Chapter 4 – Forces

Strong and weak forces

Strong nuclear force

The strong nuclear force is mediated by gluons and holds atomic nuclei together. It gets stronger with distance preventing free quarks.

Quarks carry an attribute called color charge that comes in three types called red, green and blue – each quark carries one of these colors. The name “color charge” is just a label – color charge has nothing to do with colors or charge! The label color was used because the three color charges cancel out just like red, blue and green produce white.

Gluons carry the strong force and tightly bind quarks together into combinations that have no net color charge

Protons and neutrons contain three quarks, one carrying each color charge, producing a color-neutral particle. This is why there are three quarks combined.

The strong force also holds protons and neutrons together in the nucleus of an atom overcoming the
repulsion between positively charged protons

Weak nuclear force

The weak force has very short range and is mediated by the W and Z bosons.

Weak nuclear force doesn’t push or pull; it drives radioactive decay. The force changes particle type.

One example is changing a down quark to an up quark, anti-neutrino and electron. This happens in two steps involving a transient W boson that only exists for a short time. You will see that each step of the transformation conserves charge and spin.

A neutron is down down quarks and an up quark so this decal happening to one of the quarks in a neutron turns it into a proton. That makes the decay become a neutron turning into a proton, electron and enti-neutrino.

This decay explains unexpected transformations of atoms. This can change a carbon-14 atom which has 6 protons, 8 neutrons and 6 electrons into a nitrogen-14 atom that has 7 protons, 7 neutrons and 7 electrons. The extra anti-neutrino leaves at high speed and was originally not detected so the first discovery of this decay just looked like one atom spontaneously changing into a different atom.