Best answer:
"Singularity" is a mathematical object that belongs to the domain of a function.
It does not need to be infinite. It does not need to be a point (in some functions, the "sigularity" is a volume, sometimes finite, sometimes infinite).
We have no idea what a "gravitational singularity"...
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Best answer: "Singularity" is a mathematical object that belongs to the domain of a function.
It does not need to be infinite. It does not need to be a point (in some functions, the "sigularity" is a volume, sometimes finite, sometimes infinite).
We have no idea what a "gravitational singularity" means.
In the Big Bang theory, the "singularity" is a time interval: the time interval that falls "before" the Planck Time, the first moment that can be understood with the Big Bang thoery (that moment, 13.8 billion years ago).
AT the Planck time, nothing is infinite, nothing is infinitely small. Values are finite.
IF (a big if) you attempt to push the mathematical model outside of its domain (meaning = "before" the Planck Time), energy density grows without bound. But that is because we do not understand how time itself "flows" above the Planck value for energy density (itself a finite value).
Bluntly: we do not know what the word "before" really means. So that if you try to go "before"... you are on your own.
At the Planck Time:
-- The initial energy already existed.
-- Space was already expanding.
-- Energy density was NOT infinite.
-- We think gravity already existed.
-- We know matter did not yet exist (it comes later and the theory does explain how).
this next one is conditional:
IF (a big if) the universe is now infinite in spatial extent, then it was already infinite at the Planck Time.
How was it "before"? We don't know, since we do not know that the word "before" means when you apply it to the Planck Time.
It is (a bit) like asking: how fast can you pour a glass of water, once the water is frozen in the glass.
At energy densities above the Planck density... time is "frozen" (and we do not know what that means, either).
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