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Mystery of the Coldest Spot In the CMB Solved
StartsWithABang writes: The cosmic microwave background is a thing of beauty, as not only does its uniform, cold temperature reveal a hot, dense past that began with the hot Big Bang, but its fluctuations reveal a pattern of overdensities and underdensities in the very early stages of the Universe. It's fluctuations just like these that give rise to the stars, galaxies, groups and clusters that exist today, as well as the voids in the vast cosmic web. But effects at the surface of last scattering are not the only ones that affect the CMB's temperature; if we want to make sure we've got an accurate map of what the Universe was born with, we have to take everything into account, including the effects of matter as it gravitationally grows and shrinks. As we do exactly this, we find ourselves discovering the causes behind the biggest anomalies in the sky, and it turns out that the standard cosmological model can explain it all.
If you actually bothered to read the article, you would not be claiming that's a mystery. The article explains that the void is not a big void, it's actually a fairly normal 20% less dense than average area. It just so happens to be on top of what's already a cool spot in the CMB. A a normal less dense area on top of a normal cool spot in the CMB = an appearance of an extraordinarily cold spot which is not really extraordinary at all but just a coincidence of that combination.
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I think it comes down to this: why there is a big cold spot in the CMB? Because there's a big void. Mystery solved!
Except there's still the mystery of why there is such a big void in the first place.
That is true, but it is a much lesser mystery. The previous record-holder was the Canes Venatici Supervoid at 1.3 billion light years, and an Eridanus Supervoid has been the preferred explanation for the Eridanus Cold Spot (or, humorously, CAOE: "Cosmic Axis Of Evil) for years ("parallel universe collisions" was always an exotic explanation), but the existence of such a supervoid had not been confirmed. Dr. István Szapudi of the Institute for Astronomy at the University of Hawaii at Manoa has has just announced findings that measures this supervoid at 1.8 billion light years. This is moderately bigger than the previous record-holder (40% wider), but there are quite a few that are 400-800 million light years across. This looks rather like a power law distribution, often found in nature.
The Canes Venatici Supervoid is closer as than the Eridanus Supervoid (red shift z=0.118 vs 0.22, or 1.5 vs 2.5 billion light years) as well as being smaller so there are two reasons for the Integrated Sachs-Wolfe Effect to be weaker, but apparently there is no anomalous cooling for that void at all. I would like to see someone address that.
Starships were meant to fly, Hands up and touch the sky - Nicky Minaj
Something can be uniform and fluctuating at the same time. All that's required is that the fluctuations follow the same, regular pattern everywhere. I have no idea whether this is true for the CMB, however.
It is true. Further, the fluctuations are tiny - at the parts per million level. It took 28 years after the CMB was discovered to detect any fluctations at all, requiring a sophisticated space probe (COBE) to do it.
Asserting that the CMB is "not uniform" because of these fluctuations is rather like saying the Bonneville Salt Flats are not really flat at all since the surface has millimeter scale irregularities, or your polished marble dining room floor isn't flat since it has micron sized irregularities.
Starships were meant to fly, Hands up and touch the sky - Nicky Minaj