THRESHOLD COMPLEX EXPLORATION LOG
Designation / Log ID: 20-Q17
Apparent Date/Time: 23 August 2026 / 07:41 (local) — secondary stamp reads 14:19 29 September 1971
Entry Method: Double steel door marked “G-4 GENERATOR HALL”. Both leaves sealed under residual magnetic force after entry. Exterior push-bar absent on exit side.
Environmental Baseline
Lighting: high-bay mercury vapor lamps, color temperature measured at 3850 K. Intensity constant at 240 lux.
Ambient temperature: 31.7 °C. Humidity: 41 %.
Background sound: continuous mechanical drone at 61 Hz. Amplitude 34 dB.
Air movement: none detectable. Barometric pressure 1009.8 hPa on entry; 1014.2 hPa after 9 m of travel.
Spatial Observations
Hall estimated 42 m long by 18 m wide. Laser measurement returns 37 m by 23 m.
Floor: painted concrete. Surface temperature 4.1 °C above ambient.
Walls: unpainted concrete, formwork marks still visible. Wall temperature matches ambient.
Ceiling height: 7.8 m. Six generator units spaced at 6.2 m intervals. Unit count remains fixed at six after repeated inventory.
Repeating motif: every 4.1 m a free-standing control pedestal is present. Pedestals measure 0.9 m by 0.9 m by 1.3 m. Gauge faces display identical scale and pointer angle.
Anomalies
Visual count of generator units returns 6. Physical inventory returns 6. Piston stroke direction reverses every 47 seconds without change in mechanical linkage position.
Floor remains level under spirit level. Measured vibration amplitude along long axis is 3.4 mm peak-to-peak. Amplitude remains constant while tachometer readings cycle between 0 and 1800 rpm.
Control gauges display voltages that rearrange between observations. Readings cycle through three fixed sequences at 29-second intervals. Gauge glass temperature measures 22.6 °C regardless of ambient.
Sound of piston impact arrives 1.8 seconds after the corresponding vibration is felt. Delay increases by 0.3 s for every additional 4 m of distance from entry point.
Humidity at floor level remains 41 % while condensation forms on cooling fins after 4 minutes of contact. Condensation evaporates without measurable change in local humidity.
Entity Notes
None observed.
At the 21 m mark a localized magnetic field spike of 0.7 mT occurs within a 2.4 m radius. Spike persists for 8 seconds then collapses. No visible source or current flow accompanies the change.
Exit / Continuity Status
Exit achieved by retracing path to the double steel door. Leaves opened outward with moderate resistance.
Exterior time on exit: 08:19 local. Elapsed interior time: 38 minutes. Wristwatch confirms same interval.
Residual effects: residual mechanical drone audible for 11 minutes after exit. Temporary inability to resolve gauge numerals beyond 3 m lasting 14 minutes. No other reported sequelae.