1. The problem statement, all variables and given/known data An electron travaels in an accelerator tube at a speed of 0.997 c relative to Earth. In the frame of reference of the electron, the length of the tube is 1.20 m. What is the length of the tube relative to earth? 2. Relevant equations L = Lo / γ Textbook answer: 15.5 m 3. The attempt at a solution I know it is a simple plug-in problem but when I plug in the numbers, they don't work out and I'm guessing that I'm assigning the numbers wrong. For this problem, would 1.20m be L or Lo? I'd assume it to be Lo since that's the proper length in terms of the electron's reference frame. However, the numbers do not work out then - indicating that L = 1.20 m. This does not make sense to me since 1.20 m is the length measured from the electron's frame, is it not?