What exactly is the holdup with extreme ultraviolet sources? I remember reading an article that said synchrotrons could generate x-ray beams with the power density of a blowtorch, and some others suggesting free-electron lasers should be able to generate anything down to hard x-rays with more or less arbitrarily high power density; why don't these suffice?
The reliable sources for high-power EUV light (synchotrons and free-electron lasers) are all expensive and gigantic (building sized) due to the accelerator and shielding required for the electron beam. They're completely impractical for industrial scale manufacture (you fundamentally couldn't put 100 of them into a single factory).
Heating tin in a regular laser until it forms plasma and starts emitting 13.5 nm light is much simpler to scale down (since it doesn't involve an accelerated electron beam) but you lose large amounts of power while trying to form a partially coherent beam out of the result, turning hundreds of kilowatts of infra-red laser power into mere 10's of watts of EUV power.
The high input to output ratio means that you need to be really careful that the large amount of dissipated power doesn't cause problems. Tiny misalignment problems often result in the 200kW infra-red input laser melting the entire device into a puddle of former components.
They're very expensive. (Which is also the problem with current tin plasma sources. They work, but they just aren't cost effective.)
There are interesting ideas to downsize synchrotrons though, and if we can both make synchrotrons smaller and semiconductor factories bigger, then perhaps synchrotron sources could make sense. But even then, I worry that if a $20 billion semiconductor plant has only one $1 billion synchrotron source, there is a tremendous amount of risk concentrated in that single source. If the source goes down, the rest of the $20 billion plant goes idle.
Or some more possibilities: "In the long term, new switches might be based on magnetic, quantum or even nanomechanical switching principles. One possibility would be to use changes in the spin of an individual electron to represent a 1 or a 0."[1]
Actually, the transistors mentioned in that article are still bigger than atoms. A single electron stores a 1 or 0, but that electron is still living in a pile of atoms.
(Source: I grew some of the crystals used to build those transistors in the article)
Good point. Still, the 1.5nm scale they mention is significantly smaller than anything we have now.
Is it conceivable that we will see a whole new type of electronics on a subatomic scale in the future though? (Where the structure of a chip is not even made out of atoms, but entirely of subatomic particles?)
I actually have an electrical engineering degree, but the couple of materials courses I took back in the early 2000s are starting to feel a bit dated!
It's hard to rule anything out, but I think using non-atomic matter would be very difficult for a few reasons.
(1) Subatomic particles are not necessarily smaller than atoms. Even though in the particle sense, an electron is infinitely small, in the wave sense, an electron can extend over a volume much larger than a single atom. So it's not necessarily the case that a subatomic particle like an electron is smaller than an atom. (Also, the positive charge of the nucleus actually helps shrink the electron's range. So adding positive particles can end up making the system smaller.)
(2) If you want a transistor every 1.5 nm, then you probably need at least one particle every 1.5 nm. And the only way you can pack matter that densely is if it's charge neutral (a clump of singly charged particles would immediately disperse from electric repulsion). So you either need a combination of positive and negative particles (atoms), or neutral particles like photons/neutrons/neutrinos. The problem with neutral particles is that there's no long-range forces to keep them in whatever structure you design. Gravity is too weak at that scale, and electromagnetism has no effect because they are neutral. Perhaps photons could be used for computation, but without using atoms for mirrors/lenses/waveguides/etc it's hard for me to imagine how.
TL;DR: Atoms are an efficient way to pack particles and preserve structure. It's hard to imagine doing it with a plasma or gas or something else.
http://www.scientificamerican.com/article/optical-circuits-s...
There has been some (very early) work done with photon transistors. One of its cool applications will be fibre-optic hardware, to achieve much lower processing latency, hence faster data transit.
Well you can be forgiven for that :-) That particular plot device was full of holes.
But a more interesting associated memory would be Eric Drexler's "Engines of Creation" and the discussion about obstacles to nanotechnology which include high on the list the ability to actually assemble devices.
Fundamentally, we already have self-replicating robots with nano-level structures that consume materials from their surroundings and build new copies. They're called bacteria. The interesting bit over here is not the observation, but the question why we aren't all covered in bacterial goo miles thick like run-away nano-technology. (we do have them all around us and in us for what its worth)
I think a part of the answer is that if you have free form replication that isn't perfect, then sooner or later something is going to emerge from that goo that realises that it's just more efficient to eat the goo. Combine that self correcting cycle with hard limits imposed by nature (presumably they need to have a power source to make it work - the goo would start to die the minute it gets to a millimetre because of inaccessible sunlight. Then there is toxicity, what happens to the waste? Heat dissipation. Structural issues and other things...) and you have the recipe for a shorter sci-fi series than Firefly. (Dear Mark, today we succeeded in making self replicating nano-robots. They were exponentially multiplying within the petri dish and then they stayed in the petri dish, because apparently nano-robots are tastier than glass and metal. Doesn't matter though, we cracked open the crate of champagne anyway.)
Which is also an argument against von Neumann probes, btw. Perfect replication isn't possible, so sooner or later you are going to see a ton of weird errors accumulate to unpredictable behaviour... (perhaps a shark that goes around "eating" other probes?)
Bacteria aren't capable of spontaneously organizing into multi-celled organisms when they reach critical mass.
Fungi behave much more like this. The thing we don't have an example of in nature is an intelligent creature capable of making tools that can reproduce itself from a single cell. It's definitely a hard engineering problem, but it's conceivable. It's also conceivable that such an entity could seek out and remove any malfunctioning sub-entities.
We humans actually behave a lot like that, it's just that you need at least a whole human to grow another human. It's not so strange to imagine a designed, intelligent creature that can regrow itself from a small piece.
Viral capsids are an even simpler example of self-assembly. In many types of virus, the individual subunits spontaneously piece together to form the capsid in an entirely passive process driven only by Brownian motion, and defined by the chemical composition of the subunits and the solution they are contained in.
Evolution isn't likely to happen in self-replicating robots. Evolution needs a continuous fitness landscape like DNA. A random bitflip is more likely to produce a fatal error than do something beneficial. Even worse if the code is encrypted before copying. There also aren't that many generations. At exponential growth, it only takes a few dozen generations to reach the maximum population limit and stop replicating. Not enough generations for evolution to happen.
Obviously the technical issues with self-replication are difficult, but nature was able to do it with relatively crude methods. No doubt we could eventually design something significantly better. One major advantage would be mass cooperation. Evolution has no incentive for individuals to cooperate with each other, but designed nanobots can specialize and benefit from economies of scale.
Multicelluar organisms exist but they aren't "fluid" like I described. It's not like animals will spontaneously combine into a single organism. Some plants can sort of do this, like bamboo forests. But they don't have a lot of specialization like animals do, with different organs and stuff.
Your analysis ignores the key point that bacteria operate on simple rules based entirely on local concerns, which is not the proposed case in the sci-fi story.
So you're saying that top-down management or even peer-to-peer management will exist within the grey goo scenario? I'm somewhat skeptical about top-down management, as there would be enough nano-bots within a 1cm deep layer in a city the size of NYC to far outstrip the attempts of a complex entity to control them coherently. As far as peer-to-peer communication goes, then bacteria are already doing this; http://www.hhmi.org/research/cell-cell-communication-bacteri... and they still haven't covered us in grey goo.
