Suppose I have this relatively large ball which, from where you're sitting you can probably tell where the ball is and you can tell if the ball isn't moving so you could tell its velocity. Now, suppose I go smaller. Suppose I hold up this ball. Now, once again, this is a relatively large ball. And from where you're sitting, you could probably tell that the ball isn't moving and you could tell where the ball is. Now, suppose I go even smaller.