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Gravitational waves found – Expert Reaction

Posted in Science Alert: Experts Respond on February 12th, 2016.

Scientists have confirmed the discovery of minuscule ripples in the fabric of space and time.

ligo20160211_TnThis morning (NZT) researchers from the Laser Interferometer Gravitational-wave Observatory (LIGO), confirmed they had detected gravitational waves.

A full release from LIGO is available here.

Gravitational waves are distortions or ‘ripples’ in the fabric of space-time caused by some of the most violent and energetic processes in the Universe. Albert Einstein predicted the existence of gravitational waves exactly 100 years ago in his general theory of relativity.

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 – by New Zealander Prof Roy Kerr –  but never observed.

Why are they looking for gravitational waves? According to the LIGO site: “Detecting and analyzing the information carried by gravitational waves will allow us to observe the Universe in a way never before possible.”

“This will open up a new window of study on the Universe, giving us a deeper understanding of these cataclysmic events, and usher in brand new cutting-edge studies in physics, astronomy, and astrophysics.:

The SMC the following expert commentary. Feel free to use these quotes in your reporting.

Prof Roy Kerr, Professor Emeritus, Physics and Astronomy, University of Canterbury, comments:

“This observation is the product of one of the most outstanding collaborations of science and technology ever. It not only required unbelievable technological advances to be able to measure the incredibly small gravitational vibrations but also several decades of theoretical work needed to calculate the theoretical signals that have now been observed. From the frequency of the signal it is clear that this is not two neutron stars colliding but is a pair of fairly heavy black holes. Spinning black holes exist.”

Prof Richard Easther, Professor and Head of Department, Physics, University of Auckland, comments:

“This is a huge day for physics and astronomy. LIGO’s detection of gravitational waves from a black hole merger confirms Einstein’s 100 year old prediction of the existence of gravitational waves. On top of that, it is the culmination of decades of effort by a huge, multinational team of scientists who achieved this feat by building the most sensitive scientific instrument ever constructed.

“This discovery spectacularly confirms the understanding of gravity provided by Einstein’s general theory of relativity and opens the door to a new era in astronomy and astrophysics. For astronomers, being able to detect gravitational waves is like growing a new set of eyes, as they give us an entirely new way of observing the universe.

“This first detection gives us ringside seats to the merger of two black holes, one of the most extreme events that can happen in the universe, and provides a completely new tool for understanding these objects.

“Even in this first detection, LIGO scientists could measured the size and spin of the final black hole. Intriguingly, in the “ringdown” after the merger, the new black hole seems to be evolving into a Kerr black hole, whose mathematical properties were first described in detail by New Zealander Roy Kerr in the 1960s.”

Prof Joerg Frauendiener, Mathematics & Statistics, University of Otago, comments:

“Gravitational waves exist. Gravitational physicists always knew it but now it is official. They were detected with the LIGO detectors. This is a huge achievement for science which was almost 100 years in the making. In 1916 Einstein predicted the existence of gravitational waves based on the wave-like solutions of his field equations which describe the gravitational field. It took a century to develop the technology which is necessary to actually measure these ripples in the fabric of space-time. The detection of the waves now marks a huge achievement of the human mind: the inception of the theory of relativity and the technological advance.

“The gravitational waves have literally opened up a new window to the universe. While before we relied exclusively on electromagnetic waves in the form of micro waves, light, x-rays etc. we have now an entirely new way to look at the universe. This will allow us to better understand 1. the structure of neutron stars, 2. the nature of gamma ray bursts, 3. the expansion of the universe and, related to that, 4. the origin of the universe, the `big bang’. This is most interesting since the `big bang’ has so far been hidden from our view due to the hot plasma that existed in the very early stages of the universe and which is opaque to electromagnetic waves but transparent to gravitational waves.

“Will it have an impact on everyday life? Probably not. But it is dangerous to make such claims as history shows. When Heinrich Hertz discovered  electromagnetic waves in 1888 he was similarly dismissive. But can you imagine today’s world without radio, tv, radar or phones?”

