Mystery of the Coldest Spot In the CMB Solved 45
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.
But why is there only one spot like this? (Score:2)
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Well, it's medium.com. You can't analyse it too much.
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.
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Medium.com explains it all.
It's essentially blogspot disguised as a news site.
Look forward to my article explaining how the CMB cold spot is the result of CFC's breaking down galactic ozone. Also, aliens.
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I don't think Medium has ever purported to be a news site. It's doesn't look like one, it doesn't cover the news. It's a collection of stories. Not news stories, just stories. Thinking otherwise "explains it all".
Re:But why is there only one spot like this? (Score:5, Informative)
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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If slashcode had ever evolved beyond 2001, we'd be selecting comments like this to replace the summary.
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If slashcode had ever evolved beyond 2001, we'd be selecting comments like this to replace the summary.
Slashdot Beta was evolved since 2001. Personally, I use slashdot classic and prefer it over other commenting systems.
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You make it sound like the temperature of the (empty) region averages down the background, making it colder. But something way more awesome actually happens: Photons enter one side of the Void (empty region) at an early time and travel through it. During that time, the Void expands. To escape the Void, the photon then has to lose more energy than it received when it entered. It is the slow light speed relative to these enormous scale, evolving structures that causes this effect!
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Re:But why is there only one spot like this? (Score:5, Informative)
...
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 [hawaii.edu] has has just announced findings [oxfordjournals.org] 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 [wikipedia.org] 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.
There should be less than one (Score:2)
"that the standard cosmological model can explain" (Score:3)
Aw, boring. I was hoping that everyone was wrong and we get some new physics. Misconception of scientists number one, scientists (and me) like to be shown wrong so we can go and investigate and discover new knowledge. The day it turns out that we know everything will be a very sad day indeed.
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In science, it's irrelevant if you admit it or not. Either your model works or not, and if it's not working somebody will come up with a better model and replace yours. People will use the better model because it works better. Or maybe I misunderstand you. Newton's laws of gravity works "almost right", Einstein's theory is better. But in cosmonautics and mechanics we use Newton's laws, because they are good enough.
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If we can't observe anything new. And by "new" I mean something that was not predicted by a scientific theory. Of course, there is always the possibility to observe something new, but it's like an asymptote. New scientists will be less and less excited, because they will just confirm established theories.
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I was hoping that everyone was wrong and we get some new physics.
It's a Medium article. I think if you read it in detail you'll probably find they made up some new physics anyway.
Re:Summary is contradictory (Score:5, Informative)
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.
Ghosts (Score:2)
Kludgy Mess Requires Kludgier Foundation (Score:1)
The standard cosmological model sits on top of the concept of cosmological inflation, a well known kludge adopted to explain away serious problems with the standard cosmological model, thus suggesting that it is indeed turtles all the way down.
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"A recurrent criticism of inflation is that the invoked inflation field does not correspond to any known physical field, and that its potential energy curve seems to be an ad hoc contrivance to accommodate almost any data obtainable. Paul J. Steinhardt, one of the founding fathers of inflationary cosmology, has recently become one of its sharpest critics. He calls 'bad inflation' a period of accelerated expansion whose outcome conflicts with observations, and 'good inflation' one compatible with them: "Not
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Allowing AC posts like yours have ruined this site for years now. The owners and operators of Slashdot should have fixed this by now, severely restricting who has access to AC posting.
Maybe you haven't looked at many science stories on here, but there are numerous named accounts that will make wildly inaccurate and wrong on nearly every science story of various topics. They get modded up faster than coherent replies can be made pointing out how wrong they are, and often retain a net positive mod even after a dozen replies pointing out how wrong they are, letting them post the exact same mistakes again at a later time. And not just subtle mistakes, but stuff that directly contradicts th
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Inflation was cooked up to explain most of that after the fact, though, so it's unsurprising that it does. The fundamental problem with inflation is that too much is tunable. Penrose's cyclic cosmology explains all the same stuff, and at least has the decency to make some bizarre (and very likely false) predictions outside of the early universe.
Theories of the very early universe that require new fields that there's a way to detect today are interesting. Certainly there are ideas to explain dark energy a
I reject your reality and substitute my own. (Score:2)