The pole-barn paradox is a famous variation on the twin paradox which must be addressed with the ideas of simultaneity in relativity. The fact that two events are simultaneous in one frame of reference does not imply that they are simultaneous as seen by an observer moving at a relativistic speed with respect to that frame. A 20 meter pole and a 10 meter barn in their perspective when in the same |l20m | rest frame. If the pole has speed 0.9c, then it is length-contracted by a factor of 2.29 I - and short enough to fit momentarily | 873m | within the barn, at least as seen by an observer in the barn. v=0.9c Vs