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In 1987, Joe Weber, a physicist at the University of Maryland, claimed to have detected gravitational waves at exactly the same moment that other astronomers witnessed the famous supernova of that year, SN1987A.His equipment consisted of several massive aluminium bars that were designed to vibrate in a unique way when a large enough gravitational wave passed by.His claims were ignored largely because other physicists calculated that gravitational waves ought to be several orders of magnitude too weak to be picked up by this kind of gear. (And he’d made several similar claims throughout the 60s and 70s that others had failed to repeat.)But Weber’s claims may have to be re-examined, says Asghar Qadir, a physicist at the National University of Sciences and Technology in Rawalpindi, Pakistan. He points out that predicting the strength of a gravitational wave is by no means easy and until recently, only first order effects have been considered.He and colleagues have now worked out that in certain circumstances, second order effects can enhance the waves. But this only happens when there is a certain kind of assymetry in the event that created the waves.But get this: the assymetry can enhance the waves by a factor of 10^4.
One experiment springs to mind that might be capable of seeing this effect. Gravity Probe B is a space-based experiment designed to spot the geodetic effect and frame dragging, two tiny forces predicted by general relativity.The experiment consists of four perfectly round spheres, each about the the size of a baseball, that spin rapidly and so behave like gyroscopes. Each sphere has a thin superconducting coating which allows its spin and any changes to it to be measured precisely.If there were an obvious interaction between a superconducting films and gravitational waves, wouldn't Gravity Probe B have picked them up somehow? After all, in his previous paper Chiao says that a superconducting sphere is the perfect shape for a graviational wave antenna.As it turns out, the experiment has been throwing out anomalous results ever since it was launched. The team has puzzled over them for years now and lately come to the conclusion that they are the result of some imperfections in the shape of the spheres. This seems rather unlikely given the testing regime that Gravity Probe B underwent during its tortuous history.Could the real cause of Gravity Probe B's problems be reflections from passing gravitational waves?
A 15-year experiment using some of the most advanced technology known to Man has picked up the first detection of a gravitational wave, the first direct measurement of black holes, and the first direct evidence of binary black holes. It has also opened up an entirely new field of astronomy.The signal was picked up on September 14, 2015, at 0950 UTC by the two Laser Interferometer Gravitational-wave Observatory (LIGO) detectors built for the purpose in Livingston, Louisiana and Hanford, Washington state. The team then spent four months checking and rechecking the data before publishing in the Physical Review Letters today."Our observation of gravitational waves accomplishes an ambitious goal set out over five decades ago to directly detect this elusive phenomenon and better understand the universe, and, fittingly, fulfills Einstein's legacy on the 100th anniversary of his general theory of relativity," said Caltech's David Reitze, executive director of the LIGO Laboratory.Einstein first predicted gravitational waves in 1915, although he changed his mind about them several times in the following years. He proposed that the spacetime fabric of the universe would be warped by large masses, and if they interact with each other the masses can push out energy in the form of gravitational waves that propagate out at the speed of light.
Topic: Were gravitational waves first detected in 1987? (Read 2110 times)