Gravity is indeed a fundamental force that governs the interactions between masses. The concept of mass attracting other mass provides a simple explanation for the basic behavior of gravity. However, there are several aspects of gravity that remain unknown or not fully understood. Here are a few key reasons:
Nature of the Gravitational Force: While we know that gravity exists and how it behaves, the underlying mechanism by which mass attracts other mass is not fully understood. In other words, we don't have a complete understanding of why mass creates a gravitational field and how that field interacts with other masses.
Unification with Quantum Mechanics: Gravity is not currently incorporated into the framework of quantum mechanics, which is a highly successful theory describing the behavior of particles on the smallest scales. Combining gravity with quantum mechanics to form a consistent theory of quantum gravity is an ongoing challenge in theoretical physics.
Dark Matter and Dark Energy: Observations indicate that the visible matter we can detect in the universe constitutes only a small fraction of its total mass and energy. The majority is composed of unknown substances called dark matter and dark energy. The nature of these components and their relationship to gravity is still a subject of intense research and investigation.
Gravity at Extreme Scales: Our current understanding of gravity, as described by Einstein's theory of general relativity, breaks down in extreme situations like inside black holes or during the Big Bang. Understanding gravity under these extreme conditions requires a theory that unifies gravity with quantum mechanics.
Gravitational Waves: Gravitational waves were predicted by Einstein's theory and were directly detected for the first time in 2015. While this was a significant achievement, there is still much to learn about the properties and behavior of gravitational waves, as well as their role in the universe.
Overall, while we have a good understanding of the basic principles of gravity, there are many complex and puzzling aspects that scientists continue to investigate. Gravity's interaction with other fundamental forces, its behavior at extreme scales, and its unification with quantum mechanics are among the areas where further research is needed to deepen our understanding of this fundamental force.