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Modern wind turbine blades are engineered as long, tapering airfoils, shaped much like aircraft wings, so that moving air generates lift that rotates the blade around the turbine's hub. Blade length has grown substantially over recent decades, since longer blades sweep a larger area and capture more energy from the same wind speed, though this also increases mechanical stress on the tower and foundation. Engineers address this stress by using lightweight composite materials, such as fiberglass or carbon fiber, rather than heavier metals, and by designing blades with a slight twist along their length so that each section meets the wind at an efficient angle. Turbines are also fitted with sensors that adjust blade pitch in real time, reducing strain during gusts by slightly rotating blades out of the wind's most direct force.