Wednesday, March 7, 2012

Come on, feel the noise

            COME ON, FEEL THE NOISE                      MAR 2011

I want to talk today about Noise and Bootstraps.

When I started work in 1965, no member of the public would have known what a bootstrap was (apart from real boots of course). Now, most people know what it means to ‘boot’ your PC, or your phone.

I have even had to reboot a car once. I had just arrived at the Grand Canyon in a hire car when the aircon started playing up; it was behaving strangely, and not cooling properly. I though for a moment, then turned the ignition off, waited, and restarted. It recovered perfectly – I had rebooted the car.

The reason why this process is known as ‘booting’ is that a raw computer, or other smart device, is a bit like a new born baby. It has potential, but not many well formed actions. The bootstrapping process gradually builds up levels of capability, with each level being needed to bring in the next one. Because the process starts almost from nothing, it is like pulling yourself up by your own bootlaces.

There are a lot of things that work a bit like this, and some (all?) are systems with feedback. I’ve tried to write a book about feedback, so I won’t be going into that in any detail. Sufficient to say that feedback involves feeding back some signal from a system output into an input of the same system.  I use the word ‘system’ to refer to any complex thing or organisation, like a living organism, or part of one, or a company, or a country, or a computer, or other electronics.

The thing about systems with feedback is that they have to start somewhere. If I feed back part of the output to the input, where does the first input come from? It’s a bit like the chicken and the egg. In real life it all gets rather complicated, because systems can have many inputs and outputs, and many feedback mechanisms that overlap.

But some feedback systems are fairly simple, like the well known ‘howl’ you can get from an amplifier and a microphone. This is cause by ‘positive’ feedback between the loudspeaker, the mike, and the amplifier. But it all has to start with some signal that gets amplified and re-amplified. Even in a totally quiet room the process can start. How? Well, it’s called Noise.

This doesn’t necessarily mean an audible sound – though it could be. Any electronic system always has a certain amount of internal electronic ‘noise’ – a very small electronic signal. This is caused by the random energetic motion of electrons in the system. There is always some energy present unless the whole system is at absolute zero – that’s very cold. And even then it gets complicated by quantum theory, but we definitely won’t be going into that here.

There are other electronic systems that rely on feedback; one is called an oscillator – you will have one in your watch or clock. It produces a regular signal that can be used to indicate time, and it also has to be started with a bit of noise somewhere.

The funny thing about all this is that ‘noise’ is generally regarded as a nuisance in electronics – it causes things like hiss in sound systems. But it is also a vital element in making things work. It’s a bit like friction, which causes lots of problems, but is also necessary so that we can do things like walking.

It gets even more interesting when you consider evolution. Evolution is, amongst other things, a kind of feedback system. It uses feedback from the interaction between a system and its environment to adapt the system. But it all had to start somewhere. Nobody knows exactly how, as yet anyway. But in some sense what it needed was a bit of noise – some random juggling of atoms and molecules, driven by energy from the sun, until the system started to bootstrap its way into life (literally).

There are techniques in computing called optimisation which have to solve difficult problems of finding the ‘best’ solution. These methods use various techniques which ‘explore’ the solution space or ‘geography’. Some of them are actually called ‘hill climbing’, because they resemble the problem of trying to find the highest point in a hilly area. The trouble is that you can find the highest ‘local’ point, but can’t be sure that there isn’t a higher one nearby. One of the methods used in trying to avoid this problem is to introduce a kind of ‘noise’ by randomly shifting the solution point, so that it less likely to get ‘stuck’ in a false optimum.

If the process of adding noise is repeated several times, it is referred to as ‘simulated annealing’, because it is similar to the process of repeatedly heating and cooling metal. This process itself uses a kind of noise – heat energy, which jiggles the atoms and molecules around until they find a ‘better’ solution – harder metal.

So, just as friction is something that can cause things to ‘get stuck’, so noise is something that can get things moving again. In a very real sense, noise is a fundamental part of the universe.

Science has not yet quite come up with the answer to how the universe started. This is a big subject; it isn’t even clear how many universes there are, whether they are finite, or infinite in time or space. Even framing these questions is tricky. Defining the word universe is tricky. Anyway, the point I am getting to is that starting a universe is a bootstrap process. You start with nothing, and end up with something. Maybe. And what do we need to start this up? Yup, noise.

Quantum theory (incomplete though it maybe) tells us that empty space is not, well, empty. It is actually a thriving zoo of ‘virtual’ particles popping into a quasi existence before popping off again. Sort of. Maybe. And it may be that some sort of quantum noise was the trigger that booted the whole business. As someone (can’t remember who) said: ‘Nothing’ is unstable. It wants to be something. Like Marlon Brando (on the Waterfront). And its all down to noise.

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