Final answer:
The difficulty in understanding singularities arises from the breakdown of mathematical equations within general relativity and the absence of a unified theory with quantum mechanics, compounded by the inability to observe singularities due to black hole event horizons.
Step-by-step explanation:
Understanding a singularity is challenging due to a couple of key reasons related to the theories of general relativity and quantum mechanics. In the framework of general relativity, as we approach a singularity, such as the one at the center of a black hole, our mathematical equations begin to break down and return answers of infinity, indicating infinite density and zero volume. This puts us in a quandary because our physics don't operate well with 'infinities' or 'zeros' in these contexts. Additionally, general relativity and quantum mechanics, our two great pillars of modern physics, are not yet reconciled in these extreme conditions, leaving us without a complete understanding of the physics involved.
Further complicating matters, singularities are inherently unobservable from the outside due to the event horizon that surrounds black holes, blocking any information from the singularity from reaching an outside observer. Thus, our current scientific tools and theories are not equipped to fully describe or understand the nature of singularities, making them one of the greatest mysteries in modern physics.