🐛 Bug-Rivet Paradox Calculator
Explore the bug-rivet paradox by calculating a moving rivet’s length-contracted length.
The Bug-Rivet Paradox
The bug-rivet paradox is a variation of relativistic length-contraction puzzles: a rigid rivet longer than a hole is driven toward it at relativistic speed. In the wall’s (hole’s) rest frame, the rivet is contracted per L’ = L0/γ and appears short enough to fully enter the hole, seemingly squashing a bug resting at the bottom — but in the rivet’s own rest frame, it’s the hole that contracts and appears too shallow to admit the whole rivet.
The paradox highlights that “perfectly rigid” objects don’t actually exist in relativity — no real material can transmit force faster than light, so the rivet’s tip and tail don’t stop simultaneously in every frame, and working through the details (rather than assuming perfect rigidity) resolves the apparent contradiction consistently in both frames. This calculator shows the wall-frame contracted length for conceptual, educational exploration.