Fermilab Discovery Science Resources: Nine Questions

5. Why are there so many kinds of particles?

We have discovered three families of quarks and leptons, families of fundamental particles that differ only in their masses, which range from less than a millionth of the mass of an electron to the mass of an atom of gold. Just as quantum mechanics led to an understanding of the organization of the periodic table, we look to new theories to explain the patterns of elementary particles. Why do three families of particles exist, and why do their masses differ so dramatically? review.

Tevatron Experiments
Fermilab & the LHC Research Seminars - Streaming Video