Black holes and the tragic origin of their name

José Alfonso Morera Ortiz, better known as El Hortelano, was a painter to the stars. In one of the many heavens that he invented, the Gardener named each and every one of the celestial bodies in his imaginary galaxy, baptizing one of the stars as Ouka Leele; a point of light from which Barbara Allende would take her stage name. The rest is history.

But returning to science, the Gardener always told how the philosophers of Ancient Greece thought that light came from our own eyes and, therefore, when they saw a star, they reasoned that it was because light traveled at an infinite speed to illuminate it. Today all this comes to mind, because I just read a book that the Gardener would have liked very much. It is signed by astrophysicist Rebecca Smethurst and is titled Brief history of black holes (Blackie).

Among other things, this juicy book points out the error of the Greek philosophers, because if the speed of light were infinite, as was thought, then we could see what a black hole would look like. What happens is that the maximum limit of the speed of light is 299,729,458 m/s, and since the escape speed of the black hole is greater than that of light, the light is trapped in it and therefore does not We can see what it would be like inside.

The term black hole was coined by physicist Robert Henry Dicke, inspired by a historical story that occurred on June 20, 1756, in Calcutta, in the dungeon of Fort William, to be exact. The soldiers of the aforementioned English fort tenaciously resisted the siege by the forces of Siraj ud-Daulah, the Nawad of Bengal. In the end all that became an infernal siege from which the English soldiers escaped as best they could. When the fort was taken, the surviving soldiers were taken to the dungeon: a filthy cell, a narrow space that they called: “Black Hole.”

In this way, the American physicist Robert Henry Dicke identified the bodies of the prisoners crushed in the dungeon with the compressed matter of the stars at a point in space; a “mountain of matter that we cannot see directly because not even light can escape them,” writes Rebecca Smethurst in this exciting book tailored for all those people who want to get started in astrophysics.

A book that Hortelano would have liked to read, the star painter who was always in circles with Euclid and Ptolemy who claimed that our eyes were charged with light, as if they were lanterns, and with them we could reach the distant stars instantly, all the more reason to think that the speed of light was infinite and instantaneous. It took time until Galileo arrived to measure the speed of light using flashlights from two hills that were a kilometer and a half away. The time elapsed, from when the first flashlight was uncovered until the light was seen coming from the second hill, was the time it took for the light to travel the distance between the two hills and back. But in Galileo's experiment the same time was recorded on both hills, from which it was deduced that the speed of light was infinite.

However, Galileo himself explained that light traveled too fast to be detected at a distance of a kilometer and a half. And he was right. The history of astrophysics told in such a didactic way is fascinating. There is a moment when the author imagines that she takes the book on an interstellar trip and reaches the far side of the moon with it; She opens it and shines a flashlight on it, and then the light reflected from the pages travels in a curved path around the moon and reaches the Earth, so that we can read her pages from here.

Without a doubt, these are issues that the Gardener would have thought about when listing the possibilities of a black hole to manipulate light and see things that cannot otherwise be seen.

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