This week NASA is celebrating a quarter century of discoveries from one of the most revolutionary scientific instruments of all time, the Hubble Space Telescope. Launched into orbit aboard the Space Shuttle Discovery on April 25, 1990, the Hubble changed our understanding of the age of the universe, the evolution of galaxies and the expansion of space itself. Along the way it has had the equivalent of knee and hip replacement surgery: Five times, astronauts on the space shuttle paid a visit to swap out old batteries and install new instruments. Hubble’s fate, however, is uncertain. The Hubble was designed to be serviced by the space shuttle, but the space shuttle fleet was retired in 2011, and the Hubble hasn’t had a repair job since 2009. At some point, under the laws of entropy that dominate the cosmos, the Hubble will begin to deteriorate.