Associate Professor Renate Meyer, Department of Statistics, University of Auckland, was involved in the LIGO collaboration. She comments:

“The discovery of gravitational waves is a truly momentous occasion – what would be more fitting to mark the centennial of the general theory of relativity? Gravitational waves, ripples in space-time caused by accelerating massive objects, have been predicted by Einstein’s general relativity theory in 1916. 2016 brings the stunning results from Advanced LIGO, the detection of gravitational waves and the observation of a binary black hole merger!

“This is, of course, a moment that everybody in the LIGO Scientific collaboration (LSC) and anybody involved in aspects of gravitational wave data analysis has been working towards and eagerly awaiting for the last two decades. The detection was made possible by the extensive engineering efforts expended to upgrade the world-wide network of detectors to a much increased sensitivity and last not least the development of sophisticated statistical data analysis strategies. Great to see that the data analysis methods our group initiated in 1998 and worked on continuously since then have been adopted by the LSC and employed to estimate the parameters of the binary inspiral signal waveform.

“Advanced LIGO has opened a new window to study the Universe and the forces that govern it. It can see events, such as colliding black holes and supernovae that are not observable with electromagnetic-based telescopes. Following up from detection: the statistical estimation of the gravitational waveforms will provide new insights into the cosmic events that produced them, even the Big Bang itself.”

Prof Matt Visser, Mathematics, Victoria University Wellington, comments:

“It looks like a really clean and convincing observation.”

“The effect was seen in two separate detectors on opposite sides of the American continent, with just enough time difference to be accounted for by something travelling at the speed of light.

“The two signals were basically identical.

“By comparing the shape and size of the signal to model templates that the theorists had worked out, the LIGO team was able to deduce that the signal was generated by two black-holes spiralling in to each other and merging, and to estimate the mass of both initial black holes and the final black hole, and to estimate the distance (about 1/10 of the distance across the visible universe; that is, not our own galaxy, way way out there…).

“In the final stage of the merger you had two black holes (36 and 29 times the mass of our sun) crashing into each other at half the speed of light — this lead to a final black hole of 62 times the mass of our sun, and the equivalent of 3 solar masses converted into gravitational radiation. Because it was two black holes colliding, (as opposed to two neutron stars) there was essentially no light/radio/X-rays generated, it would be almost pure gravitational radiation…

“LIGO will continue analyzing the other data they collected, we might still see more events, this one was particularly clean and strong and stood out very clearly from the background noise…

“The plan now is to get several other gravitational wave detectors up and running at the same time to improve the angular resolution, (where on the sky the event takes place). With only the two LIGO detectors you can tell when and what and how strong and how far, but you have limited position information.”

Dr Karl Wette, is alumnus of the University of Auckland and post-doctoral researcher at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in Hanover, Germany and worked on the LIGO project. He comments:

“This announcement from LIGO is a huge deal for physicists. For the first time, we have detected gravitational waves – the ripples in spacetime predicted by Einstein – in an Earth-based detector. We have witnessed two black holes colliding to form a single black hole – an event predicted but never before observed. This discovery is the icing on the cake for Einstein’s theory of gravity. Discoveries from fundamental research are not only fascinating in themselves – for what they tell us about our world – but often have all sorts of future consequences. For example, modern electronics would not exist without our understanding of atomic structure that began with New Zealander Ernest Rutherford’s pioneering work.

“This discovery has come from the hard work of thousands of LIGO scientists, engineers, and students from many countries over many decades – a true big science effort – and it’s very humbling to be able to say I was part of that effort. The feeling in the LIGO community reminds me of post-Rugby World Cup 2011 – euphoric, but also relieved, that we’ve finally achieved this milestone! We are optimistic that, as our detectors improve in the years ahead, we will be able to announce many new discoveries – and perhaps find something completely unexpected. You can help us do that – please go to Einstein at Home to find out how!”

Dr Ra Inta, alumnus of the University of Canterbury and post-doctoral researcher at Texas Tech University in Lubbock, Texas, worked on the LIGO project. He comments:

“You may have heard that “in space, no-one can hear you scream”. Well this isn’t quite true for the most violent events in the Universe.”

