At Rest with our Hubble view

In that Inflation paragraph above, NASA contributors addressed the CMB homogeneity as being problematic in regard to the standard cosmological view at that time. They call it a "cosmological problem", but it wasn't; it was simply a scientific observation supported by huge amounts of data.

The problem was with the standard view of cosmology at that time. Either the standard cosmology had to be abandoned, or amended by adding faster-than-light expansion, dubbed Inflation, so that the background temperature could be causally connected to the Big Bang. One alternative considered must have been the existence of some external greater universe as the source of the inflowing thermalized background. The problem was that would require preconditions to the big bang, and corresponding changes to the infinitely dense zero volume nature of the singularity.
 
quantum_wave said:
In that Inflation paragraph above, NASA contributors addressed the CMB homogeneity as being problematic in regard to the standard cosmological view at that time. They call it a "cosmological problem", but it wasn't; it was simply a scientific observation supported by huge amounts of data.

The problem was with the standard view of cosmology at that time. Either the standard cosmology had to be abandoned, or amended by adding faster-than-light expansion, dubbed Inflation, so that the background temperature could be causally connected to the Big Bang. One alternative considered must have been the existence of some external greater universe as the source of the inflowing thermalized background. The problem was that would require preconditions to the big bang, and corresponding changes to the infinitely dense zero volume nature of the singularity.
Click to expand...
Or the flatness was merely an initial condition of the universe.
 
PhysBang said:
Or the flatness was merely an initial condition of the universe.
Click to expand...

The problem with that is that any deviation from flatness,no matter how small, with omega either greater or less than 1, would rapidly increase.
 
AlexG said:
The problem with that is that any deviation from flatness,no matter how small, with omega either greater or less than 1, would rapidly increase.
Click to expand...
Sure. But this doesn't prevent there from being a very, very flat initial condition to the universe.
 
PhysBang said:
Sure. But this doesn't prevent there from being a very, very flat initial condition to the universe.
Click to expand...

If omega, at 1 second after the initial BB was 0.9999999999999995, then today it would be just a little over .25.
If omega was 1.0000000000000005 initially, today it would be about 1.75.

In the first case, the density would have dropped so quickly that galaxies would never have formed.
In the second case, the universe would have already collapsed.

(The Inflationary Universe Alan Guth, pp 24-25.)
 
That's great.

But irrelevant.

It doesn't influence the probability that the initial density of the universe was 1 because there is no basis on which to calculate that probability.
 
It doesn't influence the probability that the initial density of the universe was 1 because there is no basis on which to calculate that probability.
Click to expand...

It shows that unless it was exactly one, to over 16 decimal places, it would be way off by now. Given the huge range of possible values, the probability that it was exactly one is vanishingly small. So it's not at all irrelevant.

Whereas with Inflationary theory, omega would be driven to 1, no matter what it's initial value.
 
PhysBang said:
That's great.

But irrelevant.

It doesn't influence the probability that the initial density of the universe was 1 because there is no basis on which to calculate that probability.
Click to expand...

WMAP measures Omega to be 1 with a very small error bar. Guth's inflation can start at any Omega but will go to 1 very quickly. That's one of the theoretical prediction that the WMAP experiment confirms. A list of some important results from the WMAP experiment. Probably the 'least accessed' important experiment of modern times.

http://map.gsfc.nasa.gov/
 
AlexG said:
It shows that unless it was exactly one, to over 16 decimal places, it would be way off by now. Given the huge range of possible values, the probability that it was exactly one is vanishingly small. So it's not at all irrelevant.
Click to expand...
What is the probability that a universe will start with a specific set of initial conditions?

Whereas with Inflationary theory, omega would be driven to 1, no matter what it's initial value.
Click to expand...
This is not exactly true. There are many different kinds of inflationary scenarios, some of which produce a total energy density of 1, some of which do not. These should be evaluated on the evidence that they are correct, not on their ability to match a single parameter measurement.
 
PhysBang said:
What is the probability that a universe will start with a specific set of initial conditions?


This is not exactly true. There are many different kinds of inflationary scenarios, some of which produce a total energy density of 1, some of which do not. These should be evaluated on the evidence that they are correct, not on their ability to match a single parameter measurement.
Click to expand...

Oh, that's certainly not the only piece of evidence, just the one we were discussing. And all inflationary scenarios drive omega towards one.
 
AlexG said:
Oh, that's certainly not the only piece of evidence, just the one we were discussing. And all inflationary scenarios drive omega towards one.
Click to expand...

All inflation models don't require Omega to be 1. The correct model does.
 
AlexG said:
Oh, that's certainly not the only piece of evidence, just the one we were discussing. And all inflationary scenarios drive omega towards one.
Click to expand...
You certainly do read the PR of the inflationary theorists! Yes, there is some evidence for particular inflationary hypotheses, but no, not all inflationary scenarios produce flatness.
 
