The theme song "Blue Light" from "Year Seven" is set in the seventh year of the Broadcast Era, when Blue Space and Gravity jointly issued the gravitational wave broadcast that destroyed the Trisolaran world. One might ask: Why would the Trisolarans spare us? But they didn't. We destroyed their homeworld, yet they did not let us go. Four billion two million people remained trapped in Australia. In those seven years, the population was reduced to just thirty million. But this is not just a story