2023-06-04 08:38:02
A team of researchers from the Radboud University of Nijmegen in the Netherlands has just shown that Stephen Hawking did not tell everything when it comes to one of his most prominent theories. The brilliant British physicist, in fact, postulated in 1974 that certain quantum effects that take place at the very edge of the event horizon of a black hole (the invisible border beyond which nothing can escape the monster’s gravity) have the ability to gradually reduce its mass and its rotational energy. That is to say, that drop by drop and over time, for a long time, the black holes end up ‘evaporating’ until there is nothing left of them. Various experiments carried out since then confirmed the idea and, in honor of the scientist, the process became known as ‘Hawking radiation’.
But Michael Wondrak, Walter van Suijlekom and Heino Falcke, authors of a study published today in ‘Physical Review’ and which can also be consulted herehave gone much further by stating that, surprisingly, the event horizon does not play as important a role in Hawking radiation as previously thought, since ‘other things’, such as gravity and the curvature of space-time itself, also they can trigger it.
The implications of the finding are tremendous. In fact, they assume that any large object in the Universe, and not just black holes, is evaporating. And that, in the end, the entire Universe will also evaporate.
all part of the void
Hawking radiation emerges from the very nature of what we erroneously call a ‘vacuum’ and which in reality is not. In fact, the vast, seemingly deserted space that separates stars and galaxies is, although we cannot see it, a bustling place filled with incessant activity in the form of ‘quantum fluctuations’ that lead, for a very brief moment, to creation and immediate disappearance. of pairs formed by particles and their corresponding antiparticles. That is, by matter and antimatter.
As we know very well, when a particle of matter comes into contact with its antiparticle (for example, a proton with an antiproton), both are destroyed. And it turns out that the couples generated by the quantum fluctuations of the vacuum are destroyed so quickly that they barely remain for an instant in our physical reality. That is why they are known as ‘virtual particles’. Of course, when they disintegrate among themselves they ‘return’ to the Universe the energy they borrowed for their formation.
But what if the quantum fluctuations occur near a black hole, more specifically at the very edge of its event horizon? In those cases, where gravity reaches an extreme intensity, it can happen that one member of the new pair of particles forms in the ‘interior’ part of the horizon while the other does so in the ‘exterior’, that is, at a both sides of the invisible border that marks the point of no return. And that in turn implies that one of the two particles (the external one) will still be able to escape from the clutches of the black hole, although it will have to ‘steal’ some energy from it to do so.
In this way, little by little, drop by drop, the black hole will lose energy and, therefore, decrease its mass, that is, ‘evaporating’ until, following an enormously long time (the larger the hole, the greater the black) no trace of him remains. It goes without saying that this ‘evaporation’ process is only valid for black holes, which are the only objects in the Universe known to have an event horizon.
A new kind of radiation
And this is where the surprise occurs. In the new study, in effect, the researchers reviewed the entire process to find out if the presence of an event horizon is really essential, or not, for there to be Hawking radiation. To do this, they combined techniques from physics, astronomy and mathematics and examined what happens to the pairs of particles that form far from black holes. And surprisingly, the results showed that new particles can also be created well beyond the event horizon. In the words of Michael Wondrak, “we show that, in addition to the well-known Hawking radiation, there is also a new form of radiation.”
As Van Suijlekom explains, “we show that well beyond a black hole the curvature of space-time plays an important role in the creation of radiation. The particles are already separated there by the tidal forces of the gravitational field.” In other words, the work made it clear that the type of radiation described by Hawking was also produced without the presence of an event horizon, something previously thought to be impossible.
Falcke, the third of the authors, says for his part that “this means that other objects without an event horizon, such as the remains of dead stars and other large objects in the Universe, also emit this type of radiation. And, following a very long period, that would lead to everything in the Universe eventually evaporating, just like black holes do. This is a discovery that changes not only our understanding of Hawking radiation, but also our view of the Universe and its future.”
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