On Tuesday, December 26, 2017 at 11:40:23 AM UTC-7, Phillip Helbig (undress to reply) wrote:

In article , Gary
Harnagel writes:

Which came from space.com, so I don't understand your snide comment.

space.com is basically an internet newspaper. Some things they write
are formally correct, some are not. At best, you could argue that
space.com takes the standard scenario as "fact" instead of "hypothesis".

It's hard to propose experiments for something SO big. What Steinhardt
needs are some little predictions, though.

Indeed.

You think his belief system had NOTHING to do with it? Each of us has
our own model of the universe that we have developed over our lives.
I have mine and you have yours ... and Lemaitre had his.

Yes, he was a priest, but, unlike some other scientists who are
Christian (i.e., Christian scientists, not necessarily Christian
Scientists), such as Don Page, he managed to keep the two areas
separate.

I didn't realize that about Don Page, or much about him at all. From this
little treatise:

http://www.preposterousuniverse.com/...and-cosmology/

One Bob Zannelli responded, "Don Page is a first rate cosmologist, and a very
nice guy to boot. He is scrupulously honest and while I reject his evangelical
Christianity I have great respect for him."

I don't understand your denigration of him.

[[Mod. note -- For an overview of Don Page's work, see
http://arxiv.org:443/find/astro-ph/1.../0/1/0/all/0/1
Note that just searching on "Page_D" produces a mixture of Don Page's
work and those of a different person, Dany Page.
-- jt]]

The Big Bang really has little to do with the biblical creation story,
apart from the fact that in both the universe is not infinitely old.

Well, we can argue THAT sometime :-) I mean, it all depends upon the nature
of God and the definition of the universe.

This is a superficial similarity.

I agree. Either can have a previous genesis depending ....

I think we'll have to look outside our universe for the that, but it
COULD be quantum effects (brane theory is a quantum theory).

I meant "Who said that they are responsible for expansion?"

If one posits extreme temperatures at the "beginning" then it seems that
you're dealing with photons (or perhaps other relativistic particles),
so expansion is inevitable.

It seems to me that expansion is possible only if the initial
size/mass is great enough (i.e., greater than the Schwarzschild
radius.

The Schwarzschild radius is not applicable here; it is applicable in
static asymptotically flat space-times.

It seems to be quite close to that now. Why propose that it was
different in a past that we can't detect?

Because the Schwarzschild radius, as I already mentioned, applies in an
asymptotically flat spacetime. That does not describe the universe.

Well, that flat claim of yours doesn't agree with observation:

https://en.wikipedia.org/wiki/Flatness_problem

Note that a mass with density only that of water and with a radius
out to the asteroid belt would form a black hole from which nothing
could escape.

There are various estimates for the mass of the universe:

http://hypertextbook.com/facts/2006/...cPherson.shtml

varying from 1e50 to 1e60 kg (I'm ignoring the entry that proposes
infinity).
For the mass range indicated, the Schw. radius varies from 16000 to
160 trillion light-years, it being 1.6 billion light-years for
M = 1e55 kg.

Don't be confused by dimensional analysis;

That's NOT "dimensional analysis." You might repeat your claim that the
Schwarzschild model doesn't apply.

The mass and radius of a spatially closed universe correspond to those
of a black hole, basically because of "dimensional analysis", not
because the universe is a black hole.

You'll have to explain that in much more detail. I don't see (1 - 2*G*M/rc^2)
as "dimensional analysis."

the universe is not a black hole, even if it is dense enough.

How do you know this?

Maybe the moderator can insert some standard text here. Basically, a
black hole is a region WITHIN space(time).

[[Mod. note -- Ok. This is basically a question of what we mean by
the phrase "black hole". The standard definition is that it's a region
from which light rays can't escape to "far away" (from the black hole
region). Among other things, this definition relies on their being a
set of events (points in spacetime) that we're willing to call "far away"
(from the black hole(s)).

But there's no meaningful way to say that some points in spacetime are
"far away" from the entire universe. So, there's no meaningful way to
even ask the question "is the universe a black hole".
-- jt]]

Of course, this ASSUMES that the FLRW metric describes our universe. Since,
as Don Page pointed out in the link given above, "We simply do not know
whether or not our universe had a beginning."

My belief system says that it didn't. And I reject the "bounce" model, too.
IOW, "big bangs" happen repeatedly without bouncing. In such a universe
(multiverse?) curvature is only a "local" phenomenon.

Indeed. There are quantum gravity theories that equate to GR in the weak
field. String theory is one of them.

Also a problem of a lack of testable predictions.

Sure, but there are hints that may lead to testable predictions. One is
that gravity "leaks." Another is the possibility of "Alice" matter:

https://en.wikipedia.org/wiki/Mirror_matter

The weak interaction breaks parity. Why? Is it possible that not only
does gravity leak, but parity does, too? Are dark matter and Alice matter
the same thing? Beta decay is due to the weak interaction, and anomalies
in the beta decay of several isotope species have been noted:

https://arxiv.org/abs/0808.3283

Is dark matter in an adjacent brane? Is the weak interaction another way
to probe adjacent branes? Perhaps the assertion that string theory can
make no predictions is itself a belief system.