Final answer:
Einstein's remarkable insight in developing general relativity was that the effects of gravity and acceleration are indistinguishable; this principle underlies the equivalence between gravitational fields and accelerated motion, conceptualized through thought experiments such as the elevator scenario.
Step-by-step explanation:
The logical jump that Einstein made in formulating general relativity was that acceleration in a gravitational field and acceleration due to motion cannot be distinguished from each other. Einstein's theory of general relativity is based on the principle of equivalence, which posits that the effects of acceleration and the effects of gravity are locally indistinguishable. One of the classic thought experiments that illustrate this equivalence involves an elevator. Whether the elevator is accelerating upward in the absence of gravity or is stationary in a gravitational field, the effects observed inside the elevator are the same. This led to the realization that gravity is not a force between two masses but the curvature of space-time caused by mass and energy.
When we examine scenarios such as black holes or attempt to unify the forces of nature, we are engaging with concepts deeply rooted in general relativity. The theory describes the interplay between mass, energy, space, and time and has been confirmed by a range of experiments. However, the full reconciliation of general relativity with quantum mechanics, to produce a complete theory of quantum gravity, remains an open challenge in modern physics.