A short History of Nearly everything....excerpts

...."The fact is , there is a great deal , even at quite a fundemental level , that we don't know -not least what the universe is made of. When scientists calculate the amount of matter needed to hold things together, they always come up desparately short. It appears that at least 90 percent of the universe is composed of Fritz Zwicky's 'dark matter'-stuff that, for the most part, we can't even see. The two main possible culprits are said to be either WIMPs (for Weak Interacting Massive Particles, which is to say specks of of invisible matter left over from the Big Bang) or MACHOs (for MAssive Compact Halo Objects- really just another name for black holes, brown dwarfs and other very dim stars).

Assuming the above even exist (no WIMP has ever been found), two thirds fo the universe is still missing! For themoment we might very well call them DUNNOS (for Dark Unknown Nonreflective Nondetectable Objects Somewhere).