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Searching for Life in the Multiverse

Multiverse Theory

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Other intelligent and technologically capable alien civilizations may exist in our Universe, but the problems with finding and communicating with them is that they are simply too far away for any meaningful two-way conversations. But what about the prospect of finding if life exists in other universes outside of our own?

Theoretical physics has brought us the notion that our single universe is not necessarily all there is. The “multiverse” idea is a hypothetical mega-universe full of numerous smaller universes, including our own.

In this month’s Scientific American, Alejandro Jenkins from Florida State University and Gilad Perez, a theorist at the Weizmann Institute of Science in Israel, discuss how multiple other universes—each with its own laws of physics—may have emerged from the same primordial vacuum that gave rise to ours. Assuming they exist, many of those universes may contain intricate structures and perhaps even some forms of life. But the latest theoretical research suggests that our own universe may not be as “finely tuned” for the emergence of life as previously thought.

Jenkns and Perez write about a provocative hypothesis known as the anthropic principle, which states that the existence of intelligent life (capable of studying physical processes) imposes constraints on the possible form of the laws of physics.

Alejandro Jenkins. Credit: Florida State University

“Our lives here on Earth — in fact, everything we see and know about the universe around us — depend on a precise set of conditions that makes us possible,” Jenkins said. “For example, if the fundamental forces that shape matter in our universe were altered even slightly, it’s conceivable that atoms never would have formed, or that the element carbon, which is considered a basic building block of life as we know it, wouldn’t exist. So how is it that such a perfect balance exists? Some would attribute it to God, but of course, that is outside the realm of physics.”

The theory of “cosmic inflation,” which was developed in the 1980s in order to solve certain puzzles about the structure of our universe, predicts that ours is just one of countless universes to emerge from the same primordial vacuum. We have no way of seeing those other universes, although many of the other predictions of cosmic inflation have recently been corroborated by astrophysical measurements.

Given some of science’s current ideas about high-energy physics, it is plausible that those other universes might each have different physical interactions. So perhaps it’s no mystery that we would happen to occupy the rare universe in which conditions are just right to make life possible. This is analogous to how, out of the many planets in our universe, we occupy the rare one where conditions are right for organic evolution.

“What theorists like Dr. Perez and I do is tweak the calculations of the fundamental forces in order to predict the resulting effects on possible, alternative universes,” Jenkins said. “Some of these results are easy to predict; for example, if there was no electromagnetic force, there would be no atoms and no chemical bonds. And without gravity, matter wouldn’t coalesce into planets, stars and galaxies.

“What is surprising about our results is that we found conditions that, while very different from those of our own universe, nevertheless might allow — again, at least hypothetically — for the existence of life. (What that life would look like is another story entirely.) This actually brings into question the usefulness of the anthropic principle when applied to particle physics, and might force us to think more carefully about what the multiverse would actually contain.”

A brief overview of the article is available for free on Scientific American’s website.

Source: Florida State University

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The Extremely Large Telescope

The European Southern Observatory (ESO) is planning on building a massive – and I do mean massive – telescope in the next decade. The European Extremely Large Telescope (E-ELT) is a 42-meter telescope in its final planning stages. Weighing in at 5,000 tonnes, and made up of 984 individual mirrors, it will be able to image the discs of extrasolar planets and resolve individual stars in galaxies beyond the Local Group! By 2018 ESO hope to be using this gargantuan scope to stare so deep into space that they can actually see the Universe expanding!

The E-ELT is currently scheduled for completion around 2018 and when built it will be four times larger than anything currently looking at the sky in optical wavelengths and 100 times more powerful than the Hubble Space Telescope – despite being a ground-based observatory.

With advanced adaptive optics systems, the E-ELT will use up to 6 laser guide stars to analyse the twinkling caused by the motion of the atmosphere. Computer systems move the 984 individual mirrored panels up to a thousand times a second to cancel out this blurring effect in real time. The result is an image almost as crisp as if the telescope were in space.

