MIT scientists have come up with a theory to predict exactly how much light is transmitted through a material, given its thickness and degree of stretch. Using this theory, they accurately predicted the changing transparency of a rubber-like polymer structure as it was stretched like a spring and inflated like a balloon. The researchers’ experimental polymer structure and their predictive understanding of it may be useful in the design of cheaper materials for smart windows - surfaces that automatically adjust the amount of incoming light. The researchers envision covering window surfaces with several layers of the polymer structure. He says designers could use the group’s equation to determine the amount of force to apply to a polymer layer to effectively tune the amount of incoming light.