Theory 41/Sinkholes/Threshold lens
Roofs Fail on a Span Ratio
The claim
Collapse occurs above a threshold in the ratio of cavity span to roof strength, so a wide shallow cavity fails before a narrow deep one.
01Mechanism
The roof must carry its own weight across the span; the ratio determines whether it can.
02Prediction
Collapse should track the span ratio.
03Refutation
Collapse tracking depth would remove span.