This combination of incredible technological power and gigantic size mean that that the E-ELT will be able to not only detect the presence of planets around other stars but also begin to make images of them. It could potentially make a direct image of a Super Earth (a rocky planet just a few times larger than Earth). It would be capable of observing planets around stars within 15-30 light years of the Earth – there are almost 400 stars within that distance!

The E-ELT will be able to resolve stars within distant galaxies and as such begin to understand the history of such galaxies. This method of using the chemical composition, age and mass of stars to unravel the history of the galaxy is sometimes called galactic archaeology and instruments like the E-ELT would lead the way in such research.

Incredibly, by measuring the redshift of distant galaxies over many years with a telescope as sensitive as the E-ELT it should be possible to detect the gradual change in their doppler shift. As such the E-ELT could allow humans to watch the Universe itself expand!

ESO has already spent millions on developing the E-ELT concept. If it is completed as planned then it will eventually cost about €1 billion. The technology required to make the E-ELT happen is being developed right now all over the world – in fact it is creating new technologies, jobs and industry as it goes along. The telescope’s enclosure alone presents a huge engineering conundrum – how do you build something the size of modern sports stadium at high altitude and without any existing roads? They will need to keep 5,000 tonnes of metal and glass slewing around smoothly and easily once it’s operating – as well as figuring out how to mass-produce more than 1200 1.4m hexagonal mirrors.

The E-ELT has the capacity to transform our view not only of the Universe but of telescopes and the technology to build them as well. It will be a huge leap forward in telescope engineering and for European astronomy it will be a massive 42m jewel in the crown.

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Early Galaxy Pinpoints Reionization Era

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Astronomers looking to pinpoint when the reionozation of the Universe took place have found some of the earliest galaxies about 800 million years after the Big Bang. 22 early galaxies were found using a method that looks for far-away redshifting sources that disappear or “drop-out” at a specific wavelength. The age of one galaxy was confirmed by a characteristic neutral hydrogen signature at 787 million years after the Big Bang. The finding is the first age-confirmation of a so-called dropout galaxy at that distant time and pinpoints when the reionization epoch likely began.

The reionization period is about the farthest back in time that astronomers can observe. The Big Bang, 13.7 billion years ago, created a hot, murky universe. Some 400,000 years later, temperatures cooled, electrons and protons joined to form neutral hydrogen, and the murk cleared. Some time before 1 billion years after the Big Bang, neutral hydrogen began to form stars in the first galaxies, which radiated energy and changed the hydrogen back to being ionized. Although not the thick plasma soup of the earlier period just after the Big Bang, this star formation started the reionization epoch.

Astronomers know that this era ended about 1 billion years after the Big Bang, but when it began has eluded them.

We look for ‘dropout’ galaxies,” said Masami Ouchi, who led a US and Japanese team of astronomers looking back at the reionization epoch. “We use progressively redder filters that reveal increasing wavelengths of light and watch which galaxies disappear from or ‘dropout’ of images made using those filters. Older, more distant galaxies ‘dropout’ of progressively redder filters and the specific wavelengths can tell us the galaxies’ distance and age. What makes this study different is that we surveyed an area that is over 100 times larger than previous ones and, as a result, had a larger sample of early galaxies (22) than past surveys. Plus, we were able to confirm one galaxy’s age,” he continued. “Since all the galaxies were found using the same dropout technique, they are likely to be the same age.”

Ouchi’s team was able to conduct such a large survey because they used a custom-made, super-red filter and other unique technological advancements in red sensitivity on the wide-field camera of the 8.3-meter Subaru Telescope. They made their observations from 2006 to 2009 in the Subaru Deep Field and Great Observatories Origins Deep Survey North field. They then compared their observations with data gathered in other studies.

