"Permutation City" by Greg Egan - Review & Discussion

Egan is famous for his very high concept hard sci-fi fiction that leverages his academic background in mathematics plus deep knowledge of quantum physics and computer science. Permutation City is no exception, exploring an even broader scope of fascinating concepts than Schild's Ladder, which I'd read years ago.

It's one in a set of 3 novels, by him, grouped together as "subjective cosmology". But they're not linked in any way besides this categorisation of theme.

It pushes far beyond hand waving philosophy, weaving in some solid technical references, as it explores concepts of: continuity of identity, simulation of consciousness, extreme transhumanist mind modification, subjective reality, artificial life within deterministic systems, computability, parasitic computation and "dust theory". Many ideas I consider important to at least be vaguely aware of.

His characters are adequately believable and his writing style reasonably sophisticated. Although my attention/motivation struggles a little, these days, with this kind of classic novel structure: alternating chapters between several characters, telling a story largely in parallel.

Many worlds for sure!

This from NS about new successes of the Many Worlds Interpretation of QM (my emphasis) :

“The trick is to examine a quantum experiment while excluding probability theory and accepting the many-worlds interpretation.

The multiverse has a branching structure, created as the universe splits into parallel versions of itself. The thickness of the branches can be calculated solely using deterministic equations, getting around the uncertainties usually associated with quantum physics. What the Oxford gang found is that the branching structure exactly reproduces the peculiar probabilities predicted by the Born rule. The branching also gives the illusion of probabilistic outcomes to measurements.”

…which ties in nicely with what Stephen Wolfram (founder of Mathematica and general physics/maths/computing guru!) has been saying for some time and talks about in a recent article:

“The alien feeling doesn't stop there. Another thing that seems alien is the idea that our whole universe and its complete history could be generated just by starting with some particular small network, then applying definite rules.

For the past 75+ years, quantum mechanics has been the pride of physics, and it seems to suggest that this kind of deterministic thinking just can't be correct.

It's a slightly long story (often still misunderstood by physicists), but between the arbitrariness of updating orders that produce a given causal network, and the fact that in a network one doesn't just have something like local 3D space, it looks as if one automatically starts to get a lot of the core phenomena of quantum mechanics--even from what's in effect a deterministic underlying model.”

Basically Wolfram’s ‘hobby’ is hunting for the right axiom + inference rules pair (to use words from “I am a strange loop” where Hofstadter’s talking about symbolic logic and other foundations of mathmatics. More about that book at a later date!) to generate our exact universe (or set of parallel universes) for scratch!

Wolfram’s “A New Kind of Science” (that’s been sitting very heavily on my bookshelf for a couple of years now) is devoted to the study of the behaviour of very simple rules applied to simple starting conditions. This field Is basically the generation and analysis of computational chaos.

Look into John Conway’s “Game of Life” if you’re unfamiliar with it: a beautiful example of emergence from simple rules. It’s analogous to our universe in that it’s a microcosm the kind of starting point and rules Wolfram’s searching for.

This stuff might all seem obtuse, but I think it’s amazingly, fundamentally important (to everything literally). And just as Chaos was (arguably) the 3rd major revolution in Physics of the 20th century (and by that I mean the 3rd most important sea change at all; as we all know Physics underpins all the physical sciences, which in turn found society) so the integration of the computational universe with our understanding of our everyday surroundings will be a massive modification to fundamental thinking in the coming era...



[A New Kind of Science appears to be fully available online in a less likely to break your desk than the 1200 page hardback version! Honestly, it’s worth just dipping into it randomly! Here: http://www.wolframscience.com/nksonline/toc.html ]

Energy for free?

New Scientist (02/12/06):

Understanding the swing of things: "By engineering such variations, Peyrard has shown, you could make heat flow 10 times more easily in one direction than its opposite."! If this can be applied in a real world aplication, surely it would mean rewritting the 2nd law of thermodynamics for starters!

There are multiple ways of extracting useful (work) energy from a temperature difference. Generally a system that does this is called a 'Heat Engine'. Therefore, combining a brand new, state of the art, physics violating heat pump and a thermoelectric generator (using the Seebeck effect) or even a good, old fashioned, Stirling Engine, you can use any heat reservoir (i.e. any matter or radiation with a temperature, i.e. anything!) and extract *all* it's heat (within the operating temperature of this new device) into useful energy.

The article doesn't say anything of the possible uses of a real device (perhaps a conjecture too far considering the massive potential), and as always there are skeptics saying that the 1D computer model of the 'Breather' effect, slowing thermal conduction, is not applicable to the 3D world. Though, carbon nanotubes are practically 1 dimensional creations.

...D'oh!...Hang on, just figured out why my free energy idea is folly: selective resistance to heat flow can no more 'pump' heat, than a diode can pump electicity! (so the answer is a resounding NO...for now) However, you could make digital electronic circuits out of such components that use pure temperature to operate them instead of voltage. Possibly very useful, if components can be realised at a tiny scale.


Also pointed to by this edition is the Pentagon buying 1 Petaflop (10^15 calculations per second) machines off IBM/Cray, to be built in the next few years. Though they'll probably just be used to calculate simulations of nuclear weapons in excruciating detail (seeing as live tests are frowned upon these days... yes france i'm looking at you! I know Pakistan and India have been naughty too, and North Korea would like us to think the have, but you should know better!), the raw computational power available in such a machine is approximately equivalent to that of all the neurones in a human brain...... which might make for a truely interesting application, if we had more than the fintest clue how the human brain is structured! Hopefully by the time the price of a 1 Petaflop device has fallen from a state budget busting $1/4 Billion to the price of an off the shelf PC (about 2025), we'll have figured out the missing details.