Friday, March 10, 2006

Mind Googling

A google, I learned the other day, is the number of bits one scientist has estimated would be required to represent the whole of the visible universe − ten to the power of one hundred.

The same theorist, Jacob Bekenstein, has also established that the surface area of a black hole is proportional to the information it contains (or swallows).

To calculate the information content of a black hole Bekenstein divides its event horizon into planck squares (10 to the power of minus 33 cms), supposedly the smallest possible unit measurement of spacetime − the point at which it starts to go all "frothy" − and so perhaps a candidate for the fundamental pixels of our cosmos. He therefore speculates that a sphere one tenth of a lightyear across could 'contain' the visible universe.

Any hypothesis that would digitalise reality goes against the grain of theoretical physics which has traditionally been formulated using continuous phenomena like fields. In the Newtonian paradigm , it is generally agreed that the smallest computer model you could make of the universe would be the same size as the universe itself (rather like Borges' maps that fit snugly onto actual coastlines). But it goes without saying that The Matrix has made VR metaphysics extremely fashionable again, with Oxford's David Deutsch leading the way:

"It is possible to build a virtual reality generator whose repertoire includes every physically possible environment." and "Since building a universal virtual-reality generator is physically possible, it must actually be built in some universes."
One of the key challenges facing the would-be cosmological coder is the fact that there's really no such thing as empty space − which means you can't really come up with a compression routine (like JPEG) which economically encodes the void.

Meanwhile, veteran theorist John Archibald Wheeler remains convinced we live in a participatory universe where physical entities arise from underlying information content, and consciousness actively constructs physical reality through observation:

"It from bit symbolises the idea that every item of the physical world has at bottom - at a very deep bottom, in most instances - an immaterial source and explanation; that which we call reality arises in the last analysis from the posing of yes-no questions and the registering of equipment-evoked responses; in short, that things physical are information-theoretic in origin."
It has for a long time struck me as interesting that both the universe and the human mind are one thing, while appearing to be something quite different. Consciousness is a fabulously complex parallel-processing system that literally thinks it's serial, while the universe is a fundamentally inderminate place that behaves as if it were determinate. (And perhaps also analog when it is in fact digital.)

Yet from the first time it was suggested that a cat might be both dead and alive at the same time physicists have generally been uncomfortable with these kinds of dualities, separating them into distinct theoretical frameworks and hoping that mathematics rather than metaphysics will one day make sense of it all.

As for the planck squares, Masami Yamasaki has spotted another kind of duality within string theory − a mathematical one − which suggests that the physics inside a tightly wrapped up dimension at the planck length is identical to that in the larger dimensions outside. This might means that reality doesn't end at that scale after all.

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