Astronomers have wondered whether the universe underwent reionization instantaneously or gradually over time, but more importantly, they have tried to isolate when the universe began reionization. Galaxy density and brightness measurements are key to calculating star-formation rates, which tell a lot about what happened when. The astronomers looked at star-formation rates and the rate at which hydrogen was ionized.

Using data from their study and others, they determined that the star-formation rates were dramatically lower from 800 million years to about one billion years after the Big Bang, then thereafter. Accordingly, they calculated that the rate of ionization would be very slow during this early time, because of this low star-formation rate.

“We were really surprised that the rate of ionization seems so low, which would constitute a contradiction with the claim of NASA’s WMAP satellite. It concluded that reionization started no later than 600 million years after the Big Bang,” remarked Ouchi. “We think this riddle might be explained by more efficient ionizing photon production rates in early galaxies. The formation of massive stars may have been much more vigorous then than in today’s galaxies. Fewer, massive stars produce more ionizing photons than many smaller stars,” he explained.

The research will be published in a December issue of the Astrophysical Journal.

Source: EurekAlert

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New CMB Measurements Support Standard Model

New measurements of the cosmic microwave background (CMB) – the leftover light from the Big Bang – lend further support the Standard Cosmological Model and the existence of dark matter and dark energy, limiting the possibility of alternative models of the Universe. Researchers from Stanford University and Cardiff University produced a detailed map of the composition and structure of matter as it would have looked shortly after the Big Bang, which shows that the Universe would not look as it does today if it were made up solely of ‘normal matter’.

By measuring the way the light of the CMB is polarized, a team led by Sarah Church of the Kavli Institute for Particle Astrophysics and Cosmology at Stanford University and by Walter Gear, head of the School of Physics and Astronomy at Cardiff University in the United Kingdom were able construct a map of the way the Universe would have looked shortly after matter came into existence after the Big Bang. Their findings lend evidence to the predictions of the Standard Model in which the Universe is composed of 95% dark matter and energy, and only 5% of ordinary matter.

Polarization is a feature of light rays in which the oscillation of the light wave lies in right angles to the direction in which the light is traveling. Though most light is unpolarized, light that has interacted with matter can become polarized. The leftover light from the Big Bang – the CMB – has now cooled to a few degrees above 0 Kelvin, but it still retains the same polarization it had in the early Universe, once it had cooled enough to become transparent to light. By measuring this polarization, the researchers were able to extrapolate the location, structure, and velocity of matter in the early Universe with unprecedented precision. The gravitational collapse of large clumps of matter in the early universe creates certain resonances in the polarization that allowed the researchers to create a map of the matter composition.

Dr. Gear said, “The pattern of oscillations in the power spectra allow us to discriminate, as “real” and “dark” matter affect the position and amplitudes of the peaks in different ways. The results are also consistent with many other pieces of evidence for dark matter, such as the rotation rate of galaxies, and the distribution of galaxies in clusters.”

The measurements made by the QUaD experiment further constrain those made by previous experiments to measure properties of the CMB, such as WMAP and ACBAR. In comparison to these previous experiments, the The QUaD experiment, located at the South Pole, allowed researchers to measure the polarization of the CMB with very high precision. Image Credit: Sarah Churchmeasurements come closer to fitting what is predicted by the Standard Cosmologicl Model by more than an order of magnitude, said Dr. Gear. This is a very important step on the path to verifying whether our model of the Universe is correct.

The researchers used the QUaD experiment at the South Pole to make their observations. The QUaD telescope is a bolometer, essentially a thermometer that measures how certain types of radiation increase the temperature of the metals in the detector. The detector itself has to be near 1 degree Kelvin to eliminate noise radiation from the surrounding environment, which is why it is located at the frigid South Pole, and placed inside of a cryostat.

Paper co-author Walter Gear said in an email interview:

“The polarization is imprinted at the time the Universe becomes transparent to light, about 400,000 years after the big bang, rather than right after the big bang before matter existed. There are major efforts now to try to find what is called the “B-mode” signal”  which is a more complicated polarization pattern that IS imprinted right after the big-bang. QuaD places the best current upper limit on this but is still more than an order of magnitude away in sensitivity from even optimistic predictions of what that signal might be. That is the next generation of experiments’s goal.”

