Wednesday, December 29, 2010

Evidence for many Big Bangs?




Planck all-sky CMB image (Esa/HFI/LFI consortium)

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There's an idea in the area of physics known as quantum mechanics that suggests one can't measure a phenomenon without influencing the result.
It turns out that sometimes this same "observer effect" crops up in science journalism.
The story goes that, right now, there is a quiet debate happening that could have implications for how the Universe as we know it came to be - and what came before.
And the debate is being driven in part by the fact that news outlets including BBC News took a small peek into the machine of modern-day astrophysics.
It started in a fairly pedestrian way: I spotted a paper authored by someone with a familiar name, outlining analyses of what is known as the cosmic microwave background, or CMB.
Professor Sir Roger Penrose, along with his colleague Vahe Gurzadyan, had crunched through the publicly-available data on this ever-so-slightly jumbled glow of light that permeates the whole of the cosmos.
They found neat, circular rings of order in the CMB, a feature which would support a theory of Professor Penrose's: that the Big Bang is just the latest in an endless cycle, rather than a beginning per se.
"Rings" in WMAP microwave background data (VG Gurzadyan/R Penrose)The initial paper suggested these rings were echoes from before the Big Bang
As is common among cosmologists, the researchers published the idea on Arxiv.org, a repository for scientific papers before they go through the publishing process -where I found the manuscript and wrote a story on it, among other news outlets.
Three weeks later, two papers were posted to the Arxiv site refuting Professor Penrose's hypothesis: one by Hans Kristian Eriksen and Ingunn Wehus at the University of Oslo and another by Douglas Scott, Jim Zibin, and Adam Moss from the University of British Columbia.
Just two days later, a third refutation by Amir Hajian of the University of Toronto appeared.
It is rare that science works in this way; rarer still that it works at this speed. And there is some indication it's going this way in part because the BBC and others shed light on the initial paper.
In any case, the process is a remarkable, almost-but-not-quite public airing - kind of like a high-speed film of how scientific discourse can go on - with footnotes.
Anomalous
There are a number of factors driving this unusual debate. Perhaps the most obvious is the "celebrity science" factor.
"What's going on is that out of many outrageous claims made in cosmology each year, one was singled out recently for a huge amount of attention," Douglas Scott told BBC News.
"That would not have been the case had it come from someone without the reputation of Sir Roger."
It should also be said that Professor Penrose is championing a theory that, if correct, would completely upend the "inflationary cosmology" that is the current, widely-accepted best guess as to the Universe's origins.

