Lawrence M. Krauss's Quintesssence: The Mystery of Missing Mass in the
Universe.  Basic Books, New York, 2000 ($26).

"The picture of cosmology we so carefully and optimistically developed over
the 1980s, based on the fusion of ideas from particle physics and
astrophysics, is now undeniably incomplete.  Over the past five years it has
become clear that 'dark matter' alone is not abundant enough to eventually
halt the observed universal expansion."  Thus Krauss, chairman of physics at
Case Western Reserve University, introduces this revised edition of a book he
published a decade ago under the title, "The Fifth Essence."  The fifth
essence, an allusion to a term of Aristotle's, was Krauss's name for dark
matter.  Now something else must be considered; he calls it "quintessence."
It is "a nonzero vacuum energy" that "may dominate the energy of the
universe, govern its ultimate destiny, and swamp all matter, even dark
matter, in ultimate cosmic importance."  Krauss is an accomplished guide
through modern cosmology.  The rewards of the search for dark matter and
vacuum energy, he says, "could be spectacular: a window on the universe at
the earliest instants of creation, an understanding of its destiny, and
finally, an understanding of the formation of all the structure we observe."

Scientific American,  September 2000,  pg 105