As everyone knows, there are many doubts if backward time travel can be possible, since it raises many paradoxes of which the most known is probably the Grandfather paradox.

My question is the following: "According to the current state of our Physics knowledge, there is something that prevents us to build a *Backward Time Viewer*?".

By Backward Time Viewer* *I mean a machine which can display events occurring in an arbitrary date in the past (not necessarily in an arbitrary location). Clearly, this is not a precise definition, but I think is better to leave you some freedom to choose a precise definition as part of your answer.

I am not a physicist, but I thought that a Backward Time Viewer can be in contradiction with Heisenberg uncertainty principle in such a way: We measure with arbitrary precision the position of a particle at time 0. Then, at time 1, with a Backward Time Viewer we measure with arbitrary precision the velocity at time 0 of the particle. Thus we can obtain the position and velocity of the particle at time 0 with arbitrary precision, in constrast with the uncertainty principle.