Unit 2: The Fundamental Interactions
This unit takes the story of the basic constituents of matter beyond the fundamental particles that we encountered in unit 1. It focuses on the interactions that hold those particles together or tear them asunder. Many of the forces responsible for those interactions are basically the same even though they manifest themselves in different ways. Today we recognize four fundamental forces: gravity, electromagnetism, and the strong and weak nuclear forces. Detailed studies of those forces suggest that the last three—and possibly all four—were themselves identical when the universe was young, but have since gone their own way. But while physicists target a grand unification theory that combines all four forces, they also seek evidence of the existence of new forces of nature.
Content for This Unit
by David Kaplan
- Forces and Fundamental Interactions
- Fields Are Fundamental
- Early Unification for Electromagnetism
- The Strong Force: QCD, Hadrons, and the Lightness of Pions
- The Weak Force and Flavor Changes
- Electroweak Unification and the Higgs
- Symmetries of Nature
- Gravity: So Weak, Yet So Pervasive
- The Prospect of Grand Unification
- Beyond the Standard Model: New Forces of Nature?
- Further Reading
- Printable Online Text for This Unit (PDF)