Evidence spotted for universe's early growth spurt
By MALCOLM RITTER AP Science Writer
NEW YORK (AP) -- Researchers say they have spotted evidence that a split-second after the Big Bang, the newly formed universe ballooned out at a pace so astonishing that it left behind ripples in the fabric of the cosmos.
If confirmed, experts said, the discovery would be a major advance in the understanding of the early universe. Although many scientists already believed that an initial, extremely rapid growth spurt happened, they have long sought the type of evidence cited in the new study.
The results reported Monday emerged after researchers peered into the faint light that remains from the Big Bang of nearly 14 billion years ago.
The discovery "gives us a window on the universe at the very beginning," when it was far less than one-trillionth of a second old, said theoretical physicist Lawrence Krauss of Arizona State University, who was not involved in the work.
"It's just amazing," Krauss said. "You can see back to the beginning of time."
Marc Kamionkowski, a theoretical physicist at Johns Hopkins University who did not participate in the research, said the finding is "not just a home run. It's a grand slam."
He and other experts said the results must be confirmed by other observations, a standard caveat in science.
Right after the Big Bang, the universe was a hot soup of particles. It took about 380,000 years to cool enough that the particles could form atoms, then stars and galaxies. Billions of years later, planets formed from gas and dust that were orbiting stars. The universe has continued to spread out.
Krauss said he thinks the new results could rank among the greatest breakthroughs in astrophysics over the last 25 years, such as the Nobel prize-winning discovery that the universe's expansion is accelerating.
Monday's findings were announced by a collaboration that included researchers from the Harvard-Smithsonian Center for Astrophysics, the University of Minnesota, Stanford University, the California Institute of Technology and NASA's Jet Propulsion Laboratory. The team plans to submit its conclusions to a scientific journal this week, said its leader, John Kovac of Harvard.
Astronomers scanned about 2 percent of the sky for three years with a telescope at the South Pole, where the air is exceptionally dry.
They were looking for a specific pattern in light waves within the faint microwave glow left over from the Big Bang. The pattern has long been considered evidence of rapid growth, known as inflation. Kovac called it "the smoking-gun signature of inflation."
The reported detection suggests that "inflation has sent us a telegram," Kamionkowski said.
The researchers say the light-wave pattern was caused by gravitational waves, which are ripples in space and time. If verified, the new work would be the first detection of such waves from the birth of the universe, which have been called the first tremors of the Big Bang.
Krauss cautioned that the light-wave pattern might not be a sign of inflation, although he stressed that it's "extremely likely" that it is. The pattern is "our best hope" for a direct test of whether the rapid growth spurt happened, he said.
Alan Guth of the Massachusetts Institute of Technology, a creator of the idea of inflation, said the findings already suggest that some ideas about the rapid expansion of the universe can be ruled out.
It had not been clear whether the light-wave pattern would be detectable even if inflation really happened, he said, but luckily "nature is cooperating with us, laying out its cards in a way that we can see them."
Scientists say they have extraordinary new evidence to support a Big Bang Theory for the origin of the Universe.
Researchers believe they have found the signal left in the sky by the super-rapid expansion of space that must have occurred just fractions of a second after everything came into being.
It takes the form of a distinctive twist in the oldest light detectable with telescopes.
"This is spectacular," commented Prof Marc Kamionkowski, from Johns Hopkins University.
"I've seen the research; the arguments are persuasive, and the scientists involved are among the most careful and conservative people I know," he told BBC News.
The breakthrough was announced by an American team working on a project known as BICEP2.
This has been using a telescope at the South Pole to make detailed observations of a small patch of sky.
The aim has been to try to find a residual marker for "inflation" - the idea that the cosmos experienced an exponential growth spurt in its first trillionth, of a trillionth of a trillionth of a second.
Gravitational waves from inflation put a distinctive twist pattern in the polarisation of the CMB
Theory holds that this would have taken the infant Universe from something unimaginably small to something about the size of a marble. Space has continued to expand for the nearly 14 billion years since.
