Laser-interferometer

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LIGO BEGINS NEXT SEARCH FOR GRAVITATIONAL WAVES:
NSF DIRECTOR REFLECTS ON THE LASER INTERFEROMETER
GRAVITATIONAL-WAVE OBSERVATORY’S NEWEST QUEST

Statement from National Science Foundation Director France Córdova regarding news that, after a series of upgrades, researchers have reactivated the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO), and resumed the search for ripples in the fabric of space and time known as gravitational waves:

“The last time scientists from the NSF-funded Laser Interferometer Gravitational-Wave Observatory (LIGO) searched for gravitational waves, they succeeded.

They detected gravitational waves from merging black holes 1.3 billion light-years away.

Researchers devoted more than 40 years to get to this point, and the National Science Foundation – I’m proud to say – was there all along the way, providing critical support to make this scientific achievement possible.

Today, that journey continues.

Already LIGO has exceeded our expectations, and, like most of the scientific world and beyond, I am excited to see what a more sensitive, upgraded LIGO will detect next.

“The significance of this expanding ‘window to the universe’ cannot be stressed enough, as it will illuminate the physics of merging black holes, neutron stars and other astronomical phenomena that cannot be reproduced in a laboratory setting.

The world waits with eager anticipation of what we will see and learn next, all because of the long-range vision and skills of hundreds of researchers around the world.”

New laser based on unusual physics phenomenon could improve telecommunications, computing

Researchers at the University of California San Diego have demonstrated the world’s first laser based on an unconventional wave physics phenomenon called bound states in the continuum. The technology could revolutionize the development of surface lasers, making them more compact and energy-efficient for communications and computing applications. The new BIC lasers could also be developed as high-power lasers for industrial and defense applications.

“Lasers are ubiquitous in the present day world, from simple everyday laser pointers to complex laser interferometers used to detect gravitational waves. Our current research will impact many areas of laser applications,” said Ashok Kodigala, an electrical engineering Ph.D. student at UC San Diego and first author of the study.

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The black-hole collision that reshaped physics

A momentous signal from space has confirmed decades of theorizing on black holes — and launched a new era of gravitational-wave astronomy.

By Davide Castelvecchi

The event was catastrophic on a cosmic scale — a merger of black holes that violently shook the surrounding fabric of space and time, and sent a blast of space-time vibrations known as gravitational waves rippling across the Universe at the speed of light.

But it was the kind of calamity that physicists on Earth had been waiting for. On 14 September, when those ripples swept across the freshly upgraded Laser Interferometer Gravitational-Wave Observatory (Advanced LIGO), they showed up as spikes in the readings from its two L-shaped detectors in Louisiana and Washington state. For the first time ever, scientists had recorded a gravitational-wave signal.

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Scientists just announced the discovery of a second gravitational wave signal

Gravitational waves are ripples through space-time that happen when something like a star collapses or two black holes merge. The discovery of the second one was announced in San Diego by the Laser Interferometer Gravitational Wave Observatory (LIGO) which utilized extraordinary technological measures to find the signal. 

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Einstein’s gravitational waves found at last

One hundred years after Albert Einstein predicted the existence of gravitational waves, scientists have finally spotted these elusive ripples in space-time.

In a highly anticipated announcement, physicists with the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) revealed on 11 February that their twin detectors have heard the gravitational ‘ringing’ produced by the collision of two black holes about 400 megaparsecs (1.3 billion light-years) from Earth.

Ladies and gentlemen, we have detected gravitational waves,” David Reitze, the executive director of the LIGO Laboratory, said at a Washington DC press conference. “We did it!”

Continue reading via source: Nature

Infographic: Nik Spencer/Nature

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Gravitational waves finally detected

As an aspiring scientist, this news is so exciting to me!

Gravitational waves are ripples in the fabric of spacetime, caused when a massive object is accelerated. By the time they get here from distant astronomical objects, the waves have incredibly low energy and are phenomenally difficult to detect, which is why it’s taken a century to discover them since they were first predicted by Einstein’s Theory of General Relativity. Essentially every other prediction of GR has been found to be correct, but the existence of gravitational waves has been maddeningly difficult to prove directly.

Until now. And what caused the gravitational waves they detected at the Laser Interferometer Gravitational-Wave Observatory is as amazing and mind-blowing as the waves themselves: They caught the death spiral and aftermath of two huge black holes 1.3 billion light-years from Earth, merging together in a titanic and catastrophically violent event.

Mind you, we’ve had some good evidence such binary black holes existed before this, but this new result pretty much proves they exist and that, over time, they eventually collide and merge. That’s huge.

