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Scientists weigh in on whether glass is a 'true solid'

Glass is a solid from the perspective of an everyday-user, of course. But on the gaze of a microscope, it's molecules remain in motion.

By Brooks Hays

BRISTOL, England, Jan. 22 (UPI) -- Is glass a true solid? That's the question researchers at the University of Bristol, in England, and the Kyoto University, in Japan, set out to answer in a recent study.

The more accurate question is: can glass ever become a true solid? If so, how long would it take? And at what temperature? To find out, researchers used a combination of information theory and computer modeling to find out.

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"Information theory provided us with the mathematical tools to detect and quantify the movements of atoms, which turned out to move as if they were in communication with each other," explained study author Karoline Wiesner.

Glass is a solid from the perspective of an everyday user, of course. But under the gaze of a microscope, glass's molecules defy the definition -- its molecules continue to flow, even if only at infinitesimally sluggish pace. In fact, it would take more than ten million years for a pane of glass to move perceivably.

But does the age-old law of motion -- that an object in motion stays in motion -- hold true for glass? Not when chemistry gets in the way.

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According to computer simulations that projected glass's molecular behavior over millions and millions of years, the substance's atoms increasingly organize in geometric patterns over time. In other words, the solid regions of glass's makeup -- collections of atoms that form into an icosahedra, a polyhedron with 20 faces -- keep expanding.

"We found that the size of the solid regions of icosahedra would grow until eventually there would be no more liquid regions and so the glass should be a true solid," said researcher Paddy Royall.

Glass's existential crisis is explored in detail in the latest issue of Nature Communications.

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