Nonprofit Mad. Sq. Art is on a hot streak. It follows up its summer installation of Charles Long’s Pet Sounds, brightly colored blobs that emitted noises when touched, with a pair of illuminated geodesic spheres, one inside the other. The form is based on Carbon 60 molecules, named after inventor and futurist Buckminster Fuller, who popularized geodesic domes as habitable structures. The monumental sculpture, 20 feet in diameter, is composed of multicolored LED tubes that put on a changing light show dictated by computer software. Lounge in one of the surrounding wooden zero-gravity chairs and take in the hypnotic spectacle.