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In the twin paradox thought experiment, one twin travels into space near the speed of light while the other stays on Earth. When the traveling twin returns, how do their ages compare?

AThe traveler has aged less than the twin at home
BThe traveler has aged more than the twin at home
CBoth twins end up exactly the same age
DAges cannot be compared between the two twins
Answer & Solution
Correct answer: A. The traveler has aged less than the twin at home
1. The traveling twin spends the trip in a frame moving at relativistic speed relative to Earth. 2. Time dilation means less time passes for the traveling twin than for the twin who stayed on Earth. 3. When she returns, the traveling twin has aged less, while her Earth-bound twin has aged more. 4. The twins are not the same age, and their ages absolutely can be compared once reunited. 5. So the traveler aging less is correct. _Source: OpenStax Physics (CC BY 4.0), Ch 10 "Special Relativity", section 10.2 Consequences of Special Relativity_
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