The development of dangerous technologies across a broad front of technology could lead to the realization that they can't be used due to the high costs involved, similar to the development of nuclear weapons during the Cold War, where physicists quickly realized the costs of war.
Physicists have identified four fundamental forces of physics, but gravity remains a mystery, seemingly acting at a distance without any apparent carrier. While other forces have particles that express them, such as electrons and quarks, the mechanism behind gravity is still unknown.