{"id":12227,"date":"2022-05-04T00:00:00","date_gmt":"2022-05-03T22:00:00","guid":{"rendered":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/?post_type=purple_issue&p=12227"},"modified":"2022-05-11T11:09:22","modified_gmt":"2022-05-11T09:09:22","slug":"a-whole-new-whorl","status":"publish","type":"post","link":"https:\/\/c01.purpledshub.com\/bbcsciencefocus\/2022\/05\/04\/a-whole-new-whorl\/","title":{"rendered":"A whole new whorl"},"content":{"rendered":"\n

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A WHOLE NEW <\/span>WHORL<\/span><\/h2>\n\n\n\n

MANY OF US HAVE SEEN SEASHELLS ON THE BEACH AND MARVELLED AT THEIR COLOURS, AND PATTERNS OF CURVES AND RIDGES. BUT SEASHELLS ARE FAR MORE THAN JUST PRETTY OBJECTS, AND THEIR INTRICATE STRUCTURES CAN HELP US LEARN MORE ABOUT THE INHABITANTS THAT ONCE DWELLED INSIDE THEM<\/span><\/strong><\/p>\n\n\n\n

WORDS: DR HELEN SCALES<\/strong><\/span><\/p>\n\n\n\n

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PURPLE STAIN<\/span><\/h4>\n\n\n\n
ABALONE<\/span><\/h5>\n\n\n\n

Abalone shells are gleaming and shiny on the inside, thanks to layers of nacre, the same stuff that pearls are made of. Nacre is 95 per cent calcium carbonate \u2013 chalk, essentially \u2013 but try dropping an abalone shell and you\u2019ll see it\u2019s virtually shatterproof. This super strength comes down to nacre\u2019s microscopic structure of diamond-shaped crystals stacked like bricks, with layers of chitin in between. Chitin is the same tough protein that makes insect exoskeletons and shrimp shells. If the outside of the shell gets damaged, the inner nacre layer stops cracks from growing bigger. The nacreous crystals slide over one another and the chitin stretches, dampening the energy of a spreading crack and halting it in its tracks.<\/span><\/p>\n\n\n\n

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Scientists from Canada\u2019s McGill University recently mimicked the structure of nacre using glass flakes and acrylic to produce a transparent composite that\u2019s three times stronger than normal glass and five times more resistant to fractures. Easy and cheap to make, this could be the ideal material for the next generation of smartphone screens that won\u2019t smash no matter how hard they\u2019re dropped, all inspired by nature\u2019s nacre.<\/span><\/p>\n\n\n\n

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BUOYANCY AID<\/span><\/h4>\n\n\n\n
CHAMBERED NAUTILUS<\/span><\/h5>\n\n\n\n

This is the view inside the shell of a chambered nautilus that\u2019s been sliced into two halves. When the nautilus was alive, each of those chambers was filled with gas, which turned the shell into a buoyancy device. The floaty shell helps a nautilus to hover in the water column and therefore save energy.<\/span><\/p>\n\n\n\n

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Of all the cephalopods \u2013 the group of molluscs including octopuses and squid \u2013 it\u2019s only chambered nautiluses that live inside shells. All the others either abandoned their shells entirely or have modified internal shells, like the cuttlebones of cuttlefish that often wash up on beaches.<\/span><\/p>\n\n\n\n

The elegant whorl inside the shell is what mathematicians call a \u2018logarithmic spiral\u2019. Tracing the line from the midpoint outwards, the spiral expands by a constant amount for each 360\u00b0 spin. It\u2019s made by the nautilus throughout its life as it grows bigger, adding more calcium carbonate to the shell\u2019s outer edge. Logarithmic spirals pop up throughout nature, from the seeds on a sunflower to the arms of a galaxy.<\/span><\/p>\n\n\n\n