The universe is doomed to evaporate

Even stars too small to be black holes will also gradually disappear.

Research into black holes has served as a reminder of how physicists believe the universe will end: not with an explosion, but… with extinction. The key lies in Hawking radiation.

From black holes to the rest of the Universe. Black holes are not objects doomed to grow forever by absorbing matter: they can also shrink. The reason is that they release energy in the form of radiation called Hawking radiation. As we can deduce from the most famous equivalence in physics, this results in a loss of mass.

Research last year by experts at Radboud University in Nijmegen, the Netherlands, extended this phenomenon beyond black holes: to all objects with a certain mass.

Hawking radiation. How is this possible? Hawking radiation is one of the most amazing phenomena in the Universe. Not only because it allows us to make the most voracious objects in our Universe thinner, but also because it combines knowledge of quantum field theory with knowledge of the theory of gravity.

“Out of nothing“Under normal conditions, particles and antiparticles can appear “out of nowhere.” These events last for infinitesimal fractions of time, during which the particle and antiparticle annihilate each other. But there is a context in which this does not happen: in the medium the event horizon of a black hole. In this case, the particle and antiparticle may end up on opposite paths, without being able to annihilate each other.

This generates radiation escaping from the black hole, which in turn implies a loss of mass.

Be careful. Latest work published in the journal Physical Review Letterschallenges the idea that only the presence of an event horizon can create enough curvature in spacetime to avoid particle-antiparticle annihilation.

This in turn means that this particular radiative attenuation can manifest itself in objects that, despite having large masses capable of bending the fabric of spacetime, do not have an event horizon because the gravitational attraction they generate is not such as to absorb light. Thus, even those stars that are not massive enough to turn into a black hole at the end of their lives can gradually disappear.

fall short. “We show that far beyond the black hole, the curvature of spacetime plays an important role in creating radiation. There, the particles are already separated by the tidal forces of the gravitational field,” explained Walter van Suilekom, one of the authors. About the investigation. It can be said that Stephen Hawking, even if he were correct in his postulate about the decay of black holes, might have failed if he had based his analysis on the existence of singularities associated with black holes.

Finally the Universe. No one knows for sure what the end of the universe will be, but astrophysicists have a well-established hypothesis (and several alternatives with less consensus). The idea of ​​a fading Universe corresponds exactly to the most common hypothesis. Under this concept, proposed by physicists, space and everything in it will expand at ever-increasing rates. This will cause matter to move further and further in an increasingly less dense and cold Universe.

Everything that inhabits it could have disappeared by then.

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Image | Unsplash

*A previous version of this article was published June 2023.