Astronomers, apparently, has finally revealed a weak evidence of the Big Bang and subsequent rapid expansion of the Universe. The discovery confirms cosmological model some and rejects others, and, if confirmed, may qualify for a Nobel prize. Yesterday in the scientific journal has published peer-reviewed article physicists. But first things first.
Why did we choose the South pole?
The study was conducted using two radio telescopes located at the South pole, Amundsen-Scott. This arrangement is dictated by several reasons. First, the night lasts for six months. Secondly, the air of the South pole is much colder (average -60 °C) and a cleaner, less humid and, therefore, to observe the space much easier. Disturbance and water in the atmosphere does not contribute to the data collected in the play, and in the present case, it was very important, because gravitational waves, which actually was hunting astronomers, leaving barely visible traces. Scientists, of course, hoped that the present limits of sensitivity of the technique allows to "catch" them, but the chances were not many.
Water absorbs microwave signals interfering with the observation. Two more important factors − a lower pressure (due to height of location) and weak wind. And, of course, the lack of human settlements and their equipment, which creates a lot of "noise", plays an important role.
"The South pole is the closest place to space. While you are still on Earth," says John Kovac (John Kovac) from the Harvard-Smithsonian center for astrophysics, who led the collaboration of scientists working on the project "Background image space extragalactic polarization" (Background Imaging of Cosmic Extragalactic Polarization, BICEP abbreviated).
Because the stars here do not rise over the horizon, and remain almost motionless throughout the six months, the telescope is easier to collect data on the sky.
The inflationary model of the Universe
Let's try to understand what are gravitational waves and why is the evidence of their existence is so important for science and humanity as a whole. As you know, there are several models of the evolution of the Universe.
One of the main hypotheses scientists assume that the universe in the first moments after the Big Bang expanded at a rapid pace. For tens trillionth trillionth trillionth fractions of a second the Universe grew from subatomic size (i.e. smaller than an atom) to the size of a soccer ball. This was 13,8 billion years ago.
After 380 thousand years there will be gravitational waves that were emitted incandescent plasma (stars, planets and galaxies did not yet exist). In the future, they continued to spread the resulting space and turned into the radiation of the microwave range (now background noise). These perturbations and has fixed telescopes that help scientists build a picture of the background radiation or cosmic microwave background radiation.
Relict (ancient) radiation initially also existed only in theory, but in 1965, its existence was proven experimentally. Since then, physicists constantly study its properties and distribution, making maps, or rather one another.
Gravitational waves and their significance
Why gravitational waves are so important for science? The fact that inflation of the Universe (in this case means, of course, is not an economic term, and the concept of rapid expansion), according to physicists, is quantum in nature.
That is, the presence of gravitational waves suggests that gravity, like all other fundamental interactions (e.g., electromagnetic), has a quantum nature. Accordingly, this discovery, if confirmed in further, actually changing the fundamental basis of our understanding of the Universe.
In addition, the "fingerprint" of gravitational waves will help scientists to look into the interactions on the energy levels that cannot be reproduced in the laboratory (as scientists try, the temperature of the Big Bang unable to reproduce even the Large hadron Collider).
There is another important circumstance: the achievement of the team Kovac is direct evidence that gravitational waves, one of the key concepts of the General theory of relativity, exist.
"It's a totally new, independent piece of cosmological evidence that fully integrates, complements and reinforces the picture of inflation", — says the physicist and cosmologist Alan Guth of MIT, who proposed the idea of expanding the Universe in 1980. He also adds that the study is worthy of the Nobel prize.
The inflation of the Universe, in turn, explains several complex cosmological puzzles, such as why the observable universe appears to us uniform from one end to the other.
Previously, scientists actually have proven that the inflationary theory is correct, although, of course, not all scientists agree, and give their arguments. Now, we can assume that found convincing proofs of that.
What is gravitational wave?
