Well, we knew it wasn't evenly distributed well before this discovery. The Earth, the Sun, the galaxy -- they're all much more dense than the space surrounding them. I'm sure what you meant was that matter is evenly distributed on the largest of scales. Apparently what this means is, the "largest of scales" just got larger.

__________________
Everyone is entitled to his own opinion, but not his own facts.

Where do you get that?

__________________
Everyone is entitled to his own opinion, but not his own facts.

Thanks, Fortunate. I suppose that explanation makes sense and is well accepted, but it sure sounds tenuous!

In a simple expansion of the universe, without dark energy, photons approaching a large mass -- such as a supercluster of galaxies -- pick up energy from its gravity. As they pull away, the gravity saps their energy, and they wind up with the same energy as when they started.

But photons passing through matter-rich space when dark energy became dominant don't fall back to their original energy level. Dark energy counteracts the influence of gravity and so the large masses don’t sap as much energy from the photons as they pull away. Thus, these photons arrive at Earth with a slightly higher energy, or temperature, than they would in a dark energy-free Universe.

Conversely, photons passing through a large void experience a loss of energy.

I understand the expansion would be greater after the photons have passed by a large mass, but it seems this would be an extremely small effect. Besides, this would not be true for photons traveling through regions of space that are 7 or 8 billion lightyears away, when dark energy had yet to become dominant over gravitational slowing.

__________________
Everyone is entitled to his own opinion, but not his own facts.

...assuming the current dark energy model is correct

__________________
PW -- Plant Whisperer

That's A good point that I think might help Bmpbmp out. From what I gather from the article, it's more of a void than a hole.

Maybe it's the byproduct of a matter/anti-matter conversion reaction, where they each destroyed each other and the area around it. Probably some advanced ET civilization who dabbled too far in science. (J/k, but we'll probably see that theory pop up here sooner or later).

Or maybe it's just an empty space.

__________________
I'm like one of those idiot savants...well, except for the savant part.

Theory of Zombie Relativity:
1) Everyone Else is a Zombie relative to You
2) Whether or not it matters is related to the inverse square of the distance between their teeth and your brain
(Quoted from Demigrog)

I had some of the same reservations that you express, Cougar. I look forward to more comments from the astrophysicists. Not only is the void's spatial alignment with the cool spot intriguing, but also, the question of how the size of this object (I suppose this might actually be termed a nonobject) can be so far removed from the statistical grouping of the sizes of the other known voids. The article doesn't give many numbers but leaves me with the impression that, in statistical terms, the deviation is of a completely prohibitive number of sigmas, leading one to at least entertain the notion of a new mechanism.

After a little more checking, I see this was all figured out by Sachs and Wolfe and is now referred to as the Sachs-Wolfe Effect, in this case, the "late-time integrated Sachs Wolfe effect." There is a a little more detailed explanation here.

__________________
Everyone is entitled to his own opinion, but not his own facts.

Cool! The biggest hubble bubble in the universe. I hope that catches on. I like Hubble bubble a lot better than void.

__________________
I think fish is nice, but then I think that rain is wet, so who am I to judge?

It's gotten to the point where careful investigation is needed just to tell parody from reality. I think that means reality is broken.- Noclevername.

A moment of clarity for the Cougar, maybe?

The most logical reason that a local void would produce a cold spot in the CMB, is that the rest of the CMB is weakly contaminated by local stuff.
If you follow the line of reasoning in some of the articles, the CMB cools naturally with distance, and local stuff mitigates the cooling rate. In either case, since the exact density of local structure is nebulus, the cold spot should be considered the 'least contaminated' and therefore the most representived of the temperature of space at great distances.

This means that those of us who have speculated that much of the CMB is 'solar' are very likely wrong. But it also means it is reasonable to argue much of the thermal variation we see in the 'CMB' is caused by local structure. It cannot be proven to any degree of certainty that it is not.

__________________
jwj

It's ok not to know.

