8 hours ago, Cave_Dweller said:
. . . But to go back to a “time before time began,” which is the singularity before the Big Bang, is a difficult task. Because cosmologists can follow possible states back to the Planck limit of time, but they can never reach the beginning, assuming there is one, as an asymptote of time. This is due to the break down of classical space-time at the quantum level. . . .
They do not think the classical GR absolute spacetime point was the character of the cosmos at the onset of expansion, because they have reasons to expect spacetime granularity at the Planck scale (billionths of a trillionth of a trillionth of an inch-second). But we should not demand philosophically (or by habit) from scientific cosmology that there be any time before that neighborhood. Rather, to keep up, we must learn their mathematical representations and experiments that lead the scientific cosmology. (Eg. &) Time-like slices of spacetime, exactly so, are extremely good approximations for our many arenas of GR and SR.