Monday 30 March 2009

Quantum Theory - The Theory With A Big Ego

My wife and I had a fairly untypical but cerebral discussion the other day. I was reading an article about Quantum Theory (well it was filling in some time) and I tried to explain a point about its apparent absurdities when she blurted out that the whole thing was so full of its own ego.

I tried to come back with some well informed repartee or to mildly rebuke her for her lack of intelligence but as I sat and thought a moment, it seemed a very intelligent response. You have to get bit of context.

Schrodinger's Cat

Yes we all know the thought experiment involving a cat, a lead box and some poisoned milk. Until we open the door, the cat is in an indeterminate state that is neither alive nor dead until we observe it - at this point, we see if the cat is alive or dead. The idea is that our very act of observing interacts with the system and we see the result. Extending this concept to all reality, it is suggested that all matter, indeed the whole universe, is in fact in a state of complete flux and actually only takes any shape or form as we observe it. It's a difficult concept to grasp but it is the idea that if we close our eyes, the whole outside reverts to a continuous mass of energy, vibrations and whizzing particles and only forms anything of consequence when we observe it.

The act of observing changes the system around us to be something real - when we don't observe it, then it is not.

According to various uses of Heisenberg's Uncertainty Principle, the position of any electron cannot be exactly determined as the act of measuring it actually changes its position.

This is what prompted my wife's outburst. Much of Quantum Theory involves the observer taking measurements or simply observing in order to determine reality or its approximation. How egocentric is that? Why can't reality be a force of its own and we, the observers, actually form when we interact with it? It seems all too convenient to have it this way around.

I didn't like to say but obviously it is a mixture of both but it was a point well made and taken. But with all this swirling lack of reality and uncertainty around us, it is remarkable how it seems so predictable when we observe it. For instance, if I shut my eyes now, the coffee cup is in exactly the same place as I left it, I can walk 5 paces back from the window with my eyes shut if I wish and then turn left for one pace and there will be a door - the only unpredictable things will be the position and state of my dogs. I could in fact do the same thing any number of times in the next 5 minutes and nothing would have changed - in fact, the door will remain there until I choose to open it and walk past.

Reality, in my wife's definition, has little to do with the observer. Put in her succinct way, if that was the case then the world would have ceased with the deaths of Adam and Eve. Reality is more a function of time than of observers.

Entanglement

It's just as well I didn't read the rest of the article to her. I have always been baffled by such things as gravity and particularly lines of flux from a magnet. Such forces act over distance with no apparent intermediate medium with which they interact in order to take effect. Einstein would have us believe that gravity is a distortion of the space-time continuum and so in his view there is a medium which does affect the two bodies to produce the observed effect. I am sure there is a similar explanation for magnets.

Such effects are known as 'locality' - the concept of if I want to move an object I must apply a force to it through some medium like a stick or by throwing a stone at it. I could use a ray gun but that would involve some disturbance of elements in the air between the ray gun and the object in order to create the effect. Even hidden things like listening to the radio is in fact electromagnetic waves propagated via the air. There has to be a connection of some sort to create the chain of actions and reactions to cause the moving of my object or listening to a radio. Even if this is over a great distance, as gravity can act weakly, it still is something causing something to do something. We have to be somehow local. So if we are to get a full picture of the physical world it should be the sum of its constituents' stories.

Oh no - here comes 'Entanglement' and it trashes all we think we know.

So imagine then the concept of 'nonlocality'. This is the idea that two particles may behave synchronously with no intermediary over any distance. This is the idea of two particles being a known and precise distance apart yet neither particle has a definite position. In fact, Nils Bohr if he were still alive, would contend that we do not know the facts about such particles because there aren't any facts to know - in fact.

To ask the position of a single particle would be as meaningless as asking the marital status of the number five.

Such particles that are related in this way are quantum mechanically 'entangled'. The two particles may spin in exactly the opposite way yet we cannot determine which way either is spinning for definite. Entanglement may connect particles irrespective of where they are, what they are and what forces that may be exerted on one another. It could be that one is an electron, the other a neutron and one is located in some other galaxy.

