The Cave Example. Pretend that you are unlucky enough to fall into a cave without a flashlight. Suddenly, you hear a snuffling sound. To find out, you desperately toss the basketballs in the direction of the snuffling sound, and memorize where the basketballs hit. Since your basketballs are so big, when they bounce off the thing in front of you, all you can learn about its shape is that it is wide and tall.
Tennis balls are still too big to figure out the shape of the object they hit.
You only have a rough idea about the thing's outline. You toss these little balls at the being, and note that you can figure out a pretty clear image of the thing's shape. It seems to be big, hunched over, and have enormous claws. Your last, but gleeful, thought is that you used the smallest possible probe to get the most information about your fate.