Tuesday, 20 October 2015

Order From Chaos, Even In The Rocks Of Ages

Why Hexagonal Basalt Columns? | Physical Review Letters

I've never been to the Giant's Causeway in Northern Ireland, nor to Fingal's Cave on Staffa in the Outer Hebrides but they're on my bucket list. Maybe one day when I'm rich from <irony>all my book sales </irony>. What I have seen though is the Great Whin Sill alongside Hadrian's Wall at Houseteads in Cumbria.

They're not so obvious there but parts of the Whin Sill are composed of hexagonal stacks like the Giant's Causeway. At first glance it would be easy to assume that they are man-made or even superman-made (hence the legend of Benandonner and Fionn mac Cumhaill (Finn MacCool)), those remnants of the pre-Christian Irish pantheon.

You might even assume they must be some sort of massive crystalline structure. Creationists of course will insist their particular magic friend must have made them, and one of the arguments they will try to get away with is the assertion that you can't get order from chaos.

However, as this paper published in Physical Review Letters a few days ago explains, the hexagonal shape is just that - order which has emerged from chaos by nothing other than the operation of natural process. No magic involved, surprise, surprise!

Abstract
Basalt columns with their preferably hexagonal cross sections are a fascinating example of pattern formation by crack propagation. Junctions of three propagating crack faces rearrange such that the initial right angles between them tend to approach 120°, which enables the cracks to form a pattern of regular hexagons. To promote understanding of the path on which the ideal configuration can be reached, two periodically repeatable models are presented here involving linear elastic fracture mechanics and applying the principle of maximum energy release rate. They describe the evolution of the crack pattern as a transition from rectangular start configuration to the hexagonal pattern. This is done analytically and by means of three-dimensional finite element simulation. The latter technique reproduces the curved crack path involved in this transition.*

Why Hexagonal Basalt Columns?
Martin Hofmann, Robert Anderssohn, Hans-Achim Bahr, Hans-Jürgen Weiß, and Jens Nellesen
Phys. Rev. Lett. 115, 154301 – Published 7 October 2015
DOI: 10.1103/PhysRevLett.115.154301

*© 2015 American Physical Society. Reprinted with permission under licence #3732710987391

What the authors have worked out is how the pattern of cracks which form on the surface of the cooling volcanic basalt due to the random stresses of shrinkage while the body of the basalt is still molten, initially form at right angles but, as these propagate down into the cooling body.

Sid Perkins, writing in Science, explains:

They found that as the material at the surface cooled, it shrank more quickly than the underlying lava, which was still warm. That shrinkage led to a random pattern of cracks that typically intersected at 90° angles. But as the material cooled and shrank further and cracks grew downward into the solidifying slab, small cracks began to consolidate into large ones and the angles between them gradually shifted toward 120°—the angle at which the most energy is released...


There we go creationists! Science has found even more evidence that one of your cherished mantras is untrue. You can and do get order from chaos in geology no less than in cosmology and biology as well as the mundane order in crystals that we see in snowflakes. In fact, order from the chaos of superstrings and electromagnetic fields is the reason for particles, atoms and molecules.

So, how many of you will be changing your opinions now you know your opinions are based on falsehoods? How many of you will be questioning why your pseudoscientists tell you things which are known to be lies?

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