Chapter 27, Problem 9P

A spacecraft flies away from the earth with a speed of 0.6c relative to the earth and then returns at the same speed. The spacecraft carries an atomic clock that has been carefully synchronized with an identical clock that remains at rest on earth The spacecraft returns to its starting point 365 days (1 year) later, as measured by the clock that remained on earth, (a) Which clock records the proper time between the two events that correspond to leaving earth and then arriving at earth? (b) What is the difference in the elapsed times on the two clocks, measured In days? (c) Which clock, the one in the spacecraft or the ore on earth, shows the shorter elapsed time?