Friday, 30 October 2009

Observations on Observations

What The Hell Is Going On?

Last week, and in fact part of the week before, we saw the tenth anniversary of Canada's Premier Institute for Theoretical Physics celebrated with a festival: Quantum to Cosmos: Ideas for the Future. One fascinating discussion, picked up by New Scientist and widely disseminated, took place when a panel of leading physicists ran headlong into the question, "What keeps you awake at night?"

Topics in the above article include the anthropic principle; the continuous annihilation of dark matter; the nature of dark energy; emergent complexity; string theory; the holographic principle and the (cosmological) singularity; entanglement and the nature of observation; and rounding off all this, the limits of knowledge. For deeper coverage, the festival site has many video clips on a breathtaking array of subjects, in no way limited to the preceding list, and all available to watch here:

Disclaimer: the random musings that follow below are presented for amusement only, and have no connection with any person who knows what they're talking about. They're just three speculations with a slender common thread. Also, the Lottery references are to the UK National Lottery; lastly, and most importantly, there is a "u" in "colour".

Observing A System

Observers, and their universe. They observe it, don't they? Well in a way, but remember, what they actually observe is the universe that contains them; in other words, they're a part of what is being observed.

An observer can observe some small part of the universe. Another observer, for instance. Or even itself. It can be said to be observing the entirety of the universe, excepting itself - which is what I usually imagine whenever I hear the term "observer". Something outside the universe, looking in. Yet that's not really what we have here. Instead, we have a small part of the universe, observing another part of itself.

Isn't there a sense in which the spatial distinctions implied by that account are illusory? When particles are entangled, for example, they act in all respects like immediate neighbours, regardless of the distance between them. And all distances are measured over the full set of dimensions, not just three arbitrarily selected spatial ones. So, could an observer be considered as extending over multiple, seemingly disjoint and disconnected, regions of space-time?

What's an observation anyway? Just a collection of particle interactions? When I observe a sunset, electrons in my cells are receiving, or interacting with, photons that originated something over 92 million miles away. Seems to me that a single Feynman diagram should suffice to picture that situation.

Now, let's try to zoom in on the observer here. In doing so, we conceptualize ourselves as some kind of meta-observer, which seeks to reduce the sunset-beholder to its lowest terms. Those electrons in my body, the ones doing the interaction with the sun's photons, well they had certainly better be counted as comprising part of our observer. What about the atomic nuclei they associate with? Curiously, if you trace the paths of the neural signals from my retinae through to my visual cortex, you will be following electron-photon interactions, in combination with almost imperceptible gross movement of particular electrons, all the way down. The bulk of the atoms, the atomic nuclei, will play absolutely no part in the act of sunset observation, other than as a static scaffolding giving those electrons somewhere to be. Even then, it's only the outermost shell of electrons in a given atom, that play any part in this process.

Certainly at the other end of this interaction, the sun, we have a quite different process which is producing the photons in the first place. And yes, that end does in fact require some involvement on the part of the local atomic nuclei. But from that point onward, the observation event is just an electromagnetic dance, ending with certain chemical changes in my nervous system.

What makes this sequence of interactions so special? What characterizes an observation, what distinguishes it from any other situation in which photons are exchanged between electrons? Take any photon in transit from old sol. Quantum electrodynamics tells us that it can split quite spontaneously into a positron and an electron, which then recombine, eliminating each other and producing a photon. This might happen any number of times during its eight minute journey to Earth. Upon hitting the upper atmosphere, it may then find itself absorbed by one of the outer electrons of a gas atom, causing a transition to an excited state. Do any of these interactions of the photon qualify as an "observation"? If not, then how exactly do they differ from the case where that excitable electron was in my eyeball, or the middle of my head?

Much of this can be encapsulated in the thermodynamical concept of a system. When we seem to peer out at the world, observing it as we might, we treat it as one closed system - with ourselves outside of it. This works well enough for observation of everyday objects at a sensible scale, for example, the balls on a snooker table. As the system shrinks, it begins to pull me in, until I find myself trying to observe single photons, and discover that the only way I can do so is to absorb them entirely into my body. They have left the system, escaped from the experiment; or to put it another way, I have become, bodily, a part of it.

No surprise then, to discover certain corollaries to this, such as: it's impossible to measure anything without changing it. Imperceptibly perhaps, but in the end it's all just a matter of scale. A voltmeter draws a tiny current in order to operate; this current causes a corresponding drop in the voltage across the source's internal impedance, with the result that the displayed voltage is slightly different from the value prior to measurement.

Observation is interaction: all the way down.

Deal Or No Deal

One of my better high school teachers, in chemistry as it happens, had a pet theory about the symmetry of time. We are talking 1974 here, when such ideas were popular only with certain types of crackpot, and quite invisible elsewhere. One day a few of us stayed behind after class to ask him a question or two about electron orbits, and somehow we got sidetracked into this idea of his. Next thing we knew he'd produced a pack of playing cards, which he proceeded to shuffle, then demanded that I start predicting the colour, red or black, of each card as he turned it over.

I started off well. Can't remember the exact sequence, save for the fact that it had a long run of about half a dozen reds near the start, but I certainly got into double figures, somewhere between 12 and 16 cards, without getting a single guess (prediction?) incorrect. Aware of being watched by my friends, I called out every one of those colours with complete confidence.