The results, published in a paper titled Improved Measurements of the Temperature and Polarization of the Cosmic Microwave Background from QUaD in the November 1st Astrophysical Journal, fit the predictions of the Standard Model remarkably well, providing further evidence for the existence of dark matter and energy, and constraining alternative models of the Universe.

Source: SLAC, email interview with Dr. Walter Gear

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If We Live in a Multiverse, How Many Are There?

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Theoretical physics has brought us the notion that our single universe is not necessarily the only game in town. Satellite data from WMAP, along with string theory and its 11- dimensional hyperspace idea has produced the concept of the multiverse, where the Big Bang could have produced many different universes instead of a single uniform universe. The idea has gained popularity recently, so it was only a matter of time until someone asked the question of how many multiverses could possibly exist. The number, according to two physicists, could be “humongous.”

Andrei Linde and Vitaly Vanchurin at Stanford University in California, did a few back-of- the- envelope calculations, starting with the idea that the Big Bang was essentially a quantum process which generated quantum fluctuations in the state of the early universe. The universe then underwent a period of rapid growth called inflation during which these perturbations were “frozen,” creating different initial classical conditions in different parts of the cosmos. Since each of these regions would have a different set of laws of low energy physics, they can be thought of as different universes.

Linde and Vanchurin then estimated how many different universes could have appeared as a result of this effect. Their answer is that this number must be proportional to the effect that caused the perturbations in the first place, a process called slow roll inflation, — the solution Linde came up with previously to answer the problem of the bubbles of universes colliding in the early inflation period. In this model, inflation occurred from a scalar field rolling down a potential energy hill. When the field rolls very slowly compared to the expansion of the universe, inflation occurs and collisions end up being rare.

Using all of this (and more – see their paper here) Linde and Vanchurin calculate that the number of universes in the multiverse and could be at least 10^10^10^7, a number which is definitely “humungous,” as they described it.

The next question, then, is how many universes could we actually see? Linde and Vanchurin say they had to invoke the Bekenstein limit, where the properties of the observer become an important factor because of a limit to the amount of information that can be contained within any given volume of space, and by the limits of the human brain.

The total amount of information that can be absorbed by one individual during a lifetime is about 10^16 bits. So a typical human brain can have 10^10^16 configurations and so could never distinguish more than that number of different universes.

The number of multiverses the human brain could distinguish. Credit: Linde and Vanchurin
The number of multiverses the human brain could distinguish. Credit: Linde and Vanchurin

“So, the total number of possibilities accessible to any given observer is limited not only by the entropy of perturbations of metric produced by inflation and by the size of the cosmological horizon, but also by the number of degrees of freedom of an observer,” the physicists write.

“We have found that the strongest limit on the number of different locally distinguishable geometries is determined mostly by our abilities to distinguish between different universes and to remember our results,” wrote Linde and Vanchurin. “Potentially it may become very important that when we analyze the probability of existencse of a universe of a given type, we should be talking about a consistent pair: the universe and an observer who makes the rest of the universe “alive” and the wave function of the rest of the universe time-dependant.”

So their conclusion is that the limit does not depend on the properties of the multiverse itself, but on the properties of the observer.

They hope to further study this concept to see if this probability if proportional to the observable entropy of inflation.

Sources: ArXiv, Technology Review Blog

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Planck First Light

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One of the newest telescopes in space, the Planck spacecraft, recently completed its “first light” survey which began on August 13. Astronomers say the initial data, gathered from Planck’s vantage point at the L2 point in space, is excellent. Planck is studying the Cosmic Microwave Background, looking for variations in temperature that are about a million times smaller than one degree. This is comparable to measuring from Earth the body heat of a rabbit sitting on the Moon.