Inflation was first proposed in the early 1980s to explain some aspects of Big Bang Theory that appeared to not quite add up, such as why deep space looks broadly the same on all sides of the sky. The contention was that a very rapid expansion early on could have smoothed out any unevenness.
But inflation came with a very specific prediction - that it would be associated with waves of gravitational energy, and that these ripples in the fabric of space would leave an indelible mark on the oldest light in the sky -the famous Cosmic Microwave Background.
The BICEP2 team says it has now identified that signal. Scientists call it B-mode polarisation. It is a characteristic twist in the directional properties of the CMB. Only the gravitational waves moving through the Universe in its inflationary phase could have produced such a marker. It is a true "smoking gun".
Speaking at the press conference to announce the results, Prof John Kovac of the Harvard-Smithsonian Center for Astrophysics, and a leader of the BICEP2 collaboration, said: "This is opening a window on what we believe to be a new regime of physics - the physics of what happened in the first unbelievably tiny fraction of a second in the Universe."
Completely astounded
The signal is reported to be quite a bit stronger than many scientists had dared hope. This simplifies matters, say experts. It means the more exotic models for how inflation worked are no longer tenable.
The results also constrain the energies involved - at 10,000 trillion gigaelectronvolts. This is consistent with ideas for what is termed Grand Unified Theory, the realm where particle physicists believe three of the four fundamental forces in nature can be tied together.
But by associating gravitational waves with an epoch when quantum effects were so dominant, scientists are improving their prospects of one day pulling the fourth force - gravity itself - into a Theory of Everything.
The sensational nature of the discovery means the BICEP2 data will be subjected to intense peer review.
It is possible for the interaction of CMB light with dust in our galaxy to produce a similar effect, but the BICEP2 group says it has carefully checked its data over the past three years to rule out such a possibility.
Other experiments will now race to try to replicate the findings. If they can, a Nobel Prize seems assured for this field of research.
Who this would go to is difficult to say, but leading figures on the BICEP2 project and the people who first formulated inflationary theory would be in the running.
One of those pioneers, Prof Alan Guth from the Massachusetts Institute of Technology, told the BBC: "I have been completely astounded. I never believed when we started that anybody would ever measure the non-uniformities of the CMB, let alone the polarisation, which is now what we are seeing.
"I think it is absolutely amazing that it can be measured and also absolutely amazing that it can agree so well with inflation and also the simplest models of inflation - nature did not have to be so kind and the theory didn't have to be right."
British scientist Dr Jo Dunkley, who has been searching through data from the European Planck space telescope for a B-mode signal, commented: "I can't tell you how exciting this is. Inflation sounds like a crazy idea, but everything that is important, everything we see today - the galaxies, the stars, the planets - was imprinted at that moment, in less than a trillionth of a second. If this is confirmed, it's huge."
"Everything we see today - the galaxies, the stars, the planets - was imprinted at that moment"
It's not every day that a new window on the birth of the universe is thrown open. It's not every day that human beings get the chance to leap into the void and have their conceptions of space and time stretched to the limits. It's not every day that we see the wildest dreams of scientists realized, written into the fabric of space and time and light.
Today appears to be one of those days.
The Big Bang has been the dominant theory explaining the history of the universe for more than a half-century. But puzzles inherent in the idea (and in the data) led to a major addition to the theory in the 1980s: inflationary cosmology. Since then inflation, as it is called, has been a sometimes contentious but stalwart pillar of our cosmic understanding. To get inflation on solid scientific ground however meant finding ways to see farther back in time than ever before.
To understand the importance of today's discovery (Nobel worthy?) you are going to have to think small ... very, very small. You must wrap your mind around the most tiny, itsy-bitsy, sliver-o-licious, hyper-minuscule fraction of a second you have ever considered in your whole life.
Try saying this out loud: One hundred million, billion, billion, billion-th of a second after the moment of creation.
That's what we are talking about. That's what the kind folks at BICEP2 may have given us (it will need to be confirmed, of course).
