[Serious] Is the Past Real?

[Jehanne]

But it also isn't clear to me whether the *past* is determined in QM. If the information from the past mixes with the environment to a sufficient extent, it seems that the past becomes just as probabilistic as the future. When the information is impossible to retrieve, the past would be undetermined.

One observer's future event may, in some instances, be another observer's past event.