Ehrenfest paradox

Proper noun

(physics) A relativistic paradox concerning the concept of Born rigidity within special relativity, where an ideally rigid cylinder that is made to rotate about its axis of symmetry. The radius R as seen in the laboratory frame is always perpendicular to its motion and should therefore be equal to its value R₀ when stationary. However, the circumference should appear Lorentz-contracted to a smaller value than at rest. This leads to the contradiction that R = R₀ and R < R₀.

Japanese Meaning

特殊相対性理論において、ボーン剛体性の概念に関連するパラドックス。具体的には、理想的な剛体と考えられる回転する円筒で、実験室系では回転軸に対して垂直な半径は静止時と同じ値（R₀）であるのに対し、周囲はローレンツ収縮により静止時の値よりも短く観測されるために生じる矛盾を説明する。