The black holes merged to create a single black hole with a mass of 62 times that of the Sun. Some of that mass was converted into energy: the energy of the gravitational waves themselves. And the amount of energy is staggering: This single event released as much energy as the Sun does in 15 trillion years. (Source)

Vega rocket lifted off carrying spacecraft to test gravitational waves

On 3rd December, Vega rocket lifted off from Europe’s Spaceport, French Guiana carrying LISA (after Laser Interferometer Space Antenna) Pathfinder. It will test key technologies for space-based observation of gravitational waves. These ripples in the fabric of spacetime which propagate as waves, are predicted by Albert Einstein’s general theory of relativity but have not yet been directly detected.

To demonstrate the fundamental approach that could be used by future missions to observe these elusive cosmic fluctuations, LISA Pathfinder will realise the best free-fall ever achieved in space. It will do so by reducing all the non-gravitational forces acting on two cubes and monitoring their motion and attitude to unprecedented accuracy.

Copyright: European Space Agency–Stephane Corvaja, 2015

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The black-hole collision that reshaped physics

A momentous signal from space has confirmed decades of theorizing on black holes — and launched a new era of gravitational-wave astronomy.

The event was catastrophic on a cosmic scale — a merger of black holes that violently shook the surrounding fabric of space and time, and sent a blast of space-time vibrations known as gravitational waves rippling across the Universe at the speed of light.

But it was the kind of calamity that physicists on Earth had been waiting for. On 14 September, when those ripples swept across the freshly upgraded Laser Interferometer Gravitational-Wave Observatory (Advanced LIGO), they showed up as spikes in the readings from its two L-shaped detectors in Louisiana and Washington state. For the first time ever, scientists had recorded a gravitational-wave signal.

“There it was!” says LIGO team member Daniel Holz, an astrophysicist at the University of Chicago in Illinois. “And it was so strong, and so beautiful, in both detectors.” Although the shape of the signal looked familiar from the theory, Holz says, “it’s completely different when you see something in the data. It’s this transcendent moment”.

The signal, formally designated GW150914 after the date of its occurrence and informally known to its discoverers as ‘the Event’, has justly been hailed as a milestone in physics. It has provided a wealth of evidence for Albert Einstein’s century-old general theory of relativity, which holds that mass and energy can warp space-time, and that gravity is the result of such warping. Stuart Shapiro, a specialist in computer simulations of relativity at the University of Illinois at Urbana–Champaign, calls it “the most significant confirmation of the general theory of relativity since its inception”.

But the Event also marks the start of a long-promised era of gravitational-wave astronomy. Detailed analysis of the signal has already yielded insights into the nature of the black holes that merged, and how they formed. With more events such as these — the LIGO team is analysing several other candidate events captured during the detectors’ four-month run, which ended in January — researchers will be able to classify and understand the origins of black holes, just as they are doing with stars.

Still more events should appear starting in September, when Advanced LIGO is scheduled to begin joint observations with its European counterpart, the Franco–Italian-led Advanced Virgo facility near Pisa, Italy. (The two collaborations already pool data and publish papers together.) This detector will not only contribute crucial details to events, but could also help astronomers to make cosmological-distance measurements more accurately than before.

“It’s going to be a really good ride for the next few years,” says Bruce Allen, managing director of the Max Planck Institute for Gravitational Physics in Hanover, Germany.

“The more black holes they see whacking into each other, the more fun it will be,” says Roger Penrose, a theoretical physicist and mathematician at the University of Oxford, UK, whose work in the 1960s helped to lay the foundation for the theory of the objects. “Suddenly, we have a new way of looking at the Universe.”

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A century ago, Albert Einstein theorized that there was such a thing as a fabric of space and time — that the universe was malleable, and that large objects and events would cause it to bend. He was right. From studying the signals emanating from the merging of two black holes — have separate masses equal to 36 and 29 suns — scientists with the Laser Interferometer Gravitational-Wave Observatory (LIGO) were able to observe gravitational waves. (@jacksmithiv)

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Gravitational waves detected 100 years after Einstein's prediction

For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, arriving at Earth from a cataclysmic event in the distant universe. This confirms a major prediction of Albert Einstein’s 1915 general theory of relativity and opens an unprecedented new window onto the cosmos.

Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained. Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.


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Scientists begin modeling universe with Einstein’s full theory of general relativity

Research teams on both sides of the Atlantic have shown that precise modeling of the universe and its contents will change the detailed understanding of the evolution of the universe and the growth of structure in it.

One hundred years after Einstein introduced general relativity, it remains the best theory of gravity, the researchers say, consistently passing high-precision tests in the solar system and successfully predicting new phenomena such as gravitational waves, which were recently discovered by the Laser Interferometer Gravitational-Wave Observatory.

The equations of general relativity, unfortunately, are notoriously difficult to solve. For the past century, physicists have used a variety of assumptions and simplifications in order to apply Einstein’s theory to the universe.

On Earth, that’s something like averaging the music made by a symphony. The audience would hear a single average note, keeping the overall beat, growing generally louder and softer rather than the individual notes and rhythms of each of the orchestra’s instruments.

Wanting details and their effects, U.S. and European teams each wrote computer codes that will eventually lead to the most accurate possible models of the universe and provide new insights into gravity and its effects.

