What is dark matter?
Simplest guess: a ‘thermal relic’ WIMP
As the universe cools, massive particles annihilate: X+ + X- ? photons but always a few X’s left
X could be ‘supersymmetric’ particle with ~ 100 X proton mass. CERN LHC may make them in 2007
Deep mine experiments are searching directly for the cosmological WIMPS