|
|
Q:
Can WIMPs solve the dark matter problem?
A:
Yes, WIMPs could solve the dark matter mystery, but not just any
old WIMP will do. The only type of WIMP that has been observed
(maybe) is one type of neutrino with mass. However, the mass of
this neutrino is too small to have any effect on the dark matter
problem, so WIMPs remain a theoretical concept. The WIMP with
the most-favored status these days is a cold WIMP, meaning that
it is moving slowly, so it clumps easily into galaxy sized
masses which then gather together over billions of years to form
galaxy clusters. The problem is, they don't seem to form galaxy
clusters quickly enough, so maybe a few hot (fast moving) WIMPs
are needed to help form big structures. Another problem with
WIMPs is that the theoretical predictions all insisted that the
Big Bang would produce enough WIMPs to give the universe the
critical density (critical density = density that is the
dividing line between a universe that expands forever, and one
that will ultimately collapse). This prediction is apparently
not true --observations indicate that the density is 3 or 4
below the critical value. The most recent models for the
universe have a mixture of ordinary matter, some WIMPs to solve
the dark matter problem, and a cosmic "dark energy" that causes
the expansion of the universe to speed up. If you find this
confusing, then you are in good company. Most astrophysicists
don't know what to make of it either, but they are optimistic
that a host of new telescopes including Chandra, will in the
coming decade pin down how much dark matter and dark energy
there is in our universe. Whether they will then understand what
it is, is another question. Refer to the dark matter mystery
section for more info at http://chandra.harvard.edu/xray_astro/dark_matter.html
| Index | Next
|
