http://www.youtube.com/watch?v=uiyMuHuCFo4


I wouldn't have expected that behavior.


comment:
His theory is not wrong but there's a more direct explanation. Each ring
gets slightly more tensile force from above than from below, exactly
equal to the weight of that ring. This tensile force only depends on
local extension. When the top is released, tensile force everywhere else
is still the same so the lower parts have no reason to come down. Top
ring comes down, tension immediately below is reduced, next ring starts
moving too. Effect decreases exponentially, so limited to short distance.