1. The problem statement, all variables and given/known data Spherical planet has only one inhabitant that can move freely on the surface of the planet with speed u. A spaceship approaches the planet with velocity v. Show that if v/u > 10, the spaceship can always see the inhabitant regardless of his movement. 2. Relevant equations No idea. 3. The attempt at a solution I have no idea where to start. Is this supposed to be a relativistic problem or a classical mechanical one? Any hints are more than welcome!