Quantum Chromodynamics 101

What is particle physics?


When most of the general public thinks of the smallest bits of matter, they usually think of the protons, neutrons, and electrons from their elementary and high school physics classes.  We were taught that the interactions of these three particles formed all of the matter on Earth?  We were also taught that these were the smallest forms of matter on Earth.  Everything was made from protons, neutrons, and electrons.

But humans are a naturally inquisitive being.  The next questions to arise were:  What if we get even smaller?  What are protons, neutrons, and electrons made of?  This is the role of particle physics, to probe further into the particles looking for THEIR fundamental particles.  Scientists have been able to find these fundamental particles with reasonable success.


The six particles to make up protons and neutrons (electrons will come later) are called quarks.  Each quark has a whimsical name given to it by an equally whimsical scientist.  U = up, D = down, T = top, B = bottom, C = charmed, S = strange.  These quarks, along with their associated forces, are the key to particle physics success.

As was introduced above, the forces are as important to particle researchers as the particles themselves.  Particle physicists are developing a system to measure the strength of these forces within the atom.  The four forces that affect our life on Earth are…

            Gravity - holds us on the Earth

            Weak force - causes radioactive decay

            Electromagnetic force (EMF) - binds atoms together to form computers, desks, etc.

            Strong force - binds quarks together to form protons and neutrons

Particle research is mostly concerned with the strong force and its interaction with quarks, but in order to understand the strong force one has to understand the other forces as well as their relative strengths.

Click the arrow below to find out more about the four forces.