8
From Idea to Reality: The Neutrino Story
Unfolds in Slow Motion
The neutrino hypothesis resolved a major puzzle in physics and rescued the
sacred principle of energy conservation in physics. But is the neutrino a real
particle or just an artifice to satisfy our minds? If the particle were never
discovered, it would remain an enigma, and to be sure, there was a lot of
skepticism about the neutrino idea. For one thing, according to Pauli’s idea,
the neutrino resides inside the nucleus, but how a light particle can stay hidden
inside the nucleus was a mystery.
Nearly 4 years passed before anyone took the neutrino idea seriously. For
theorists, it was a puzzle to understand how the neutrino could stay hidden
inside the nucleus. Even if, somehow the neutrino was inside the nucleus, how
the nucleus would suddenly “cough” out a neutrino in the process of beta decay
was another mystery. The “coughing up” of particles was of course not a new
phenomenon, since photons (light) being “coughed out” in electromagnetic
processes was already considered before 1930, but the guideline for that was
already there in the classical theory of electricity. So, one could use the classical
theory as a model for the photon, but there was no such example for the
neutrino. Then in 1934, Enrico Fermi wrote a theory of how neutrinos could
be emitted from the nucleus. He used his knowledge of the emerging field of
Quantum Field Theory to write his theory. Quantum Field Theory before
1930 was applied only to discuss the interaction of light with matter, and
Fermi’s genius was to extend it to understand beta decay. This is known as
Fermi’s theory of beta decay and the strength of this interaction, denoted by
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer
Nature Switzerland AG 2021
R. N. Mohapatra, The Neutrino Story: One Tiny Particle’s Grand Role in the Cosmos,
https://doi.org/10.1007/978-3-030-51846-2_8
57
From Idea to Reality: The Neutrino Story
Unfolds in Slow Motion
The neutrino hypothesis resolved a major puzzle in physics and rescued the
sacred principle of energy conservation in physics. But is the neutrino a real
particle or just an artifice to satisfy our minds? If the particle were never
discovered, it would remain an enigma, and to be sure, there was a lot of
skepticism about the neutrino idea. For one thing, according to Pauli’s idea,
the neutrino resides inside the nucleus, but how a light particle can stay hidden
inside the nucleus was a mystery.
Nearly 4 years passed before anyone took the neutrino idea seriously. For
theorists, it was a puzzle to understand how the neutrino could stay hidden
inside the nucleus. Even if, somehow the neutrino was inside the nucleus, how
the nucleus would suddenly “cough” out a neutrino in the process of beta decay
was another mystery. The “coughing up” of particles was of course not a new
phenomenon, since photons (light) being “coughed out” in electromagnetic
processes was already considered before 1930, but the guideline for that was
already there in the classical theory of electricity. So, one could use the classical
theory as a model for the photon, but there was no such example for the
neutrino. Then in 1934, Enrico Fermi wrote a theory of how neutrinos could
be emitted from the nucleus. He used his knowledge of the emerging field of
Quantum Field Theory to write his theory. Quantum Field Theory before
1930 was applied only to discuss the interaction of light with matter, and
Fermi’s genius was to extend it to understand beta decay. This is known as
Fermi’s theory of beta decay and the strength of this interaction, denoted by
© The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer
Nature Switzerland AG 2021
R. N. Mohapatra, The Neutrino Story: One Tiny Particle’s Grand Role in the Cosmos,
https://doi.org/10.1007/978-3-030-51846-2_8
57