Sphere Spatio-Temporelle BS 7523 belongs to a series of two-dimensional optical geometric works created in Paris starting in 1973. In this piece, Enrique Careaga interlaces the relationship between light and movement with that of time and space through the juxtaposition of geometric shapes—mainly spheres, lines, squares, or two-dimensional structures—on a completely black surface. Each work presents these shapes in a range of color that varies in tone to create movement and volume depending on the light. The colors are usually green, blue, yellow, bright pink, or orange, colors that vibrate with light in certain shades. Sphere Spatio-Temporelle BS 7523 consists of three green spheres suspended on a black background. Each of them is comprised of a group of green bands. This group has a lighter center that darkens gradually and evenly on both sides, until disappearing into the density of the background. At the center of each sphere is an oval of dark bands, which creates another range of green that, in turn, creates the illusion of three different volumes. As the two larger spheres are juxtaposed, a three-dimensional illusion is created, where the biggest sphere seems to be the most protruding closer to the viewer. The second largest sphere is in the middle, and the smallest further in, or further away. At the bottom of the canvas there is a set of steps in dark shades of green that create the illusion of depth. This piece was shown at the Enrique Careaga of Paraguay exhibition organized by the OAS in 1975 and it was acquired for the permanent collection that same year. Born in Asunción, Paraguay, Enrique Careaga studied architecture at the Universidad Nacional de Asunción and art at the Escuela de Bellas Artes Lucinda Moscarda in the same city. In 1964 he created the group Los Novísimos, along with Paraguayan artists Ángel Yegros, José Antonio Pratt Mayans, and William Riquelme. It was because of his participation in this group that Careaga broke into the Paraguayan art scene in the 1960s. During this decade, and as soon as he had finished his studies, he experimented with several styles. He quickly developed a strong interest in geometry, which he would continue to explore for the rest of his career. At first he focused on constructivism, but he ended up moving into optical art. In 1966 he took part in the creation of the Museo de Arte Moderno de Asunción. That same year, he traveled to Europe on a scholarship from the French government to study with Victor Vasarely. He remained in France until 1978, where he fully dedicated himself to kinetic and optical art at the School of Paris. He thus became part of the second generation of Latin American geometric artists. In 1973 he began a series that explored the relationship between space and time, as well as the connection between light and movement. In 2003 he reappraised the work he had done in Paris and, based on that, he began to seek greater participation from the viewer through a play on light and movement using motors. He participated in the São Paulo Biennial between 1964 and 1969, as well as the Córdoba Biennial in Argentina in 1966 and the Paris Biennial in 1969. In 1974 he showed in the Agam, Careaga, Rivers, Riley, Le Parc, Vasarely, Soto exhibition at the Stanford Museum. He exhibited at the OAS in 1975 and at the Lillian Heidenberg Gallery in New York in 1976. These are just some of his most renowned exhibitions, as he showed his work actively both nationally and internationally throughout his career. In 2005 el Museo del Barro organized the retrospective El retorno.