Black holes: what we think we know, we don’t

It took Albert Einstein 10 years to find the equations of general relativity, but German astrophysicist Karl Schwarzschild only needed a few months to solve them. Schwarzschild’s solution describes the gravity of an isolated, spherical and unchanging object — the enigmatic black hole — but it was not understood for many years. Black holes helped to explain new astronomical discoveries, becoming essential ingredients of astrophysics. Science regarded black holes as abstractions