우주 천문학자들, 다른 우주와 우리 우주간 상호 작용(CMB)의 증거 발견.

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A new study submitted to the Astrophysical Journal has claimed to have found evidence of interactions between our universe and other universes by looking at the cosmic microwave background (CMB). The scientist discovered an anomaly associated with some regions of the CMB, and he believes it is evidence for alternate universes.

Dr Ranga Chary, the author of the study, wrote that his observations could "possibly be due to the collision of our universe with an alternate universe whose baryon to photon ratio is a factor of about 65 larger than ours." A pre-print of the study, which is yet to be peer reviewed, is available on ArXiv.

The CMB is the first light that shone in the universe. It was emitted 370,000 years after the Big Bang when the universe was cool enough for hydrogen to form and the original photons were free to move without getting absorbed by the primordial matter.

Although it is very uniform, there are small but detectable differences in the CMB which correspond to regions of slightly different densities: the slightly denser areas are the seeds where galaxies and stars eventually formed.

The CMB is not the only microwave emission in the sky. Hot dust and magnetic fields are responsible for producing microwaves as well. When the CMB was mapped all those emissions were carefully modelled and eliminated; this was to make sure that the signal observed was made up exclusively of the CMB photons.

Using these maps, Dr Chary from CalTech has detected an anomalous emission associated with five cold spots of the CMB (the blue areas in the map above), areas which were slightly denser after the Big Bang. The researcher claims that these emissions are consistent with a collision with an alternate universe. 

Of course, this is just one possible explanation and a pretty unverifiable theory at the moment. It is also not the first time that researchers have made exceptional claims about the CMB. Roger Penrose claimed to have detected concentric anomalies which were consistent with his idea that the universe iterates through infinite cycles.

Others have claimed that, as the CMB looks the same from every region of the universe, it is the perfect place for aliens or divine beings to leave a message. If that were to be the case, you might hope for something along the line of Douglas Adams’ suggestion, where God’s final message to his creation is: “We apologize for the inconvenience.”

The paper suggests also a more commonplace and perhaps more realistic explanation as, in 30% of the cases, the emission is consistent with foreground sources which have not been exactly taken into account in the map. 

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There’s something exciting afoot in the world of cosmology. Last month, Roger Penrose at the University of Oxford and Vahe Gurzadyan at Yerevan State University in Armenia announced that they had found patterns of concentric circles in the cosmic microwave background, the echo of the Big Bang.

This, they say, is exactly what you’d expect if the universe were eternally cyclical. By that, they mean that each cycle ends with a big bang that starts the next cycle. In this model, the universe is a kind of cosmic Russian doll, with all previous universes contained within the current one.

That’s an extraordinary discovery: evidence of something that occurred before the (conventional) Big Bang.

Today, another group says they’ve found something else in the echo of the Big Bang. These guys start with a different model of the universe called eternal inflation. In this way of thinking, the universe we see is merely a bubble in a much larger cosmos. This cosmos is filled with other bubbles, all of which are other universes where the laws of physics may be dramatically different from ours.

These bubbles probably had a violent past, jostling together and leaving “cosmic bruises” where they touched. If so, these bruises ought to be visible today in the cosmic microwave background.

Now Stephen Feeney at University College London and a few pals say they’ve found tentative evidence of this bruising in the form of circular patterns in cosmic microwave background. In fact, they’ve found four bruises, implying that our universe must have smashed into other bubbles at least four times in the past.

Again, this is an extraordinary result: the first evidence of universes beyond our own.

So, what to make of these discoveries. First, these effects could easily be a trick of the eye. As Feeney and co acknowledge: “it is rather easy to find all sorts of statistically unlikely properties in a large dataset like the CMB.” That’s for sure!

There are precautions statisticians can take to guard against this, which both Feeney and Penrose bring to bear in various ways.

But these are unlikely to settle the argument. In the last few weeks, several groups have confirmed Penrose’s finding while others have found no evidence for it. Expect a similar pattern for Feeney’s result.

