Explaining the shortcomings or limitations of Albert Einstein's theory of general relativity without delving into technical and mathematical details can be challenging, but I will do my best to provide a simplified explanation. Please keep in mind that this is a high-level summary, and some nuances may be lost in the process.
Incompatibility with Quantum Mechanics: One of the main challenges with general relativity is that it is not fully compatible with quantum mechanics, which is another fundamental theory of physics. General relativity describes gravity and the behavior of large-scale objects, while quantum mechanics deals with the behavior of particles at the smallest scales. These two theories have different mathematical frameworks and principles, and attempts to merge them into a unified theory have not yet been successful.
Singularities and Black Holes: General relativity predicts the existence of singularities, which are points of infinite density and curvature. These singularities are found in certain scenarios, such as at the center of black holes. However, the theory fails to explain what happens within a singularity, as it reaches the limits of our current understanding. This means that general relativity breaks down in extreme conditions and cannot provide a complete picture of what occurs at those points.
Dark Matter and Dark Energy: General relativity struggles to account for the observed phenomena of dark matter and dark energy. Dark matter is believed to make up a significant portion of the mass in the universe, yet it does not interact with light or other forms of electromagnetic radiation, making it challenging to detect. Dark energy, on the other hand, is thought to be responsible for the observed accelerated expansion of the universe. General relativity has difficulty explaining the nature and origin of these mysterious components.
It's important to note that while there are areas where general relativity has limitations or open questions, the theory has been extensively tested and confirmed in many situations. It remains one of the pillars of modern physics and has provided a solid framework for understanding gravity and cosmology on a large scale. Scientists continue to explore and develop new theories that may extend or refine our understanding of the universe beyond general relativity.