The initial survey yielded maps of a strip of the sky, one for each of Planck’s nine frequencies. Each map is a ring, about 15° wide, stretching across the full sky.

The the differences in color in the strips indicate the magnitude of the deviations of the temperature of the Cosmic Microwave Background from its average value, as measured by Planck at a frequency close to the peak of the CMB spectrum (red is hotter and blue is colder).

The large red strips trace radio emission from the Milky Way, whereas the small bright spots high above the galactic plane correspond to emission from the Cosmic Microwave Background itself.

In order to do its work, Planck’s detectors must be cooled to extremely low temperatures, some of them being very close to absolute zero (–273.15°C, or zero Kelvin, 0K).

Routine operations are now underway, and surveying will continue for at least 15 months without a break. In approximately 6 months, the first all-sky map will be assembled.

Within its projected operational life of 15 months, Planck will gather data for two complete sky maps. To fully exploit the high sensitivity of Planck, the data will require delicate adjustments and careful analysis. It promises to return a treasure trove that will keep both cosmologists and astrophysicists busy for decades to come.

Source: ESA

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What! No Parallel Universe? Cosmic Cold Spot Just Data Artifact

Rats! Another perplexing space mystery solved by science. New analysis of the famous “cold spot” in the cosmic microwave background reveals, and confirms, actually, that the spot is just an artifact of the statistical methods used to find it. That means there is no supervoid lurking in the CMB, and no parallel universe lying just beyond the edge of our own. What fun is that?

Back in 2004, astronomers studying data from the Wilkinson Microwave Anisotropy Probe (WMAP) found a region of the cosmic microwave background in the southern hemisphere in the direction of the constellation of Eridanus that was significantly colder than the rest by about 70 microkelvin. The probability of finding something like that was extremely low. If the Universe really is homogeneous and isotropic, then all points in space ought to experience the same physical development, and appear the same. This just wasn’t supposed to be there.

Some astronomers suggested the spot could be a supervoid, a remnant of an early phase transition in the universe. Others theorized it was a window into a parallel universe.

Well, it turns out, it wasn’t there.

Ray Zhang and Dragan Huterer at the University of Michigan in Ann Arbor say that the cold spot is simply an artifact of the statistical method–called Spherical Mexican Hat Wavelets–used to analyze the WMAP data. Use a different method of analysis and the cold spot disappears (or at least is no colder than expected).

“We trace this apparent discrepancy to the fact that WMAP cold spot’s temperature profile just happens to favor the particular profile given by the wavelet,” the duo says in their paper. “We find no compelling evidence for the anomalously cold spot in WMAP at scales between 2 and 8 degrees.”

This confirms another paper from 2008 also by Huterer along with colleague Kendrick Smith from the University of Cambridge who showed that the huge void could be considered as a statistical fluke because it had stars both in front of and behind it.

And in fact, one of the earlier papers suggesting the cold spot by Lawrence Rudnick from the University of Minnesota does indeed say that statistical uncertainties have not been accounted for.

Oh well. Now, on to the next cosmological mysteries like dark matter and dark energy!

Zhang and Huterer’s paper.

Huterer and Smith’s paper (2008)

Rudnick’s paper 2007

Original paper “finding” the cold spot

Sources: Technology Review Blog, Science

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The Big Bang Writ Little

If you are into Twitter (as I am), you might enjoy this: New Scientist challenged their readers to encompass the Big Bang into a Tweet. That means the description of the event that started everything that is needs to be 140 characters or less –and actually it was only 133 characters because to qualify, the Tweet had to include the #sci140 hashtag so the folks at New Scientist could gather them all together. Some went the complete science route by trying to summarize the physics (at least one person fit in the equation for Hubble’s Law), others quoted (“In the beginning the universe was created. This has made a lot of people very angry and has been widely regarded as a bad move.” — Douglas Adams), others took a religious bend, and still others described the event in how it might sound (boom, bang, kaboom or tweeeet). Here’s my favorite:

@newscientist < &#8734 #sci140 yanikproulx

A fun exercise in brevity.

