In 2012, a 20-year-old astronaut leaves her twin on earth and goes on a rocket to explore the galaxy. The rocket moves at 2.7 108 m/s during the voyage. It returns to earth in the year 2042. a. Using relativity, calculate the age of the returning astronaut. b. Find the length of the rocket in earth's frame of reference when it is moving, given that the rest length is 120 m. Assume you are a stationary observer viewing the rocket from the side.