Neutrons - "Obvious lack of Knowledge"

“Obvious lack of knowledge”, that is the criticism aimed by four retired nuclear physicists who have read my book. The basis for this claim has been (in all four cases) the characterization of a neutron as being “made up of a proton and an electron”.

Is a neutron “made up of a proton and an electron”?

Neutrons are large subatomic particles. Subatomic particles can be “fundamental” or “elementary” as we once thought atoms were or “composite”, being made up of other subatomic particles.

Neutrons are composite subatomic particles, made up of elementary particles, in this case quarks and gluons. Quarks are further characterized by “flavor” – up, down, strange, charm, bottom, and top. (I am not making this up!)

Both neutrons and protons have three quarks. This number cannot change. The neutron is made up of two down quarks and one up quark and is about 0.2% more massive than a proton. Neutrons decay with an average half life of 10.3 minutes. “Decay” in neutron terms involves one of the down quarks converting to an up quark; two up quarks and one down quark makes a proton. The difference in mass is given off as an electron plus an electron antineutrino.

Neutrinos and antineutrinos were completely omitted from From Hiroshima to Fukushima to You because they have no electrical charge and apparently don’t affect living tissue. They do account for the tiny bit of energy left over when the proton and electron are formed at the decay of a neutron.

So in summary: In relatively quick succession, the average lifetime of a neutron being 10.3 minutes, the down quark becomes an up quark and the neutron becomes a proton, now making up the greater part of the original mass. With the formation of a proton, the electron plus energy is released.

Is a neutron “made up of a proton and an electron”? Technically no but that’s what we get when neutrons decay. Shucks, I should have said "effectively made up of a proton and an electron".

There is also a tendency among the retired physicists to get their shirts in knots over calling neutrons “glue that holds a nucleus together”.

(One physicist whose real issue is about nuclear power used this to harass a professor using my book as text to indicate that I know nothing about which I speak.)

Let me quote Dr. Ken Mellendorf from Illinois Central College:  “Neutrons hold the nucleus together.”  His explanation is slightly different than mine.

Protons are positively charge and normally would repel one another. At the close range of a nucleus, something called the “Strong Force” takes over – it is more powerful than the existing electrical repulsion. However, except at “absolute zero”, protons still have a tendency to be a bit uneasy and move around. They need extra holding force.

Neutrons have no electrical charge and are similarly affected by the Strong Force so they are attracted to both the protons and other neutrons. As nuclei become larger for larger atoms, more and more neutrons are required to create the force to hold the collection of protons and neutrons together.

Sounds like “glue” to me!