the past isn't here now

​Question: You write [in endnote 59] “In fact, the past, like the future, isn’t uniquely determined either, as we shall see.”  Then you cite: The Grand Design, [by] Stephen Hawking: “Quantum physics tells us that no matter how thorough our observation of the present, the (unobserved) past, like the future, is indefinite and exists only as a spectrum of possibilities.  The universe, according to quantum physics, has no single past, or history.” 

Could you please elaborate a bit on that (the “past” not being determined)?  Is this because the (meaning of the) past is regenerated continuously in the now?  Or something else on top of that?
 
Response: The past is not determinable simply because “it” doesn’t exist—i.e., persist.  Even for a nanosecond.  See Chapters 19 and 24 (including endnotes) in The Grand Delusion.