From: Hal Finney (hal@rain.org)
Date: Mon Mar 02 1998 - 09:31:27 MST
This is not a new idea, simply the old cosmological constant. Einstein
found that his new theory of general relativity predicted that the
universe would be expanding or contracting (or expanding then contracting).
Since it was thought to be static, he found that he had to modify the
equations. Rather than all forces being caused by matter/energy, he
had to assume that there was an inherent force in the vacuum itself.
This could counter the attractive force of gravity and make the universe
stable.
Later, when the universe was found to be expanding, he made his famous
comment about this being his greatest blunder, otherwise he could have
claimed the prediction of an expanding universe as a success of general
relativity. (BTW it's kind of curious that one man's decision can change
whether a theory is considered a success or not. Why isn't "GR minus
CC" considered to have successfully predicted the universe's expansion,
regardless of whether Einstein chose to present it that way? Do theories
make predictions, or people?)
The recent measurements show that the rate that the universe is expanding
appears to be speeding up, while GR would predict that it is slowing
down due to the attractive effects of gravity. This would indicate that
there is a CC which is so strong that it is overcoming the attraction due
to the mass.
Recall a month ago that there were reports that there was insufficient
mass to slow the universe's expansion. I believe that was based on
similar measurements to these more recent results. If there actually is
a strong CC, then we can no longer conclude that there is a lack of mass;
there may be plenty of mass, but it is simply that the CC is stronger.
This could imply that the universe is spatially closed (if you go far
enough in one direction you come back where you started) but will still
never collapse back on itself.
Most physicists really dislike the CC, which appears as an ad hoc fudge
factor in the equations of GR. I'm sure there will be a lot of work done
to try to disprove the recent results, or find a way to fit them into a
more elegant theory.
Hal
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