It is an indirect view of the universe at approximately one hundred million, billion, billion, billion-th of a second after it was born. Written mathematically, that is 10-35 of a second or a decimal point with 34 zeros after it, which looks like this:
T = 0.00000000000000000000000000000000001 second
For comparison, when it you mistakenly grab a hot tea kettle it takes a full 0.01 second for the electrical signal screaming "DROP IT!" to run from your hand to your brain.
We are talking about a very, very, very young universe.
Which finally brings us back to the importance of today's monumental discovery. In the 1980s, Big Bang theory got a major upgrade with the addition of Back then paradoxes and puzzles kept popping up which threatened to topple the Big Bang. Scientists like Alan Guth realized that, in order to make the idea work, there must have been a brief moment very early in cosmic history when a little sliver of post-Big Bang space-time began expanding much faster than its surroundings. Like an inflating balloon blown up by a high-powered compressor, this tiny "pocket" of space-time stretched very, very quickly to become our entire observable universe.
But almost as rapidly as it began, this period of inflation ended and left us with what we have now: the leisurely expansion we see today. In spite of its brevity, this brief period of Inflation was all-important. It was inflation that set us on the trajectory for everything that has happened afterward: galaxies, stars, planets and us.
The bottom part of this illustration shows the scale of the universe versus time. Specific events are shown such as the formation of neutral Hydrogen at 380,000 years after the big bang. Prior to this time, the constant interaction between matter (electrons) and light (photons) made the universe opaque.
But inflation was a contentious idea from start. No one had a firm handle on what the universe was like at such a ridiculously early point in time. The densities and temperatures of cosmic matter were so high that its physics could only be drawn in outlines. While inflation cured many problems for cosmologists, it seemed to lots of researchers like wishful thinking written in advanced math.
Where was the proof?
Over the last few decades a slim kind of proof for inflation arrived via tiny bumps and lumps in the ancient cosmic gas that can be directly observed through what's called the Cosmic Microwave Background (CMB) radiation. The CMB is made of fossil photons left over from the period just 300,000 years after the Big Bang. Lumps and bumps in the density of gas can be traced all the way back to quantum mechanical burps that occurred during inflation. But there are many versions of inflation theory and the proof that came from the density wiggles did not tell us which version was correct or provide many details about the early, early universe. In other words the density wiggles were a blunt instrument.
Space-time wiggles, though, are another story entirely.
The violence of the early universe was so extreme that it would leave space-time itself ringing like a bell. Almost as soon as inflation was proposed some scientists predicted that it would leave a "gravity wave" signature.
Ripples in the fabric of space-time are an essential prediction of Einstein's theory of relativity. While we have never captured a gravity wave directly, we already have indirect proof of their existence by watching how pairs of orbiting pulsars (dead hyper-dense stars) spiral around each other.
Thus more than two decades ago physicists were predicting the existence of a gravity wave signature for the inflationary epoch. Even more important, by looking at which gravity waves got the most energy scientists could cut through different versions of inflation theory. They could even tell if inflation itself was entirely wrong since there are alternative models for the early universe that don't involve inflation and make different predictions for the gravity wave spectrum.
So gravity waves are the key. If we could see them (directly or indirectly, as BICEP has done) they would represent a way to distinguish between different models for the early universe. And comparing data with models — that is what science is all about, after all.
Even on its own, finding new evidence for Einstein's much-sought-after gravity waves is a major achievement. But finding evidence for them from the early universe means we have a new tool for exploring the most extreme, mind-blowing event that ever occurred: the birth of everything. Today it seems that evidence may have been found.
哈哈哈哈 O(∩_∩)O哈哈~ 好久不来了，不小心看了一眼自己主页，发现自动关联了自己以往发过的帖，点进这个看了一眼，笑个半死。。。敢情我当初还发过这么搞笑的东西啊，我自己完全不记得了 
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发表于 2014-3-18 05:58:20
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发表于 2014-3-18 06:10:47
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