Petals and particles

Popular (and unpopular) science frequently relies on the use of metaphor in explanations. Metaphors have occasionally even been responsible for scientific discovery; in 1865 August Kekulé dreamt of a snake biting its own tale. He said this was the inspiration to his figuring out the structure of benzene.

The description of the expanding universe as a balloon being pumped up is ubiquitous in cosmology. But this ubiquity can be a problem; too often the metaphor ‘becomes’ the thing you are describing, and nothing is ever exactly the same as anything else. Any description of reality is limited in its accuracy by its reliance on words.

In quantum physics, light can either be thought of as particles or as waves, depending on how you observe it (the same is true of sub-atomic particles, i.e. they can equally well be thought of as sub-atomic waves). Thomas Young’s famous experiment at the beginning of the nineteenth century showed that light makes diffraction patterns when travelling through parallel slits. Diffraction is a property of waves. Conversely, Einstein’s early work showed that the photo-electric effect, in which light strikes a metal surface and liberates electrons, can only be explained if you treat light as a particle. So, clearly, our everyday concepts of ‘particles’ or ‘waves’, which are complementary, are inadequate to explain the true nature of light.

But physicists never let mere paradoxes stop them and this drawback was elevated to ‘the complementarity principle’ by Niels Bohr. He stated that something can be both one thing and its opposite, and that it didn’t matter, because physics can only be concerned with what you observe and not with the true underlying nature of reality. ‘There is nothing outside the experiment.’ (A nice counterpoint to Derrida’s ‘there is nothing outside the text’.) Different experiments show different aspects of reality, but there is no reason to suppose that you can have an experiment which shows all aspects.

The complementarity principle is an interesting riposte to those people who accuse scientists of having one-track minds, unable to see the subtleties inherent in reality. Keats claimed that Newton ‘unweaved the rainbow’ by explaining the physics behind this phenomenon. On the contrary, Newton deepens our perception of the rainbow through his description of light being diffracted by water droplets in the atmosphere.

Ezra Pound’s famous poem ‘In a Station of the Metro’ runs (in its entirety)
‘The apparition of these faces in the crowd;
Petals on a wet, black bough.’

The two images in this poem are so finely balanced that they mirror each other and it is never clear which is the metaphor and which is the reality. Dangerous for science, but prescient in its complementarity. Pound wrote this in 1913, when Bohr was developing his model of the atom.

Which comes first, style or content?

When I write, I worry about both style and content. I want my sentences to be pleasing aesthetically, but also meaningful.

Perhaps I am displaying my scientific roots by always making aesthetics play handmaiden to the characters and the story - the actual 'facts'. And yet – there is a powerful appreciation of aesthetics running through science, as well as maths. There is always the search for ‘an elegant solution’ to the problem in hand. What is meant by elegance here? I think it’s something to do with simplicity and conciseness, and perhaps novelty.

Aesthetically pleasing science makes apparently complex phenomena simple. Why are there so many different species of finches on the Galapagos – all with different habits? Darwin said that they’ve each evolved to fit a precise environmental niche.

It can relate disparate phenomena by revealing the underlying laws. Newton showed the movements of orbiting planets and falling apples can be explained by a universal force called gravity. Maxwell’s equations brought together all the different observations of changing electric and magnetic fields to show that each is a transformation of the other.

It leads to new areas and gives big bang for your bucks. (It’s no good having a good-looking theory if you can’t do much with it.) Einstein’s concept of light as a particle led to a whole new understanding of the structure of the atom.

It can decide between different ideas. Penzias and Wilson’s discovery that the thermal noise they detected at Bell laboratory was the remnant of an early stage in the evolution of the universe (and not pigeon droppings which was their initial assumption), ruled out the steady state model in favour of the big bang one.

It may even be visually pleasing in some way. Crick and Watson’s analysis of DNA revealing its double helix structure, has created an image now embedded in our collective consciousness.

Behind many of these aspects of aesthetics lies simplicity. Simplicity is a powerful driver in creating science. Occam’s razor says that we should not ‘multiply entities’ unnecessarily; so if you’re fitting a mathematical model to your data, you choose the one with the fewest parameters. And a new scientific theory should have as few arbitrary factors as possible. But in judging competing scientific theories, it’s not always obvious which one best obeys Occam’s razor.

For example, the Copenhagen interpretation of quantum mechanics says that a wave function is attached to each possible outcome of an event. Once a particular outcome is measured, the wave functions corresponding to all the other outcomes collapse. Until that happens everything related to the event is in a sort of probability ‘fuzz’ (for example, the cat in the box is both dead and alive, until you open the box and discover its fate). But what exactly is a measurement? By definition, it has to be a non-quantum event, otherwise you just get more fuzz. So, the interpretation fundamentally limits what quantum mechanics can describe, by saying there always needs to be something outside its description!

The Many Worlds Interpretation avoids this in-built limitation, but only at the expense of having to start up a new universe each time an event happens. This seems to be multiplying entities to an extreme degree; and quite wasteful.

So which is the ‘simpler’ explanation of quantum reality? They clearly both have their problems, and not ones which can easily be resolved by examining their aesthetics.