Black holes of stellar mass are rather small objects in The Universe. They consist of – as we have seen in previous pages – the remnants of collapsed red giants which in their part are made of tiny elementary particles. As a consequence of that, the world of the tiny must have an enormous significance for the world of the Biggest, the Universe. Everything, black holes included, is composed of atoms, or as today´s physicists say - of baryon matter.
The stunning similarities between the inner structure of black holes and elementary particles brought some physicists to the believe that they must basically be the same. This will be particularly true in the case of the micro holes which CERN strives to fabricate in Geneva with its LHC.
The elementary particles – this means electrons, protons and neutrons - possesses charge, mass and angular momentum, just as do black holes. The core of the atom is orbited by clouds of electrons, similarly the accretion ring, surrounding a black hole.
All this is reason enough to take a closer look into the atomic construction inside the world of the smallest. Here the author gives a short overview of the former, standard model of particles, the Bohr atom, and the later standard model which is now in use. We begin with the classical Bohr model.
The Bohr model, introduced 1913 by Niels Bohr and later revised by Rutherford, is a relatively primitive model of the hydrogen atom (see also page 42) and considered a planetary-model atom. Based upon that model, all of the 92 naturally occurring elements have a core of heavy particles with some electrons in the orbit. The core, consisting of protons and neutrons, provides almost the entire mass. Heavier atoms have more protons in the nucleus, and more electrons to cancel the charge. Neutrons in the nucleus (having no charge) are needed to retain the protons (having same charge) within the nucleus. They play the role of "glue". The entire atom is in balance and free of charge, if seen from a distance. It soon became obvious that most of an atom would be empty space. Earlier voices had claimed that eventually, nature could significantly shrink the atoms within neutron stars or even black holes, under the influence of gravitational forces. Subsequently outdated, the Bohr model became obsolete but has regained merit because it can explain most but not all effects oberved by physicists. Today´s model of the atom is much more complex .
The modern Standard Model of particles:
Since the late 20th century, the Standard Model of particles has replaced the model of the Bohr atom. It is a theory concerning the electromagnetic and nuclear forces of sub-atomic particles and is characterised by implementing additional particles like Quarks. Unfortunately, it is not a complete theory of fundamental interactions because it makes some simplified assumptions. For that reason, this model is sometimes regarded as a "theory of almost everything".
Quarks & Hadrons:
Both, the Quarks and the Hadrons, have replaced the former protons, neutrons and electrons. There are six types of quarks, known as up, down, strange, charm, bottom and top. Up and down quarks are stable and the most common in the Universe, whereas the others can only be produced in high energy collisions. Quarks belong to the family of Hadrons.
Fermions:
There are 12 elementary particles having spin, known as Fermions and classified by the charges they carry. There are six quarks and six leptons forming fermions. Lepton is the name of a group containing the electron, neutrino, muon and tau particles. Fermions carry colour, charge and the strong force of interaction.
Bosons:
These are defined as force carriers that mediate the strong, weak and electromagnetic fundamental interactions of particles. This interaction happens by exchanging other particles, known as force mediating particles.
Higgs boson:
The Higg boson confers mass to hadrons and quarks. It plays a unique role in the Standard Model, by explaining why other elementary particles are massive. Its counterpart is a hypothetical particle called a ‘graviton‘ which has never been detected. It might be that the Higgs particles and the gravitons are one and the same.
The four fundamental forces in the Universe:
Fundamental interactions or interactive forces are recognized as gravitational, electromagnetic, strong nuclear and weak nuclear. The cohesion of quarks within the core of atoms is achieved by the strong nuclear force and particles with the name gluons acting literally, as a glue amongst them. The atom itself is held together by electromagnetic force. The weak nuclear force induces radioactivity and other electromagnetic radiation.
Since 2012 the existence of Higgs-particles seems to have been confirmed. The detection of particles having just the right energy level, proved the Higgs boson. The picture shows traces following collision of protons in the LHC at high energy level (By courtesy of CERN)
