ABSTRACT. One hundred years ago we did not know how stars
generate energy, the age of the Universe was thought to be only
millions of years, and our Milky Way galaxy was the only galaxy
known. Today, we know that we live in an evolving and expanding
Universe comprising billions of galaxies, all held together by
dark matter. With the hot big-bang model, we can trace the
evolution of the Universe from the hot soup of quarks and
leptons that existed a fraction of a second after the beginning
to the formation of galaxies a few billion years later, and
finally to the Universe we see today 13 billion years after the
big bang, with its clusters of galaxies, superclusters, voids,
and great walls. The attractive force of gravity acting on tiny
primeval inhomogeneities in the distribution of matter gave rise
to all the structure seen today. A paradigm based upon deep
connections between cosmology and elementary particle physics -
inflation + cold dark matter - holds the promise of extending
our understanding to an even