No Shadow From the Big Bang?

ultracool writes "In a finding sure to cause controversy, scientists at The University of Alabama in Huntsville (UAH) found a lack of evidence of shadows from "nearby" clusters of galaxies using new, highly accurate measurements of the cosmic microwave background (WMAP). Other groups have previously reported seeing this type of shadows in the microwave background. Those studies, however, did not use data from WMAP, which was designed and built specifically to study the cosmic microwave background."

Comments

I've always wondered about that...

[Capt'n Hector]

How do we know that the ±0.0001 K (or whatever it is exactly) fluctuations in the CMB isn't just from nearby galaxies? How do we know it is truly background information? No subtraction algorithm is THAT perfect.

Not so simple as it seems

[Nuffsaid]

It is easy to form a layman idea about the geometry involved in this phenomenon. A wrong idea, that is. The article's drawing shows a galaxy cluster between us and a distant wall of light, casting a shadow cone. It is rather intuitive that the "wall of light" is actually part of a sphere surrounding us in every direction, with a radius of 13.7 billion light years. The sphere is actually a magnified image of the Universe as it was some time after the Big Bang, when it cooled down to the temperature required for the emission of the observed microwave radiation. And it is magnified not by some optical effect, but by the expansion of space itself. If you were in the cluster's position you would continue to see yourself at the center of such a sphere with radiation coming from all directions. Actually, this would be true for any place in the Universe. Add the fact that things move, light travels at a finite speed, and that the "wall of light" was essentially "here" 13.7 billion years ago, when the light was emitted. Throw in all the relativistic factors required on such scales, and what seemed like a simple geometry problem becomes a job for expert astronomers, not for me.

My favourite explanation is that light and dark travel at different speeds...

Shadows really expected?

[maxwell demon]

As a physicist (but no cosmologist or astrophysicist), I'm surprised that shadowing was expected. As far as I understood the article, the shadowing effect is expected not due to absorption/inelastic scattering (where I could understand the shadow effect), but due to elastic scattering (the photons just change their direction).

Now it is obvious that the number of photons reaching us from behind is reduced by the elastic scattering process. However one of the basic properties of the cosmic background radiation is that is is nearly isotropic. And that means there should be an about equal amount of radiation scattered into our direction which would not have reached us otherwise.

So is there anything I'm missing?

Re:Shadows really expected?

[aadvancedGIR]

IANAP, but I would tend to consider the lack of shadow as a proof for the big bang, not against.
If this radiation comes from the big bang, then it comes from every direction and this cluster of galaxies is as much the center of the universe as the earth itself. OTOH, having a "bright" and a "dark" side of this cluster would indicate that this radiation has a located source and therefore would invalidate the big bang theory.

Of course, there are tons of effects I don't know or don't unerstand, so please explain to me how a shadow would be supposed to appear despite the invariance and isotropy of the universe and how a mere little cluster of galaxies could alter in a measurable way a radiation that literally crossed half the universe and existed forever.

Re:No Big Bang, just cycles of expansion/contracti

[arun_s]

Not very convincing when you link to a free-energy crank site.
On the other hand, are there decent alternatives to the Big bang theory these days? All I can remember from college are the steady state and oscillating ones.
For that matter, this news doesn't disprove the theory either. AFAIK other factors like the distribution of stellar matter are still suggestive of a Big Bang.

Re:Grrrrrr!

[Anonymous Coward]

Their 'theory' excludes both evolution and big bang.
They think that by proving evolution wrong, this will automatically prove their proposed alternative 'theory' as correct! So, if god created the universe, there you go bye-bye bingbang as well.

The strange is that it might be easier for them to disprove bigbang rather evolution.
I don't know why, maybe their audience is amused with arguments based on every day observed staff about live,cats and flowers, rather than microwave shadows.

Re:Grrrrrr!

[Anonymous Coward]

You've got your history of science pretty much backwards.

One of the original inventors of the Big Bang was a Catholic priest, Fr. Lemaître. And some scientists were uncomfortable with the idea of the Big Bang, partly because it seemed suspiciously like the traditional Jewish (and Christian and Muslim) accounts of a creation of the universe at some finite time in the past.