The principle states it is impossible to 'simultaneously' know the position and momentum(velocity)of an object. Position is something that can be noted at a particular instant, as from a photograph whereas velocity is something that can only be measured over a period of time,as from a movie. The principle doesn't prevent us from knowing the exact position of an object. Thus isn't it possible to take "photographs" of the particle for a long enough period and to know the trajectory it traces? So is it that, it is possible to know the momentum and position of a particle at any instant in the past and impossible to know at the present moment?