Physics Help
Fundamental Forces
Gravitational Force | Electromagnetic Force | Weak Force | Strong Force
Fundamental force
In
physics, four fundamental forces are known thus far:
1)
Gravity is by far the weakest force, but is the force that has the greatest
large-scale impact on the universe. Unlike the other forces, gravity works
universally on all matter and energy, and is (so far as we know) universally
attractive. Any matter or energy anywhere and at any time in the universe
attracts all other matter and energy in the universe, as long as it is inside
its
light cone. This is explained in detail in
General Relativity, which describes gravity in terms of
spacetime. One active area of research involves merging the theories of
general relativity and
quantum mechanics into a more general theory of
quantum gravity. It is widely believed that in a theory of quantum gravity,
gravity would be mediated by a particle which is known as the
graviton.
An interesting theory,
negative gravity (also called
dark energy), arose while trying to explain the recent discovery that the
expansion of the universe is actually accelerating.
2)
Electromagnetism is the combination of
electrostatic and
magnetic forces. It is the force between charged particles, such as the
force between two electrons, or the force between two current carrying wires.
The quantum theory of electromagnetism is known as
quantum electrodynamics (QED). In QED,
virtual photons transfer this force.
3) The
weak nuclear force mediates
beta decay. The weak force is transferred by W and Z bosons.
Neutrinos interact with other matter only through the weak nuclear force and
gravity, and hence can pentrate large amounts of matter without being scattered.
Electromagnetism and the weak force can be seen as two aspects of the same
underlying force, the
electroweak force.
4) The
strong nuclear force is the force holding together the protons and neutrons
inside the atomic nucleus. The strong force is transferred by
gluons and it acts on particles that carry "color charge", i.e.
quarks and gluons.
Most particle physicists perceive the existence of different
forces each with separate theories to describe them to be inelegant and believe
that all of the forces can be described in a general
theory of everything. In the late
1960s and early
1970s, a successful theory which forms part of the
standard model was proposed to unify electromagnetism and the weak force
into a single
electroweak force. There is also active work on various forms of
grand unified theories which attempt to unite the strong and electroweak
forces. Many of these theories predict
proton decay which has not been observed.
Much more speculative are theories that attempt to reconcile
quantum field theory with
General Relativity, in order to find a successful theory for
quantum gravity, and then to combine this into a general
theory of everything. Unlike grand unified theories, most propsed theories
of everything do not yet give experimentally testable predictions.
What
physical scientists call the four fundamental
forces of nature are:
It is currently believed that all interactions can be
explained in terms of these four forces. For instance,
friction is a result of the electromagnetic force.
However, an exotic
fifth force has been proposed by some physicists from time to time, mostly
to explain discrepancies between predicted and measured values of the
gravitational constant. As of 2003, all of the experiments which seem to
indicate a fifth force have been explainable in terms of experimental errors.
Also of note is that all four of these forces are
conservative forces which is to say that the effect of the force on an
object moving from one point to another is independent of the path of the
object.
Home | Physics | Theories | Concepts | Fundamental Forces | Particles | Subfields | Methods | Tables | History
Unsolved Problems | Related Fields | License
Physics Help, made by MultiMedia | Free content and software
This guide is licensed under the GNU
Free Documentation License. It uses material from the Wikipedia.
| 
