99 robotic mirrors continuously move throughout the day to follow the sun like sunflowers. These mirrors, arrayed across two 5 meter tall towers and one 15 meter long track, each emit a beam of sunlight into a cloud of water mist. The beams are computationally aligned so that together they draw a bright circle in the air. Dependent entirely on the presence of the sun for its completion, the work explores the possibilities and limitations of technology to capture what is out of reach, to harness nature and bring the sun down to earth. Collaborating with the natural fluctuations in the climate, Halo appears only for moments when the wind, sun, water, and technology coincide, creating a form which exists between the material and immaterial.