Yes, you're right, and this occurred to me after I posted but while I was in the shower so I couldn't correct it :-) I should have said "if it is possible to b

Yes, you're right, and this occurred to me after I posted but while I was in the shower so I couldn't correct it :-) I should have said "if it is possible to bring all of the constituent particles in a system to rest for a non-zero time..."