A Disturbance in the Force
For more than seventy years, nuclear physicists have credited the strong force with holding protons and
neutrons together within the nucleus. The force was born out of the need for a mechanism to overcome the
strong repulsive electrostatic force, generated by the protons in the nucleus, after neutrons replaced
electrons as nuclear components in 1932. Although a widely accepted concept, this force has proven to be a
challenge for nuclear scientists to characterize. Declared a fundamental force like gravity and the electrical
force, intuitively one might expect that a few simple rules govern the behavior of this force. However, in
reality, the strong force does not appear to be simple at all.
There have been several attempts to explain the strong force, but all are somewhat complex and lacking in
some respect. In 1935, Hideki Yukawa proposed that the force holding two nucleons together was due to the
nucleons exchanging particles called mesons. Other attempts at explaining the force include the liquid drop
model proposed in the 1930s by Neils Bohr, and the shell theory proposed by Maria Goeppert-Mayer in the
1940s. The Standard Model nuclear binding theory, quantum chromodynamics, or QCD, was proposed in
the early 1970s. It also relies on particle exchange to generate the strong force, using particles called
gluons. According to the theory, quarks exchange gluons across nucleon boundaries to create the strong
force.
Scientists consider the strong force a fundamental force like gravity and the electric force. However, unlike
gravity and the electrical force, which behave in relatively simple ways, the strong force appears to be a very
complex phenomenon. There is no inverse-squared relationship, or proportionality to mass or charge
associated with the strong force as there are for the gravitational and electrical forces.
For more than seventy years, nuclear physicists have credited the strong force with holding protons and
neutrons together within the nucleus. The force was born out of the need for a mechanism to overcome the
strong repulsive electrostatic force, generated by the protons in the nucleus, after neutrons replaced
electrons as nuclear components in 1932. Although a widely accepted concept, this force has proven to be a
challenge for nuclear scientists to characterize. Declared a fundamental force like gravity and the electrical
force, intuitively one might expect that a few simple rules govern the behavior of this force. However, in
reality, the strong force does not appear to be simple at all.
There have been several attempts to explain the strong force, but all are somewhat complex and lacking in
some respect. In 1935, Hideki Yukawa proposed that the force holding two nucleons together was due to the
nucleons exchanging particles called mesons. Other attempts at explaining the force include the liquid drop
model proposed in the 1930s by Neils Bohr, and the shell theory proposed by Maria Goeppert-Mayer in the
1940s. The Standard Model nuclear binding theory, quantum chromodynamics, or QCD, was proposed in
the early 1970s. It also relies on particle exchange to generate the strong force, using particles called
gluons. According to the theory, quarks exchange gluons across nucleon boundaries to create the strong
force.
Scientists consider the strong force a fundamental force like gravity and the electric force. However, unlike
gravity and the electrical force, which behave in relatively simple ways, the strong force appears to be a very
complex phenomenon. There is no inverse-squared relationship, or proportionality to mass or charge
associated with the strong force as there are for the gravitational and electrical forces.
| Copyright © 2009 by William L. Stubbs |
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