Here’s the rest of their top 10:

Timeless energy, / all dressed up, no place to go: / had to create space. / – #BigBang #haiku #sci140 – haiQ

God said delB=0 etc, & then light (sym breaking), separation light from darkness (recombination), man created from dirt (evolution) #sci140 – dmadance

#sci140 starburst, molecule, amino acid, protein, cell development, cell division, sex, technology, war, religion, OK magazine. – jonotrumpeto

@newscientist #sci140 Antimatter and matter duke it out. Matter wins 1 billion and one to 1 billion. The matter left expands and makes us. – zeroentropy

#sci140 A place for everything, and everything in one place. Then — kaboom, everything all over the place. – tui4

@newscientist The Big Bang: the moment the universe vanishes when extrapolating its expansion backwards into the past #sci140 – hubi1857

For t<0 some say there was no matter, others say it does not matter. For t>0 its a matter of life and death – as a matter of fact #sci140 – thebeerhunter

an argument between the 9th and 10th dimensions overspilled into the 1st, 2nd, 3rd and 4th. #sci140 – AlexStavrinides

The Big Bang: Basically a ballooning of bosons, belatedly bloating into our beautiful universe. Brought to you by the letter ‘B’. #sci140 – CoyoteTrax

Source: New Scientist

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New Way to Measure Curvature of Space Could Unite Gravity Theory

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Einstein’s general theory of relativity describes gravity in terms of the geometry of both space and time. Far from a source of gravity, such as a star like our sun, space is “flat” and clocks tick at their normal rate. Closer to a source of gravity, however, clocks slow down and space is curved. But measuring this curvature of space is difficult. However, scientists have now used a continent-wide array of radio telescopes to make an extremely precise measurement of the curvature of space caused by the Sun’s gravity. This new technique promises to contribute greatly in studying quantum physics.

“Measuring the curvature of space caused by gravity is one of the most sensitive ways to learn how Einstein’s theory of General Relativity relates to quantum physics. Uniting gravity theory with quantum theory is a major goal of 21st-Century physics, and these astronomical measurements are a key to understanding the relationship between the two,” said Sergei Kopeikin of the University of Missouri.

Kopeikin and his colleagues used the National Science Foundation’s Very Long Baseline Array (VLBA) radio-telescope system to measure the bending of light caused by the Sun’s gravity to within one part in 30,000 3,333 (corrected by NRAO and updated here on 9/03/09 — see this link provided by Ned Wright of UCLA for more information on deflection and delay of light). With further observations, the scientists say their precision technique can make the most accurate measure ever of this phenomenon.

Bending of starlight by gravity was predicted by Albert Einstein when he published his theory of General Relativity in 1916. According to relativity theory, the strong gravity of a massive object such as the Sun produces curvature in the nearby space, which alters the path of light or radio waves passing near the object. The phenomenon was first observed during a solar eclipse in 1919.

Though numerous measurements of the effect have been made over the intervening 90 years, the problem of merging General Relativity and quantum theory has required ever more accurate observations. Physicists describe the space curvature and gravitational light-bending as a parameter called “gamma.” Einstein’s theory holds that gamma should equal exactly 1.0.

“Even a value that differs by one part in a million from 1.0 would have major ramifications for the goal of uniting gravity theory and quantum theory, and thus in predicting the phenomena in high-gravity regions near black holes,” Kopeikin said.

To make extremely precise measurements, the scientists turned to the VLBA, a continent-wide system of radio telescopes ranging from Hawaii to the Virgin Islands. The VLBA offers the power to make the most accurate position measurements in the sky and the most detailed images of any astronomical instrument available.

