Getting Small

Particle physics attempts to answer two questions:

What is the smallest unit of everything? What are the most fundamental building blocks of the universe?

How do those building blocks interact to create everything around us?

In order to get to the foundation we need to start here, on our scale. Imagine we have a cup of water, and we want to get to the smallest unit of water. So we stick our finger in and take out a drop. We start flicking away water until we're left with a wet finger. Where is the smallest unit? If we zoom into the wet finger, we will find the smallest lump of water. This lump is a molecule: the smallest unit of water that still has the properties of water. Things get weird at this scale, for example, temperature does not exist.

So we found the smallest unit of water. But is there something smaller? (Hint: yes)

Getting Smaller

So the smallest unit of water is actually a combination of two hydrogen atoms and an oxygen atom. The thing is, once we break up this combination, we no longer have water. These atoms are NOT the smallest thing! (Even though atom means indivisible in Greek). Atoms are made up of subatomic particles known as protons, neutrons, and electrons. Protons and neutrons hang out in the densely packed center known as the nucleus while electrons swirl around the outside of the nucleus.

So electrons, as far as we know today, are fundamental. This means that we cannot break them into smaller pieces. We reached the first building block of nature. However, those protons and neutrons, are made up of some smaller things.

Getting Smallest

Protons and neutrons are made up smaller particles known as quarks. Three quarks to be exact. Quarks come in a few different flavors (not making this up). Protons are made of two up quarks and one down quark. Neutrons are made of two downs and an up. Quarks are not found alone in nature, they always come along with some quark friends. If you tried to pull a quark away from its buddies, you would have to use so much energy that new quarks would be created! Almost everything you experience, and everything you will experience, is just various combinations of up quarks, down quarks, and electrons. Every war in human history is simply a pile of quarks and electrons interacting in interesting ways. We've reached the fundamental particles. The next bit of the discussion describes all the different particles. Here is table that organizes them all. This table is known as the standard model:

Source: Wikipedia

 

The particles that make up matter are called fermions. These particles take up space so they build all the stuff around us. Fermions interact by exchanging another type of particle known as bosons. Bosons are responsible for all the forces of nature. The nucleus of atoms is held together through the strong nuclear force. The gluon is the boson responsible for this force. The boson for gravity is known as the graviton and the boson for electricity and magnetism is the photon (the particle of light!).

The conversation then moves to the experiments of particle physics. We discuss the gargantuan particle accelerators running today and why smashing particles together at high energies makes new particles. We briefly discuss quantum field theory and the different "realms" of physics. Particle physics lives in the realm of quantum field theory. We finish the discussion by answering an important question: why do we do particle physics? Why should we care? When it really comes down to it, particle physicists are deeply curious people and their motivation is simply to uncover the mysteries of the universe.