While simulations of the universe and the structures within it have been the subject of scientific discovery for decades, these codes have made some simplifications or assumptions. These two codes are the first to use Einstein’s complete theory of general relativity to account for the effects of the clumping of matter in some regions and the dearth of matter in others.

Both groups of physicists were trying to answer the question of whether small-scale structures in the universe produce effects on larger distance scales. Both confirmed that’s the case, though neither has found qualitative changes in the expansion of the universe as some scientists have predicted.

“Both we and the other group examine the universe using the full theory of general relativity, and have therefore been able to create more accurate models of physical processes than have been done before,” said James Mertens, a physics PhD student at Case Western Reserve University who took the lead in developing and implementing the numerical techniques for the U.S. team.

Mertens worked with John T. Giblin Jr., the Harvey F. Lodish Development Professor of Natural Science at Kenyon College and an adjunct associate professor of physics at Case Western Reserve; and Glenn Starkman, professor of physics and director of the Institute for the Science of Origins at Case Western Reserve. They submitted two manuscripts describing their work to the arXiv preprint website on Nov. 3, 2015.

Less than two weeks later, Marco Bruni, reader in cosmology and gravitation at the University of Portsmouth, in England, and Eloisa Bentivegna, Senior Researcher and Rita Levi Montalcini Fellow at the University of Catania, Italy, submitted a similar study.

Letters by the two groups appear back-to-back in the June 24th issue of Physical Review Letters, and the U.S. group has a second paper giving more of the details in the issue of The Physical Review Part D to be published on the same day. The work will be highlighted as Editors’ Suggestion by Physical Review Letters and Physical Review D and in a Synopsis on the American Physical Society Physics website.

The researchers say computers employing the full power of general relativity are the key to producing more accurate results and perhaps new or deeper understanding.

“No one has modeled the full complexity of the problem before,” Starkman said. “These papers are an important step forward, using the full machinery of general relativity to model the universe, without unwarranted assumptions of symmetry or smoothness. The universe doesn’t make these assumptions, neither should we.”

Both groups independently created software to solve the Einstein Field Equations, which describe the complicated interrelationships between the contents of the universe and the curvature of space and time, at billions of places and times over the history of the universe.

Comparing the outcomes of these numerical simulations of the correct nonlinear dynamics to the outcomes of traditional simplified linear models, the researchers found that approximations break down.

“By assuming less, we’re seeing something new,” Giblin said.

Bentivegna said that their preliminary applications of numerical relativity have shown how and by how much approximations miss the correct answers. More importantly, she said, “This will allow us to comprehend a larger class of observational effects that are likely to emerge as we do precision cosmology.”

“There are indeed several aspects of large-scale structure formation (and their consequences on, for example, the cosmic microwave background) which call for a fully general relativistic approach,” said Sabino Matarrese, professor of physics and astronomy at the University of Padua, who was not involved in the studies.

This approach will also provide accuracy and insight to such things as gravitational lensing maps and studying the cross-correlation among different cosmological datasets, he added.

The European team found that perturbations reached a “turnaround point” and collapsed much earlier than predicted by approximate models. Comparing their model to the commonly assumed homogeneous expansion of the universe, local deviations in an underdensity (a region with less than the average amount of matter) reached nearly 30 percent.

The U.S. team found that inhomogeneous matter generates local differences in the expansion rate of an evolving universe, deviating from the behavior of a widely used approximation to the behavior of space and time, called the Friedmann-Lemaître-Robertson-Walker metric.

Stuart L. Shapiro, professor of physics and astronomy at the University of Illinois at Urbana-Champaign, is among the acknowledged leaders of solving Einstein’s equations on the computer. “These works are important, not only for the new results that they report, but also for being forerunners in the application of numerical relativity to long-standing problems in cosmology,” said Shapiro, who was not involved in the studies.

No longer restricted by the assumptions, researchers must abandon some traditional approaches, he continued, “and these papers begin to show us the way.”

Bruni said galaxy surveys coming in the next decade will provide new high-precision measurements of cosmological parameters and that theoretical predictions must be equally precise and accurate.

“Numerical relativity simulations apply general relativity in full and aim precisely at this high level of accuracy,” he said. “In the future they should become the new standard, or at least the benchmark for any work that makes simplifying assumptions.”

Both teams are continuing to explore aspects of the universe using numerical relativity and enhancing their codes.

Bentivegna and Bruni used the Einstein Toolkit, which is open-source, to develop theirs. The U.S. team created CosmoGRaPH and will soon make the software open-source. Both codes will be available online for other researchers to use and improve.

IMAGE….In a simulation of the universe without commonly made simplifications, galaxy profiles float atop a grid representing the spacetime background shaped by the distribution of matter. Regions of blue color contain more matter, which generates a deeper gravitational potential. Regions devoid of matter, darker in color, have a shallower potential. Credit James Mertens