One interesting (unbelievable?) implication of time dilation is contained in what is called the twin paradox. Imagine identical twins who decide to perform an experiment to test the accuracy of Einstein’s predictions about time dilation. After synchronizing their (identical) clocks, one of the twins enters a spaceship and travels to a distant star at a speed 95 percent that of light. Upon arrival, the traveling twin immediately turns around and heads home at the same speed. According to the twin on Earth, the clock aboard the spaceship runs slower than the one on Earth, so that the traveling twin ages less than the Earth-bound sibling. But according to the spacefaring twin, it is the clock on Earth that is running too slowly, making the stay-at-home twin the younger of the two. This is the paradox: each twin argues that the other will be younger at the end of the trip. How can this paradox be resolved?

Which of the two twins is correct in their analysis, and why? If the trip requires a total time of 5 years to make as measured by the clock on Earth, what will be the time recorded for the trip by the clock on board the spaceship?