Tombstone of the Starry Sky

In 2147 AD, humans have set foot on Mars and found traces of primitive life under the ice of Europa, but they hit an invisible wall at the edge of the solar system. Not a wall in the physical sense. It's about information. After operating for forty years, the "Deep Space Network"—an array composed of 3,600 detectors designed to monitor electromagnetic signals in the universe—finally captured an abnormal signal from the direction of Proxima Centauri, four light-years away. That's not the regular ticking of a pulsar, or the furious roar of a black hole's accretion disk. It is a code, a code with a clear mathematical structure that can be interpreted.