain how femtotech might come about.

Subatomic particles fall into two categories: fermions and bosons. These two categories each contain pretty diverse sets of particles, but they’re grouped together because they also have some important commonalities.

The particles that serve as the building blocks of matter are all fermions. Atoms are made of protons, neutrons and electrons. Electrons are fermions, and so are quarks, which combine to build protons and neutrons. Quarks appear to occur in nature only in groups, most commonly groups of 2 or 3. A proton contains two up quarks and one down quark, while a neutron consists of one up quark and two down quarks; the quarks are held together in the nucleus by other particles called gluons. Mesons consist of 2 quarks – a quark and an anti-quark. There are six basic types of quark, beguilingly named Up, Down, Bottom, Top, Strange, and Charm. Out of the four forces currently recognized in the universe – electromagnetism, gravity and weak and strong nuclear forces – quarks are most closely associated with the strong nuclear force, which controls most of their dynamics. But quarks also have some interaction with the weak force, e.g. the weak force can cause the transmutation of quarks into different quarks, a phenomenon that underlies some kinds of radioactive decay such as beta decay.

On the other hand, bosons are also important – for example photons, the particle-physics version of light, are bosons. Gravitons, the gravity particles proposed by certain theories of gravitation, would also be bosons.

The nucleus of an atom contains protons and neutrons. The electrons are arranged in multiple shells around the nucleus, due to the Pauli exclusion principle. Also note this sort of “solar system” model of particles as objects orbiting other objects is just a heuristic approximation; there are many other complexities and a more accurate view would depict each particle as a special sort of wave function.

The carbon atom, whose electrons are distributed across two shells.

Finally, just one more piece of background knowledge before we move on to femtotech. Fermions, unlike bosons, obey the Pauli exclusion principle, which says that no two identical fermions can occupy the same state at the same time. For example, each electron in an atom is characterized by a unique set of quantum numbers (the principle quantum number which gives its energy level, the magnetic quantum number which gives the direction of orbital angular momentum, and the spin quantum number which gives the direction of its spin). If not for the Pauli exclusion principle, all of the electrons in an atom would pile up in the lowest energy state (the K shell, the innermost shell of electrons orbiting the nucleus of the atom). But the exclusion principle implies that the different electrons must have different quantum states, which results in some of the electrons getting forced to have different positions, leading to the formation of additional shells (in atoms with sufficient electrons).

The Future of Femtotech

So what’s the bottom line – is there still more room at the bottom?

Nanotech is difficult engineering based on mostly known physics. Femtotech, on the other hand, pushes at the boundaries of known physics. When exploring possible routes to femtotech, one quickly runs up against cases where physicists just don’t know the answer.

Degenerate matter of one form or another seems a promising potential route to femtotech. Bolonkin’s speculations are intriguing, as are the possibilities of strangelets or novel weakly confined multi-quark systems. But the issue of stability is a serious one; nobody yet knows whether large strangelets can be made stable, or whether degenerate matter can be created at normal gravities, nor whether weakly confined quarks can be observed at normal temperatures, etc. Even where the relevant physics equations are believed known, the calculations are too hard to do given our present analytical and computational tools. And in some cases, e.g. strangelets, we run into situations where different physics theories held by respected physicists probably yield different answers.

Putting my AI futurist hat on for a moment, I’m struck by what a wonderful example we have here of the potential for an only slightly superhuman AI to blast way past humanity in science and engineering. The human race seems on the verge of understanding particle physics well enough to analyze possible routes to femtotech. If a slightly superhuman AI, with a talent for physics, were to make a few small breakthroughs in computational physics, then it might (for instance) figure out how to make stable structures from degenerate matter at Earth gravity. Bolonkin-style femtostructures might then become plausible, resulting in femtocomputing – and the slightly superhuman AI would then have a computational infrastructure capable of supporting massively superhuman AI. Can you say “singularity”? Of course, femtotech may be totally unnecessary in order for a Vingean singularity to occur (in fact I strongly suspect so). But be that as it may, it’s interesting to think about just how much practical technological innovation might ensue from a relatively minor improvement in our understanding of fundamental physics.

Is it worth thinking about femtotech now, when the topic is wrapped up with so much unresolved physics? I think it is, if for no other reason than to give the physicists a nudge in certain directions that might otherwise be neglected. Most particle physics work – even experimental work with particle accelerators – seems to be motivated mainly by abstract theoretical interest. And there’s nothing wrong with this – understanding the world is a laudable aim in itself; and furthermore, over the course of history, scientists aiming to understand the world have spawned an awful lot of practically useful by-products. But it’s interesting to realize that there are potentially huge practical implications waiting in the wings, once particle physics advances a little more – if it advances in the right directions.

So, hey, all you particle physicists and physics funding agency program managers reading this article (and grumbling at my oversimplifications; sorry, this is tough stuff to write about for a nontechnical audience!), please take note – why not focus some attention on exploring the possibility of complexly structured degenerate matter under Earthly conditions, and other possibly femtotech-related phenomena such as those mentioned in Hugo de Garis’s companion essay?

Is there still plenty more room at the bottom, after the nanoscale is fully explored? It seems quite possibly so – but we need to understand what goes on way down there a bit better before we can build stuff at the femtoscale. Fortunately, given the exponentially accelerating progress we’re seeing in some relevant areas of technology, the wait for this understanding and the ensuing technologies may not be all that long.

Continue reading (Long Read) - There’s Plenty More Room at the Bottom: Beyond Nanotech to Femtotech

Read also:
Searching for Phenomena in Physics that May Serve as Bases for a Femtometer Scale Technology
From DNA Computing to Femtocomputing?
X-Tech and the Search for Infra Particle Intelligence

No comments:

Post a Comment