“Today, the LIGO-Virgo collaboration announced the first direct detection of ripples in the very fabric of space-time, known as gravitational waves. This detection is a historical event, kicking open a completely new window to astronomy. What makes this detection even more exciting is that it came from an unexpected astronomical event: two very large black holes—each about thirty times the mass of our Sun—eating each other up in a few seconds. This not only provides evidence for one of the most mysterious objects in the Universe, a black hole, but, prior to this observation, we didn’t know of any stellar-mass black holes anywhere near this massive.

“This event was so energetic, that the total mass of three Suns was dumped into pure space-time geometry, which is what the LIGO detectors measured. In this sense, observing gravitational waves is more like listening to the Universe than looking at it. However, this detection is so wild, it’s like a deaf person suddenly being thrust into the most mind-blowing concert ever! This event was detected pretty much as soon as the LIGO detectors had been upgraded, so watch this space!”

Prof David Wiltshire, Professor of Physics, University of Canterbury, comments:

“The announcement that gravitational waves have been directly captured for the first time ever, from the collision of two black holes, opens a new age of astronomy. From now on we will be able to “listen” to the Universe with “ears” that are not limited by the electromagnetic spectrum, completely changing our understanding. It is a moment in history every bit as important as when Galileo first pointed his telescope at the stars and planets, or when the first radio, X-ray, infrared or gamma ray telescopes were first turned on by 20th century astronomers.

“It is also a story of many human triumphs. For Albert Einstein, whose theory of general relativity first predicted gravitational waves exactly 100 years ago, it is a triumph. For New Zealander Roy Kerr, who found the solution of Einstein’s equations which describes rotating black holes, but had to struggle to be listened to by astronomers on announcing his result in a 10-minute conference talk in 1963, it is a triumph. For the numerical relativists, such as Frans Pretorius at Princeton who in 2005 solved a decades-long struggle of how to split space and time in Einstein’s equations on a computer, to determine how gravitational waves are produced when black holes collide, it is a triumph.

“And above all, for the hundreds, the thousands of ingenious and skilled experimental physicists who have struggled with their lasers, mirrors and suspensions for decades to make the most sensitive measurements ever achieved by humankind, it is a triumph.

“We have now made a measurement so sensitive it’s like measuring the width of a human hair at the distance of Alpha Centauri.”

Read extended commentary from Prof Wiltshire here (available for use as an op-ed).

Commentary collected by Science Media Centre of Japan:

Hitoshi Murayama, Director, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), University of Tokyo &Professor of Physics, University of California, Berkeley

“I’m very excited by the news that Advanced LIGO detected gravitational wave from the merger of two black holes.  This confirms the prediction by Einstein that spacetime can vibrate.  It is also an amazing technical feat that they managed to detect such tiny ripples that move the mirror by 10-16 cm, a thousandth the size of the proton.  This is the dawn of new era in astronomy now that we can “hear” invisible black holes using gravitational wave.  It is also great news for KAGRA in Kamioka our colleagues are working on.  The combination of KAGRA, LIGO, and VIRGO in Europe will pin point events in the sky, so that we can also follow them up with Subaru for optical counterparts.  Looking forward to great discoveries in the near future!”

Hirosi Ooguri, Principal Investigator, Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU), University of Tokyo & Director, Walter Burke Institute for Theoretical Physics, California Institute of Technology, comments:

“It is wonderful to see that the new window to the universe is opened by LIGO with the direct detection of gravitational waves from the binary black hole merger. The result also provides important tests of general relativity in the strong-field regime of gravity. Collaborations of LIGO, KAGRA, and their counterparts in other countries will make great progress in gravitational wave astronomy and will provide us new insights into the universe. I would like to express my hearty congratulations to scientists at LIGO on the success with their bold vision and perseverance.”

Our colleagues at the AusSMC collected the following commentary:

A/Prof Peter Veitch, Head of Physics at the University of Adelaide. He is a member of the Australian Consortium for Interferometric Gravitational Astronomy that contributed to the gravitational waves discovery. He comments:

“The University of Adelaide developed and installed ultra-high precision optical sensors used to correct the distortion of the laser beams within the LIGO detectors, enabling the high sensitivity we needed to detect these minute signals. We’ve been assisting with the assembly and operation of the detectors and one of our PhD students, Elli King, was working at the LIGO Hanford Observatory when the gravitational wave was discovered. She was part of the team that conducted the exhaustive checking to make sure that signal was genuine.

