Re: Open universe? [Was "expansion of the universe"]

[Tucker Hiatt <hiattu00@USFCA.EDU>]

John Denker wrote:

> ... But wait a minute!  What is the
> evidence that the universe had size=0 at t=0?
> I don't think there is any such evidence.  All
> we have is evidence that the universe had pretty
> high density and pretty high temperature back when
> t was small, but more than that we cannot say.
> AFAIK the evidence is perfectly compatible with
> the notion that the high-temperature high-density
> universe was already infinite in extent.
>
> If anybody has evidence to the contrary, please
> explain.


Thanks, John.  I think I can imagine a universe born infinite.  And I
think I can help my students to imagine it.  But this is not the
popular picture of the big bang that is usually (ever?) presented.
And I'm still not sure that this is the best mental image that we can
offer.

If my difficulties in envisioning modern cosmology are typical of
well-informed layfolk, then cosmologists are not doing a good job of
popularizing their efforts.  I am referring to the poverty of
*conceptual* cosmological models.  Perhaps the mathematical models
are beautiful, but if such models do not translate into mental
images, then cosmologists ought to say so bluntly.

Edwin Taylor and John Wheeler come close to "saying so" in their
recent "Exploring Black Holes: Introduction to General Relativity"
(Addison Wesley Longman, 2000).  They write:  "Cosmology has made
great strides in recent years, but as yet no one model of the
Universe has won general acceptance." (page G-14)

Here, Taylor and Wheeler are speaking of general mathematical models,
I think, and not merely whether the universe is open, closed, or
critical.

In the same work, Wheeler, in particular, says that he does not
believe the recent purported evidence of accelerating expansion.  He
says that he doubts the accuracy of the supernova evidence, and that
such an expansion would contradict a view of cosmology "too simple to
be wrong." (page G-11)  John Wheeler "favors the model Universe that
recontracts, in part because this model has no difficulties with
boundary conditions."  (page G-1)

Nevertheless, the layperson's *conceptual* difficulties, as we have
discussed, certainly seem to revolve around the issue of boundary
conditions.  Especially if we accept the recent data and admit that
our model had better include the big bang AND an infinite amount of
space.

- Tucker Hiatt