All the known matter in the Universe consists of the following fundamental particles:
The Up Quark and its heavier cousins, each of which has an electric charge of +2/3.
The Down Quark and its heavier cousins, each of which has an electric charge of -1/3.
The electron and its heavier cousins, each of which has an electric charge of -1.
And the neutrinos, each of which has an electric charge of zero.
Each particle has an associated anti-matter particle with the same mass,
but the opposite electric charge, thereby doubling the number of particles.
We now need to double the number of particles again because
there are actually two versions of each matter and each anti-matter particle.
One version has what we call a “Left Handed Chirality” and
the other version has what we call a “Right Handed Chirality.”
The Chirality of a particle is related to, but not the same thing as its “Helicity”,
which can also be left handed or right handed.
The “Helicity” refers to the component of spin in the direction of the particle’s motion.
For a particle travelling at the speed of light,
the Helicity of the particle is always equal to its Chirality.
Massless particles always travel at the speed of light,
but particles with mass must always travel slower than the speed of light.
The slower a particle is travelling,
the less likely there is to be any correlation between its Helicity and its Chirality.
Chirality is a purely quantum mechanical property
that has no analogy in classical physics.
It deals with what direction the complex numbers describing
the particle’s quantum state rotate around the complex plain
when the particle is rotated around its direction of motion.
Gravity, electromagnetism, and the Strong Nuclear Force
treat Left and Right Chiral particles in exactly the same way,
so from their perspective, the Left and Right Chiral versions of a particle
can be thought of as if they are the exact same particle.
The only known phenomena in existence that distinguishes between
the Left and Right Chiral particles is the Weak Nuclear Force.
The Weak Nuclear Force only affects the Left Chiral version of the matter particles
and the Right Chiral version of the anti-matter particles.
Only the Left Chiral version of the matter particles
and the Right Chiral version of the anti-matter particles
are able to absorb and emit the force carriers
of the Weak Nuclear force, the “W” and “Z” bosons.
The other known fundamental particles that are bosons
are the photon, the gluon, and the Higgs boson,
each of which have an electric charge of zero.
The “Z” boson also has an electric charge of zero.
But the “W” boson has an electric charge of either +1 or -1.
Like all other phenomena in the universe,
the weak nuclear force obeys the conservation of electric charge,
meaning that if a positive charge is created,
a negative charge must be created by an equal amount.
The Weak Nuclear Force allows a quark with a charge of -1/3
to transform into a quark with a charge of +2/3.
And it allows a quark with a charge of +2/3
to transform into a quark with a charge of negative one third -1/3.
These transformations occur either by emitting a W boson…
Or by absorbing a W boson.
A quark and an anti-quark can combine to become a W boson…
And a W boson can split into a quark and an anti-quark…
...Provided that the total electric charge is conserved.
Note that another property that is always conserved is the difference
between the total number of quarks and the total number of anti-quarks.
Similarly, the standard model also states that another property
that is always conserved is the difference between the total number of leptons
and the total number of anti-leptons.
The electron’s heavier cousins are called the “muon” and the “tau.”
The electron, the muon, and the tau each have their own associated neutrino.
The electron, the muon, and the tau are the “charged leptons”,
and the three neutrinos are the “uncharged leptons.”
The emission or absorption of a W boson can cause
a neutrino to transform into its associated charged lepton.
The emission or absorption of a W boson can cause
a neutrino to transform into its associated charged lepton,
or for a charged lepton to transform into its associated neutrino.
Unlike the case with quarks, when the W boson interacts with leptons,
we actually have three different conservation numbers:
One for the electron, one for the muon, and one for the tau.
We now know that as the three different types of neutrino’s travel through space,
they can transform into one another,
thereby violating these three individual lepton conservation numbers.
However, at the moment of interaction with a W boson,
the three individual lepton conservation numbers are still obeyed.
Therefore, when a W boson splits into a lepton and an anti-lepton…
Either the lepton and the anti-lepton are both associated with the electron…
Or the lepton and the anti-lepton are both associated with the “Muon”…
Or the lepton and the anti-lepton are both associated with the “Tau.”
To conserve electric charge, either the lepton or the anti-lepton must be a neutrino,
due to the fact that the W boson has a charge of either positive one or negative one.
Unlike the W boson, the Z boson has a charge of zero.
A Z boson can split into a matter particle and its associated anti-matter particle.
A matter particle and its associated anti-matter particle
can combine to become a Z boson.
The Z boson can also be absorbed or emitted by matter or by anti-matter particles.
But, unlike the case of the W boson, exchanges of the Z boson
do not transform a particle from one kind of particle to another.
Both the W boson and the Z boson have an extremely large rest mass.
The Top Quark has a much larger rest mass,
but all the other quarks and leptons have a rest mass
much smaller than that of the W or Z bosons.
Therefore, unless the particle has an extraordinarily large amount of kinetic energy,
when any particle other than the Top Quark emits a W or Z boson,
this momentarily violates the conservation of energy.
In these cases, the W and Z bosons exist only as “virtual” particles.
The greater the violation of the conservation of energy,
the smaller the duration of time for which it can occur, and the lower the
probability that an interaction involving these virtual particles will happen.
As a result, for all particles except the Top Quark,
interactions with the W and Z bosons are very rare.
This is the reason why the Weak Nuclear Force is so incredibly weak.
However, this limitation does not apply to the Top Quark,
which has a rest mass larger than the W or Z bosons.
When dealing with a Top Quark,
the “Weak Nuclear Force” is usually the strongest force in existence.