Sunday, September 06, 2009

Lost in Actuality

In my third SF story, I need to get the hero out of his closed prison cell via new physics. In the old physics we simply blow a hole in the wall with some explosives, but of course the guards will never let him have any. In physics terms, the trapped scientist is enclosed by the potential fields of the inter-molecular forces in the cell walls. An explosion simply dumps energy which disrupts these bonds and off the fragments go.

How do things work with new physics?

My first thought was new fields. So I started to look at the inflation field of the early universe, or some of the new stuff in supersymmetry. This is still something I’m researching but I’ve come to believe they don’t really help. The coupling between new fields and the potential barrier would still be via energy so it’s another explosion - and I’ve no idea what a controlled local inflation field would do but it doesn’t seem very survivable.

A more promising approach is via the many-world interpretation of quantum mechanics. For example, in chapter 15 of his book ‘The Labyrinth of Time’, Michael Lockwood describes a variant model involving an ‘actuality’ dimension, i.e. space-time-actuality, although this is probably just a fancy description of Hilbert space. So we have to imagine that alongside our hapless scientist there are an infinite number of his copies adjacent in actuality. ‘Farther away’ there are worlds where the prison was never built and it’s just prairie, or whatever, (the metric in actuality is related to probability).

What the story needs is a spherical volume enclosing our scientist, to put him in a quantum superposition across all the variants of actuality, and then adjust the amplitudes to zero for those worlds where the hero is presently incarcerated. Then his only copies will be free ones, and he can walk away across the prairie. His next step will be to reverse the process and dial his probabilities back to his original world. Reminds me of the “Infinite Improbability Drive”!

How can we do such ‘amplitude engineering’? Well, in a sense we do it already whenever we set up situations where interference can occur. But on this scale we really need some new science.

I think the answer lies in paradox. If we set up a paradoxical situation, then we will find the amplitude (and therefore probability) of that outcome is zero. And the best paradox is time travel. So what we need is a ‘worldline mirror’ which the prisoner can set up to reflect his worldline into the past.

What will actually happen is that his worldline will diffract into alternative worlds in actuality where the mirror doesn’t exist*. And a worldline mirror – a kind of time machine – requires space-time engineering: in other words quantum gravity. So maybe this is a fancy way for him to do some quantum tunnelling with non-vanishing probability.

So now we have it. The scientist makes a discovery in grand unified theory, and his colleagues on the outside build him a controllable worldline mirror hidden in an MP3 player. Twiddle some knobs, walk a few hundred metres, twiddle some more and he’s free!

* Arguably, in terms of CPT invariance, on time-reflection he will simply turn into antimatter and annihilate with himself!