Scientists now have a brand new tool to study the cosmos, thanks to Albert Einstein. The first direct detection of a gravitatiol wave by two US observatories in Washington and Louisia is being hailed as a milestone in experimental physics. It is expected to kick off an exciting era of gravitatiol wave astronomy, offering huge possibilities of research into other high-energy phenome in the universe over the next few years. The detection, made with the Laser Interferometer Gravitatiol Wave Observatory (LIGO), was of astounding sensitivity. On September last year, the two LIGO observatories located 3,000 kms apart simultaneously detected a split-second ripple through space-time caused by a cosmic cataclysm that occurred 1.3 billion years ago. Two rapidly spinning black holes, one with about 29 times the mass of the Sun and the other having about 36 times the solar mass had spiralled together to merge into a single black hole. Lasting only 20 milliseconds, the event is estimated to have had a peak power output about 50 times the output of all the stars in the visible universe. About three solar mass worth of gravitatiol waves travelled through the universe at the speed of light. This shock wave caused everything in its path to vibrate back and forth, reaching the Earth only on September last.
Designed to detect such gravitatiol shock waves, the twin LIGO detectors were shaped like the two legs of an ‘L’ with equal lengths of 2.5 miles. With a laser beam split into both legs and reflected back and forth through mirrors, the system could measure any minute difference which would push the split laser beams out of phase. Even discrepancies between the two beams of the order of ten-thousandth the width of a proton could be detected by this amazing device. The idea was that if a gravitatiol wave passed through, it will squeeze one leg and stretch the other, thereby creating the miniscule discrepancy. In its earlier from 2002 till 2010, the LIGO had drawn a complete blank, raising questions about its design. After an upgrade that took five years, the advanced version made the detection within 3 days of starting up. Such are the levels of sensitivity required to prise out the secrets of ture by physicists, who have to devise ingeniously indirect methods mostly to go about their work. When he formulated his General Theory of Relativity in 1915, Einstein had theorised that gravitatiol waves would be produced in cataclysmic cosmic events like collisions between bodies with enormous gravity like black holes or neutron stars. But he despaired of ever seeing his prediction being tested by instruments of sufficient sensitivity, so far was he ahead of his time. It took decades to test the mind-bending predictions of Special and General Relativity, of time speeding up or slowing down around bodies depending on the mass they have, of light losing energy when moving against gravity, of matter stretching and warping space-time, of the geometry of space-time experienced as gravity.
Einstein has been proved right in every test once the apparatus was sensitive enough to make the detections he had predicted. Still, many scientists were sceptical that gravitatiol waves would be strong enough to detect while others rejected their existence. So after the LIGO detection in September last year, its two teams took months to check and recheck the data and subject it to exhaustive alysis using supercomputers. This is because even a faraway earthquake or a nearby passing truck or an instrument malfunction could have mimicked the sigl. One scientist likened this to measuring the sun shift its position by a hair’s breadth towards the nearest star! Filly, they established beyond doubt the distinctive upward sweep in frequency of the sigl as predicted by the General Relativity field equations. So now scientists have added gravitatiol waves to the tools of visible light, infrared waves, radio waves and X-rays to study the heavens. Unlike light waves which are affected by gas and dust while passing through space, gravitatiol waves are theorised to carry more information about their source as they pass through objects without changing. This property is expected to help scientists see inside distant cosmic objects, map the universe better and formulate better theories about its origin. Gravitatiol waves can also come in at audio frequencies, so these can be played as an audio file to recreate the sound of the universe. The LIGO team has expressed wonder that Einstein’s field equations have now been found to be equally valid in diverse cosmic environments ranging from our gentle solar system to the extremely violent conditions of merging black holes. The vindication of his masterful work yet again is expected to inspire another generation to take up scientific research in right earnest.