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Einstein’s 100-Year-Old Relativity Theory Proved! A few weeks ago, scientists announced that they had finally proven the last, elusive bit of Einstein’s General Theory of Relativity, with the observation of gravitational waves arriving at the Earth from a cataclysmic event in the (very!) distant past. But what are gravitational waves and why are they relevant? Image courtesy NASA Gravitational Waves: “The scientific discovery of the 21st century” by Ross Tester M ost parts of Einstein’s General Theory of Relativity were relatively (pardon the pun!) easy to demonstrate and/or prove. But one part, the existence of gravitational waves, proved not only elusive but impossible to confirm given the lack of equipment at the time – even until quite recently. They remained just a theory, even though Taylor and his student Hulse earned a Nobel prize for Physics in 1933 for “proof” of their existence. These waves carry information about their dramatic origins – and about the nature of gravity itself – that cannot otherwise be obtained. Now for the first time, scientists in the USA, with more than a little help from researchers at the University of Western Australia, have detected gravitational waves by the twin Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors in both Livingston, Louisiana, and Hanford, Washington. LIGO, first proposed in the 1980s as a means of detecting gravitational waves, is a consortium of more than 1000 18  Silicon Chip scientists from 90 universities in 15 countries. The University of Western Australia team has spent the past seven years putting together gravitational-wave detector equipment. The detectors in the USA use powerful lasers to measure vibrations of mirrors suspended four kilometres apart at the ends of huge vacuum pipes. UWA researchers contributed to the project by using high power lasers at the Gingin Gravitational Research Centre to observe and test newly-discovered ways of scattering the laser beams. They developed methods for preventing instabilities in the detectors. A major upgrade to LIGO increased the sensitivity of their instruments compared to the first generation, enabling a large increase in the volume of the universe probed – and the discovery of gravitational waves during its first observation run. Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second siliconchip.com.au 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. A few false starts “Discoveries” of gravitational waves have been announced a few times in the past. In the 1960s, an American physicist, Joseph Weber, claimed he had detected them but no-one could reproduce his methodology so his findings were discredited. Then as recently as 2014, a team at the South Pole reported evidence of the waves but their results turned out to be from cosmic dust. And as reported overleaf, excited LIGO scientists were about to report they had detected gravitational waves . . . but their joy was short-lived when they discovered their data had been “hacked” as part of the LIGO quality control. But now it appears to be real Announcing the discovery to the world’s media, David Reitze, LIGO executive director, said “Ladies and gentlemen, we have detected gravitational waves. We did it. The things we’ve surmised and speculated about will become the subjects of detailed study.” To say the world’s scientists were excited by the announcement would be a massive understatement. Already, there is a huge amount of information on the ’net about gravitational waves and what their discovery will mean. Indeed, a Google search only a few days after the news broke in February last revealed more than 16 million results, many of them attempting to describe just what gravitational waves were! Yet more reports showed how far this research has already spread. It is being applied to mineral exploration, time standards, quantum computing, precision sensors, ultra-sensitive radards and pollution monitors. Where to from here? The discovery of gravitational waves is significant for two main reasons. First, this opens up a whole new way of studying the Universe, allowing scientists to infer the processes at work that produced the waves. Second, it proves a hypothesis called inflation. The Big Bang theory, which was first hypothesised by Computer-generated image of the moment before two black holes collide. In those last microseconds, an enormous amount of energy is released, generating gravitational waves. Until now, they’ve been theoretical – but have now been detected. See the video – and much more besides – at www.theverge.com/2016/2/11/10965312/einsteingravitational-waves-discovered-announced-video siliconchip.com.au What are Gravitational Waves? In 1916, the brilliant theoretical physicist Albert Einstein (pictured above) discovered a mathematical way to explain gravity – and called it his general theory of relativity. Part of this theory predicted the concept of gravitational waves. General relativity states that mass distorts both space and time in the same way a heavy bowling ball will distort a trampoline. When any object accelerates, it creates ripples in space-time, just like a boat causes ripples in a pond (and also similarly an accelerating electrical charge produces an electromagnetic wave). Even you moving about will, according to the General Theory of Relativity, distort space-time. These space-time ripples are gravitational waves. They are extremely weak so are very difficult to detect. In fact, any ripple you cause would be so weak it would (with today’s technology) be utterly impossible to detect. It takes something with an immense mass, far bigger than anything we can imagine, to produce a gravitational wave of any significant magnitude. Scientists have long believed that the best hope of detecting gravitational waves here on Earth would come from two black holes or pulsars collapsing into each other. But even that was not enough – to detect them, a huge breakthrough in technology was also required. And thus it was with the gravitational waves detected on September 14, 2015: the waves came from the very last microseconds of a pair of black holes colliding out in space 1.3 billion years ago, with a force beyond anyone’s comprehension. It was this force which created the ripples detected on Earth and brought a smile to thousands of scientists the world over. Why? Gravitational waves are important in telling us about the origins of the universe – a snapshot, if you like, of the universe only a few hundred thousand years after it started. Indeed, “primordial” gravitational waves, which were generated in the first moments of the universe, would carry vital information about how the universe began Although there was strong circumstancial evidence of their existence they had never been detected . . . until now. April 2016  