An Elementary Primer on Elementary Particles and their Interactions
Some introductory material on elementary particles How did we get here? What is a fundamental particle? Quark and lepton interactions: the weak and electromagnetic forces QED in a little more detail A more modern view of the weak interaction Quark interactions: the color force So where does the old "nuclear" force come from? Symmetry and angular momentum: particles are classified as either fermions or bosons Internal symmetry and interactions Tables of leptons and quarks The four spectroscopies For further reading
Some introductory material on elementary particles Just as high school students for the past 60 years have been taught chemistry around the periodic table of the elements, you might expect that a table of quarks and leptons (and their interactions) would have joined inclined planes, Newton's law and magnetic induction as a part of a modern high school physics education. Sadly, this is not generally the case. High school physics is a chance for motivated students, who are learning a little calculus, to see how things work and how mathematics can be used to estimate things they are familiar with. It's also a chance to get introduced to the important discoveries in the past 50 years, and the way physicists think about the world. The following gives that subset of discoveries and models that relate to both the particles that are presently believed to be "elementary" and some of the composite particles that are built from them. The level of description is mixed; I hope there are ideas here that are of interest to people with science backgrounds ranging from zilch to physics majors.
There are many references for information and answers to questions about physics. I list some useful books at the end of this primer. Additionally, you may be amused and/or enlightened by some of the following: There is an informative web page (PhysLink.com, an online educational and reference service) for questions and answers on physics, where you ask a question by entering key words in a search engine. This seems to work very well. Fermi National Accelerator Lab also has a web page for questions and answers on physics. Here, you look in a tree of links for your question, rather than through a database. It doesn't seem to work as well as the PhysLink page. If you want to read about particle physics in Italian, where you'll find entrancing words like leptonica, barionica and adroni, check out Breve Storia della Fisica delle Particelle Elementari for a simple historical review. I've provided an IAQ (Infrequently Asked Questions) on elementary particle physics. Only a small number of questions are asked and answered. If you have a question that intrigues you, and the question and answer web page(s) mentioned above didn't help, this is your big chance. Mail to: bloomberg at ieee.org. How did we get here? We will zip through the 19th and 20th centuries to get quickly to 1940. Nearly 200 years ago, Guy-Lussac found that volumes of gases combine in chemical reactions in integer ratios. The inference was made by Avogadro that the observed integer ratios reflected a simple underlying rule for combination. For example, water molecules are composed of more elementary objects, hydrogen and oxygen, that combine with a ratio of two parts hydrogen to one part oxygen. Water can be broken into oxygen and hydrogen by passing an electric current (electrolysis), and the two gases can be separately collected. At room temperature, oxygen and hydrogen are diatomic molecules in a gas state, and the number of molecules of each can be inferred from the volume they occupy as a gas. (Well, not the actual number, but the relative number. To get the actual number you need to know that 6 x 1023 molecules occupy 22.4 liters of volume at a standard temperature and pressure.)
