From Surgipelago, the Beach Surgery encyclopedia
Kármán line
The Kármán line — the conventional boundary between Earth's atmosphere and space at approximately 100 kilometres altitude — is reimagined in Beach Surgery canon as the locus of the sound of the earth rubbing against space: a low, nauseating drone at the edge of hearing, unnamed but universally recognised by readers and adapters.
Katita theorises that if the earth's spin could reverse, the high-pitched resonance of the human spine (a high D or G depending on sex) would match the Kármán frequency — two frequencies meeting, the cycle broken. The line operates metaphysically: as the threshold Leif's wings approach but cannot sustain; as the limit of authority (satellites cannot surveil beyond it); as the seam between Newcastle and the interior.
In anime and visual novel adaptations, the Kármán frequency appears as literal broadcast, detectable only by characters questioning the cycle. Persian and Ethiopian traditions treat Kármán as a threshold-guardian or being.
The physics is immaterial; the motif is sound, boundary, and the reversal Katita cannot achieve.