Overview of the Structure of Physics Where do Statistical &Thermal Physics fit in? Niels Bohr 1922 Nobel Prize in Physics for “His services in the investigation of the structure of atoms and of the radiation emanating from them.”

Interesting Trivia (to me)! Neils Bohr is the Only Nobel Prize winner to have also been an Olympic Medalist! In the 1908 Olympics, he & his brother Harald * were on the Danish soccer team, which won a sliver medal! *Harald Bohr later became a world famous mathematician!

Classical Physics is The Foundation of pure & applied (macroscopic) physics & engineering! Newton’s Laws + Electromagnetism + Statistical Mechanics + Thermodynamics. These give a good description of most of the macroscopic world. Classical Mechanics (Newton, Lagrange, Hamilton,..) The Physics of the 17 th & 18 th Centuries. Still useful in the 21 st Century!! The Structure of Physics

Classical Electromagnetism & Optics (Newton, Coulomb, Gauss, Faraday, Maxwell,..) The Physics of the 18 th & 19 th centuries. Still useful in the 21 st Century! High Speeds (v ≤ ~ c)  Special Relativity (Einstein,..) 20 th Century Physics! Small Size (atomic & smaller): Quantum Mechanics (Bohr, Schrödinger, Heisenberg….) 20 th century physics! Physics Structure

“Mechanics” HOW objects move (behave) under given forces. (Usually) Does not deal with the sources of forces. Answers the question: Given the forces, how do objects move? Forces in the universe are classified into 4 types: The 4 Fundamental Forces Of Nature! Some version of Mechanics applies to all four!

The 4 Fundamental Forces of Nature The sources of the forces, in order of decreasing strength The Strong Nuclear Force: Binds nuclei together. Explained by “Standard Model” & Quantum Chromodynamics. Still being researched. The Electromagnetic Force: E&M phenomena. Chemical forces. Most everyday forces. Maxwell, Coulomb, Ampere, Faraday,... The Weak Nuclear Force: Nuclear decay. Fermi, Bethe, others. Electroweak Theory. The Gravitational Force: Newton (classical mechanics), Einstein (general relativity), Hawking….

The 4 Fundamental Forces of Nature The sources of the forces, in order of decreasing strength

The Four Fundamental Forces The “Electro-Weak” Force Since ~ the late 1960’s, in some sense, the 4 fundamental forces have been reduced to three! That is, the Electromagnetic Force & the Weak Nuclear Force were combined into one theory. This was first done by S. Weinberg & A. Salaam. For this work, they received the 1972 Nobel Prize in Physics!

The Standard Model of Particle Physics The “Periodic Table for Elementary Particles”! Quantum Chromodynamics (QCD) & the Electroweak Theory Protons & Neutrons consist of 3 Quarks each.

The Standard Model

The Rest of Physics! What we’ve mentioned so far is  all of physics except: Statistical Mechanics: (This course ≡ “Stat Mech” ) “Stat Mech” is the mechanics of systems of huge numbers (>> ~ ) of particles. Statistical Mechanics 1. Uses Probability & Statistics to calculate macroscopic properties from microscopic force laws. 2. Applies to BOTH the Classical & the Quantum worlds! 3. Is the major link between microscopic & macroscopic physics! 4. Contains Thermodynamics as a sub-theory!