Aris traced the boundary condition back. The coherent thermal oscillation wasn't natural. It was a 0.003 hertz signal—the exact frequency of the station-keeping thrusters on the orbital ring. They fired every 92 minutes, just enough to correct for tidal drag. The thermal wave propagated down the ribbon, hit the jet stream, reflected, and came back in phase .
But Aris had a ritual. Every night, after the junior engineers went home, she would open the raw solver output—not the pretty contour plots, but the dense matrices of eigenvalues. And for the past three nights, the 1,204th natural frequency mode had shifted by 0.003 hertz. Aris traced the boundary condition back
It was 0.87 .