Introduction to physics The Feynman Lectures on Physics

Introduction to physics • The Feynman Lectures on Physics Vol. I, III • http: //www. feynmanlectures. info/

Schedule • 4 hrs lectures every week, mainly following Feynman but also some other references: 赵凯华， 新概念物理教程 • 2 hrs recitations (辅导） • + labs • Homework • Language: both English and Chinese (双语），will use Chinese but encourage English

Rules of lectures • Don’t be late：A piece of paper keeping record • Don’t play with cell-phone, read other books • Don’t talk to each other • Don’t eat and drink • Don’t sleep • …

Lecture 1： What is physics?

First lecture • The goal of physics is to find the simple principle (rules of game) behind complicated phenomena. (Reductionist) • Approach: observe (measurement), model (explanation), model (prediction), verification (observe again): Scientific method • Model, approximation, use of math • Observation, invention of instruments (Nobel prize) • Reductionist approach (Amalgamate), • emergent phenomena, human life • Physics knowledge is useful • Scientific method is useful • limitations

Goal of physics • Find the simplest principle (rules of game) behind complicated phenomena. (Reductionist!) • Real world is very complicated, all sorts of phenomena • Light, Color, motion, people, clouds, water flow, bird fly, stars, winds, rain. . . • Analogy: watching chess games…. There a few simple rules governing the games: secrets of nature! • Physicists want to find the secrets of nature!

Very useful skills • Detectives！ • 007 (James Bond)! • In fact, if you want to do anything well in life, you need to find the simple rules behind phenomena, such as complicated human relationships: • • Be courteous to others, do not offend people Listen carefully, do good investigation Be responsible Care about others • Physicists are in hot demand!

Reduction vs. emergent phenomena • If you just know a bunch of rules about chess games, you may not be a good chess player. • Just to find the secrets? well, some call these people reductionist. • One shall also learn to build beautiful things out of the simple rules (art, human being) • A pretty talking girl is not just a collection of atoms, molecules and cells… • Is emergent phenomenon fundamental? Some argue “of course”

How do we find rules: scientific methods • Observe (measurements), eyes, instrumentations, inventing new instruments, an extremely important part of physics! (experimental physicists) • Imagination (smart), approximation (art), models, explanations, here math is very useful. We will talk about more about math later. (theorists) • Prediction (model or theory must be falsifiable. ), without prediction, the model is essential useless. (theorists) • Verification: observe or experiment again. (experimenters)

Measurements • Tools: money (rich)+invention, time (human resources) • Inventing instruments • 70% of Nobel prize is related to invention of instruments for measurements. See what people have not seen before! • Not many Chinese students are interested in expt. , not a good phenomena. (no money before, but…) • Experimental physics is directly related to new technology! • China needs more experimenters, more technology to become a real world leader (not just money!)

Theorists and computation • Making models needs math, one learns a lot of math: Calculus, more complicated ones: geometry, algebra, applied math… lot of tricks • A lot of math tools were developed for physics problems (differential and algebraic geometry). • Another important tool is computer! Computer simulations become indispensable. China has the largest computer in the world. But computational physics is not very advanced. I hope there are more people devoted to computational physics.

What physics studies • Matter (gas, liquid, solid) and their motion and microscopic structure • Mechanics (motion and force) • Electricity and magnetism (force) • Laws of physics at many distance scales, very small one to very large one: such as the scale of the universe • One of the most important area is the microscopic structure of matter (20 th century)

Physics is very useful! • The knowledge we obtained from physics has changed our lives forever! • Mechanics: cars, buildings, bridges • Electromagnetism: phone, bulbs, computer, information, • Heat: air-condition, refrigerator, energy sources • Atoms: new materials, medicine, energy sources, quantum computers • However, the original goal of studying physics is not meant to be useful. It meant to understand how nature works, curiosity driven research… Highenergy physics internet!

Scientific method is useful Physics method is the origin of scientific method which now has wide use! • Engineering • Astronomy • Chemistry, biology • Computer • Social sciences • Money market • Medicine • Archeology • ….

Limitations of the scientific method • If you cannot measure or see, science cannot tell you anything. • One can speculate, or believe in something which cannot be verified. That is called religion, or ideal! • Science cannot tell you everything about life, for example, philosophy • Science is not a substitute for everything, for example, love. • Science can be a way of life!