Two days before the false alarm, Observation Unit #1 operates from the old Ringier-Fitzroy Station on the outer edge of the asteroid belt. Its upgraded telescope, the largest visible-light telescope ever built, lets astronomer Widnall see a star as a disk for the first time, while Sublieutenant Vasilenko reminds Widnall that their true duty is to serve as sentries watching for photoids.

Fleet Command orders the station to observe the destroyed Trisolaran system. Widnall and Vasilenko see the system as a glowing nebular graveyard: only one of the three stars was destroyed, but the remaining stars turn the scattered matter into a lethal radiation furnace, confirming that the dark forest strike made the system permanently uninhabitable.

While examining the image, Widnall notices a faint, enormous, transparent bubble-like structure near the Trisolaran system, and then another much larger one about six thousand AU away. Vasilenko recognizes the second location as the place where the Second Trisolaran Fleet entered lightspeed. The two conclude that curvature propulsion leaves persistent spatial trails when ships enter or exit lightspeed.

This discovery explains why the Trisolaran fleet traveled far from its home system before using curvature propulsion: the Trisolarans were trying not to expose their location through such trails. Widnall fears that human experiments with lightspeed ships could mark the Solar System in the same way, so he and Vasilenko send an alarm-level report to Fleet Command. The message is leaked and misread as a photoid attack warning, causing the global panic two days later.

Further analysis suggests that the earlier dark forest strike on Trisolaris may have come quickly because a curvature trail inside that system, combined with the broadcast coordinates, made it appear especially dangerous. Over the next month, Observation Unit #1 finds six more curvature propulsion trails, including one only 1.4 light-years from the Sun, proving that advanced civilizations using lightspeed travel are common nearby. As a result, humanity bans curvature propulsion research, leaving only the Bunker Project and the Black Domain Plan as viable survival strategies.