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Physicists Gear Up To Catch a Gravitational Wave
sciencehabit writes: A patch of woodland just north of Livingston, Louisiana, population 1893, isn't the first place you'd go looking for a breakthrough in physics. Yet it is here that physicists may fulfill perhaps the most spectacular prediction of Albert Einstein's theory of gravity, or general relativity. Structures here house the Laser Interferometer Gravitational-Wave Observatory (LIGO), an ultrasensitive instrument that may soon detect ripples in space and time set off when neutron stars or black holes merge. Einstein himself predicted the existence of such gravitational waves nearly a century ago. But only now is the quest to detect them coming to a culmination. Physicists are finishing a $205 million rebuild of the detectors, known as Advanced LIGO, which should make them 10 times more sensitive and, they say, virtually ensure a detection.
That being said I fully expect gravitational waves to be discovered.
I am not so sure. There have been other experiments that should have detected them, but didn't. If this experiment also comes up empty, then physics may be facing another Michelson–Morley moment.
Well, it wouldn't be the only hole in Relativity, but it would be a huge hole in Relativity. Which otherwise describes the observed Universe very, very well. It's not the best-tested theory in science; that probably goes to QED. Plus then you have to account for observations of massive stellar objects spiraling towards each other, which lose energy more-or-less as predicted by GR. See also the 1993 Nobel. New Physics is always fun, but I'm afraid that a null result would be better explained as experimental design flaws. You know, the way that every other similar experiment to date has been explained. The parallels with aether measurements are hard to avoid, but the alternative theories of gravity are, well...insufficiently predictive. Also aether was more of an assumption than a theory per se: there was never any evidence for it. Contrast with Relativity, which is undeniably a true description of reality.
All told, while I agree with you about finding new things beyond the delineations of our theories, I don't think that a null result here would necessarily lead to much. IANAP, any corrections are appreciated.
Yes, they are amazingly sensitive seismometers. However, I don't think they'll ever detect gravitational waves. Physcists are divided over whether the waves can be detected by the devices so far created. They rely on special and general relativity to not cancel each other out when it comes to compressing the wavelenghts of light over a long distince. The small signal strenght combined with noise combined with nearly complete cancellation probably dooms the experiment from the start.
That being said I fully expect gravitational waves to be discovered.
I am not so sure. There have been other experiments that should have detected them, but didn't. If this experiment also comes up empty, then physics may be facing another Michelson–Morley moment.
I agree. Gravity waves are unlikely. In theory, we can test the idea with a direct experiment, but the cost would be in the multiple billions, and require spacecraft to loft a tetrahedral constellation of some very large masses, and then you'd have to fling another large mass at an appreciable fraction of the speed of light, probably via solar slingshot, and (effectively) have it "instantaneously appear" intersecting a non-orthogonal plane vector through the tetrahedral constellation. That'd basically give you a wave delta that you could see based on laser interferometry along the vertices of the tetrahedron.
Assuming gravity propagates at the speed of light as a force, rather than being an artifact of space-time, which would mean you don't get any waves. Which we've so far not been able to detect, probably because they don't exist. 8-).