The only way to settle this will be to confirm‎ or refute the findings with better data. As luck would have it, new data is forthcoming thanks to the Planck spacecraft that is currently peering into the cosmic microwave background with more resolution and greater sensitivity than ever.

Cosmologists should have a decent data set to play with in a couple of years or so. When they get it, these circles should either spring into clear view or disappear into noise (rather like themysterious Mars face that appeared in pictures of the red planet taken by Viking 1 and then disappeared in the higher resolution shots from the Mars Global Surveyor).

Planck should settle the matter; or, with any luck, introduce an even better mystery. In the meantime, there’s going to be some fascinating discussion about this data and what it implies about the nature of the universe. We’ll be watching.

Ref:

http://arxiv.org/abs/1012.1995: First Observational Tests of Eternal Inflation

http://arxiv.org/abs/1011.3706: Concentric Circles In WMAP Data May Provide Evidence Of Violent Pre-Big-Bang Activity

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THE curtain at the edge of the universe may be rippling, hinting that there’s more backstage. Data from the European Space Agency’s Planck telescope could be giving us our first glimpse of another universe, with different physics, bumping up against our own.

That’s the tentative conclusion of an analysis by Ranga-Ram Chary, a researcher at Planck’s US data centre in California. Armed with Planck’s painstaking map of the cosmic microwave background (CMB) – light lingering from the hot, soupy state of the early universe – Chary revealed an eerie glow that could be due to matter from aneighbouring universe leaking into ours.

This sort of collision should be possible, according to modern cosmological theories that suggest the universe we see is just one bubble among many. Such a multiverse may be a consequence of cosmic inflation, the widely accepted idea that the early universe expanded exponentially in the slimmest fraction of a second after the big bang.

Once it starts, inflation never quite stops, so a multitude of universes becomes nearly inevitable. “I would say most versions of inflation in fact lead to eternal inflation, producing a number of pocket universes,” says Alan Guth of the Massachusetts Institute of Technology, an architect of the theory.

Energy hidden in empty space drives inflation, and the amount that’s around could vary from place to place, so some regions would eventually settle down and stop expanding at such a manic pace. But the spots where inflation is going gangbusters would spawn inflating universes. And even areas within these new bubbles could balloon into pocket universes themselves.

Like compositions on the same theme, each universe produced this way would be likely to have its own spin on physics. The matter in some bubbles – the boring ones – would fly apart within 10-40 seconds of their creation. Others would be full of particles and rules similar to ours, or even exactly like ours. In the multiverse of eternal inflation, everything that can happen has happened – and will probably happen again.

That notion could explain why the physical constants of our universe seem to be so exquisitely tuned to allow for galaxies, stars, planets and life (see “Just right for life?“).

Sadly, if they do exist, other bubbles are nigh on impossible to learn about. With the space between them and us always expanding, light is too slow to carry any information between different regions. “They could never even know about each other’s existence,” says Matthew Johnson of York University in Toronto, Canada. “It sounds like a fun idea but it seems like there’s no way to test it.”

Bubble trouble

However, if two bubbles started out close enough that they touched before expanding space pushed them apart forever, they could leave an imprint on each other. “You need to get lucky,” Johnson says.

“If two bubbles started out close enough that they touched, they could leave an imprint on each other”

In 2007, Johnson and his PhD adviser proposed that these clashing bubbles might show up as circular bruises on the CMB. They were looking for cosmic dance partners that resembled our own universe, but with more of everything. That would make a collision appear as a bright, hot ring of photons.

By 2011, they were able to search for them in data from NASA’s WMAP probe, the precursor to Planck. But they came up empty-handed.

Now Chary thinks he may have spotted a different signature of a clash with a foreign universe.

“There are two approaches, looking for different classes of pocket universes,” Johnson says. “They’re hunting for lions, and we’re hunting for polar bears.”

Instead of looking at the CMB itself, Chary subtracted a model of the CMB from Planck’s picture of the entire sky. Then he took away everything else, too: the stars, gas and dust.

