  I consider the isolation of general relativity research from the rest of
theoretical physics during the 1930s-1950s, and the subsequent reinvigoration
of the field. I suggest that the main reason for the isolation was that
relativists of the time did not develop heuristic concepts about the physics of
the theory with which they could communicate with other physicists, and that
the revival happened when they began to develop such concepts. A powerful
heuristic today is the concept of a black hole, which is a robust and stable
component of many astronomical systems. During the 1930s relativists could only
offer the "Schwarzschild singularity". I argue that the change occurred at
least partly because key theoretical physicists schooled in quantum theory
entered relativity research and began to approach problematic issues by asking
questions about observable effects and the outcomes of thought experiments. The
result was the development of a physical intuition about such things as black
holes, which could then be communicated to non-specialists. Only then was it
possible to integrate general relativity fully into the rest of physics.