Cosmologists assumed that the initial ultrafast expansion of the Universe was to leave its mark — the very gravitational waves (similar to ripples in the fabric of space-time). In one direction is stretched and the other compressed.
Gravity according to Einstein is the curvature of space-time near massive objects. The curvature in this case does not necessarily remain near the object, it can propagate through the Universe (similar to seismic waves during an earthquake). In this case gravitational waves can travel even through completely empty space at the speed of light.
Here is how the example of towels (space-time), Apple (a star) and the ball ping-pong table (less massive object passing by the stars) a correspondent of New Scientist quite clearly explains what gravitational waves.
Valerie Jameson (Valerie Jamieson) tells the following. The warping of the "fabric" of space-time (towel) a massive object causes gravity, which in turn acts on the objects passing by a massive body, gave rise to this curvature.
Gravitational waves — a consequence of the very rapid expansion of the early Universe. Over time, due to further expansion they are weakening (the folds in the towel are smoothed a bit). However, they continue to affect the radiation propagating in the Universe, and therefore this impact can be fixed.
How to catch a weak signal?
As we have said, over the past billions of years, the ancient "vibrations" has weakened considerably. Catch them directly with modern instruments is almost impossible. However, they have influenced the background relic radiation, palarikova it.
Here comes one complex but important concept of B-mod.
The polarization of the CMB can be decomposed into two components: non-rotational E-fashion and eddy B-fashion. The first was recorded in 2002. Second, according to calculations of physicists-theorists, appears in two processes: because of the impact on the background radiation, gravitational lenses, or because of inflationary expansion of the Universe.
Gravitational lenses serve any large objects of the Universe (e.g., galaxies). With huge mass, they twist their gravitational influence of the direction of radiation propagation. The result of this process the B-mode polarization, scientists caught in October 2013. Then they helped "the South pole Telescope" (SPT) and space telescope "Herschel" (Herschel).
B-mode, which appeared during the initial rapid expansion of the Universe, was not caught. And here the other day about the opening of the group said John Kovac. The scientists analyzed data gathered by the BICEP2 telescope, which is located just a few metres from SPT.
Detection required complex calculations and the incredible precision of measurements (ten millionth part of the Kelvin). The effects of gravitational waves on the cosmic background radiation had to be separated from the effects of even the smallest particles of galactic dust.
Physicists have tried to eliminate all other possible causes.
First, the researchers had accurately set up the position BICEP2, sending it 512 superconducting detectors of microwave radiation on the part of the sky where, according to the calculations, any external disturbance is minimal.
Secondly, the researchers compared the new data with the old, which were obtained during the experiment, BICEP1. Then they were able to show that the signal generated by the dust, you'll be on top.
Thirdly, the researchers used a new, more accurate information on the polarization of the collected array of Keck (Keck Array). The latter was set at "the South pole Telescope" in 2012 and will operate for another two years. And in this case, the result was the same.
"The fact that we saw the same signal on two different telescopes, have convinced us of the correctness of conclusions," he says.
The opinion of other scientists
"Details still to be clarified, but from what I know, I can conclude that this is exactly what we've been waiting for, – said Nature John Carlstrom (John Carlstrom) from the University of Chicago, one of the leading researchers SPT. — The discovery of gravitational waves generated by inflation."
"For me, the new data look very convincing. It's like the discovery of dark energy or background radiation — this happens once in several decades," says cosmologist mark him, the Field (Marc Kamionkowski) from Johns Hopkins University, who first calculated, should look like a "fingerprint" of gravitational waves in the relict radiation.
Interestingly, the intensity of the detected signal BICEP2 was very surprised by catching his researchers. She was two times higher than expected by previous experiments.
According to theoretical calculations of physicists, the intensity of B-mode shows how fast the universe expanded during inflation, and therefore reflects the energy state of the cosmos in those days.
Recent data indicate the time when the Universe was 10-37 seconds old and the temperature reached (in energy terms) 1016 GeV. According to the Theory of Grand unification, this was an extremely high energy corresponds to that at which become indistinguishable from each other three of the four fundamental interactions — strong, weak and electromagnetic.
