origin, evolution, fate of material universe
Ripples in the energy of primordial light
The field of cosmology has experienced an
explosion of activity since the discovery of ripples
in the energy of the primordial light of the big bang.
Cosmology is the study of the origin, evolution, and fate of
objects in the observable universe. These include
our Milky Way, a vast collection of stars spanning many thousands of
light years. The key to the birth and evolution of
such objects lies in the primordial ripples observed through
light shining through from the early universe.
Big Bang: the universe began hot and dense
and thereafter expanded and cooled.
Gravitational Instability: Stars, galaxies,
clusteres of galaxies ("structure") formed from the
gravitational pull of small density ripples in the early
As cosmologists, the main paradigms we work under are known
(rather inapproprately) as the big-bang model for the global
evolution of the universe and the gravitational instability
paragdigm for the formation of objects or structure in the
The big bang model says that the universe began hot and dense
but is expanding and cooling.
The gravitational instability models says: we know large
masses like the earth attract, for example by the fact that
you remain on the surface of the earth rather than flung off
of it as it spins, like water off a wet dog. Even a small
mass attracts, so that small ripples in the mass density
early on in the history of the universe can grow into
the galaxies we see today in the night sky.
Based on a public talk presented at the IAS, October 25, 1996.
Viewgraphs for the talk are available as a
3MB PDF file.
Use of this material
is granted but please cite this site and its author
as the source.
Post WMAP update of this talk available as a
34(WARNING!!!) MB PDF file
or a more managable
2 MB PDF file [Hu & White, Sci. Am., 290 44 (2004)]