A thought experiment in which one twin (A) travels into space at nearly the
speed of light and returns to find she has aged less than her sibling (B) who
has remained on Earth. This result is paradoxical because of the seemingly
symmetric roles played by A and B in the story. In fact, A returns younger than
B because only A travels in a non-inertial (accelerating) reference frame. From
Bs point of view, A experiences time dilation, but from As point of view
the distance traveled is shortened because of length contraction.
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