By Tarik Wortham from Avenues’ Hi, Science 2024 Winter Issue.

If I were to tell you there exists an infinitesimally small entity with infinite density and mass, you might find it hard to believe. But such an entity exists (in theory), and it is called a singularity. Theories suggest that singularities may have initiated the big bang and live at the center of black holes. 

Scientists postulate that at the center of a black hole, gravitational attraction is so intense and overwhelms all other forces. This results in a singularity—a point where matter is compressed to have infinitely large density and infinitely small volume. You may be asking yourself, how can a singularity have a size that is infinitely close to zero? If you have a more advanced understanding of physics, you may ask yourself, doesn’t this violate Planck’s length (which defines the smallest possible length of an object to be 10^-33 centimeters)? Well, singularities exist under such extreme conditions that known laws of physics break down in examining them. In fact, we understand space-time as a fabric that large objects warp, but this concept falters in the presence of singularities. It isn’t quite clear what would happen if you were to place something with infinite mass on fabric. 

Understanding singularities is also difficult because of the inherent differences between general relativity and quantum mechanics. General relativity provides a framework for understanding gravity as the curvature of space-time caused by mass and energy. It accurately describes the behavior of massive objects like planets, stars, and black holes on large scales. When gravitational forces become extremely strong, such as near a singularity, the equations of general relativity yield results that suggest infinite densities and curvatures, mathematical inconsistencies which are known as gravitational singularities. On the other hand, when quantum mechanics—which describes the behavior of particles at the smallest scale—is applied to extreme gravitational conditions near a singularity, the theory breaks down and its predictions become unreliable.

Scientists are still learning about singularities and there are constant arguments for and against their existence. Current calculations are just not sufficient for predicting what happens inside black holes. All in all, understanding singularities requires a deeper understanding of the fundamental nature of spacetime and gravity under conditions of extreme density and curvature, a task that remains one of the most significant unresolved puzzles in theoretical physics.