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As far as the public is concerned, in a situation like [this one] the publicity may happen too fast to get out the news that there were big errors with the work; once the errors are found, the story has died down and the media have moved on”
Jim ZibinUniversity of British Columbia
Or, as Hans Eriksen put it: "The story contained a rather explosive mix of pre-Big Bang physics, black holes and Roger Penrose - any science journalist has got to love that."
And so we did. But Dr Eriksen hinted also at another factor surrounding the story - that the public nature of the data made the analysis easy to repeat - and refute.
That is, the current best-available data on the CMB are free to download; for now, that comes from the Wilkinson Microwave Anisotropy Probe, or Wmap.
Jo Dunkley, a University of Oxford astrophysicist and part of the Wmap team, explained that the hunt for "anomalies" like that posited by Professor Penrose is a common pursuit.
"That's a whole industry in our field, to look for unusual things in the maps," Dr Dunkley tells me.
"In the map of the sky, you can see an 's' and an 'h' if you look carefully. People have joked that it's Stephen Hawking's signature on the sky, but obviously we don't think that's significant.
"The nice thing about Penrose's theory is that it's a theory that you then go and test; that's exactly what we should be doing."
She's right. While all of this is going on, another paper is posted on the Arxiv that purports to see "bruises" of other universes in the CMB. That, too, should be tested for significance - perhaps before it gets media attention.
Error bars
The standard first test is to plug the new idea into simulations of the sky; you create a model on the basis of everything that is known and the result should replicate what observations bear out in the real CMB data.
It is here that the authors of the three rebuttal manuscripts suggest that Gurzadyan and Penrose have got it wrong. They say the original paper shows nothing more than what your common-or-garden inflationary cosmologist would have predicted on the basis of existing theory.
To prove the point, Douglas Scott and colleagues showed that a hunt for triangles in the CMB was statistically as successful as that for the circles that support Professor Penrose's theory.
After that, but before the third paper was published, Penrose and Gurzadyan had posted their riposte; it is clear that the subtleties of the argument are still being discussed, principally through the medium of the Arxiv site.
For some corners of science, this "preprint" culture is faster than the traditional refereed journal approach, in which results are sent to journals, who choose appropriate but anonymous experts to sign off the veracity or merit of the work.
Planck telescope first images (SPL)The Planck telescope will soon be providing significantly more detailed data on the CMB
But preprint servers are to that process as YouTube is to Cannes: you can find more, faster, but you can't know much about the quality of what you'll see.
"The new technology raises new problems but also provides the means to resolve them quickly," Jim Zibin told BBC News. "In a sense... the old refereeing system is not fast enough to respond, and a new, informal form of refereeing appears to fill the void.
Preprints and these debates can be seen as a workshop, then - but Amir Hajian says it is important to have a home for the finished product.
"The debates finally end - that is the nature of science," he told BBC News.
"Unknowns will be knowns sooner or later; what is important is to have trusted refereed journals to publish the final polished version of each work."
In the interim, Dr Zibin hinted that media interest kicks off the "observer effect" in the delicate experimental setup.
"As far as the experts are concerned, incorrect work will either be corrected via Arxiv comments, the standard review process, or more slowly over many years and many papers, or will simply go unnoticed and forgotten.
"But as far as the public is concerned, in a situation like [this one] the publicity may happen too fast to get out the news that there were big errors with the work. Once the errors are found, the story has died down and the media have moved on."

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Before the Big Bang - evidence for cyclical universe - Roger Penrose

reposted from: http://www.bbc.co.uk/news/science-environment-11837869


Cosmos may show echoes of events before Big Bang

"Rings" in WMAP microwave background data (VG Gurzadyan/R Penrose)The variation in the background shifts sharply within the rings

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Evidence of events that happened before the Big Bang can be seen in the glow of microwave radiation that fills the Universe, scientists have asserted.
Renowned cosmologist Roger Penrose said that analysis of this cosmic microwave background showed echoes of previous Big Bang-like events.
The events appear as "rings" around galaxy clusters in which the variation in the background is unusually low.
The unpublished research has been posted on the Arxiv website.
The ideas within it support a theory developed by Professor Penrose - knighted in 1994 for his services to science - that upends the widely-held "inflationary theory".
That theory holds that the Universe was shaped by an unthinkably large and fast expansion from a single point.
Much of high-energy physics research aims to elucidate how the laws of nature evolved during the fleeting first instants of the Universe's being.
"I was never in favour of it, even from the start," said Professor Penrose.
"But if you're not accepting inflation, you've got to have something else which does what inflation does," he explained to BBC News.
"In the scheme that I'm proposing, you have an exponential expansion but it's not in our aeon - I use the term to describe [the period] from our Big Bang until the remote future.
"I claim that this aeon is one of a succession of such things, where the remote future of the previous aeons somehow becomes the Big Bang of our aeon."
This "conformal cyclic cosmology" (CCC) that Professor Penrose advocates allows that the laws of nature may evolve with time, but precludes the need to institute a theoretical beginning to the Universe.
Supermassive find
Professor Penrose, of Oxford University, and his colleague Vahe Gurzadyan of Yerevan State University in Armenia, have now found what they believe is evidence of events that predate the Big Bang, and that support CCC.
They looked at data from vast surveys of the cosmic microwave background - the constant, nearly uniform low-temperature glow that fills the Universe we see.
They surveyed nearly 11,000 locations, looking for directions in the sky where, at some point in the past, vast galaxies circling one another may have collided.
The supermassive black holes at their centres would have merged, turning some of their mass into tremendous bursts of energy.
WMAP dataThe microwave background has, on average, only minor variations
The CCC theory holds that the same object may have undergone the same processes more than once in history, and each would have sent a "shockwave" of energy propagating outward.
The search turned up 12 candidates that showed concentric circles consistent with the idea - some with as many as five rings, representing five massive events coming from the same object through the course of history.
The suggestion is that the rings - representing unexpected order in a vast sky of disorder - represent pre-Big Bang events, toward the end of the last "aeon".
"Inflation [theory] is supposed to have ironed all of these irregularities out," said Professor Penrose.
"How do you suddenly get something that is making these whacking big explosions just before inflation turns off? To my way of thinking that's pretty hard to make sense of."
Shaun Cole of the University of Durham's computational cosmology group, called the research "impressive".
"It's a revolutionary theory and here there appears to be some data that supports it," he told BBC News.
"In the standard Big Bang model, there's nothing cyclic; it has a beginning and it has no end.
"The philosophical question that's sensible to ask is 'what came before the Big Bang?'; and what they're striving for here is to do away with that 'there's nothing before' answer by making it cyclical."
Professor Cole said he was surprised that the statistical variation in the microwave background data was the most obvious signature of what could be such a revolutionary idea, however.
"It's not clear from their theory that they have a complete model of the fluctuations, but is that the only thing that should be going on?
"There are other things that could be going on in the last part of the previous aeon; why don't they show even greater imprints?"
Professors Penrose and Cole both say that the idea should be shored up by further analyses of this type, in particular with data that will soon be available from the Planck telescope, designed to study the microwave background with unprecedented precision.
Planck data (Esa)Planck will provide a plethora of data that may prove or disprove the idea

