Physical
Ladder Paradox (Barn-Pole Paradox)
A long pole fits inside a shorter barn due to length contraction
Overview
A paradox in special relativity about length contraction and simultaneity.
A pole moving at high speed undergoes length contraction and fits inside a shorter barn (from barn's frame). But from the pole's frame, the barn is contracted and the pole doesn't fit. Both can't be right - or can they?