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The sixty years between Blue Space's broadcast and the photoid that kills Trisolaris — the era when humanity learns it has, by surviving, killed itself.
The Broadcast Era is the era of borrowed time. Once Blue Space and Gravity broadcast Trisolaris's coordinates, both civilizations are condemned. The Trisolarans evacuate Earth and try to flee in their second fleet. Humanity, freed of immediate occupation but staring at a death sentence on the order of a few centuries, frantically pursues two strategies: the Bunker Plan and lightspeed escape. Yun Tianming's call decodes both. The era ends when Trisolaris is destroyed by an unrelated dark-forest hunter, leaving humanity alone in the dark — and waiting.
An era of frantic motion: lightspeed-research labs reopened, the Bunker Project authorized, the population recovering from the resettlement, the Trisolarans withdrawing from Earth without explanation. Yun Tianming's call comes mid-era; the fairy tales reshape physics and policy in the years after. The Trisolaran sun's light arrives in the late Broadcast Era as a faint red shift — humans observe their enemy's death in real time.