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14
The Standard Model
of Elementary
Particle Physics
14.1 INTRODUCTION
When we look at this world we live in, it appears to be a very complex place made up
of millions of structures from inanimate objects like oceans, mountains, planets, and
stars, to a vast variety of plants and animals, including us. Is our universe composed
of an almost in nite number of different objects, or is there a basic, simple set of
fundamental building blocks of matter from which everything else is made?
This is a question that goes back some 2,500 years, when Aristotle proposed that
air, earth, re, and water were the basic building blocks, and other Greek ph