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R. N. Mohapatra
7.1 Missing Energy Puzzle in Beta Ray Emission
“Are there any more fundamental particles beyond the proton, electron and
the neutron?” was a question that came to people’s mind in the 1920s. The
answer came from some puzzling findings in the early part of this century.
Conservation of total energy is one the edifices of modern physics. It is
based on sound physical principles and says that in any physical process, the
total energy remains constant as the system of particles involved in the process
evolves in time. Whatever energy is in the system at the initial stage, the same
energy comes out in the final stage. It is a principle obeyed by all physical
systems. Are there any systems that do not obey it? No one has found one yet,
and if any one does, that would be a profound discovery that would shake
up human civilization in many ways. Energy conservation is connected to the
somewhat mysterious principle that as we move in time, the system remains
unchanged overall. In physics lingo this is called “time translation invariance.”
Before Einstein proposed his theory of relativity, total energy was considered
to be the sum total of kinetic energy plus the potential energy inside the system.
Kinetic energy is the energy of motion, such as a moving car’s energy due to
its motion. Potential energy, on the other hand, is the energy in a physical
situation even when nothing moves. For instance, if you are holding a stone
ten feet above the ground, the stone has the potential to do work when it falls
to the ground, even though it was not moving prior to falling. That hidden
energy in the stone is called potential energy. Another example of potential
energy is when two electric charges are held separated by a distance.
After the theory of relativity, the mass of the particles participating in
the process was to be added to the total energy, since mass and energy
became interchangeable, one converting to the other. As noted earlier, this is a
principle that eventually led the construction of nuclear reactors where part of
the mass of the nucleus gets converted to energy. This principle became a part
of physics after 1905, when Einstein proposed the theory of relativity. Energy
conservation has been a useful principle in understanding many observed
phenomena in nature. No deviation had been observed until a nuclear process
in the early 1890’s was analyzed, which threatened to contradict this sacred
principle, as described below.
In 1896, French physicist Henri Bacquerel, a descendant of a line of
well known physicists, discovered rays similar to X-rays while studying the
phenomenon of fluorescence from a compound of uranium. They were also
discovered by Rutherford. The discovery of beta rays (as Rutherford called
them) generated a great deal of curiosity among physicists who wanted to
R. N. Mohapatra
7.1 Missing Energy Puzzle in Beta Ray Emission
“Are there any more fundamental particles beyond the proton, electron and
the neutron?” was a question that came to people’s mind in the 1920s. The
answer came from some puzzling findings in the early part of this century.
Conservation of total energy is one the edifices of modern physics. It is
based on sound physical principles and says that in any physical process, the
total energy remains constant as the system of particles involved in the process
evolves in time. Whatever energy is in the system at the initial stage, the same
energy comes out in the final stage. It is a principle obeyed by all physical
systems. Are there any systems that do not obey it? No one has found one yet,
and if any one does, that would be a profound discovery that would shake
up human civilization in many ways. Energy conservation is connected to the
somewhat mysterious principle that as we move in time, the system remains
unchanged overall. In physics lingo this is called “time translation invariance.”
Before Einstein proposed his theory of relativity, total energy was considered
to be the sum total of kinetic energy plus the potential energy inside the system.
Kinetic energy is the energy of motion, such as a moving car’s energy due to
its motion. Potential energy, on the other hand, is the energy in a physical
situation even when nothing moves. For instance, if you are holding a stone
ten feet above the ground, the stone has the potential to do work when it falls
to the ground, even though it was not moving prior to falling. That hidden
energy in the stone is called potential energy. Another example of potential
energy is when two electric charges are held separated by a distance.
After the theory of relativity, the mass of the particles participating in
the process was to be added to the total energy, since mass and energy
became interchangeable, one converting to the other. As noted earlier, this is a
principle that eventually led the construction of nuclear reactors where part of
the mass of the nucleus gets converted to energy. This principle became a part
of physics after 1905, when Einstein proposed the theory of relativity. Energy
conservation has been a useful principle in understanding many observed
phenomena in nature. No deviation had been observed until a nuclear process
in the early 1890’s was analyzed, which threatened to contradict this sacred
principle, as described below.
In 1896, French physicist Henri Bacquerel, a descendant of a line of
well known physicists, discovered rays similar to X-rays while studying the
phenomenon of fluorescence from a compound of uranium. They were also
discovered by Rutherford. The discovery of beta rays (as Rutherford called
them) generated a great deal of curiosity among physicists who wanted to