In the case of a black hole radiating or leaking Hawking radiation, its energy will be reduced. In accordance with Einstein´s formlula e=mc², the hole will lose mass and diminish. Just how small can black holes become? Is it possible that tiny Holes exist and could they become entirely extinct through out the Universe? These kinds of questions are discussed in the community of astrophysicists. Since 2008 at the world largest particle accelerator, the Large Hadron Collider (LHC) at CERN (Centre Européen pour la Recherche Nucléaire) in Geneva, high speed protons have been emitted. Black holes are expected to be produced if these particles do collide with each other.
Criticism and concern arose from people, anxious about the possibilty that tiny Black Holes which could grow rapidly, might be created, with the obvious danger that these could present. In 2012 it led to a lawsuit at a court in Münster/Germany trying to bring these experiments to an end. The fear was that these ´man made´ Black Holes could lead to an apocalypse not to mention the end of the world. It was argued that a Black Hole if created, could grow very rapidly absorbing all matter inside the collider, wolfing the collider itself and later on Geneva and the rest of the entire world. Doomsday might have arrived. Understandably, this needed to be viewed with concern.
The court rejected the objection, giving its reasons for refusal: the majority of the scientists believed that CERN´s trials at the LHC in Geneva would not endanger the world. Indeed, the physicists themselves had earlier predicted the creation of small black holes in experiments carried out at the LHC. Because of the low energy levels which were to be applied, it should result in very small black holes about the size of an atom. There would be no danger because any micro Black Holes would degrade quickly, collapse and simply disappear. Anxieties were assuaged.
The huge accelerator at CERN in the form of a ring and is situated underground, having a length of 27 km. Close to the airport (By courtesy of CERN)
The micro Black Hole was not (yet) discovered at CERN, operation being at too low energy level, about 4 TeV – the rig was not yet fired up to full power level. But another particle, on a list of the most wanted: the Higgs-particle was found. In July 2012 CERN claimed that an new, elementary particle had been detected, already theorised in 1964 by a British scientist. This particle having no charge and zero spin, was one of the most sought-after particles in modern physics. It is also called ´The God Particle´ because of the ability to give rise to the masses of all the elementary particles. Mass means gravity. Revealing the secrets of gravitation is revealing secrets of Black Holes. Scientists at CERN were encouraged by obtaining results so soon despite functioning at such low energy levels. When the facility is eventually fired up at the full power of 7 TeV, new discoveries are anticipated.
Just how Small can Black Holes be?
Chandrasekhars calculations had shown that the minimum mass of a stellar black hole has to be about triple that of our Sun. How do the physicists expect to get micro small Holes with the help of the LHC at CERN? Do they even exist ? Schwarzschild did not regard any physical limitation for the size of black holes (see his formula on page 28).
Indeed, due to Hawking´s work, there is no lower limit for the minimum size of a black hole. Micro black holes are not excluded by the theory but are obviously very rare in space. Perhaps they might be formed if a certain level of energy were applied at the LHC. Yet if that happened, they would surely have too short a life span to interact with other, surrounding matter. It is quite interesting to investigate what diameters black holes might have. The chart shows the proportional dependencies between the Schwarzschild-radius versus the initial mass:
