Read Online Spirals in Time: The Secret Life and Curious Afterlife of Seashells by Helen Scales - Free Book Online
Authors: Helen Scales
Tags: science, History, Non-Fiction, Nature, Life Sciences, Social History, Marine Biology, Seashells
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The enormous mainframe IBM 7090 was a state-of-the-art scientific computer that was intended for the design of missiles, nuclear reactors and supersonic aircraft, but for a short time Raup channelled its power into making shells. He plugged in a few combinations of values for T, W and D and programmed the computer to draw the corresponding shells on a Calcomp x-y plotter. The computer’s output was a series of dots outlining several shells in cross-section, which were then interpreted into three dimensions by an artist. These drawings appeared in Raup ’s 1962 paper in the journal Science . To make more of these scatter plots would have taken way too long and been too expensive on computer time. Raup knew that the available technology was limiting his work.
His next step was to team up with an electrical engineer, Arnold Michelson, and together they tried a more affordable set-up, the PACE TR-10 analogue computer (which despite its gargantuan size was one of the earliest desktop computers,although presumably only for a rather large desk). They plugged in a wide range of values for T, D and W from Raup’s shell model, hooked the computer up to an oscilloscope that traced the shapes of shells as fast-moving circles across the screen, then stood back and watched.
Unfolding before their eyes was a stunning collection of shells that looked like thousands of tiny X-rays. Among the PACE TR-10 output were examples of just about every type of shell, from the nautilus through to all sorts of coiled snails and even flattened clams and scallops. Their findings were so stunning that one of their virtual shells made it to the front cover of Science . Raup and Michelson had shown that from a simple set of rules emerges the great complexity of real shells. And their imaginary shell collection contained plenty more besides. Once they had traced out the shapes of all these shells, Raup turned his attention to the next big question: which of these shells can be seen in the real world?
Back inside the virtual museum of glass seashells, we can now understand how things are arranged: along one wall the thin, wormy shells become chubbier, as values for D shift from zero to one; in another direction the shells become gradually taller, as the values for T start at zero and run along to four; and from ceiling to floor, shells have progressively higher W values, from one to a million, and snails morph into clams. The glass shells are versions of the output from Raup and Michelson’s PACE TR-10 computer program of all possible shells.
Now something changes in our museum. The main lights are dimmed and individual glass shells, here and there, begin to glow (funnily enough, like light bulbs). These are the models that closely resemble real shells, living or extinct. And as parts of the room light up, something becomes obvious: large regions of the museum remain in darkness.
I illuminated the real species among our glass shell models and Raup did a similar thing on paper. He plotted a graphwith three axes (for D, T and W) and shaded in areas where real mollusc shells can be found, as well as the brachiopods, which are only distantly related to molluscs but even so make similar shells. Drawing in the boundaries of reality onto his imaginary shell museum, Raup immediately saw that only a small fraction of his theoretical shells have ever actually evolved. Substantial regions seem to be out of bounds. He theorised that some of the empty space in his museum was filled with ‘bad’ shells that, in reality, don’t work. Maybe they would be too heavy or too weak, or would leave their inhabitants in some way vulnerable to attack? There is an empty region filled with shells that suffer from what Raup referred to as the ‘problem of bivalveness’. Clams, mussels and scallops would be permanently clamped shut if their gentle whorls overlapped (the only option for opening up would be to build a new hinge on the outside and keep moving it as the mollusc
His next step was to team up with an electrical engineer, Arnold Michelson, and together they tried a more affordable set-up, the PACE TR-10 analogue computer (which despite its gargantuan size was one of the earliest desktop computers,although presumably only for a rather large desk). They plugged in a wide range of values for T, D and W from Raup’s shell model, hooked the computer up to an oscilloscope that traced the shapes of shells as fast-moving circles across the screen, then stood back and watched.
Unfolding before their eyes was a stunning collection of shells that looked like thousands of tiny X-rays. Among the PACE TR-10 output were examples of just about every type of shell, from the nautilus through to all sorts of coiled snails and even flattened clams and scallops. Their findings were so stunning that one of their virtual shells made it to the front cover of Science . Raup and Michelson had shown that from a simple set of rules emerges the great complexity of real shells. And their imaginary shell collection contained plenty more besides. Once they had traced out the shapes of all these shells, Raup turned his attention to the next big question: which of these shells can be seen in the real world?
Back inside the virtual museum of glass seashells, we can now understand how things are arranged: along one wall the thin, wormy shells become chubbier, as values for D shift from zero to one; in another direction the shells become gradually taller, as the values for T start at zero and run along to four; and from ceiling to floor, shells have progressively higher W values, from one to a million, and snails morph into clams. The glass shells are versions of the output from Raup and Michelson’s PACE TR-10 computer program of all possible shells.
Now something changes in our museum. The main lights are dimmed and individual glass shells, here and there, begin to glow (funnily enough, like light bulbs). These are the models that closely resemble real shells, living or extinct. And as parts of the room light up, something becomes obvious: large regions of the museum remain in darkness.
I illuminated the real species among our glass shell models and Raup did a similar thing on paper. He plotted a graphwith three axes (for D, T and W) and shaded in areas where real mollusc shells can be found, as well as the brachiopods, which are only distantly related to molluscs but even so make similar shells. Drawing in the boundaries of reality onto his imaginary shell museum, Raup immediately saw that only a small fraction of his theoretical shells have ever actually evolved. Substantial regions seem to be out of bounds. He theorised that some of the empty space in his museum was filled with ‘bad’ shells that, in reality, don’t work. Maybe they would be too heavy or too weak, or would leave their inhabitants in some way vulnerable to attack? There is an empty region filled with shells that suffer from what Raup referred to as the ‘problem of bivalveness’. Clams, mussels and scallops would be permanently clamped shut if their gentle whorls overlapped (the only option for opening up would be to build a new hinge on the outside and keep moving it as the mollusc
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