Spontaneous Quantum Tunnelling

FACT:There is a small but finite chance that here, today, you will suddenly change into a horse. A good physicist will confirm this. The down-side is exactly how improbable this event is: the probability isn't zero, but is so close that for all practical considerations it might as well be. If you've played the National Lottery, you might know that the odds of picking the same six numbers as the draw are approximately thirteen million to one against. Imagine if you had to choose several billion numbers from a near-infinite range: that's the chance we're looking at here! But it is possible. How? According to classical "Newtonian" physics, science holds no "maybes": everything is either possible, or it isn't: black or white; on or off. For most practical purposes this is good enough to be taken as true, but scientists began discovering phenomena at an atomic scale that appeared to break the rules. In radioactivity, a beta particle is a high-energy electron emitted from an atomic nucleus. By classical physics, the attraction of the nucleus is far too high to ever permit the electron to escape, and yet it undeniably happens. However, by applying Quantum Mechanics, it was discovered that there was a small but definite chance that some particles could 'break the rules' and escape. This is called Quantum Tunnelling: the particles give the appearance of cutting through the barriers that ought to stop them behaving this way. Quantum Mechanics is a difficult subject to get a good grasp of. It is anything but intuitive: usually several pages of complex maths are needed to illustrate the simplest of atomic events. Put simply though, the upshot is that nothing -nothing at all- is actually impossible. It can be so improbable that the universe would have to endure for hundreds of times its current age before it occurred even once, but is still possible. Interesting, but not useful. What else can Quantum Mechanics do? Allow me to introduce the philosophical example of Schroedinger's Cat. For reasons unknown, Mr Schrodinger has decreed that his cat is under sentence of death. He puts it in a sealed box with a canister of cyanide, and links the canister to a device which will release it at a random time in the future. It is absolutely impossible to tell when the cyanide will be released. The box is opaque (and for the sake of argument, fitted with life-support so the cat doesn't suffocate in the mean time). The only way the cat's continued existence can be determined is by opening the box to have a look. As long as the box remains sealed, there is a possibility that the cat is alive, and a possibility that the cat is dead. It is, in effect, both dead and alive. Mathematically, it can be shown that the wave-function describing the cat's state of existence is a combination of both possibilities. In other words, it's no illusion: unless we actually check, the cat really is both dead and alive. If we open the box, the wave function will collapse to one possibility or the other. You may be forgiven for thinking this is a load of waffle: the cat surely has a very good idea of whether it is alive or dead: it can't be both at once. Well, no, but the important thing that Einstein and a lot of other very intelligent people discovered was that everyone exists in their own unique universe: we all see a similar world, but in detail our perceptions differ. It has been shown that when nearing the speed of light, objects undergo length contraction. If the USS Enterprise passed you at Warp-point-nine and you measured its length (very quickly of course), you would find it shorter than you would if it were stationary. This is no illusion: it really has shortened. But to the crew, you are the one that has shortened. You can't both be right, can you? Well, yes, you can. By the same token, in the cat's universe, the cat has either died or survived. In your universe, until you open the box, it is both! It defies common sense, because in everyday life we simply don't see things behaving this way, but they do happen all around us. So where does this leave us? Okay: now we set up the experiment this way: our intrepid wouldbe equine enters a sealed chamber. It is closed. Instantly, his universe is seperated from ours: unless we open the chamber again, we cannot tell anything about him. Now, remember the small but definite chance that he might change into a horse spontaneously? As long as we can't see him, that possibility exists! He is both human and horse! Of course, by the same token, he could be anything else, too. Probability is overwhelmingly in favour of him staying human, but he could spontaneously become a horse. All we need then, is the equivalent of the Hitch-Hiker's Guide Improbability Drive: a way to pick and choose amongst the possibilities of Quantum Mechanics and ensure that when the chamber is opened, our "equinaut"'s wave function collapses to the result we select, in stead of blind chance ruling. Whether the universe will actually allow such a device to be constructed and how it might be done is way beyond us at the moment. The old view was that we could eventually know everything about the universe we inhabit. The new view is that there are things that are inherantly unknowable. But it's fun to speculate!

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