Let P be a compound quark characterized by its enthalpy 
, its inertia 
and its specific volume 
. The numbers 
and c are constants. Definition: the number m is called the rest mass
or more often just the mass of P. If P is a point particle, then the volume is small enough to write
| Quark Mass |
| ζ | z z | mc2 (MeV) |
| 1 | u u | 0 |
| 2 | d d | 0 |
| 3 | e e | imaginary |
| 4 | g g | imaginary |
| 5 | m m | 0.03 |
| 6 | a a | 0.02 |
| 7 | t t | 149 |
| 8 | b b | 85 |
| 9 | s s | 50 |
| 10 | c c | 53 |
This expression conveniently isolates the two main properties that affect the mass. It can mathematically represent laboratory observations to within experimental uncertainty for about 25 well known nuclear particles. Another handful have deviations of less than one percent. For more detail, click here.
Quarks are characterized by their mass, and quark-types are named accordingly. The baryonic sort have much larger masses than other quarks. Their name is derived from the Greek term barys (βαρύς) which means heavy. The leptonic kind have smaller but non-zero masses. Their name comes from the Greek word leptos (λεπτός) which means thin or small. The rotating quarks have no mass.
Other particles are also classified by their mass. If m is zero, then we say they are aethereal after Aether (Αἰθήρ) the mythical Protogenos who personified the breath of Gods. So the rotating quarks are aethereal. If m is greater than zero then we say that P is a material particle. And if
then we say a particle is heavy. The baryonic quarks are examples of heavy particles. We also consider some compound quarks that have an imaginary mass using the mathematical meaning of the term. But in a colloquial sense, these particles are no more or less imaginary than any other nuclear particle; they are all very imaginary compared to, say, a glass bead like the ones in the accompanying photograph.
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| Bead Panel from a baby carrier, Bahau people, Borneo 20th century, 30 x 24 cm. From the Teo Family collection, Kuching. Photograph by D Dunlop. |
Theorem: particles and anti-particles have the same mass. We have already seen how the enthalpy and inertia of particles and anti-particles have the same magnitude but opposite sign when conjugate symmetry is assumed. But for point particles, the mass depends on these quantities squared. So for point particles
Sensory interpretation: enthalpy characterizes the magnitude of all classes of sensation, whereas the inertia represents just audio-visual sensations. The mass is defined by their difference, which is due to thermo-acoustic sensation. For heavy particles, perceptions of heat are more prominent than visual sensation. But for aethereal particles, the two types are equal to each other.
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| Next step: lifetime. |
