I put some balls (denser than water) in a bucket. I took a stirring rod, and swirled the water in one direction. The water became low in the middle, and high along the edges (centrifugal force). But the balls at the bottom clustered in the middle. Even when I tried to dislodge them with the stirrer, they would quickly return to the center.
Why did they not go out to the edge of the bucket, especially since they are denser?
