Zeno was a greek philosopher who first asked this question and similar questions (he would tell a soldier to run away from arrow fire because then it could never catch them up... they still died... ).
Read more about his paradoxes here.
Zeno's paradoxes - Wikipedia, the free encyclopedia
His paradoxes still are talked about today, and gives philosophers a lot to think about in terms of the nature of distance and time. His theory might be wrong, but his thinking was genius!