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The Question
(Submitted August 21, 1998)
I was listening to a few scientists talk on the radio about a force that is
causing or assisting the expansion of the universe. I only had a brief moment
to catch the radio show before having to go to work. They where saying that
an anti gravity is causing the universe to expand. Is any one familiar with
these ideas that may be able to point me in the right direction to get more
information on this?
The Answer
You ask very good questions, that astronomers, physicists, and
cosmologists are debating intently right now. A group of researchers
recently published findings that the universe may be expanding faster
now than in the distant past. This would imply a non-zero value for the
'Cosmological Constant' (CC).
Einstein's original cosmological model was a static, homogeneous model
with spherical geometry. The gravitational effect of matter caused an
acceleration in this model which Einstein did not want, since at the
time the Universe was not known to be expanding. Thus Einstein
introduced a cosmological constant into his equations for General
Relativity. This term acts to counteract the gravitational pull of
matter, and so it has been described as an anti-gravity effect.
see: http://www.astro.ucla.edu/~wright/cosmo_constant.html (http://www.astro.ucla.edu/%7Ewright/cosmo_constant.html)
for a good but technical description of the 'force'.
Until recently people just put a value of zero in for the (CC), now
things may be different. We have yet to see what will hold up with
newer instruments such as MAP. http://map.gsfc.nasa.gov/ coming online.
The March 1998 issue of Sky & Telescope magazine also has a report on
this same item.
I hope this helps,
Mike Arida and Tim Kallman for the Ask a High-Energy Astronomer Team
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