The real ball is damped by the fluid in the Glass, It's a BALANCE (slip/skid) only. The Turning "thing" is the ears semicircular Canals. You don't have to speculate about this. It's covered in Human Factors and other references. After a while the inner ear ceases to register the TURNING and if you stop turning it thinks you are going the other way. The seat of the Pants detects accelerations and "G" changes. Nothing is there to tell which way you are going unless you SEE it. Nev