The International Space Station is about to pass a remarkable milestone. In November, the giant spacecraft will have been in orbit around our planet for a quarter of a century. For the past 25 years, hundreds of astronauts have made temporary homes there while other visitors have included frogs, worms, shellfish and butterflies: each has been the subject of experiments aimed at uncovering the effects of weightlessness, radiation and other extraterrestrial phenomena on living creatures. In addition, astronauts have carried out studies of dark matter, cosmic rays and Earth’s ozone layers. Yet the days of this 100-metre-long behemoth – which…