Logical... until you discover that foreground contamination is already considered and accounted for. As the preprint notes....

"Several studies have claimed that the properties of the cold spot are most likely an effect of incorrect foreground subtraction (Chiang & Naselsky 2004; Coles 2005; Liu & Zhang 2005; Tojeiro et al. 2006). This possibility has been investigated in detail for both the first year (Vielva et al. 2004; Cruz et al. 2005, 2006) and third (Cruz et al. 2007) year WMAP data. The arguments against foreground subtraction errors can be summarized in three main points – 1) The region of the spot shows no spectral dependence in the WMAP data. This is consistent with the CMB and inconsistent with the known spectral behavior of galactic emission (as well as the SZ effect). The flat (CMB-like) spectrum is found both in temperature and kurtosis, as well as in real and wavelet space. 2) Foreground emission is found to be low in the region of the spot, making it unlikely that an over-subtraction could produce an apparent non-Gaussianity. 3) Similar results are found when using totally independent methods to model and subtract out the foreground emission (Cruz et al. 2006), namely the combined and foreground cleaned Q-V-W map (Bennett et al. 2003) and the weighted internal linear combination analysis (Tegmark et al. 2003)."

__________________
Everyone is entitled to his own opinion, but not his own facts.

So this is where Azathoth resides... While in the void, you can hear Zann's violin screaming--even across the vacuum

Thanx for the great links. I am not clear, though, how late ISW applies, since the void is "6-10 billion light years" away, and the the photons passed through it before ISW came into play (unless I misunderstood something).

The preprint apparently has a handle on this....

"The contribution of the late ISW [late integrated Sachs-Wolfe effect] along a given line of sight is given by

[unreproducible fancy equation]

where the dot represents differentiation with respect to the conformal time η, dη = dt/a(t), and a is the scale factor. The integrand will be non-zero only at late times (z<1) when the cosmological constant becomes dynamically dominant."

And besides, they're calling the void "local," or at least z<=1.

__________________
Everyone is entitled to his own opinion, but not his own facts.

Thanx again, Cougar. Well, the linked article colloquially translated "late"as "right around now," but if it just means z<1, then I'm OK.

AAAAH!! Don't even ask me what "early" and "late" mean with respect to the universe. Particularly since....

Galaxies are often called early (E and S0) or late (Sb,Sc, Irr) in type, a remnant of early notions that galaxies physically evolve along the Hubble sequence. Unfortunately, this nomenclature is opposite to that of the dominant stellar population in these types, and to the early-late nomenclature in the Yerkes classification.

So I guess I should determine what I think it should mean, and then just go with the opposite of that.

__________________
Everyone is entitled to his own opinion, but not his own facts.

Hubble bubble = the visible universe. Void = a large scale region devoid of galaxies.

__________________
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

I found an article called "WMAP Cold Spot Extragalactic Radio Sources." I'm having trouble providing links (don't ask), but you can Google the title directly. The article examines various possible explanations for the cold spot, and cites a large void as one of them. How large would the void have to be? They calculate that for 0.5<z<1 the void would have to be on the order of 280 Mpc (913 million light years). They calculate the probability of finding a 280 Mpc void as 5x10^-10. Bet they never thought that horse would pay off.

Bmpbmp,
Perhaps the choice of words is the source of confusion. This is not a gigantic black hole, or something to fall into, or anything like that. This is simply a volume of space where the astronomers expected to find galaxies but didn't. there are other parts of the universe that don't have any galaxies, but this recently discovered part is much, much bigger than the others and the question is how did it form. It is so far away that there is no way that it could possibly influence the Milky Way or the Solar System for at least the next 10 or 20 billion years. In all likelihood it will never influence our part of the universe.

BTW bmpbmp, welcome back. I hadn't seen your posts in a while. I'm glad you're still following astronomy news. After you read the nonsense from other web sites, remember to keep coming here to get the real story. We haven't been wrong yet and we won't be wrong in the future either.

__________________
Rock is dead. Long live Paper and Scissors.