On Saturday, December 23, 2017 at 8:30:10 AM UTC-7, Phillip Helbig (undress to reply) wrote:

In article , Gary
Harnagel writes:

"Inflation isn't falsifiable, it's falsified -- BICEP did a wonderful
service by bringing all the Inflationists out of their shell, and
giving them a black eye." - Roger Penrose

Despite his substantial contributions, Penrose is now an outsider.

So the inflationists voted on physics?

I'm not sure what you mean here. Of course, science is not a democracy;
the majority can be wrong. However, there is a consensus that
inflation probably happened and that Penrose is probably wrong on this
point. In any case, there is debate, and the issue is not solved by
quoting arguments from only one side (especially the minority).

The "arguments" from the "other side" are taken as FACT:

https://www.space.com/52-the-expandi...-to-today.html

"The universe was born with the Big Bang as an unimaginably hot, dense point.
When the universe was just 10-34 of a second or so old -- that is, a hundredth
of a billionth of a trillionth of a trillionth of a second in age -- it
experienced an incredible burst of expansion known as inflation, in which
space itself expanded faster than the speed of light."

The only argument I see FOR inflation is the uniformity of the CMBR.
Steinhardt has another take on it.

"Even from the beginning, inflation looked like a kluge to me-- I
rapidly formed the opinion that these guys were just making it up
as they went along" -- Neil Turok

Turok has his own axe to grind, with Steinhardt. Check it out. Do you
think that it is more believable?

Sure they have their own ax to grind. So did Lemaitre. So does Hawking.

The point is that the quote makes it sound like they have some
independent evidence against inflation, whereas in fact they are touting
their own alternative theory.

Sure. It's another way to explain a conundrum: How the heck did the CMBR
get so uniform? I think it's a good thing to have alternate theories. It
keeps one's mind loosened up and not moribund.

As for Lemaitre, he had a hypothesis
which went beyond what was known at the time; it was not a rival to
another hypothesis attempting to explain the same thing.

So he was a smart guy and found a way to propose a theory consistent with
both GR and his religion.

Is there anything to the claim made at the end of "Theory of Everything"
that Hawking is now trying to refute that time had a beginning?

Whether or not time had a beginning does not alter the fact that we can
trace the evolution of the universe back to a time when it was very hot
and very dense.

Sure, but not so dense that collapse is inevitable. And it doesn't matter
that quantum effects "may" prevent a singularity. It's unlikely that they
can be responsible for an expansion. It seems to me that expansion is
possible only if the initial size/mass is great enough (i.e., greater than
the Schwarzschild radius.

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.

By convention, the time at which it had infinite
density according to a naive extrapolation (which no-one believes
accurately describes the very early universe) is known as the big bang.

So what do you think obviates infinite density? More importantly, what
prevents all the initial matter from being inside the Schw. radius?

And it's funny that mathematics with singularities is used
to validate predictions, no?

No, because they are not used to validate predictions in the regime with
singularities. I can navigate fine with latitude and longitude as long
as I am not at the north or south pole.

There is no new physics at the poles. You just need a different math.
In the case of cosmology, are you hoping for a new mathematics or a new
physics? Steinhardt's theory proposes a new physics, but he needs a new
mathematics to make predictions to validate his theory.

A question I've had: How can the CMBR be light from the BB? Shouldn't
that light have passed us long, long ago?

[[Mod. note -- That's a FAQ. See, for example
http://www.askamathematician.com/201...ady-passed-us/
https://www.quora.com/Why-is-the-cos...d-still-around
-- jt]]