Otro de los desarrollos que culminaron en el siglo XX, es la existencia de CUATRO fuerzas fundamentales. Su descubrimiento es una larga historia, si bien ya en tiempos de Maxwell, en el siglo XIX, se hizo claro la existencia de las dos fuerzas más conocidas, la gravedad y el electromagnetismo. Leo:
In addition to these developments, four fundamental forces had been recognized to exist in nature. Let us have a brief look at them.
One of them is the force of gravity. This force has been known since antiquity, but it was first described accurately by Isaac Newton. Gravity underwent a profound reformulation in Albert Einstein"s theory of general relativity. In this theory, the spacetime arena of special relativity acquires a life of its own, and gravitational forces arise from the curvature of this dynamical spacetime. Einstein"s general relativity is a classical theory of gravitation. It is not formulated as a quantum theory.
The second fundamental force is the electromagnetic force. As we discussed above, the electromagnetic force is well described by Maxwell"s equations. Electromagnetism, or Maxwell theory, is formulated as a classical theory of electromagnetic fields. As opposed to Newtonian mechanics, which was modified by special relativity, Maxwell theory is fully consistent with special relativity.
The third fundamental force is the weak force. This force is responsible for the process of nuclear beta decay, in which a neutron decays into a proton, an electron, and an antineutrino. In general, processes that involve neutrinos are mediated by weak forces. While nuclear beta decay had been known since the end of the nineteenth century, the recognition that a new force was at play did not take hold until the middle of the twentieth century. The strength of this force is measured by the Fermi constant. Weak interactions are much weaker than electromagnetic interactions.
Finally, the fourth force is the strong force, nowadays called the color force. This force is at play in holding together the constituents of the neutron, the proton, the pions, and many other subnuclear particles. These constituents, called quarks, are held so tightly by the color force that they cannot be seen in isolation.
En el próximo post volveremos a la primera unificación de estas fuerzas en el siglo XX
Angel "Java" Lopez