Friday, 27 November 2009

More (un)certainty, or do I mean something else?

Following on from my last blog, the event on poetry and astronomy at Royal Observatory in Greenwich went very well. Jocelyn Bell Burnell gave a great talk and invited members of the audience to read aloud the poems on astronomy she had selected. These readings were fantastic; and I think helped the discussion with the audience to flow more freely.

At one point during this discussion I said that perhaps scientists aim to be more ‘certain’ in their writings than poets, and aim to get a more definite response in their readers. A lady in the audience rightly reminded me that since 1927 physicists have been wrestling with uncertainty, and in particular the uncertainty principle and its implications for reality.

One of the problems with trying to understand the uncertainty principle is the word ‘uncertainty’. It’s a translation from the original German phrase used by Heisenberg when he formulated the physics. But he actually used several German words. It’s a shame that the English equivalent has invariably been ‘uncertainty’ and perhaps we accord that specific word too much weight.

What Heisenberg actually deduced, and what he summarised in this principle, is that not every physical property of a system exists with infinite precision at every point in time. Furthermore, these physical properties are connected; so that the more precise the position of a particle is, the less precise is its momentum.

You often see this explained as due to the practical problems of measurement; if you measure the position of a particle, you use light photons to do this and they will hit the particle, inevitably leading to a change in its momentum. This way of thinking implies that there is an underlying physical certainty, but that we just can’t measure it. It leads to approximately the right mathematical formulation of the principle, but it’s wrong-headed. It’s a metaphor that’s been stretched too far.

The uncertainty principle is telling us something much more fundamental about reality than that. It’s telling us that reality itself has an inexactness; there is nothing beyond what we can measure. There is no underlying, more precise, reality. This can perhaps be better expressed in some of the other words that Heisenberg used, for example; ‘indeterminability’.

So, some of the misunderstandings about this principle derive from the English word ‘uncertainty’, and the fact that this translation of Heisenberg’s original words has become rather too crystallised, perhaps even too ‘certain’. It’s taken on a shorthand meaning of a general vagueness, and even a general limit to scientists’ ambitions about their work.

An additional layer of uncertainty has been added by the requirement to translate Heisenberg’s words from German, and this influences the way we’re able to discuss the subject in English. (It’s obviously more precise to go to the maths, but there was an analogous ‘translation’ problem in the 1920s, when both Heisenberg and Schrödinger came up with very different mathematical formulations for quantum physics. It took some time before they realised that one formulation could be translated into another.)
Is it easier to talk about this principle in the original German? Answers on a postcard, please.

Finally, there will be more actual (as opposed to online) discussions about poetry and science; we’re having a ‘social sessions’ event on 13 January in Edinburgh at the Scottish Poetry Library. Do come!

1 comment:

  1. I am often torn between the scientist and artist in me.