Is the cosmological prinicple wrong? Is Big Bang wrong?

[marcus]

as I was starting to feel the Inquisition had grabbed me up and was going to burn me at the steak for heresy.
Doesn't GR break down at the quantum scale? Could it be possible that it breaks down on some gigantic cosmic scale also? I seem to have heard this somewhere. Thanks again.

heh heh maybe you SHOULD be burnt at the stake for heresy, but not yet.
GR breaks down at very small scale yes, if you mean break down at very high energy density which means very high curvature. the breakdowns are called "singularities"
the technical meaning of the word singularity comes from mathematics and means the failure of a theory or model, or the failure of a mathematical function to compute meaningful values------like where the function blows up, that is a singularity.

In an ordinary low energy low curvature regime, GR doesn't actually break down AFAIK, it is just that people are suspicious that it doesn't give a good description at very small scale. There are good reasons to mistrust it.

But at least it doesn't blow up. Practically speaking, the main places it blows up are the big bang and in black holes.

It could also be wrong at very large scale. Some people are working on modifications that take over at large scale---they want to see if they can fit data better with modified GR.

I guess the situation as I see it is paradoxical. On the one hand GR is overwhelmingly prevalent in cosmology. virtually everybody's research is based on it. On the other hand there are people constantly poking and prodding GR to find soft spots, trying to tweak it to make it do better, dreaming up ways to test it and maybe find a flaw. maybe that is normal. maybe a dominant theory always has some scientists attracted to trying to discover its faults, while the rest just go on using it.

 

[Garth]

heh heh maybe you SHOULD be burnt at the stake for heresy, but not yet.

But note Loki that “It is a heretic that makes the fire, not she which burns in it”!(William Shakespeare)

Garth

 

[Garth]

To my knowledge, there are no data sets that could really answer this question as yet. The trouble is that it's extremely difficult to conduct a wide-angle spectroscopic survey at high redshift because the tracer objects are either too dim (as with ordinary galaxies) or too sparsely distributed (as with quasars) to tell us much about large-scale structure.

At low redshift, my thesis work suggested that LCDM did very well at predicting the length and width distributions of filaments, though it's not yet clear how sensitive a test that is.

Thank you ST for your answer, I appreciate the observational difficulties.

It is great that we can see so far out and probe the early universe albeit in small areas of sky.

I understand the \LambdaCDM model fits observations at low z, my idea of a test for the \LambdaCDM model, would be to see if it does the same at high z as well.

Garth

 

[SpaceTiger]

I understand the \LambdaCDM model fits observations at low z, my idea of a test for the \LambdaCDM model, would be to see if it does the same at high z as well.

It would be nice to make the constraint more precise, even at low z. Believe it or not, at low z, we're actually more limited by our methodology than by our data.

Although Nereid's link (and the many other similar studies) don't directly address your question, they are suggestive of the answer. If the morphology of structure at low z matches the simulations, the two-point statistics match at intermediate redshifts, and we know from the CMB that it all started from a gaussian random field, then it's very hard to imagine that we'll see surprises in the morphological properties of large-scale structure at intermediate redshifts. Nevertheless, I agree that the study should be done and am in fact in the process of producing some results in that direction. Stay tuned!

 

[Garth]

Nevertheless, I agree that the study should be done and am in fact in the process of producing some results in that direction. Stay tuned!

Will do!

Garth

 

[Loki Mythos]

I have been looking at some of Van Flandern's work. The idea of how gravity waves could effect red shift. The more I think about it, the more the Big Bang Theory looks like a polished turd.

I would hope that fans of the BB here could answer some of Flandern's questions.

A short list of the leading problems faced by the big bang in its struggle for viability as a theory:
1.Static universe models fit the data better than expanding universe models.
2.The microwave "background" makes more sense as the limiting temperature of space heated by starlight than as the remnant of a fireball.
3.Element abundance predictions using the big bang require too many adjustable parameters to make them work.
4.The universe has too much large scale structure (interspersed "walls" and voids) to form in a time as short as 10-20 billion years.
5.The average luminosity of quasars must decrease with time in just the right way so that their mean apparent brightness is the same at all redshifts, which is exceedingly unlikely.
6.The ages of globular clusters appear older than the universe.
7.The local streaming motions of galaxies are too high for a finite universe that is supposed to be everywhere uniform.
8.Invisible dark matter of an unknown but non-baryonic nature must be the dominant ingredient of the entire universe.
9.The most distant galaxies in the Hubble Deep Field show insufficient evidence of evolution, with some of them apparently having higher redshifts (z = 6-7) than the faintest quasars.
10.If the open universe we see today is extrapolated back near the beginning, the ratio of the actual density of matter in the universe to the critical density must differ from unity by just a part in 1059. Any larger deviation would result in a universe already collapsed on itself or already dissipated.
From: Meta Research Bulletin, v. 6, #4, December 15, 1997. The full list and details appeared in "The top 30 problems with the Big Bang", Meta Research Bulletin, v. 11, #1, March 15, 2002.