“Our current model of the universe is derived largely from information carried by electromagnetic waves emitted by only a small component of the universe. The gravitational wave LIGO detected was emitted by objects we can’t see. Now we will be able to eavesdrop on the violent dark side of the universe. Who knows what else we will find now that we can both look and listen to the universe?

“The Advanced LIGO detectors are a technological triumph and the discovery has provided undeniable proof that Einstein’s gravitational waves and black holes exist. I have spent 40 years working towards this detection and the success is very sweet. We are on the threshold of a potential revolution in which gravitational astronomy could dramatically change our understanding of the universe and its evolution.”

Professor Andrew Melatos is from the School of Physics, Faculty of Science at the University of Melbourne. He is a member of the Australian Consortium for Interferometric Gravitational Astronomy that contributed to the gravitational waves discovery, and comments:

“At the University of Melbourne we analyse LIGO data on massive supercomputers to hunt for persistent signals from neutron stars, some of the most extreme objects in the Universe. This is a huge computing challenge.

“The discovery confirms Einstein’s prediction that gravitational waves exist, validating one of the pillars of modern physics. It confirms that black holes exist and orbit each other in binary systems, teaching us important lessons about how stars are born and live their lives.

“It is incredibly exciting to be participating as scientific history is being made. Every aspect of this research is elegant and beautiful. The LIGO detectors are genuine marvels of precision engineering. Einstein’s theory of relativity, which predicts the existence of gravitational waves, brings together the concepts of geometry and gravity in a wonderfully inspiring way. The sources that LIGO detects, like black holes, are the home of some of the most fascinating physics in the Universe. It is very exciting to think that we now have a new and powerful tool at our disposal to unlock the secrets of all this beautiful physics.

“Humanity is at the start of something profound and perpetual. We now have a new way of looking at the Universe and we will never stop looking. Gravitational waves are neither scattered nor absorbed by the material they pass through, so they let us peer right into the heart of some of the most extreme environments in the Universe, like black holes and neutron star, to do fundamental physics experiments under conditions that can never be copied in a lab on Earth.

“The possibilities are endless.”

Winthrop Professor David Blair is the Director of the Australian International Gravitational Research Centre (AIGRC) at the University of Western Australia. He is a member of the Australian Consortium for Interferometric Gravitational Astronomy that contributed to the gravitational waves discovery. HE comments:

“University of WA was involved in stabilising the detectors to enable continuous operation. We ran an independent analysis of the data to verify the signals, and we searched the sky with our Zadko robotic telescope to see if there was any explosion visible in light.

“Gravitational waves are akin to sounds that travel through space at the speed of light. Up to now humanity has been deaf to the universe. Suddenly we know how to listen. The universe has spoken and we have understood!

“We have just passed through the threshold from being deaf to the universe, to being able to hear and understand. This is the tip of an iceberg. A whole new spectrum is open to us. This is like Heinrich Hertz’s first detection of radio waves.  He never guessed  that it would revolutionise life in the next century.

“We have opened a whole new frontier by creating exquisite and almost unimaginable technologies that have allowed us to measure vibrations as small compared with atoms as atoms are compared to people.

“By measuring the smallest amount of energy ever measured, we have detected the most powerful explosion ever observed in the universe, in which three times the  total mass energy of the sun was emitted in pure explosion of gravitational energy in a time of less than one tenth of a second.”

Dr Eric Thrane is from the School of Physics and Astronomy at Monash University.He is a member of the Australian Consortium for Interferometric Gravitational Astronomy that contributed to the gravitational waves discovery, and comments:

“This is a watershed moment in the history of astronomy. LIGO’s detection represents a whole new way of doing astronomy that can unlock the secrets of the universe. It has been a privilege to work with the international LIGO collaboration toward this discovery.

