What is the world made of, how do the constituents fit, and what are the fundamental rules they obey? We discuss the history of human understanding of atoms and sub-atoms, and articulate some primary ideas in particle physics, focusing on what we know well.
Where do we stand in our understanding of the smallest building blocks of the world? The Standard Model of particle physics is one of the greatest quantitative success stories in science. What are the players, what are the forces, and what are some of the concepts and buzzwords?
We summarize the scientific evolution of atomism: pre-scientific ideas, the classical world view of Isaac Newton, and finally the modern ideas of fundamental constituents. How could a famous physicist say physics was done in 1899?
We explore the transition from 19th-century classical physics to 20th-century modern physics. This is the story of Planck, Rutherford, Einstein, and the early quantum physicists. We gain our primitive first understandings of the realistic structure of atoms.
A qualitative introduction to the work of Schrödinger, Heisenberg, and Dirac in describing electrons, this lecture looks at how the first fundamental particle was discovered. We introduce such concepts as spin and quantum electrodynamics (QED), and conclude with the experimental discovery of antimatter and the neutron.
This lecture conducts a survey of particle physics in the first half of the 20th century: cosmic rays, the discovery of the muon, Yukawa's theory of nuclear force, and the discovery of the pion. We conclude by discussing the electron volt (ev) as a tool to make sense of the particle discoveries to come.
What is a weak interaction, and how is it connected to radioactivity? What is an interaction, anyway, and how does it differ from a force? We discuss the carriers of weak forces, W and Z particles, and introduce neutrinos, ghostlike particles with no mass.
Particle accelerators, born after World War II, were in some respects the origin of big science in the United States. We discuss how these machines worked and the steady stream of new particles discovered through their use.
Some new particles exhibited a curious mix of strong and weak properties. The proper description of these strange particles was crucial in understanding the particle zoo. This lecture introduces lots of new lingo;mesons and baryons, hadrons and leptons, bosons and fermions.
This lecture covers the concept of a field and the early problems involved in constructing the modern theory of quantum electrodynamics (QED). We examine the 1947 Shelter Island conference, the problem of infinities, the concept of renormalization, and Feynman diagrams.
Hadrons (strongly interacting particles) are fundamental but not elementary. Could they be made of something else? This is the breakthrough idea of quarks. This lecture explores early quark conditions.
If quarks are the fundamental particles, how do they interact? The answer: They carry a new charge, a strong charge described by color. We introduce these concepts as part of the fledgling theory of quantum chromodynamics (QCD) from the 1970s.
What does symmetry mean to a physicist? Pretty much what it means to you: an aesthetic property of a system, a pattern that appears the same when viewed from different perspectives.
Symmetry is sometimes slightly broken or badly broken. Either way, there is something useful to be learned about the world. This lecture explores (a seemingly obvious) mirror symmetry, also called parity, and the stunning surprise that it is not perfect (parity violation).
In November of 1974, two simultaneous experimental discoveries rocked the world of particle physics. A new particle, a new quark, had been found. The charmed quark changed the scientific paradigm for physicists overnight.
The last great surprises: a new generation of particles. The tau lepton is discovered, and symmetry arguments tell scientists that the tau neutrino, and bottom and top quarks, have to be there ... and they are!
Progress in the 1960s and '70s was not limited to strong forces and quarks. This is the story of the theory of Weinberg, Salam, and Glashow; the electroweak theory;that unified the fundamental weak, electric, and magnetic forces. We can now summarize the Standard Model.
The Standard Model of particle physics is an impressive accomplishment. Its unparalleled success includes qualitative and quantitative measurements, with years of increasingly precise tests.
The Higgs particle is the least understood piece of our story so far, and the one central part not yet directly verified. What is this particle, and what role does it play in the Standard Model?
We have always assumed that neutrinos are massless, but what if they did have mass? Why are there far fewer neutrinos coming from the sun than there should be? What does it mean to talk about neutrinos changing flavor?
The SSC may be dead, but experimental particle physics is alive and vibrant! What are some of the burning issues? Among those we will discuss are the search for violations of matter-antimatter symmetry, and neutrino beams that will travel through the Earth from source to target.
The Standard Model is a great success. So why are many physicists looking for a more fundamental theory of nature? We'll begin with the missing link of gravity; issues of simplicity, unification, and grand unification; then two developments that to many physicists seem to be the best candidates for new physics: supersymmetry and string theory.
What does cosmology, the study of the universe as a whole, have to do with particle physics? Matter at the very largest scales requires understanding of matter at the very tiniest. We'll discuss how particle physics fits in with the Big Bang, the more recent theory of inflation, and the newly discovered dark matter and dark energy.
What have we learned after more than 100 years of intense study of fundamental particles? What puzzles remain? What you might take out of this course is a sense of physical order and understanding of the constituents of the larger world.