In essence, this new field of thought from quantum computation and cryptography, is the idea of something affecting something else without touching it or any series of entities in between. I could punch your face as you read this without actually affecting a single thing between us. Entanglement has profound consequences, one of which is that poor old Einstein has once again had his quaint theory of Special Relativity broken - then, he did write it back in the 1920's so he could not have known all things at that time, fair play. But he did.

Einstein had thought of it but merely dismissed it as some kind of mathematical anomaly and so was rarely, if ever it at all, observed in reality. He, with some colleagues, produced a paper which stated that no genuine physical nonlocality exists in this world and that the experimental predictions of quantum mechanics are correct. Nils Bohr had contended the results of the paper and particularly had issue with Einstein and his colleagues' use of the word 'reality' and its definition. Whilst Bohr agreed we do not observe nonlocality, he argued its potential existence was a good reason why we should revise our view of what reality is.

He argued fiercely that we should not use algorithms and equations to predict what is a realistic picture of the world we see from moment to moment, but he argued that this shady, dark view of the world we see is in fact as good as it gets.

It was a philosophical answer to a very scientific question and Douglas Adams' vast computer had produced the answer of 42 as the response to the question 'what is the meaning of life?' Bohr had abandoned such thoughts and said forget it, this is what we see so be happy with it.
And science basically drew a line under it.

John Bell And Reality

30 years ago, scientist John Bell, produced a mathematical proof of nonlocality but some have argued that this proof has some get out clauses. Bell argued from the basis that quantum experiments have unique outcomes. But the 'many-world' protagonists assert that quantum measurements in fact split the world into an infinite number of branches representing the possible outcomes - and all different outcomes actually do occur. Frankly, this does not explain why we observe so many predictable things like the door behind me or my coffee cup - surely by now I will have gone down another quantum reality track and ended up in a world of beautiful women where I am the only man? Maybe it doesn't work like that.

Many believe that Bell started by assuming that the world conforms to local realism and he therefore proved that either locality or realism is violated. Thus the world could be local if it violates realism.

But this seems to be a loop of logic that just goes round and round in ever decreasing circles before disappearing up one's own backside.

Subtlety Is Out, Reality Is Where It's At

This quote is from a friend of mine, Duncan Read, many moons ago while sitting in a bar in Spain. Quite what he meant, we had no idea at the time, nor perhaps had he and things have not changed much since. What he was clamouring for, as many do, is some explanation of what reality is and why we observe the things we do. Why does time flow one way? Why does entropy always increase? These are not the questions he was asking but our manifestations of these phenomena actually shape the world we observe and how we observe it.

My wife and Duncan have a point - reality is indeed where it's at. The world goes on irrespective of what we observe and long after we are dead as well as long before we were born; reality existed and continues like the flow of time. Quantum Theory and the concepts of nonlocality, I think are fundamental to the make up of our world, our universe. Things go on which are far beyond our comprehension and our obsession with everything being observed by us and therefore being our only view of the world seems to place constraints and limitations on our thinking and so our views.

Locality is the theory of all that we see about us is only real as we act upon it by observing it. Einstein's theory talks of relativity, we all observe things essentially relative to ourselves. Locality is therefore reality by our own interaction with the world around us. This does not explain the fact that the door will always be in the same place no matter if I am observing it or not, as will the coffee cup. It will be in the same place even if an alien in Alpha Zog IV cannot, or has not, observed it either.

Reality exists irrespective of the observer and therefore locality cannot be the only possible explanation of what we see in this world.

Our imagination is perhaps the key to unlocking concepts far beyond me.

1 comment:

BackwardPoint said...

Hi Nigel, isn't the idea of nonlocality quite elegantly dealt with by string theory? I can't remember the details as my university days fade from memory with every passing day. I also think there is a rather promising new theory which has something to do with triangles - I'll try and dig out the article...

Michael