13th Annual Meeting of the Northwest Section of the APS
Volume 56, Number 10
Thursday–Saturday, October 20–22, 2011;
Corvallis, Oregon
Session H2: Astrophysics, Cosmology and Gravity
1:30 PM–4:02 PM,
Saturday, October 22, 2011
LaSells Stewart Center
Room: Agriculture Production Room
Chair: James Imamura, University of Oregon
Abstract ID: BAPS.2011.NWS.H2.2
Abstract: H2.00002 : Cosmological ``Truths''
2:06 PM–2:42 PM
Preview Abstract
Abstract
Author:
Greg Bothun
(Univeristy of Oregon)
Ever since Aristotle placed us, with certainty, in the Center of the Cosmos,
Cosmological models have more or less operated from a position of known
truths for some time. As early as 1963, for instance, it was ``known'' that
the Universe had to be 15-17 billion years old due to the suspected ages of
globular clusters. For many years, attempts to determine the expansion age
of the Universe (the inverse of the Hubble constant) were done against this
preconceived and biased notion. Not surprisingly when more precise
observations indicated a Hubble expansion age of 11-13 billion years,
stellar models suddenly changed to produce a new age for globular cluster
stars, consistent with 11-13 billion years. Then in 1980, to solve a variety
of standard big bang problems, inflation was introduced in a fairly ad hoc
manner. Inflation makes the simple prediction that the net curvature of
spacetime is zero (i.e. spacetime is flat). The consequence of introducing
inflation is now the necessary existence of a dark matter dominated Universe
since the known baryonic material could comprise no more than 1{\%} of the
necessary energy density to make spacetime flat. As a result of this new
cosmological ``truth'' a significant world wide effort was launched to
detect the dark matter (which obviously also has particle physics
implications). To date, no such cosmological component has been detected.
Moreover, all available dynamical inferences of the mass density of the
Universe showed in to be about 20{\%} of that required for closure. This
again was inconsistent with the truth that the real density of the Universe
was the closure density (e.g. Omega = 1), that the observations were biased,
and that 99{\%} of the mass density had to be in the form of dark matter.
That is, we know the universe is two component -- baryons and dark matter.
Another prevailing cosmological truth during this time was that all the
baryonic matter was known to be in galaxies that populated our galaxy
catalogs. Subsequent observations showed that a significant population of
baryons was contained in both a) a population of not easily detected
galaxies (i.e. they had been missed for decades) and b) in intergalactic
space. In 1999, the balloon borne Boomerang experiment gave good evidence
that space was flat (total energy density = 1). Around this same time,
various lines of evidence suggested that the ``cosmological constant''
(Lambda) maybe non-zero meaning we now live in a three component universe of
baryons, dark matter and dark energy. The WMAP mission a few years later
then produced our current cosmological truth that 5{\%} of the Universe is
baryons, 20{\%} is Dark Matter, and 75{\%} is Dark energy. What happened to
Dark Matter dominance? Where did it go? Is this a fine tuned Universe?
Our current cosmological truth, as defined by the WMAP results, rests on two
important assumptions: a) that we fully understand gravity as a long range
force and that alternative models, such as Modified Newtonian Dynamics
(MOND) can therefore be dismissed and b) observationally we are fully
confident that we understand supernova explosion physics to the point that
they can be used as reliable cosmological indicators. This talk will attempt
to summarize this evolution of cosmological truths, cast doubt on the
certainty of the previously stated assumptions, and to culturally suggest
that we should not continue with arrogance of Aristotle is assuring
ourselves that we do in fact, know the ``truth''.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.NWS.H2.2