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Monday, December 27, 2010

Microwave radiation map hints at other universes


Collisions between our cosmos and other universes may have left round "bruises" in a map of ancient cosmic radiation.
The four candidate "bruises" are in the lower-right quadrant of this all-sky map of the CMB, in green, light blue, red and orange (edge of image) (Image: S. Feeney and colleagues)
Our universe is thought to have expanded rapidly in a process called inflation in the first moments after the big bang. Some physicists suspect inflation is still happening, starting up in some regions while stopping in others, such as the part of the universe we live in. In this picture, called eternal inflation, new universes are continually popping into existence like bubbles in a vast, expanding sea of space-time.
Many of these universes should be carried away from one another as soon as they form. But universes born close together could collide if they are expanding faster than the space between them.
If our universe was hit by another bubble universe, the impact would release colossal bursts of energy. If this occurred before inflation ended in our patch of the universe, it could leave an imprint that might still be detectable today. Now Stephen Feeney of University College London and colleagues say they may have spotted such imprints in the cosmic microwave background (CMB), the all-sky glow that comes from photons emitted when the universe was less than 400,000 years old.

Hot and cold

A collision would alter how long inflation lasted in the impact zone. If the expansion continued for longer than it otherwise would, the density of matter in the impact zone would be lower than in surrounding regions. This would show up as a cold spot in the CMB. Conversely, a shorter period of inflation would create a warm spot in the CMB.
The team calculated the likely temperature profiles for such impacts and searched for them in CMB data from NASA's Wilkinson Microwave Anisotropy Probe.
The search turned up four circular patches, each spanning
an area of sky equivalent to at least eight full moons 
The search turned up four circular patches, each spanning an area of sky equivalent to at least eight full moons (arxiv.org/abs/1012.1995 and arxiv.org/abs/1012.3667). One is a cold spot that had already been cited as evidence of another universe interacting with our own.
"There's no obvious, boring explanation for the features," says team memberMatthew Johnson of the Perimeter Institute for Theoretical Physics in Waterloo, Canada.

Calling cards

If collisions with other universes did indeed create these patches, they should have left other calling cards in the CMB, such as a telltale signature in the orientation, or polarisation, of CMB photons. The European Space Agency's Planck satellite, which launched in 2009, should be able to detect these signs. Its first full maps of the sky are expected in 2012.
Even if just one of these spots turns out to be a bubble collision, it would be "a discovery of the first magnitude", says Thomas Levi of the University of British Columbia in Vancouver, Canada. The finding would bolster theories – such as string theory – that call for a vast number of universes with different properties.
"It is encouraging they found some candidates," says Alexander Vilenkin of Tufts University in Medford, Massachusetts. But he adds that even if bubble universes exist, they might not form at a rate that would guarantee one would have collided with our universe.