PhysBang said:
You certainly do read the PR of the inflationary theorists! Yes, there is some evidence for particular inflationary hypotheses, but no, not all inflationary scenarios produce flatness.
Click to expand...

The PR? Some evidence? Every prediction was confirmed. You need to do some reading. Or not depending whether you give a crap about the accuracy of comments you make on the subject of this science.
 
PhysBang said:
You certainly do read the PR of the inflationary theorists! Yes, there is some evidence for particular inflationary hypotheses, but no, not all inflationary scenarios produce flatness.
Click to expand...

Can you point me to an Inflationary hypothesis which does not drive omega to 1?
 
brucep said:
The PR? Some evidence? Every prediction was confirmed. You need to do some reading. Or not depending whether you give a crap about the accuracy of comments you make on the subject of this science.
Click to expand...
What predictions are you talking about? As far as I can tell, the only solid evidence for inflationary theory is some of the features of the anisotropies of the CMB. And that this is something that is very dependent on a number of assumptions.
AlexG said:
Can you point me to an Inflationary hypothesis which does not drive omega to 1?
Click to expand...
Given that the evidence is not conclusive about the overall density, those who support the theory better hope that inflation doesn't always produce flatness.

Madsen & Ellis 1998 showed how inflationary theories could produce essentially any value for the overall mass-energy density. Madsen, M. S. and G. F. R. Ellis (1988), "The evolution of [Omega] in inflationary universes", Monthly Notices of the Royal Astronomical Society 234: 67-77.

http://adsabs.harvard.edu/abs/1988MNRAS.234...67M
 
PhysBang said:
What predictions are you talking about? As far as I can tell, the only solid evidence for inflationary theory is some of the features of the anisotropies of the CMB. And that this is something that is very dependent on a number of assumptions.

Given that the evidence is not conclusive about the overall density, those who support the theory better hope that inflation doesn't always produce flatness.

Madsen & Ellis 1998 showed how inflationary theories could produce essentially any value for the overall mass-energy density. Madsen, M. S. and G. F. R. Ellis (1988), "The evolution of [Omega] in inflationary universes", Monthly Notices of the Royal Astronomical Society 234: 67-77.

http://adsabs.harvard.edu/abs/1988MNRAS.234...67M
Click to expand...
Read some paper on the subject that isn't 25 years old. Read the WMAP papers and the detailed predictions from Guth's inflation. Read how the CMBR was empirically evaluated during this experiment. The flatness is THIS universe. There's no requirement that any other universe have Omega 1. This universe is Omega 1 as Guth's Inflation predicts. The empirical evidence confirms this to within an error bar of .004. It's fascinating that most folks who proclaim an interest in modern physics and Cosmology are thirty years behind on how our universe came into being. Based on Carl Sagan's comment, in 'Contact', that 95% of the human race believes in a creation event initiated by some diety they believe in. The evidence on the density IS conclusive. Maybe you think the science isn't conclusive. Read Hawking's comment on the occasion of the WMAP team getting that award. I've been following this stuff since I read the first edition of Hawking's book and he talked about his cosmological model 'The No Boundary Proposal'.
 
AlexG said:
Chaotic models seem to provide a mechanism whereby omega could be considerably less than 1, but do not rule out an omega of 1.

http://link.springer.com/chapter/10.1007/978-94-011-3410-1_30#page-1
Click to expand...

They can't rule out an Omega of 1. Omega 1 is the obvious outcome of inflation so models with Omega's < 1 had to be considered to account for this physics. Linde was formulating his initial inflation model 'incommunicado' behind the iron curtain. A major issue in the beginning was finding a way for the inflation model to describe the evolution of a universe whose known observable matter was only a very small percentage of Omega 1. Thats the same paper Physbang linked. What I just described was the Omega Problem. The empirical study done by WMAP confirmed Guth's model. The Omega problem was eliminated for this universe.
 
brucep said:
Read some paper on the subject that isn't 25 years old. Read the WMAP papers and the detailed predictions from Guth's inflation.
Click to expand...
You are now contradicting yourself. Guth's inflation is quite old and has been replaced by newer hypotheses.

But, yes, the modern WMAP papers are the source of evidence for inflationary theories. But what else is there?

The empirical evidence confirms this to within an error bar of .004.
Click to expand...
For some WMAP papers, perhaps, with a host of assumptions that WMAP adds. Supernovae observations tend to skew to a density higher than critical. There are still some challenges to be addressed in this work.
The evidence on the density IS conclusive. Maybe you think the science isn't conclusive.
Click to expand...
I only know what I read in the actual scientific papers.
 
You must log in or register to reply here.
Back
Top