Sun's Path in Sky in Front of Quasars, 2005. Credit: NRAO
Sun's Path in Sky in Front of Quasars, 2005. Credit: NRAO

The researchers made their observations as the Sun passed nearly in front of four distant quasars — faraway galaxies with supermassive black holes at their cores — in October of 2005. The Sun’s gravity caused slight changes in the apparent positions of the quasars because it deflected the radio waves coming from the more-distant objects.

The result was a measured value of gamma of 0.9998 +/- 0.0003, in excellent agreement with Einstein’s prediction of 1.0.

“With more observations like ours, in addition to complementary measurements such as those made with NASA’s Cassini spacecraft, we can improve the accuracy of this measurement by at least a factor of four, to provide the best measurement ever of gamma,” said Edward Fomalont of the National Radio Astronomy Observatory (NRAO). “Since gamma is a fundamental parameter of gravitational theories, its measurement using different observational methods is crucial to obtain a value that is supported by the physics community,” Fomalont added.

Kopeikin and Fomalont worked with John Benson of the NRAO and Gabor Lanyi of NASA’s Jet Propulsion Laboratory. They reported their findings in the July 10 issue of the Astrophysical Journal.

Source: NRAO

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New Limits on Gravitational Waves From the Big Bang

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The only way to know what the Universe was like at the moment of the Big Bang requires analysis of gravitational waves created when the Universe began. Scientists working with the Laser Interferometer Gravitational-Wave Observatory (LIGO) say their initial investigations of these gravitiation waves have turned up nothing. But that’s a good thing. Not detecting the waves provides constraints about the initial conditions of the universe, and narrows the field of where we actually do need to look in order to find them.

Much like it produced the cosmic microwave background, the Big Bang is believed to have created a flood of gravitational waves — ripples in the fabric of space and time. From our current understanding, gravitational waves are the only known form of information that can reach us undistorted from the beginnings of the Universe. They would be observed as a “stochastic” or random background, and would carry with them information about their violent origins and about the nature of gravity that cannot be obtained by conventional astronomical tools. The existence of the waves was predicted by Albert Einstein in 1916 in his general theory of relativity.

Analysis of data taken over a two-year period, from 2005 to 2007, yields that the stochastic background of gravitational waves has not yet been discovered. But the nondiscovery of the background, described in a new paper in the August 20 Nature, offers its own brand of insight into the universe’s earliest history.

“Since we have not observed the stochastic background, some of these early-universe models that predict a relatively large stochastic background have been ruled out,” said Vuk Mandic, assistant professor at the University of Minnesota and the head of the group that performed the analysis. “We now know a bit more about parameters that describe the evolution of the universe when it was less than one minute old.”

According to Mandic, the new findings constrains models of cosmic strings, objects that are proposed to have been left over from the beginning of the universe and subsequently stretched to enormous lengths by the universe’s expansion; the strings, some cosmologists say, can form loops that produce gravitational waves as they oscillate, decay, and eventually disappear.

“Since we have not observed the stochastic background, some of these early-universe models that predict a relatively large stochastic background have been ruled out,” said Mandic. “If cosmic strings or superstrings exist, their properties must conform with the measurements we made—that is, their properties, such as string tension, are more constrained than before.”

This is interesting, he says, “because such strings could also be so-called fundamental strings, appearing in string-theory models. So our measurement also offers a way of probing string-theory models, which is very rare today.”

The analysis used data collected from the LIGO interferometers in Hanford, Wash., and Livingston, La. Each of the L-shaped interferometers uses a laser split into two beams that travel back and forth down long interferometer arms. The two beams are used to monitor the difference between the two interferometer arm lengths.

The next phase of the project, called Advanced LIGO, will go online in 2014, and be 10 times more sensitive than the current instrument. It will allow scientists to detect cataclysmic events such as black-hole and neutron-star collisions at 10-times-greater distances.

The Nature paper is entitled “An Upper Limit on the Amplitude of Stochastic Gravitational-Wave Background of Cosmological Origin.”

Source: EurekAlert