Then I paused, saying aloud, something like "This is too freaky. I'm going to start getting them wrong now." And the next half dozen or so were indeed wrong, just as I predicted. After that, I stopped and refused to continue. For some reason unknown, I had become fearful of getting one guess incorrect!

At the age of 16 I had an undeniable desire to impress my peers, and I'm certain that had a lot to do with the outcome of our little experiment; and perhaps, with my sudden desire to stop before the first, inevitable, failure. But what are the chances of getting this sequence of results? That's an easy calculation: somewhere between 1 in 262,144 (assuming 12 cards in my first run, followed by 6 correctly predicted mismatches) and 1 in 4,194,304 (assuming 16 + 6).

Throughout the trial, I had the unmistakable feeling - consistent with my teacher's pet theory - that I was in some sense reaching a little into the very immediate future, and somehow capturing a "memory", which I would rather term a "conviction", of what colour the next card would turn out to be. The closer you are to an event in time, he reckoned, the easier it should be to "remember" - regardless of whether it's a past or a future event.

Scott Adams, he of Dilbert fame, has written about this at some length, although he frames it very differently. When he talks about affirmations, for example in The Dilbert Future (p. 246, also Appendix A), I detect the same as-yet poorly understood phenomenon, the tricking with time, the constant falling-through into particular possible futures. Recently, Noel Edmonds has made much capital of a poorly understood, mysticised and new-aged-up version of the same idea, awkwardly framed as half philosophy, half self-help guide.

Richard Feynman's Quantum Electrodynamics, The Strange Theory of Light and Matter, contains a lucid account of the summing-over-all-histories method of prediction. At any given point in space-time, a given quantum has a certain propensity to move to any other such point. A lot of these propensities cancel out; others are bunched up in a particular direction, and hey presto, if that's not just where the darned thing goes.

Propensity: might be a good term to use for the complex square root of a probability! Better than Amplitude, at any rate.

When the Lotto [UK] balls tumble on a Saturday night, all fourteen million possible outcomes are represented by such propensities. Is there any way to force these to "bunch up" in a particular direction, so that a predetermined set of six numbers comes out?

Actually the signs aren't all that good. Under some modern interpretations of quantum mechanics, all of these possible worlds cascade forward into actual existence. Picture fourteen million distinct new realities, complete new universes, splitting off in unknown dimensions from a common starting point, the Saturday night lottery machine. Each new universe contains a replica of me, and most of these - almost all of them, in fact - have not just won the lottery.

Would there be any visible, observable indications if this interpretation were incorrect? Maybe there is but one actual reality, after all. Maybe I can bunch up the fibres of propensity in my favour, perhaps by leaving lots of little notes lying around, notes whose existence, or whose observation, would make certain lottery outcomes much less likely than others?

Observation is interaction: all the way down.

The Digital Universe

The majority of physicists today, when they can be pressed to opine on the matter (and many refuse), appear to be of a consensus that our universe is a simulation. At least, that's my impression of that community, from what I've read, both in the popular science press, and here on the web. However there's so much material available on the subject, it would be fatuous to pick out one such reference to "prove" my assertion. So you'll just have to do your own research, and form your own impression.

True or not, academically popular or shunned, this has undeniably been a favourite theme of much science fiction since the first half of the 20th century, and a favourite subject of philosophers much further back than that. It's inevitably one of those possibilities that enters your head when wrestling with quantum mechanical concepts. But in either of those contexts, it can't be said to have any more validity than, say, extrapolating the model of the atom as a solar system, in an indefinite recursion, without paying heed to the many and fundamental differences and incompatibilities between the two pictures.

What brought it home to me, after more than 35 years of programming these wonderful little digital systems, was a development in Loop Quantum Gravity. Specifically, a proposal to measure the stretching out of the spectrum of light coming to us across billions of light years, to see whether the discrepancies between the red and the blue predicted by quantized space were actually present. And why should the universe be quantized? Maybe because it's nothing more than the state of a digital simulation!

It seems likely that if anything is quantized (the available energy levels of an electron, for instance), then everything will be, including space-time. And by that is obviously meant, the entire M-dimensional manifold of our being, whatever that value of M eventually turns out to be.

Now consider the digital system on which our simulation is running. From our experience of software development, our knowledge of mathematics, the availability and impossibility of various algorithms, and the success of the neural net approaches, we would probably admit that the system software of this universe is genetic in its nature and approach. And once again, when it's laid out like that, it becomes clear. Of course nature uses genetic algorithms, where else would our brains - products of these methods - have picked up the idea?

Now, can we divine any information about who might be running this simulation? If the general argument is valid, making it vanishingly unlikely that we are not such a phenomenon, then it can be applied recursively to establish that we are "almost certainly" a simulation being run by a simulation, much as recent Sims games have your little creations running their own Sims. And so on, ad absurdum.

Actually there are several ways out of this reductio, each more fascinating than the next; see Paul Davies's Goldilocks Enigma for a full treatment.

At first glance, there doesn't seem to be much that we can infer about any of those higher levels, just from looking at this great universe of ours. However, if we assume that we are a simulation with a purpose, then it becomes likely (or at the very least, rational to assume) that we are observed. Shouldn't there be implications for our ability to detect such acts of observation?

Observation is interaction: all the way down.

And Finally: How It All Fits Together

Erm... on second thoughts actually, details are left as an exercise for the reader. Don't say I'm not good to you.

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