THE IRRATIONALITY OF THE INFINITE
A singularity is not real and cannot exist physically. Simply stated the term is shorthand for the idea that the universe, which is everything which does exist, shrinks to a smaller and smaller volume without limit as time progresses. But giving something a name does not make it real. This is because a singularity is not so much a thing as the unrealizable end point of a physical process.
It is of interest in physics because the well verified equations of Einstein’s General Relativity predict an expanding universe. And so if we run these equations backwards in time, the volume of the universe is predicted to shrink without limit as we approach a definite point in earlier time. This is mathematically described as an asymptotic limit. It may be a fine point, but this does mean that the volume gets arbitrarily smaller as we go ever further backwards in time but rather that the volume shrinks without limit as we approach a particular instant of time in the past.
If matter and energy behaved in the past as it does now we can calculate how it behaved in the earliest moments when the universe was simply a speck of space.