Back to Standard Model

**Table of Contents**

#### Key Ideas

- Fundamental Interactions / Forces
- Classical Physics vs Quantum Physics
- Fields and Particles

#### 17th Century

- 1687 Classical Mechanics
- Phenomena exert forces on objects directly and instantaneously.

- Classical Physics…
- … tracks objects through space and time
- … generates deterministic predictions
- … uses continuous quantities

#### 19th Century

- 1808 John Dalton revived the atomic theory to explain chemical phenomena
- 1864 Theory of Electromagnetism
- Charged particles exert forces on other charged particles, indirectly by electric and magnetic fields propagating at the speed of light.

#### 20th Century

- 1897 The first subatomic particle, the electron, was discovered
- 1905 Special Relativity
- The speed of light is the same in all non-accelerating reference frames, with the result that;
- The elapsed time of an event may be different in different reference frames
- The length of a rod may be different in different reference frames

- The speed of light is the same in all non-accelerating reference frames, with the result that;
- 1911 Rutherford’s Planetary Model of the Atom
- Rutherford’s idea was that the electromagnetic force from nuclear protons keeps the electrons in orbit, just as the gravitational force from the Sun keeps the planets in orbit.
- The idea fails because, per the laws of electromagnetism, the orbiting electrons would quickly lose energy and crash into the nucleus.

- 1915 General Relativity
- The core idea of General Relativity, Einstein’s theory of gravitation, is that gravity is the curvature of spacetime.

- 1925 Quantum Mechanics
- In contrast to Classical Mechanics, Quantum Mechanics…
- … does not track particles through space and time
- … generates probabilistic predictions
- … uses discrete (quantized) quantities

- Sean Carroll: the two greatest revolutions in physics:
- Newton’s development of classical mechanics in the 1600s
- The replacement of Newton’s theory with Quantum Mechanics

- In contrast to Classical Mechanics, Quantum Mechanics…
- 1940s Quantum Electrodynamics (QED)
- QED governs the electromagnetic interaction

- 1960s Electroweak Theory (EWT)
- EWT governs the weak and electromagnetic interactions

- 1973 Quantum Chromodynamics (QCD)
- QCD governs the strong interaction

- 1975 Standard Model of Particle Physics (SMPP)
- The Standard Model postulates
- Quantum Fields and their particles
- The equations governing their behavior, Quantified Field Theory

- The Standard Model postulates