Black holes are the dreamed paradise of garbage dumps: everything that goes into them disappears from the universe, nothing comes out. However, the solution to Einstein’s equations of general relativity that predict the existence of black holes can also be read backwards: instead of seeing it as the ultimate collapse of a celestial object they can also be read as an outward expansion. of an object from a singularity: this is a white hole .
The first to realize this was Martin Kruskal, a plasma physicist at Princeton University, in the mid-1950s. Interestingly, the physicist never bothered to publish it. Only John Archibald Wheeler, the physicist who named black holes as such, realized the importance of this work, wrote an article with the calculations, put Kruskal’s name on it, and published it in 1960 in Physical Review . Later, on the other side of the Atlantic, the English mathematical physicist Roger Penrose perfected Kruskal’s representation and turned it into a diagram.
Where do these jobs take us? Because white holes are the inverted images of black holes . If one does one thing, the other does just the opposite and invested in time. Thus, while the event horizon of a black hole is a place that cannot be exited, the anti-horizon of a white hole is a place that cannot be entered. If the black hole swallows everything, the white hole ejects everything.
You don’t have to be very perceptive to realize that the Big Bang, the explosion that gave birth to the universe, has all the earmarks of a white hole : all matter and energy that exists today was created in that sudden explosion. This is what Alon Retter and Shlomo Heller suggested in 2012: The universe emerged from a white hole, which they called ‘Small Bang’.
In the white holes nothing can enter, everything bounces
But where can we find those white holes? Some have pointed out that Gamma Ray Burst (GRB), gamma ray bursts associated with extremely energetic bursts in distant galaxies, are white holes. It’s not far-fetched: GRBs are the most luminous explosive events in the universe. But it is not time to cast the bells to the flight. In 1974 Douglas Eardly, from CalTech (California), found that white holes are very unstable and would disappear shortly after being born, becoming a black hole. This is so, Eardly reasoned, because the energy that arises from the central singularity does not escape into space away from the hole, but accumulates outside, around the anti-event horizon. In this way, layer after layer, we will have a white hole surrounded by a dense protective screen of energy that Eardly called “blue sheet.” Following the rules of general relativity, this wall of energy turns the region into a black hole . As the calculations show, this process depends on mass: for a white hole of 10 solar masses the conversion would take place in less than a thousandth of a second; for another one million soles, in just over a minute.
So there are no white holes in the entire universe? The theoretical physicist Carlo Rovelli is one of those who believes that all is not lost. If we apply the rules of quantum mechanics, white holes are going to be the future of black holes . That is, in the second half of its life, and after a quantum transition, black holes turn white and matter, when falling on them, bounces. This is so thanks to the so-called Hawking evaporation , discovered by the famous physicist and who says that, due to quantum effects, black holes evaporate slowly, losing all the energy they have accumulated inside until they disappear. According to Rovelli, just when the black hole has evaporated to a point where it can no longer contract because spacetime is impossible to compress into something smaller, the dying black hole becomes a white hole.
If so, where can we find them? Rovelli suggests that white holes could be the ones behind the mysterious dark matter in the universe . The Italian physicist has calculated that only one small white hole is needed for every 10,000 cubic kilometers, much smaller than a proton and with a mass of approximately one millionth of a gram, “equal to the mass of a 12 cm human hair” , to account for the dark matter found in the galactic environment of our Sun. These white holes would not emit radiation and as they are infinitely small, they would be invisible, as is dark matter. If a proton were to hit one, the hole white “would just bounce,” says Rovelli: “They can’t swallow anything.”
