Possible Duplicate:
Vortex in liquid collects particles in center
Sorry for my bad English. :-) Hello !
Here is my question : If you enjoy some cup of tea, you may see that there are some tea dust in suspension in your cup. If you turn your spoon in the liquid, the tea will rotate, and the dust will concentrate in the bottom of the cup (because the dust is denser than the water) but too in the center !
This is conter intuitive for me. The dust have to spread near the sides of the cup, because it's more denser than the water ! No ?
Edit : We can think to the centrifugation of the blood. When the blood is collected from a people, the pocket pass into a centrifuge (? do you see what I mean ? top of the pocket in the center, bottom of the pocket near the walls) and the diverse parts of the blood finish separated in function of their density. But the denser, the closer of the bottom of the pocket...
