The Ultimate Structure of Matter

Chapter 13

Great Idea:All matter is made of quarks and leptons, which are the most fundamental building blocks of the

universe that we know.

Chapter Outline

• Of What is the Universe Made?• Discovering Elementary Particles• The Elementary Particle Zoo• The Four Fundamental Forces

Of What is the Universe Made?

The Library

• Superficial description– Fundamental building blocks

• Books; rules for organization

• Basic– Words; grammar

• Ultimate description– Letters ; spelling

Library

Reductionism

• Reductionism– Ultimate building blocks

• How simplicity gives rise to complexity

• True nature– Thought – Experiment – Observation

The Building Blocks of Matter

• Fundamental building blocks– Changed over time

• Atom• Nuclei and electrons• Elementary particles

The Fundamental Building Blocks of the Universe

Discovering Elementary Particles

Cosmic Rays

• Cosmic Rays– Particles emitted by stars

• Used to understand nucleus– Found new elementary particles

Cosmic Ray Producing a Spray of Particles

Technology

• Detecting elementary particles– How do we know they are there?

Particle Accelerators:The Essential Tool

• Particle accelerator– Artificial cosmic rays

• Ernest O. Lawrence– Cyclotron

• Synchrotron• Linear accelerator

Ernest O. Lawrence

Giant Particle Accelerators

Technology

• The large Hadron collider

The Science of Life

• Accelerators in medicine– Cancer treatment

The Elementary Particle Zoo

Leptons, Hadrons, andAntimatter

Science in the Making

• The discovery of antimatter– Carl Anderson’s experiment

The Ongoing Process of Science

• How does the brain work?

Quarks and Leptons

• Quark– Fundamental building blocks of hadrons– Fractional electrical charge– Only six kinds

• Leptons– Six kinds– Outside nucleus

Properties of Quarks

Quark Confinement

• Individual quarks– No experimental isolation of a quark

• Elementary particles– Difficult to isolate

The Four Fundamental Forces

The Four Fundamental Forces

Force as an Exchange

• Forces cause matter to accelerate• Gauge particle

– Produce fundamental forces

Analogy for the Exchange of a Gauge Particle

Exchange Diagrams Introduced by Feynman

Unified Field Theories

• Unified field theories– Fundamental forces seen as different

aspects of one force– Four fundamental forces may be

different aspects of a single force

• Electroweak force• Standard model• Theories of everything

Unification of the Four Forces

Higgs

String Theories

• String theories– Smallest building blocks as vibrating

strings– Vibrate in 11 or more dimensions