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The Standard Model Part I: The Periodic Table of Physics

Gluon? Quark? Neutrino? Is this an alien language? Despite being Greek to us, these are the names of the building blocks of all the matter that we can see and touch. Air, water, plastic, oil, mother of pearl, even gummy worms are all made out of the 92 naturally occurring elements of the periodic table. This table of elements is a systemic way to break down all the types of chemicals into groups based on how they act.

Similarly, the particles of the Standard Model are a system to break down the things that atoms are built from and how all the pieces interact with each other (with one VERY important exception!). These pieces can be ordered, like the elements, into their own table of groups with similar properties. This structure includes matter, electrical and magnetic phenomena and the forces that hold atoms together:

Standard Model Periodic Table.png
A Very Strange Table Indeed

The number on the top left of each tile is the mass (exactly what you'd think, but expressed in electronvolts (eV) because physicists are quirky). Below this is the electrical charge, where an electron and proton are charges of -1 and +1 respectively. Beneath charge is spin. A spin that is a whole number means that any number of those particles can be in the same "state," which is to say the same place with the same energy. Spin of ½ means that only two particles can be in the same state. This is why electrons reside in pairs in systems of intricate orbitals instead of all together. The enormous variety of different electron configurations is what gives rise to the unique behaviors of the different elements in the periodic table!

"Quarks" are the six purple members on the top left. These particles only exist packed together in groups. A proton is two "Ups" and a "Down" while a neutron is two 'Downs' and an 'Up'. The nucleus of every atom in the universe (that we know of!) is made of only these two quarks. The other quarks are only present in far stranger places such as atom smashers or possibly microseconds after the Big Bang.

The second to bottom row are the neutrinos, which have very little impact on anything that we observe. A neutrino interacts with matter so rarely that you can shoot one through a light-year of lead before it hits anything! Something like 40 billion or more neutrinos pass through your body every second and maybe a handful will ever hit you in your entire life!

The electron needs no introduction. Muons are formed when cosmic rays hit the atmosphere, and they account for a part of the background radiation you receive every day living on earth. The tau particle breaks up almost immediately after it is formed and is rarely observed.

The far right column contains the particles that transmit force. In old-school physics, things could interact with each other by sitting far apart and pushing invisibly through empty space. In particle physics they interact with one another by shooting particles back and forth between them. The photon is the particle that transmits electric and magnetic forces. Photons are what our eyes see as light! The gluon transmits the forces that hold together the quarks in the proton and neutron as well as holding the neutrons and protons together in the nucleus! The W and Z bosons carry the "weak force" which effects radioactive decay and some other nuclear processes but is of less immediate importance.

Notice that there is no gravitational force particle here! This is a huge omission and the main reason that physicists are unhappy with the Standard Model. Part II will discuss what the Standard Model predicts and what it cannot say.

Tom Hartsfield
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