Discrete Planck time scale ends even before we go back to consider what existed at or before the big bang occ, i..e planck time mathematics end even before asking the question what existed at or before the big bang.
Got 25:15 or thereabouts to understand what nobody knows the answer too and can only speculate about.
One of my views is that all that exists at and before is the a brief moment --at best or worse--- is the sine-wave { as observed time v^v^v ergo relativity }, dissipates from inside/internal to the primary 2D field of occupied space existence, and briefly is only immersed in the geodesic Gravity field ( ), and briefly transfer on Gravitational spiral geodesics to the Dark Energy geodesic field )(.
Gravity and Dark Energy field = primary/fundamental occupied space.
Observed { relativity of reality } Time = relative observed time of occupied space
In this scenario, the invaginations/cleavages ^^^^^ from Dark Energy ----arrive via Gravity ( ( ( ( geodesics--- and the invaginations/cleavages, gradually accumulate enough, that a big bang type inflation occurs inside/internal to the 2D field and I believe are 3D, Space-time Horn Tori.
This expansion process ---invaginations/cleavages-- begins on Dark Energy side until, eventually in future the observed relative reality time dissipates once again into the geodesic field, again, and this process repeats eternally.
The contraction process is 2-fold:
1} the outer Gravity geodesics feeding over to the inner Dark Energy, and Dark Energy feeding back to the outer Gravity,
1} the outer Gravity geodesics feeding over to the inner Dark Energy, and Dark Energy feeding back to the outer Gravity,
2} the invaginations/cleavages of from Gravity field vvvvvvvv, and from the invaginatnions/cleavages from diametrically opposite Dark Energy field ^^^^^^
These two outer and inner invaginations/cleavages are the relative time sine-wave ^v^v aspect that accelerates from the inner ---because of accumulation increasing accumulation--- Dark Energy field towards the outer Gravity field, only to briefly dissipate again into Gravity field, and etc......
....................................................................................................................................................Outer Gravity Field
.............................................................................................................____entropy______________
.....................................................entropy...............................................^v^v^v^v^v^
.........................entropy............................................................^v^v^v^v
............................................................................^v^v^v^v
............entropy................................................^v^v^v^
.................................................^v^v^v
................................^v^v^v^v^
.......................^v^v^
...............^v^
..........^v
.....^
Inner Dark Energy Field
The flat line line near Gravity field represents entropy i.e. observed time becomes one very large very flat photon as the heat death { cold } of Universe.
R Penrose asks why is the Universe so homogeous/equlibrious at begining of Universe, ergo is Conformal Cyclic Universe scenario of the 2D Escher-like ultra-micro subdivision of equanimity of similar shape just subdividing to ultra-smaller scales of existence. Not no existence!