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> The unification of physics Issue: 2006-3 Section: Science



It all started in 1820, when Hans Christian Oersted from Holland (1777-1851), experimentally verified that there was a relation between electricity and magnetism, two phenomena the study of which dates back to the time of the Greek Thalis of Militos. A really big number of researchers who studied this relation followed, the most significant of which were Michael Faraday (1791-1876), Marie Ampere (1775-1836) and James Clerk Maxwell (1831-1879).

In 1864, Maxwell presented a complete series of laws that would explain each and every one of the electromagnetic phenomena (including light, which, according to what Maxwell said was an electromagnetic wave). In that way, he managed to realize one of the greatest achievements of humanity: the development of the electromagnetism theory and as a consequence the unification of electricity and magnetism.

Maxwell’s achievement became part of the so-called endeavor to unify physics: the development of a complete, consistent theory that would explain every kind of field within the universe. Einstein devoted the last years of his life trying to develop a similar theory, albeit inconclusively.

Nowadays, it is believed that the fundamental particles join together to form matter in all the different scales (from the quarks which join to form protons and neutrons, to the huge conglomerations of matter in stars and galaxies) through four fundamental interactions, which we call forces.

The most familiar force is gravity; it keeps our feet on the ground, and the planets in motion around the stars. It appears among particles due to their mass. Although gravity is by far the weakest of the four fundamental interactions, it is the dominant one in our everyday life thanks to two of its characteristics: it acts on long distances and is always attractive.

The next, most powerful force is the electromagnetic one, which manifests itself in the effects of the electromagnetic phenomena. It occurs due to electric charge and acts only on electrically charged particles. It is the force which holds the negatively charged electrons in motion around the positively charged nuclei, as well as the atoms to form molecules due to their charged substructure.

The next interaction is the weak one. We do not sense this force in our daily routine, but it is the one responsible for the nuclear fission (radioactivity effect), as well as for the decay of particles to other particles (e.g. of a neutron to a proton, an electron to an anti-electron neutrino via a virtual, mediating W- particle).

The most powerful force is the strongest one. Although we have no sense of this interaction either, it is the most responsible for the existence of life. Thanks to it, quarks bind to form protons and neutrons, and protons do not repel each other in nuclei due to their positive charge (residual strong interaction).


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