Postbusters.
Where’s Angua when we need her?
fixt
In the interest of getting back to something substantive…
As I understand it, “structure” is anything held together by gravity. Galaxies and clusters of galaxies are all structures based on that definition.
As for the background on the issue - I don’t know all that much besides what is in the article. However, the article does let us know that scientists already knew there were lots of galaxies and clouds of gas there. The “new” discovery is that they’ve connected the dots and shown that all of these are interconnected, and that there are many additional faint objects we’d never seen before. It’s fascinating to me that there’s so much out there that we haven’t seen because the faintest objects require so much telescope time to pick up.
I’ll first note that the research reported here is about seven years old. (The linked article is from 2006 but the relevant publications are from 2004/5.)
The evolution of the structure in and of the universe is modeled remarkably successfully by something called Lambda-CDM, which incorporates general relativity on the cosmological scale, folding in the potential for dark energy and dark matter. Lambda-CDM correctly explains a variety of observables:
- the acceleration of the universe’s expansion
- the abundances of light isotopes produced in the first tens of minutes after the Big Bang (in particular: hydrogen, deuterium, helium, lithium, and beryllium)
- the patterns of fluctuations encoded on the cosmic microwave background radiation
- the large-scale structures in the universe: galaxy clusters, superclusters, filaments
(In reality, such observed data are used to continually constrain the settings on the free knobs in the LCDM model. But it could have happened that no settings of the model’s knobs could describe what it seen, and that hasn’t happened, despite impressively precise and varied types of measurements.)
The last item in the list above is the relevant one here. The largest structures of galaxy clusters are formed from upward fluctuations in the matter density that were around from the start. How these fluctuations form and evolve is itself an interesting story, but suffice it to say that LCDM has a prediction for the distribution of such structures. (As a hint to the complexity: slightly denser regions will have slightly higher rates of particle interactions, resulting in slightly higher rates of neutrino production. These neutrinos will stream out of the denser regions and into less dense regions, in effect smoothing out the clumpiness. LCDM can even be used to put a constraint on the mass of the neutrino this way (by looking at galaxy structures!) and in fact this produces the tightest upper limit on neutrino mass so far.)
In any case, the very largest structures should be quite rare. These researcher have found a large one and have reported some of its properties. This same region was discovered many years earlier, and what these guys have done is taken a wider view at it to discover that it is in fact much larger than what was previously seen. However, it doesn’t break anything, as such structures should be present. It’s just kind of nice to have an even bigger one in hand now to study and to confront LCDM against.
Merely a filament of your imagination.
Honey Badger is but a typing monkey amongst a sea of a million typing monkeys…
Thanks so much. I’m on an iPhone, so I’ll take some time to think (mirabile dictu!) before getting to a machine where I can type a bit better.
A personal question:
Do you actually do (and/or get paid for) the studying and confronting specifically of this topic? Or are you speaking for the whole gang?
It can’t be you only do considerate replies to laymen blegs.
Also, thanks to dracoi and all the other posters, ninjas and all.
Don’t make me get out my mayonnaise jar full of golfballs and beer-sand.
As long as it hasn’t evolved into something covered with Mayan script that will hit any minute, I’m good.
Great post, Pasta.
I’m going to have to do that search, Leo Bloom, because I’ve never thought about what wedgehead brought up, and I think I threw a mental rod when I read it.
I was speaking as a physicist in a general way, with a sort of “we’re all in this together” tone. My research has contact with some of the same cosmological and astroparticle physics questions, but I do not currently do cosmological modeling or observation.
Thanks! 
“Expanding ballon” is the search term I should have said. It comes up as a metaphor often for what I was trying to say, and what others say for real.
If you think thats big, you should check out an axle-nut from a mid-80’s Harley.