Why does nature create patterns? A physicist explains the molecular-level processes behind crystals, stripes and basalt columns
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Why does nature always create a pattern? – Saloni G., age 16, Alwar, Rajasthan, India
The reason patterns often appear in nature is simple: The same basic physical or chemical processes occur in many patterned substances and organisms as they form. Whether in plants and animals or rocks, foams and ice crystals, the intricate patterns that happen in nature come down to what’s happening at the level of atoms and molecules.
A pattern in nature is any regularly repeated arrangement of shapes or colors. Some of the most striking examples include the hexagonal arrays of rocks at Giant’s Causeway in the United Kingdom, the beautiful fractal arrangements of florets on a Romanesco broccoli and the colorful stripes and spots on tropical fish.
Patterns like these begin to form at a small scale when materials undergo processes like drying, freezing, wrinkling, diffusing and reacting. Those changes then give rise to complex patterns at a larger scale that people can see.
Patterns in ice and rock
Imagine delicate frozen crystals on a windowpane during a cold day. What creates that pattern?
When water freezes, its molecules begin clustering together. Water molecules have a particular bent shape that causes them to stack into clusters shaped like hexagons as they freeze.
As the cluster grows, many outside factors, including humidity and temperature, begin to affect its overall shape. If the water is freezing on a windowpane, for example, small and random imperfections on the glass surface redirect the stacking and create the larger pattern.
This same process of stacking molecules is responsible for the striking variety of snowflake shapes.
What about the amazing patterns of the basalt columns at Giant’s Causeway? These formed 50 million to 60 million years ago, as lava – hot rocky fluid from deep underground – rose to the Earth’s surface and began to lose heat. The cooling caused the top layer of basalt to contract. The deeper, hot layers resisted this pulling, creating cracks in the top layer.
As the lava cooled, the cracks spread deeper and deeper into the rock. The particular molecular qualities of basalt, as well as the basic physics of how materials fracture apart – laws of physics universal to all substances on Earth – caused the cracks to meet up with one another at certain angles to create hexagons, much like the stacking water molecules.
Eventually, the cooling basalt broke into the hexagon-shaped…