Part 3/8:
Initially dismissed, black holes were reconsidered when Karl Schwarzschild solved the equations of general relativity. He showed that if matter were dense enough, it would form an event horizon beyond which nothing could escape. However, doubts remained about how such high densities could be achieved in reality.
Progress in understanding black holes continued with Robert Oppenheimer and Hartland Snyder’s work in 1939, demonstrating how a perfectly symmetrical mass could collapse into a black hole. Despite this, skepticism lingered, as the natural universe seldom presents such neat conditions.