I have a hypothetical situation that I am trying to work through... Say there are two spin 1/2 particles, and the system is known to be in a total spin state of Stot=0. An observer comes along and determines the first particle to have a spin component (S1z) of hbar/2. Now say another observer comes along and measures the z component for the second particle (S2z). What is the outcome? My solution is this: I believe the Stot information is lost when the first observer measures S1z, so that then there is a 50% chance of the second observer measuring hbar/2, and a 50% chance for -hbar/2. Is this right? Thanks very much.