The difference between quantum mechanics and love

What makes you angry? Sometimes it's so easy to see: someone jumps the queue at the bus stop and you end up standing all the way, usually with some poor, frail old lady, who is also forced to stand because of someone's selfishness; someone meanders down the platform at a snail's pace so you can't 'overtake' and you have to keep 'chopping' your stride to avoid running into them; someone barges past you in the supermarket and grabs the last packet of pappadelle. But sometimes, it's all a mystery.

Strange, I have a weird sense of deja vu about that last paragraph.

I got invited on to someone's blog last week, ostensibly because I have an interest in quantum mechanics. They have a theory which turns out to be 'infinitely expanding atoms' creating spacetime as they go. Now I raised a few 'objections' to potential issues here and after getting 'non replies' and references to Newton and Einstein decided I was not going to waste my time trying to argue the toss with someone who was going to 'lower the net' for their every return. (Thanks to Dan D for that one. Wonderful analogy he uses when discussing 'conversations' with creationists. A tennis match. Your serve is that rational, well substantiated argument that your opponent insists you serve, so you do, but lo and behold as soon as they swing, down comes the net and what is returned is neither rational nor well substantiated. Well, two can play that game! But just as you're about to make your backhand cross court pass, up comes the net again! No wonder those games never finish!)

Anyway, I really had to stop myself from leaving a less than polite Parthian shot. But more to the point, I couldn't understand why I was so angry; you read stuff like that all the time. Part of it at least, I think, is that it saddens me to think that people who usually get no further than 'What the bleep do I know?' but think they would like to know more about quantum mechanics might actually get sucked in by such unsubstantiated and unscientific twaddle and end up thinking they know what the science is about. So to deflect the anger, I put the net back up and had a think :)

It wasn't a long sustained think, I'm not Descartes; more a 'punctuated equilibrium' think. Long periods of statis punctuated by short bursts of evolutionary vigour. The stasis being provided by Dick Feynman's description of the covered mirror and diffraction grating experiment which I had gone to check on because it formed part of my musings. I wanted to verify that I had remembered it correctly. (I had:) However, as a result of Dick's guiding hand and soothing, but self mocking, tone, a light bulb switched on and I realised what it is that's annoying about any discussion over quantum mechanics which doesn't end up in frantic equation scribbling on beer mats. People don't get how 'wrong' it is!

Just about any scientific theory you'll come across has as a very basic, but tacit, assumption: there is an objective reality out there which you can measure, observe, speculate on and discuss in verbal terms because everyone shares that same reality to a very large degree and they will also share, to a large degree, although not completely, language which assigns common values to that reality. If you show a picture of a German Shepherd dog to a Frenchman and say: "Un chien?" The chances are he'll agree with you. A dog= un chien. The mappings are usually not as simple as that but you get my drift.

However you can't do that with quantum mechanics! I hear hoots of disagreement! "What about 'A brief history of time'?" you cry. "'The emperor's new mind'?" "Schroedinger's cat?" And therein lies the rub. Quantum mechanics is so keen to have itself understood that it forgets to tell you that it is all about number crunching not about words, even, really, about ideas. At root, it is a recipe book. Follow the instructions, feed in the ingredients (more numbers) and out pops an answer. Go and do an experiment and see if you get the same answer. If you do, move on to the next problemette. This is what physicists know in the bottom of their hearts but are too coy to say, for fear of alienating people. Only the numbers and the symbols count! :)

You see, according to quantum theory, the world, the galaxy, the universe, you, me, they're not composed of protons, mesons, quarks, photons or any other 'ons' you can think of. The universe is simply composed of probability amplitudes. One giant 'what might be', not one giant 'what is'. This should be, as it was to Einstein, deeply distressing to anyone. No wonder we all hide, even the physicists. But there isn't anything we can do about it. At that level, that's how it is. Somehow from all those 'just probabilities' comes what we experience.

Now there is no doubt in my mind that quantum physicists think pretty much like you or I think. I am quite sure that when Murray Gell Mann first started thinking about the scattering experiments that seemed to show that the proton wasn't just this singular object and actually seemed to have 'hard bits' and 'not hard bits' he did not immedaitely rush to the blackboard. I am sure that he probably thought that it could be a bit like a few ball bearings tightly packed in some kind of soft, spherical condom, but, and this is my point, he did, eventually, go to the blackboard. He did start frantically scribbling equations. No-one gets a Nobel prize for Physics for a quaint analogy. Quantum Chromodynamics stands or falls on the equations and their predictive qualities not on the analogy.

It took me a long time to realise what was fundamentally unsatisfying about commentaries/books, often by science journalists, on research in quantum mechanics. It took a physics graduate demonstrating to a bewildered penguin how a 'constant' (the penguin forgets which one but remembers it was quite important and crops up all over the shop) falls quite naturally out of running through a set of equations, it just 'appears', as if by magic. This is quantum mechanics not the analogies for the 'too disinterested to learn the maths' brigade. The last is not an insult, a cheap jibe, the penguin too has little enough time, or aptitude he thinks, to learn what must be learned but the penguin knows it must be learned if one is truly to grasp what the theory says and he therefore adjusts his thinking processes accordingly until a time when there is a spacetime enough to contemplate polynomials. God is in the maths.

A postscript. Quantum Electrodynamics is, perhaps, the supreme predictive quantum mechanical view. The interaction between light and matter. It is predictively accurate to 5 or 6 decimal places, in Feynman's words "... equivalent to measuring the distance between New York and Los Angeles to the thickness of a human hair" and yet it is fundamentally flawed. Feynman himself admitted 'renormalisation' is a trick, a way of removing infinities from equations, but a trick that works! Perhaps that's all we can ever hope for. Tricks, that work!

And finally, as a postscript to a postscript, a little movie clip (just click the play button). What today's blog was going to be about but ended up not being about. Perhaps a later one will revisit it. Those who have read earlier posts will know why this resonates, the rest will have to engage in some reading practice. :) The film should have ended here, but didn't, for which I dock 0.5 points. The director should have had the courage of his scriptwriter's convictions. So it's only 9.5 on a scale of 10 but, in the comfort of the penguin's own cinema, with control over WHEN it ends, it always scores a perfect 10!

Here's looking at you, kid