poly: Grav diffusion w/o dark matter

From: Robin Hanson <hanson@econ.berkeley.edu>
Date: Mon May 04 1998 - 10:58:07 PDT

This was a richter scale 7.0 on my "Wow!" detector:

SCIENCE-WEEK May 1, 1998 - Issue #53

R.J. Britten (California Institute of Technology, US) presents a
model that without dark matter quantitatively describes the flat
rotation curves of galaxies and the mass-to-light ratios of
clusters of galaxies. The hypothesis is that the agent of
gravitational force is propagated as if it were scattered with a
mean free path of about 5 kiloparsecs. As a result, the force
between moderately distant masses separated by more than the mean
free path diminishes as the inverse first power of the distance,
following diffusion equations, and describes the flat rotation
curves of galaxies. The force between masses separated by < 1
kiloparsec diminishes as the inverse square of the distance. The
excess gravitational force (ratio of 1/r:1/r^2) increases with
the scale of structures from galaxies to clusters of galaxies,
but there is reduced force at great distances because of the
approximately 12 billion years available for diffusion to occur.
This model with a mean free path of about 5 kiloparsecs predicts
a maximum excess force of a few hundredfold for galactic clusters
with dimensions of a few megaparsecs. With only a single free
parameter, the predicted curve for excess gravitational force vs.
size of structures fits reasonable well with observations from
those of dwarf galaxies through galactic clusters. Under this
diffusion model, no matter is proposed in addition to the
observed baryons plus radiation, and thus the proposed density of
the universe is only a few percent of that required for closure.
The author suggests that although the model does not follow from
present calculations based on the general theory of relativity,
it is not necessarily inconsistent with the general theory
because the diffusing gravitational elements might be interpreted
as spatial curvatures (e.g., distortions of the metric inducing
distortions in adjacent regions). The author further suggests
there is much at stake because of the scale of the intellectual
investment and the subtle arguments in cosmology that make use of
the general theory of relativity, and that the challenge of a
theory of intrinsic "beauty" may not be met at this time because
"beauty" is a subtle concept.
QY: Roy J. Britten (rbritten@etna.bio.uci.edu)
<A HREF="mailto:rbritten@etna.bio.uci.edu">EMAIL</A>
(Proc. Natl. Acad. Sci. US 31 Mar 98 95:3351)
(Science-Week 1 May 98)

Robin Hanson
hanson@econ.berkeley.edu http://hanson.berkeley.edu/
RWJF Health Policy Scholar, Sch. of Public Health 510-643-1884
140 Warren Hall, UC Berkeley, CA 94720-7360 FAX: 510-643-8614
Received on Mon May 4 18:02:56 1998

This archive was generated by hypermail 2.1.8 : Tue Mar 07 2006 - 14:45:30 PST