“The discovery of this gravitational wave suggests that merging black holes are heavier and more numerous than many researchers previously believed. This bodes well for detection of large populations of distant black holes – research carried out by our team at Monash University. It will be intriguing to see what other sources of gravitational waves are out there, waiting to be discovered.”

Professor Susan Scott is a general relativist at the Australian national university. She is a member of the Australian Consortium for Interferometric Gravitational Astronomy that contributed to the gravitational waves discovery. She comments:

“This event did not generate light or neutrinos so the only way to observe it was through its gravitational wave emission. We have now unlocked the door to major processes and components of our Universe which only have a gravitational wave signature.

“Einstein’s General Relativity has been a highly successful theory passing all tests conducted in our Solar System in the weak gravity regime. With the detection of gravitational waves from this binary black hole merger, it has passed with flying colours its first test in the strong gravity regime which is a major triumph.

“We now have at our disposal a tool to probe much further back into the Universe than is possible with light, to its earliest epoch.”

Dr Philip Charlton is a Senior Lecturer in Mathematics at Charles Sturt University. He is a member of the Australian Consortium for Interferometric Gravitational Astronomy that contributed to the gravitational waves discovery, and comments:

“Charles Sturt University has contributed to detector characterisation, validation of the calibration of the instruments and development of the detection pipeline for the stochastic background of gravitational waves.

“This discovery is the first direct detection of gravitational waves, predicted in 1916. It is a further confirmation of the validity of general relativity as the correct theory of gravity.

“The most exciting thing is that it opens the door to a new window on the Universe. In the same way that radio astronomy led to the discovery of the cosmic microwave background, the ability to ‘see’ in the gravitational wave spectrum will likely to lead to unexpected discoveries.

“This detection marks the beginning of the age of gravitational wave astronomy.”

Dr Simon Johnston is the Head of Astrophysics at CSIRO, comments:

“This is an immensely important discovery for physics and astronomy. Gravitational waves exert a powerful appeal. Back in 1915 Einstein proposed that space-time is a four-dimensional fabric that can be pushed or pulled as objects move through it.

If you run your hand through a still pool of water waves will follow in its path, spreading throughout the pool. Now that we’ve caught these waves, we can use them to see the Universe in entirely different ways to what was previously possible.”

From the UK SMC

Prof Brian Cox, Royal Society Professor for Public Engagement in Science, said:

“This is a very exciting discovery for two reasons. Firstly, it confirms yet again that Einstein’s theory of General Relativity, published 101 years ago, is a supremely precise description of space and time, gravity and the evolution of the Universe. This result is a highly non-trivial prediction, and it is a triumph of high-precision experimental physics that such subtle shifts in spacetime at the level of a millionth of the size of an atom have been detected.

“Secondly, and even more excitingly, this opens up an entirely new way of observing the Universe. We can now observe collisions between black holes, probing gravity in ever more exotic and extreme situations, and look back in time far closer to the big bang than ever before. Gravitational wave astronomy opens up an entirely new window on nature.”

Prof Alex Halliday FRS, Vice President and  Physical Secretary of the Royal Society, said:

“100 years ago Albert Einstein, a foreign member of the Royal Society, predicted the existence of gravitational waves. It’s a brilliant example of science in action that a century on scientists at Caltech and MIT have now found the evidence to support Einstein’s hypothesis.

“Being able to see these ripples in space-time, which are the signature of massive collisions in space, will advance our understanding of fundamental physics in new directions and could give us more clues about the birth of the universe at the big bang.

“This exciting news is a breakthrough in our knowledge about the universe. It shows just how much more there is left for the next generation of cosmologists to discover.”

Prof Tom McLeish, FRS, Chair of the Education Committee at The Royal Society and Professor of Physics at Durham University, said:

“The last time anything like this happened was in 1888 when Heinrich Hertz detected the radio waves that had been predicted by James Clerk Maxwell’s field-equations of electromagnetism in 1865.  But this time it has taken over a century of waiting from Einstein’s field equations of gravity, and their prediction of waves, to detecting them at last.  But the wonderful connectivity of physics is shown by more than history: both Maxwell’s and Einstein’s waves travel at the speed of light.  This news has sent my head spinning with delight.”

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