|
|
|
Force: (Physics) Any action between two bodies which changes, or tends to change, their relative condition as to rest or motion; or, more generally, which changes, or tends to change, any physical relation between them, whether mechanical, thermal, chemical, electrical, magnetic, or of any other kind; as, the force of gravity; cohesive force; centrifugal force. (Webster's Revised Unabridged Dictionary, 1913)
|
|
There are 4 fundamental forces in the Universe, the Strong, Weak, Electromagnetic and Gravitational forces. Each exhibit different properties and it has been the aim of Physics to unite these four forces from one common metaphysical foundation.
Properties of the Fundamental ForcesThe strong interaction is very strong, but very short-ranged. It acts only over ranges of order 10-13 centimeters and is responsible for holding the nuclei of atoms together.
The electromagnetic force causes electric and magnetic effects such as the repulsion between like electrical charges or the interaction of bar magnets. It is long-ranged, but much weaker than the strong force. It can be attractive or repulsive, and acts only between pieces of matter carrying electrical charge.
The weak force is responsible for radioactive decay and neutrino interactions. It has a very short range and, as its name indicates, it is very weak.
The gravitational force is weak, but very long ranged. Furthermore, it is always attractive, and acts between any two pieces of matter in the Universe since mass is its source.
The four fundamental forces all play central roles in making the Universe what it is today, but with respect to the large-scale issues that are of interest to cosmology it is gravitation that is most important. This is because of two of its basic properties that set it apart from the other forces: (1) it is long-ranged and thus can act over cosmological distances, and (2) it always supplies an attractive force between any two pieces of matter in the Universe.
Thus, although gravitation is extremely weak, it always wins over cosmological distances and therefore is the most important force for the understanding of the large scale structure and evolution of the Universe.
Unification of the Forces of NatureTheories that postulate the unification of the strong, weak, and electromagnetic forces are called Grand Unified Theories (often known by the acronym GUTs). Theories that add gravity to the mix and try to unify all four fundamental forces into a single force are called Superunified Theories (see Theory of Everything). The theory that describes the unified electromagnetic and weak interactions is called the Standard Electroweak Theory, or sometimes just the Standard Model.
Grand Unified and Superunified Theories remain theoretical speculations that are as yet unproven, but there is strong experimental evidence for the unification of the electromagnetic and weak interactions in the Standard Electroweak Theory. Furthermore, although GUTs are not proven experimentally, there is strong circumstantial evidence to suggest that a theory at least like a Grand Unified Theory is required to make sense of the Universe.
Editor: Haselhurst
|
|