Shipment of Theseus

One track, shape of a ring. No beginning, no end. Five hundred boxes at each of five hundred stops. Five hundred boxes on the train. No more, no less. Every stop, remove and add. Remove one, add one. Remove two, add two. Remove a hundred, add a hundred. Twenty-three miles from stop to stop. One mile, one hour. One stop, one hour. Every day, another stop. The train has seen every stop before, will see every stop again. It has been moving as long as I have been alive. I have never not been alive.