Overview
This lecture traces the evolution of physics from Galileo's early experiments through Newton's gravity, Maxwell's electromagnetism, and Einstein's revolutionary theories of relativity and quantum physics.
Early Pioneers: Galileo and Newton
- Galileo performed experiments with rolling balls, pendulums, and falling objects to study motion and gravity.
- Despite controversy with the Church, Galileo's findings became foundational for modern physics.
- Isaac Newton identified gravity as a universal force pulling objects downward, explaining orbits and motion.
Electromagnetism: Maxwell
- James Clerk Maxwell unified electricity and magnetism into a single force: electromagnetism.
- His work resolved mysteries in physics until new phenomena emerged around 1900.
Challenges and Breakthroughs: X-rays and Einstein
- Discoveries like X-rays and radioactivity did not fit existing physics models, causing uncertainty (as noted by Lord Kelvin).
- In 1905, Albert Einstein proposed that light behaves both as a wave and as packets (particles).
- Einstein published E = mc², stating mass and energy are equivalent.
- He also proposed that the speed of light is constant, regardless of observer motion.
Theory of Relativity and Quantum Physics
- Einstein’s special relativity showed time and space are not absolute, but relative to the observer's motion.
- Time appears to slow down and lengths contract for fast-moving objects relative to a stationary observer.
- His work led to concepts foundational to nuclear energy and the operation of particle accelerators.
- General relativity predicted black holes and the Big Bang.
Key Terms & Definitions
- Gravity — Force attracting objects toward one another, explained by Newton.
- Electromagnetism — Unified force combining electricity and magnetism, defined by Maxwell.
- E = mc² — Einstein’s equation showing mass and energy are interchangeable.
- Special Relativity — Einstein's theory that the laws of physics and speed of light are the same for all observers.
- Quantum Physics — Branch of physics dealing with the behavior of energy and matter at atomic scales.
Action Items / Next Steps
- Review concepts of gravity, electromagnetism, and relativity.
- Prepare questions on how Einstein’s theories challenged classical physics.