With our universe scrubbed away, nothing should be left except noise. But in a certain frequency range, scattered patches on the sky look far brighter than they should. If they check out, these anomalous clumps could be caused by cosmic fist-bumps: our universe colliding with another part of the multiverse (arxiv.org/abs/1510.00126).

These patches look like they come from the era a few hundred thousand years after the big bang when electrons and protons first joined forces to create hydrogen, which emits light in a limited range of colours. We can see signs of that era, called recombination, in the light from that early hydrogen. Studying the light from recombination could be a unique signature of the matter in our universe – and potentially distinguish signs from beyond.

“This signal is one of the fingerprints of our own universe,” says Jens Chluba of the University of Cambridge. “Other universes should leave a different mark.”

“This signal is one of the fingerprints of our own universe. Others should leave a different mark”

Since this light is normally drowned out by the glow of the cosmic microwave background, recombination should have been tough for even Planck to spot. But Chary’s analysis revealed spots that were 4500 times as bright as theory predicts.

One exciting explanation for this is if a surplus of protons and electrons – or something a lot like them – got dumped in at the point of contact with another universe, making the light from recombination a lot brighter. Chary’s patches require the universe at the other end of the collision to have roughly 1000 times as many such particles as ours.

“To explain the signals that Dr Chary found with the cosmological recombination radiation, one needs a large enhancement in the number of [other particles] relative to photons,” Chluba says. “In the realm of alternative universes, this is entirely possible.”

Of course there are caveats, and recent history provides an important reality check. In 2014, a team using the BICEP2 telescope at the South Pole announced another faint signal with earth-shaking cosmological implications. The spirals of polarised light, spotted in the cosmic background, would have provided more observational evidence for the idea of inflation and helped us understand how inflation occurred. But it turned out that signal came from dust grains within our galaxy.

Princeton University’s David Spergel, who played a major role in debunking the BICEP2 finding, thinks dust may again be clouding our cosmological insights. “I suspect that it would be worth looking into alternative possibilities,” he says. “The dust properties are more complicated than we have been assuming, and I think that this is a more plausible explanation.”

Joseph Silk of Johns Hopkins University in Baltimore, Maryland, is even more pessimistic, calling claims of an alternate universe “completely implausible”. While he thinks the paper is a good analysis of anomalies in Planck data, Silk also believes something is getting in the way. “My view is that they are almost certainly due to foregrounds,” he says.

Chary acknowledges that his idea is as tentative as it is exciting. “Unusual claims like evidence for alternate universes require a very high burden of proof,” he writes.

He makes an effort to rule out more prosaic explanations. If it is dust, Chary argues, it would be the coldest dust we’ve ever seen. It’s probably not noise masquerading as a signal. It could be carbon monoxide moving toward us, but we don’t usually see that. It could be faraway carbon, but that emission is too weak.

“I am certain he made every effort to ensure that the analysis is solid,” says Chluba. Even so, foregrounds and poorly understood patterns could still be the source of the signals. “It will be important to carry out an independent analysis and confirm‎ his finding,” Chluba says.

Sensitive solutions

One obstacle to checking is that we’re limited by the data itself. Planck was hyper-sensitive to the cosmic microwave background, but it wasn’t intended to measure the spectral distortions Chary is looking for. Johnson’s team also plans to use Planck to look for their own alternate universes, once the data they need is released to the public – but they estimate that Planck will only make them twice as sensitive to the bubble collisions they’re looking for as they were with WMAP.

An experiment that could help might be on its way. Scientists at NASA’s Goddard Space Flight Center plan to submitPIXIE, the Primordial Inflation Explorer, to be considered for funding at the end of 2016.

PIXIE’s spectral resolution could help characterise Chary’s signals if they really are there, Chluba says. But even if they aren’t, reconstructing how inflation happened could still lead us once again back to the multiverse – and tell us what kind of bubble collisions we should look for next

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https://www.newscientist.com/article/mystery-bright-spots-could-be-first-glimpse-of-another-universe/

http://www.technologyreview.com/view/421999/astronomers-find-first-evidence-of-other-universes/

http://www.iflscience.com/space/scientist-claims-there-evidence-other-universes-cosmic-microwave-background

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