In particle physics, an attempt to explain all of the fundamental forces and
their relationships between elementary particles in single framework was
accomplished in theory by the g.u.t. by the grand unification theory. In
relation to physics these forces can be described as fields that mediate
interactions between separate or distant objects. These theories such as
eltromagnetism and general relativity started to attempt the unification of
theories, however they would emerge as the fundamental basics of the g.u.t. Or
the grand unification theory. At sub atomic levels, these fields are described
as quantum field theories, which started the ideas of quantum mechanics. In the
1940’s the ideas quantum electrodynamics (QED), the quantum field theory of
electromagnetism, became fully developed. In QED, charged particles interact as
they emit and absorb photons (minute packets of electromagnetic radiation), in
effect exchanging the photons in a game of subatomic "catch." This
theory has become the prototype for theories of the other forces. During the
1960s and '70s particle physicists discovered that matter is composed of two
types of basic building block--the fundamental particles known as quarks and
leptons. The quarks are always bound together within larger observable
particles, such as protons and neutrons. They are bound by the short-range
strong force, which overwhelms electromagnetism at sub nuclear distances. The
leptons, which include the electron, do not "feel" the strong force.
However, quarks and leptons both experience a second nuclear force, the weak
force. This force, which is responsible for certain types of radioactivity
classed together as beta decay, is feeble in comparison with electromagnetism.
At the same time that the picture of quarks and leptons began to crystallize,
major advances led to the possibility of developing a unified theory. Theorists
began to invoke the concept of local gauge invariance, which postulates
symmetries of the basic field equations at each point in space and time. Both
electromagnetism and general relativity already involved such symmetries, but
the important step was the discovery that a gauge-invariant quantum field theory
of the weak force had to include an additional interaction--namely, the
electromagnetic interaction. Sheldon Glashow and peers independently proposed a
unified "electro weak” theory these forces based on the exchange of four
particles: the photon for electromagnetic interactions, and two charged W
particles and a neutral Z particle for weak interactions. During the 1970s a
similar quantum field theory for the strong force, called quantum thermodynamics
(QCD), was developed. In QCD, quarks interact through the exchange of particles
called gluons. The aim of researchers now is to discover whether the strong
force can be unified with the electro weak force in a grand unified theory
(GUT). There is evidence that the strengths of the different forces vary with
energy in such a way that they converge at high energies. However, the energies
involved are extremely high, more than a million times as great as the energy
scale of electro weak unification, which has already been verified by many
experiments. Grand unified theories describe the interactions of quarks and
leptons within the same theoretical structure. This gives rise to the
possibility that quarks can decay to leptons and specifically that the proton
can decay. Early attempts at a GUT predicted that the proton's lifetime must be
in the region of 1032 years. This prediction has been tested in experiments that
monitor large amounts of matter containing on the order of 1032 protons, but
there is no evidence that protons decay. If they do in fact decay, they must do
so with a lifetime greater than that predicted by the simplest GUTs. There is
also evidence to suggest that the strengths of the forces do not converge
exactly unless new effects come into play at higher energies. One such effect
could be a new symmetry called supersymetry, which is part of the g.u.t.