2. Twin sisters, Anna and Zelma, are twenty years old. Anna stays on the Earth while Zelma gets on a 20.0-meter-long spaceship that travels at constant speed 0.98c to a distant star. The star is 9.00 lightyears away as measured by Anna. Zelma immediately turns around and travels back to the Earth at the same speed of 0.98c. a) What length does Anna measure for the spaceship while it is moving? b) Upon Zelma's return, which twin is seen to be older now on Earth and what is the age difference?

2. Twin sisters, Anna and Zelma, are twenty years old. Anna stays on the Earth while Zelma gets on a 20.0-meter-long spaceship that travels at constant speed 0.98c to a distant star. The star is 9.00 lightyears away as measured by Anna. Zelma immediately turns around and travels back to the Earth at the same speed of 0.98c. a) What length does Anna measure for the spaceship while it is moving? b) Upon Zelma's return, which twin is seen to be older now on Earth and what is the age difference?