[Serious] Is the Past Real?

[polymath257]

i think to put it even more fundamentally, knowable for event A means event A can in principle influence some event B such that progress of event B depends on the specifics of event A

And what if A is in a superposition state?

What is required for your scenario to happen is that the state of A decay *irreversibly* and then affect B. But what happens if the decay isn't irreversible over the long run? Then B also goes into a superposition state and all we can say about A is probabilities, not anything definite.