"Any sufficiently advanced technology is indistinguishable from magic." -- Arthur C. Clarke.
After the hours and days spent researching many of mankind’s historic events the human race has evolved as a whole new level of consciousness. Seeing what history really was made mankind realize how evil they were and how lucky they were to have survived. With much of histories mysteries explained and certain historic objects and events recreated in VR simulations and on display at museums. Literature, art, and music are once again blooming in society. Further time travel research has been halted and not likely to continue.
35% of the galaxy has been explored by the remaining AI robots and certain powerful humans. Space charts and maps mark where sustainable atmospheres are available for energy consumption. The alien signal never was responded to. So humans expect that non-intelligent sources were behind it or it was an ancient computer signal of help from a now destroyed civilization which the AI astronauts have found evidence to support on nearby planets.
The one question that has not been answered however is, what is death? The death process has been stopped ever since the late 21st century and has almost been forgotten. Remaining individual humans study death and realize that it is the way to travel between parallel dimensions and certain space- time events. Humans are perfecting a way to travel outside of their bodies a new form of transportation called soul travel!
Plastics and waste substances degenerate and disappear from the world entirely!