ABSTRACT
Imagine a set of athletes about to start a race without knowing how far they are going to have to run. Do they prepare starting blocks and launch themselves at the sound of the starting pistol at great speed, so that the leader disappears in a cloud of dust ahead of all the others, or do the athletes gently lean forward in order to pace themselves for a steady and prolonged jog around the track? The distance of the race will determine which option the athletes select. The speed of the athlete can only be understood in the context of the distance they have to run.