19 LIGO Observatory, Hanford, Washington LIGO Observatory, Livingston, Louisiana The LIGO Observatories. . . and Australia’s AIGO LIGO is the world’s largest gravitational wave observatory and a “cutting edge” physics experiment. Unlike optical or radio telescope observatories, though, LIGO is “blind”. LIGO’s detector is a laser interferometer – it is designed to detect unbelievably tiny changes in laser light reflected from unbelievably high precision mirrors at each end of a vacuum “tube”. Unbelieavable? Almost! It cannot see electromagnetic radiation like other observatories (eg, light, radio waves, X rays, etc). But the data collected will have far-reaching effects on a variety of physics fields, including gravitation, relativity, astrophysics, cosmology, particle physics and nuclear physics. The LIGO collaboration has two widely-separated observatories in the USA, one north-west in Washington (state) and one southeast in Louisiana (both shown above). These are funded by the National Science Foundation. Incidentally, LIGO stands for Laser Interferometer Gravitational wave Observatory. Each facility is shaped like a giant “L”; the “arms” of the L are two vacuum-sealed 1.2m-diameter tubes stretching 4km long, with mirrors at each end. Each of the tubes is encased in a 3m-wide concrete enclosure to protect it from interference. When a gravitational wave passes, one mirror gets closer while the other retreats; scientists measure this phenomenon by bouncing lasers off the mirrors. Changes in the amount of time it takes a laser to bounce off a mirror indicate a gravitational wave. We’re talking about measuring changes almost beyond our comprehension – equivalent to a couple of millimetres in 1x1023m. The gravitational wave measurements from the black holes were also converted into audible form, what LIGO calls a “chirp.” Just as the black holes merge, the frequency of the resulting gravitational waves increases up until the moment of collision. As a sound, that movement becomes a high-pitched note that sweeps through the octaves really quickly (it’s been likened to the note from a cello). The gravitational waves only move LIGO’s instruments by about one ten-thousandth the size of a proton. This means Earth isn’t the ideal place to look for waves, since movements from people or traffic can potentially cause interference. For instance, LIGO kept getting “readings” that were actually the result of cars rolling over a nearby bump in the road. A couple of years ago, LIGO operators created “fake” gravitational waves to see if they were detected. The excited scientists were just about to announce their “discovery” to the world when it was 20  Silicon Chip revealed that it was all part of LIGO quality control! However, it would appear that the latest discovery is the “real deal”, the holy grail that has eluded scientists for 100 years. Australian AIGO The University of Western Australia is one of the partners in LIGO. In 1990, the UWA School of Physics established the Australian International Gravitational Observatory (AIGO) at Gingin, north of Perth. Through strong national and international participation, the research centre concentrates on the development of advanced technologies driven by the goal of the next generation large scale gravitational observatory construction. As well as their primary objective of gravitational wave research, one spin-off was the development of the Sapphire Clock, the only one in the world stable enough to allow atomic clocks to reach their ultimate precision. These are required for the International Space Station for the next generation of precision GPS navigational systems. Gravity wave detection research provided the technology which allowed the clock, which uses pure crystals of synthetic sapphire, to be developed. Another spin-off from this research has been state-of-the-art radar oscillators, achieving microwave signals of unprecedented purity. The improvement in performance has both military and commercial aircraft applications. Finally, they also developed the gravity gradiometer, highy advanced equipment already being used for rapid airborne mineral exploration. AIGO Research Centre, Gingin, Western Australia siliconchip.com.au FABRY-PEROT CAVITIES LASER BEAM SPLITTER PHOTO DETECTOR Simplified diagram of a laser interferometer. The idea is that gravitational waves will push the mirrors apart one way and contract them the other, enabling precise measurement using the laser. Georges Lemaitre, a Belgian priest and physicist, was called “the day without yesterday” because it was the moment when time and space began. However, not all matter could have come from the Big Bang (as originally conceived). In the 1970s, cosmologists came up with another theory, called inflation, which suggests that in the infinitessimally small time after the Big Bang there was a sudden enlargement of the universe. Only inflation can amplify the gravitational wave, so formed, to make it detectable. So if gravitational waves have been detected, inflation must have taken place. The scientists at LIGO have opened up a whole new field of astronomy – gravitational wave astronomy, that in time will let us see way back in time; everything from the heart of a black hole to the moments after the big bang. It’s akin to when radio telescopes were invented – they opened up the sky with millions of new radio sources that were previously unknown. Gravitational wave research will further expand man’s knowledge of the universe, no doubt leading on to yet more discoveries. FULL DUPLEX COMMUNICATION OVER WIRELESS LAN AND IP NETWORKS Into space? Because of the errors and distortions caused by earthbound observation, the next step will be to establish gravitational wave detection in space. Last December, the LISA Pathfinder mission (a partnership between NASA and the European Space Agency) launched a spacecraft to test the technologies needed for future space-based detectors, thus elminating earthly disturbances and interference. Instead of 4km-long interferometers, in space they could be literally millions of kilometres long. The larger the interferometer, the smaller the gravitational wave it can detect. And there’s a lot more room up there! IP 100H Icom Australia has released a revolutionary new IP Advanced Radio System that works over both wireless LAN and IP networks. The IP Advanced Radio System is easy to set up and use, requiring no license fee or call charges. If you’re struggling with the concept of gravitational waves, the three-minute animated video at www.independent.co.uk/news/science/gravitational-waves-simpleexplanation-video-a6869761.html is among the best we’ve seen and well worth watching! SC siliconchip.com.au To find out more about Icom’s IP networking products email sales<at>icom.net.au WWW.ICOM.NET.AU ICOM5006 Watch . . . and learn! April 2016  21