Stephen Hawking's last article: How to escape from a black hole

The cosmologist and popular science icon Stephen Hawking, who died last March on Einstein's birthday, recently spoke in front of the grave in the form of his latest scientific article. This document, which suits a man on the other side, explains how to escape a black hole.

Purified from his abstract mathematics, the document is a hymn to memory, to loss and to the oldest of human desires, the desire for transcendence. As Bruce Springsteen's convicted Atlantic City character says: "Everything dies, baby is a fact, but maybe everything that dies comes back someday."

Hawking was the manifestation of perseverance with Lou Gehrig's disease, he manages to conquer the wheelchair universe The fate of the material or information captured in a black hole is the one that defined his career and that became the 39, one of the deepest problems of physics.

Black holes are objects so dense that, according to Einstein's law of general relativity, even light can escape. Mr. Hawking returned these objects and the rest of the physics, and he discovered, to his great surprise, that the random quantum effects that rule the microscopic world would cause leaks in black holes and eventually an explosion and disappearance. .

With the pbadage of time (which in many cases would be longer than the current current) the age of the universe), all the mbad and energy falling into the hole would come out. But, according to Einstein's clbadic equations, black holes are of a disturbing simplicity. their only properties are mbad, electric charge and kinetic moment. All the other details about what falls in a black hole disappear from the memory banks of the universe. The saying said, "A black hole presents no complications, no hair …"

The source of material and energy coming out of a black hole would therefore be random, pointed out Dr. Hawking in a document from 1975. If you fall in one of them and come back out, you would miss all the details that had shaped you: man or woman, blue or brown eyes, Yankees fan or Red Sox . The equation describing this fate is inscribed on Mr. Hawking's gravestone in Westminster Abbey, where it is likely to last.

This is a kind of incarnation . If nature can forget you, she could forget everything – a fatal blow to the ability of science to reconstruct the past or predict the future. "It's the past that tells us who we are," said Dr. Hawking at a conference at Harvard a few years ago. "Without that, we lose our identity."

Indeed, Dr. Hawking baderted in his 1975 paper that the paradoxical quantum effects that Einstein once dismissed, claiming that God did not play dice, added an additional forgetting of nature. "Not only is God playing dice," Dr. Hawking writes, "but he often throws them where they can not be seen."

These were words opposed to other physicists; It was a fundamental principle that the proverbial film of history could be put together to reconstruct what happened, for example, in the collision of a pair of subatomic particles in a collider. at high energy.

Recent years have brought a glimmer of hope. . Andrew Strominger of Harvard has discovered that, from an exact mathematical point of view – that of a light ray directed to the infinite future – black holes are more complicated than we thought. They have what Dr. Strominger has called "soft hair," in the form of these imaginary rays of light, which can be wrinkled, caressed, twisted, or otherwise arranged by material entering the black hole. In principle, this hair could encode information on the surface of the black hole, recording all the details that Einstein's equations would have omitted.

In his recent posthumous report that drew a crowd of journalists, Mr. Hawking and his colleagues tried to show how this optimistic idea could work. In addition to Dr. Hawking, the authors of the paper were Dr. Strominger, as well as Malcolm Perry and Sasha Haco from Cambridge University.

The Pixar / Disney "Coco" movie I recently watched with my daughter tells the story of a young Mexican boy who travels to the land of the dead to find an ancestor able to help him. in his quest to become a musician. The Land of the Dead is a living place, but its inhabitants can only stay there, it seems, as long as someone remembers it. When the memories disappear, the animated skeletons disappear

. Some astronomers now say that even this pale version of salvation could be threatened. A mysterious force called dark energy accelerates the expansion of the universe. One day, say these experts, if the expansion continues, causing the galaxies to fly faster and faster, the rest of the universe will definitely be out of our sight, and we'll be always. It would be as if we were surrounded by a black hole in which all our information and our memory disappeared.