The Coarsely Structured Sky of X-Ray
Sources Seen with ROSAT
Why is the Universe Lumpy?
- The universe that we see today is very lumpy. There are planets, stars,
galaxies, and clusters of galaxies. Yet when we look at the afterglow from
the Big Bang we see an unbelievably smooth glow all across the sky. How
did the matter in the universe congregate to become so lumpy after starting
out so smooth?
- Most astronomers believe that the force of gravity shaped the evolution
of the lumps in the universe that we see today. The gravity between different
chunks of matter caused the chunks to pull together into one body, and
then that unified body pulled in more material.
- It takes time for gravity to do the job. We now believe that the universe
is about 15 billion years old. Was this enough time? The only way that
gravity could have worked in such a "short" time span is if most
of the material in the universe is some form of exotic dark matter that
does not interact with light. The young universe was very hot that normal
matter would not have been able to clump together until the universe expanded
and cooled enough. The clumping could have started very early on with most
of the material in the universe in the form of exotic dark matter.
- If the young universe started perfectly smooth, then we would see no
clumping of material today. Things must have been at least slightly uneven
when the universe was in its infancy. These slight variations were first
discovered by NASA's Cosmic Background Explorer (COBE) satellite in 1992.
- Astronomers believe that the universe started out with very tiny lumps,
discovered by NASA's COBE mission, and that an exotic form of dark matter
helped gravity along to develop the much larger lumps that we observe today.
But what caused the original tiny lumps? What is this exotic dark matter?
Does this picture really hold together? Astronomers require new windows
on the cosmos to answer these questions.
The Smooth Glow of the Big Bang
Thermal Radiation Seen With COBE
T = 2.728 degrees Kelvin
DIMES, MAP, SAMBA