Physical
Bell's Spaceship Paradox
Does a thread break between two accelerating spaceships?
Overview
A relativity paradox about length contraction and simultaneity in accelerating frames.
Two spaceships connected by a thread accelerate identically according to Earth. Does the thread break? From Earth's frame, the distance between ships stays constant while the thread contracts (relativity), so it breaks. From the ships' frame, they stay at rest relative to each other, so it shouldn't break.