Large galaxies stopped growing 7 billion years ago

[joe_smith]

I found this article (http://www.ras.org.uk/news-and-press/217-news2011/1947-nam-03-large-galaxies-stopped-growing-7-billion-years-ago) from Claire Burke from the Astrophysics Research Institute at Liverpool John Moores University pretty interesting.

Do you think this data fits in the cyclic model of the universe as put forth by Paul J. Steinhardt and Neil Turok?, is it more proof for their model or not?

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[CraigS]

Hi Joe;

Great post ! Very thought-provoking (at least, for me. :) )



I'm sure someone will think up a plausible reason for the apparent stationary growth of Brightest Cluster Galaxies (BCGs) observed. However, it is certainly intriguing.

I have a soft spot for the Steinhardt–Turok model, for the large scale picture, because it incorporates modern M-Theory and Chaotic dynamics thinking. I have a feeling this is a good direction for Science to explore for a while. The static growth at the galaxy level, may loosely support the 'lull' between cycles of expansion and contraction. However the S-T Theory is still a theory, with very little other clear, empirical evidence supporting it.

In this case, there are two scales, and confined focuses in action here:

i) growth of a set of BCGs at the galaxy end of the scale and;
ii) a narrowly constrained galaxy type (BCGs only).

I'd think it would be a bit early to 'toss the baby out with the bathwater', on these bases alone.


I would say that there is no direct disproof evident here, for the classical model.
The theories can co-exist until evidence appears, disproving one or the other.
:)
I'm not sure we could ever provide substantial evidence for the cyclic model by making observations spanning (backwards) over only 7 billion years … what we need is evidence which spans back past 13.75 billion years, or some good supportive evidence of the validity of Strings and Ms.

(Ie: I don't think observations made in the middle of a cycle, will ever tell us much about the initial or final defining states of that cycle).

My 2 cents worth, anyway.
:)
Cheers

[joe_smith]

So do I, for me it makes more sense, and I like their view of the W-MAP.

Turok and Steinhardt explain it pretty good in the series "Through the worm hole" in episode 4 What Happened Before the Beginning (http://topdocumentaryfilms.com/through-the-wormhole-what-happened-before-the-beginning/)? The big bang was not the beginning of the universe but a collision between branes. Also the fact that "The lack of growth of the most massive galaxies" points to inflation, as explained by the balloon example being not quite right for me. As if the universe and everything in it is expanding why has some of it supposedly stopped? as they explain in there book science is at exciting point in time as the two models claim the prize, and we are able to see it unfold :)

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[CraigS]

I think we need to be careful not to mix things up here.

Under BBT, inflation happened very early on, just after the BB. It was introduced to explain the flatness, homogeneity and isotrophy of the observable universe. It also explains the large scale structures, (super clusters etc). With its incorporation into the Standard Model, it also predicted what has now been measured in the CMBR.

What we have now, is the 'metric expansion of space', which operates roughly at the scale of superclusters. Gravity operates at the smaller galaxy cluster level, causing clumping of normal matter. These clumps do not expand but they do recede from one another. This all has direct observational evidence - Hubble's measurements, redshift, etc.

The expansion we see at present, is partly explained by simple inertia and, partly due to a repulsive force (dark energy). Inertia dominated early on, and the repulsive force will dominate in the future. At present, they contribute in roughly equal amounts.

All of this is based on observed empircal evidence. This forms the basis of constraints on any theory .. no matter which one … even the S-T Model would have to account for these measurements.


The expansion at the BCG level would not have been expected anyway, as it is only apparent (from measurements), at the larger scales.

Cheers

[CraigS]

Yes Joe;
Just watched the 'Through the Wormhole' episode.

There's a fair bit of hype and (over) dramatisation about it all.

I'm not sure why they see the S-T Theory as an alternative to BBT/Inflation. The way I see it, its kind of an extension, which provides some theoretical framework/explanation of how BBT could be extended by introducing extra dimensions and branes.

It all sits quite nicely with me. I have no major probs with the S-T Theory.

As I said earlier, the thing which is missing, is any empirical evidence … we should remember that M Theory is an extension of String Theory .. and there's only just now appearing, the beginnings of some types of empirical tests, formulated to enquire into the sanity (or otherwise) of Strings.

The major quest is to understand the concepts defined by BBT and then move onto M-Theory. Both can co-exist, I believe.

Cheers