well, for starters, you're not quite accurate there yourself. An inch is an inch. And a second is a second. Measurement itself may be a theoretical construct that we overlay onto the world but that doesn't threaten its precision. Your connundrum is similar to Zeno's paradox which you should look into. Suffice it to say, time still passes and objects can still move, so see if you can't find a solution to this quandry.