Supersymmetry
Many physicists have developed theories of
supersymmetry, particularly in the context of
Grand Unified Theories, which
attempt to unify the Strong, Weak, and
Electromagnetic interactions to help explain
why particles have the masses they have. The supersymmetric
theory postulates that every particle we observe has a massive
"shadow" particle partner. For example, for every quark there may be a
so-called "squark" tagging along.
No supersymmetric particle has yet been seen, but experiments
underway at CERN
beginning in Autumn 1995 have searched for the
partner of the W boson, and experiments at
Fermilab are looking for
the partners of the quarks and gluons.
One of the supersymmetric particles
(the "neutralino") might make up the missing
dark matter.