If Einstein's theory of general relativity were proven to be incorrect, it would require the development of a new theory that can adequately explain and predict the behavior of gravity and the nature of spacetime. The search for such a theory is an active area of research in theoretical physics. While I can't predict the specifics of what would replace general relativity, I can provide you with some potential avenues that scientists are exploring:
Quantum Gravity Theories: One possibility is the development of a theory that unifies general relativity with quantum mechanics. Such a theory would be able to describe gravity on both large and small scales, encompassing the behavior of spacetime and particles at the quantum level. Examples of quantum gravity theories include string theory, loop quantum gravity, and causal dynamical triangulation.
Modified Gravity Theories: Another approach is to modify general relativity itself by introducing new terms or equations that account for phenomena not explained by Einstein's theory. These modifications could potentially account for observed cosmic acceleration (dark energy) or provide an alternative explanation for the gravitational effects observed in galaxies without invoking the presence of dark matter.
Emergent Gravity: Some researchers propose that gravity could emerge from more fundamental principles or underlying structures, similar to how the behavior of fluids emerges from the interactions of individual molecules. In this view, gravity would not be a fundamental force but a collective phenomenon arising from the interactions of other entities or fields.
Other Paradigm-Shifting Theories: It is also conceivable that an entirely new paradigm or theoretical framework may be required to replace general relativity. This could involve revisiting fundamental assumptions about space, time, and the nature of physical laws, leading to a radical shift in our understanding of the universe.
It's important to note that while scientists are actively exploring these and other possibilities, no definitive theory has emerged to replace general relativity so far. Any new theory would need to satisfy various experimental tests and observations and provide predictions that differ significantly from those of general relativity in certain regimes.