When light travels through glass, it slows down (the amount it slows is measured by a number called the refractive index).

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Dr Feld also has plans to use beams of different colours, since each colour has a slightly different refractive index in a given material.

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Inside the BEC, the so-called refractive index (which measures the slowing of light) becomes enormous: as high as 100 trillion times greater than that of glass.

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Shining an appropriate light on such a wire from the outside would alter its refractive index (a measure of how fast light travelling inside the wire can move).

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