They started out as a curious concept, but theories and demonstrations showed that they are real. His knowledge has been the result of a great collective effort, not the contribution of specific celebrities

Sir Roger Penrose, Andrea Ghez and Reinhard Genzel received the Nobel Prize in Physics for their research on black holes. Their work has required facing the mysteries of singularities or measuring the position of a star near the center of the Milky Way with great precision. But his achievements are not an individual success, but the culmination of a collective effort that spans several decades, if not centuries. Or, as Sir Isaac Newton wrote: “If I have seen further it is because I stood on the shoulders of giants.”

The concept of a black hole is at least 200 years old. Its roots lie in Sir Isaac Newton’s laws of gravity (published in 1687), which a hundred years later led astronomer John Mitchell to imagine a star so large and heavy that “light would return to it as a result of of its own force of gravity. In 1796, the French mathematician Pierre-Simon de Laplace reached a similar conclusion in the midst of the French Revolution.

However, these dark stars were forgotten until more advanced theories for light, gravity and matter came from the hand of Albert Einstein and his theory of relativity.

The first step: the Schwarzschild radius

Just a few months after Einstein introduced his General Relativity and showed that gravity affects the motion of light, in 1916 artillery lieutenant and astronomer Karl Schwarzschild solved Einstein’s equations for a point in a vacuum, paving the way for the current concept of a black hole: Schwarzschild, of course, found the first solution of Einstein’s equations that represents the simplest black hole.

The German’s calculations showed that some of the parameters of Einstein’s equations became infinite from a certain distance to the heart of the hole (the Schwarzschild radius). Thus, the singularity began to be born, a point where relativity does not work and some magnitudes acquire infinite values.

This idea was not very attractive to many scientists, starting with the father of relativity himself. Interestingly, Einstein was always very skeptical about black holes. He thought that the laws of physics would conspire so that black holes could never form in the real world. This attitude persisted in him even when there was already very strong evidence that it was not so. Perhaps it was because the singularity inside the black hole is the place where Einstein’s equations break down.

In 1931, and facing fierce criticism from prestigious astronomers, the Indian Subrahmanyan Chandrasekhar estimated a mass limit beyond which the electron degeneracy pressure would not be enough to stop the gravity-driven collapse (this is known as the Chandrasekhar limit). .

Stopped time

In 1939, Robert Oppenheimer, one of the fathers of the atomic bomb, among others, predicted that a neutron star could collapse for reasons presented by Chandrasekhar. Later, he interpreted the singularity, from the Schwarzschild radius, as a bubble where time stopped, for external observers, but not for observers who fell into the jaws of the hole.

For a time, black holes fell back into oblivion and became mathematical curiosities. At the same time, relativity came to be regarded as a very beautiful but not very useful theory. However, from the sixties the situation changed completely and a golden age of black holes and relativity began.

The golden age of black holes

In 1958, David Finkelstein identified the eerie surface outlined by Oppenheimer as the event horizon. Jocelyn Bell confirmed the existence of pulsars by showing that neutron stars were not just a theoretical curiosity, and that very massive and compact structures could actually be produced in nature. In 1963, Roy Kerr found the explicit solution that describes rotating black holes, which are the ones that surely appear in real formation processes.

Later, Roger Penrose began the study of qualitative theorems on singularities and horizons, and Stephen Hawking completed the Penrose program and discovered the quantum evaporation of black holes. These works of Hawking were completed when he in 1974 he predicted the effect known as Hawking radiation. Finally, Jacob Bekenstein made the first connection between black holes and information theory.