Since inflation occurred during the "reign" of quantum physics, the discovery of gravitational waves that emerged in that era, is the first experimental confirmation of the quantum nature of gravity (and this is another very important for science achievement!). That is, the gravitational waves is evidence that gravity (the phenomenon of classical physics) basically relies on the laws of quantum physics, like all other three fundamental interactions.
However, despite this clear Association of two physicist, scientists have yet to figure out how to explain the observed from the point of view of the theory.
The research team conducted a large-scale work and has posted several articles in scientific journals, as well as provided exhaustive information on the project website.
Now similar work is carried out by groups that collect data with the help of balloons, space telescope 'plank", "South pole Telescope" and other ground-based observatories.
Scientists involved in the analysis of data from Planck, and planning to sum up the end of the year, most likely, will present more extensive data on polarization and B-mode (space telescope can observe the whole sky), as well as in the parameters of inflation and its driving forces. They will also be able to confirm the current results. If they consider the findings of the current team of researchers is correct, then the science that studies the formation of the Universe, will truly enter a new era.
The team's results Kovacs have yet to recheck and confirm or refute many other scientific groups. Here, says Paul Steinhardt (Paul Steinhardt) from Princeton: "there is No doubt, if gravitational waves were to be confirmed, it will kill a cyclic model and epirotiki the scenario suggested by my colleagues and me. We are always very clearly spoken on this topic. But as I speak the word if."
By the way, the two above-mentioned hypotheses argued that the universe is expanding, and then compressed, thus constantly reborn.
Another famous skeptic – Neil Turok (Neil Turok) said the portal physicsworld.com that he is concerned with the differences in the new results and those data that were obtained during the operation of spacecraft "Planck" and WMAP: "I believe that if these "Strip" to be aligned with new, they will present compelling evidence against inflation!"
"I still think that there remains a high probability that the signal polarization E - and B-modes is not cosmological. This is a very interesting result, but I won't take sides until you have received confirmation in other experiments, adds astrophysicist Peter Coles (Peter Coles) from the University of Sussex. — To consider the opening of a direct proof of the inflation theory, we must categorically decide that [the signal] is not generated by any other process. But I don't think we'll ever be able to say".
Another scientist who urges caution — Charles Lawrence (Charles Lawrence), working with the data "Bar": "This is a very exciting discovery, but, as with any other measurement, you have to be careful."
Public discussion of result
June 19, 2014 one of the articles of the group of Kovac was published in the journal Physical Review Letters. All data have been tested by reviewers. However, many scientists still doubt in the interpretation of results and continue to look for errors and inconsistencies in the original work.
Mostly, the criticism comes down to the fact that a similar effect can meet the dust of the Galaxy. In the article the team of Kovacs concludes: "We cannot completely exclude the possibility that the entire excess signal can be explained by the bright emission of the galactic dust". Meanwhile, even critics acknowledge that this result requires new data that will help provide an independent verification by other research groups.
Finally we bring to your attention a video that shows how the adjunct Professor Chao-Lin Kuo (Chao-Lin Kuo) from Stanford surprised Professor Andrei Dmitriyevich Linde the news about the discovery of evidence for the inflation theory of the Universe. Linda in the 80-ies of the last century became famous for the development of the chaotic theory of inflation.
"I have a surprise for you, — said from the doorway To nothing understands Linde and his wife Renata Even (Renata Kallosh), an MSU alumnus, now working as Professor of theoretical physics at Stanford. Five Sigma".
The last statement in the language of physicists means that scientists have enough reliable data and can confidently talk about the results.
"Discovery?" exclaims in response To Renata and hugs. "What?!" – at least emotionally asks shocked Linda. What To answers him that BICEP2 "with probability" Sigma 5 discovered gravitational waves that confirm the theory of inflation of the famous physicist.
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