Share General relativity makes very specific predictions about what black holes are and how they should appear, as shown in this simulation. GODDARD SPACE FLIGHT CENTER/JEREMY SCHNITTMAN After decades of effort, scientists are finally seeing black holes—or are they? Jan. 7, 2021 , 1:45 PM While working on his doctorate in theoretical physics in the early 1970s, Saul Teukolsky solved a problem that seemed purely hypothetical. Imagine a black hole, the ghostly knot of gravity that forms when, say, a massive star burns out and collapses to an infinitesimal point. Suppose you perturb it...