An interstellar voyage explores the ‘paradox’ of twins separated by light years

Albert Einstein’s introduction of special relativity at the dawn of the 20th century left physicists with any number of peculiar new puzzles to work through. One of the most famous is the thought experiment that came to be known as the ‘twin paradox’, which considers how twins would age in relation to one another if one were to journey light years into space and back while the other remained on Earth. Using the twin paradox as a launch pad, this animation from TED-Ed takes viewers on a journey into the knotty world of time dilation. In particular, the short details why it would be a mistake to view the spaceship and Earth as two equally stationary objects, which would have caused each twin to have, paradoxically, aged faster from the perspective of the other once they were reunited.