text: Townes's last major technological creation was the Infrared Spatial Interferometer with Walt Fitelson, Ed Wishnow and others. The project combined three mobile infrared detectors aligned by lasers that study the same star. If each telescope is 10 meters from the other, it creates an impression of a 30-meter lens. Observations of Betelgeuse, a red giant in the shoulder of the constellation Orion, found that it is increasing and decreasing in size at the rate of 1% per year, 15% over 15 years. ISI produces extremely high angular and spatial resolution. The technology is also playing an important role in the search for extraterrestrial life in collaborations with Dan Werthimer of Search for Extraterrestrial Intelligence (SETI).