Space Forum / Astronomy / November 2007

Well, there's the official history of the flat universe, and, dare I
say it, the real history, which has an important social component.
Dates are approximate.

The Official History (very brief):  After the FRW model gained
widepread acceptance in the 1960's, the universe was considered to be
at "critical density", such that expansion was in-between a
perpetual-expansion state, and reversion to contraction.  This
provided for a flat manifold.  In 1998, BoomeranG observations showed
the CMB to be displaying a flat manifold.  WMAP has since improved
these observations.  (end of the official history)

The REAL History:  With acceptance of the FRW model in the 1960's,
came the concept that the geometry of the universe depended on whether
it was permanently expanding (hyperbolic manifold), at critical
density (flat), or eventually reverting to contraction (spherical).
There were, however, problems with the FRW model, notably the horizon
problem (how such uniformity is possible), and the size problem (how
the universe attained its large size).  In 1977 Alan Guth made a
breakthrough with his revolutionary (I would say "magic wand") theory
of inflation.  The engine of inflation is such that it is both
constrained by, and producing of, a flat space-time.  This is to say,
inflation and the flat universe are ONE AND THE SAME, operationally.  

Armed with Guth's inflation,  many problems were resolved, but at the
(gladly paid) price of an enforced flat universe.  The "critical
density" universe was now gospel in that it was a requirement of
inflation.  This went on into the 1990's, even as observational
problems began to multiply.  In the 1990's, supernova observations
became seriously discrepant with the critical density universe.
However, the critical density universe could not be discarded without
discarding inflation as well.  Remember that it was still the paradigm
that a perpetually-expanding universe would be a hyperbolic continuum.
Since inflation was an absolute requirement for the FRW model to work,
the critical density universe had to be adhered to.  This went on for
a few uncomfortable years in the mid 1990's.

Enter the BoomeranG observations!  Carried by high-atmosphere
balloons, detailed observations were made of the CMB.  The black body
contours were revealed.  These were interpreted as observational
evidence for a flat universe.

(Here's the important part)  Suddenly, the pressure was off!  No
longer was the critical density universe the only observational
confirmation of the flat universe.  Now there was new confirmation.
And almost immediately, the supernova data was published and the
critical density universe was refuted.  A new paradigm of perpetual
expansion was promulgated, but without the previous requirement that
this would entail a hyperbolic universe.  No, with the BoomeranG
observations "confirming" the flat universe, the gap between old
paradigm and new paradigm was filled with DARK MATTER and DARK ENERGY.
In this way, the flat universe is retained, and so inflation is
retained, and so the FRW model is retained.  Thanks, BoomeranG!  And
thanks, WMAP!

But, this is the message of the synchronicity of the supernova
publications, and BoomeranG.  The first would not have been possible
without the second.  The flat universe had to be retained at all costs!  

So you see, this is what I have meant about the circular "evidence"
for a flat universe which is holding up the FRW cosmology.  IN FACT,
the concept came first (with "inflation"), and the evolution of the
model is allowed only under the mandatory constraint that the flat
universe be retained.  It has gone so far, that it has now become
acceptable to model the universe as consisting MOSTLY of invisible
matter and unknowable energy.  Crazy!!

People, the hyperbolic universe is out there, waiting to be found.
How can we slip out of the straight-jacket of inflation and the flat
universe?

Eric Flesch