A singularity, as described in the context of black holes, is a point of infinite density and zero volume. It is a prediction of general relativity where the gravitational field becomes infinitely strong. However, the exact nature of singularities is still an area of active research, and our current understanding suggests that they are points where our understanding of physics breaks down.
At a singularity, the laws of physics, including our current theories of fundamental forces, cannot be applied because the extreme conditions overwhelm our current understanding of the universe. It is widely believed that a theory of quantum gravity, which combines general relativity and quantum mechanics, will be necessary to fully comprehend the behavior of singularities.
As for the notion that time has no relevance at a singularity, it stems from the fact that the equations of general relativity break down at such extreme conditions. Time, as we understand it, is a part of the fabric of spacetime. In the vicinity of a singularity, spacetime is highly distorted, and the concept of time as we know it may no longer have a meaningful interpretation. Therefore, our understanding of time and its behavior near a singularity is currently limited.
It's important to note that the nature of singularities and the behavior of physics within them are still active areas of research and remain subjects of ongoing theoretical investigation. Scientists are exploring various avenues, including quantum gravity and other theoretical frameworks, to better understand the fundamental nature of singularities and their implications for our understanding of the universe.