Location from remembrance-of-earths-past by
Humanity's home — a stable single-star world the Trisolarans coveted for four hundred years, surveilled by sophons for the same span, force-resettled to Australia in the Broadcast Era, and finally flattened to a Van Gogh smear by the dual-vector foil.
Earth is the trilogy's only protagonist that does not get to die offscreen. We watch the planet through the four-hundred-year Crisis, the half-century Deterrence balance, the brief ugly Broadcast Era when Sophon herds the species into Australia, the Bunker Era retreat to the gas giants' shadows, and the final two-dimensionalization. Most of the entities in this codex were born on Earth. Only a handful leave it alive.
From space: blue and white and brown, single moon, single yellow sun. By the late Crisis Era there are bright orbital rings of habitats and elevators visible from the surface. By the Bunker Era the sky over Australia is full of refugee craft and Trisolaran droplet escorts. By the end of Death's End: a flat painting of itself, no thicker than a sheet of paper, drifting.