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The Discovery Of The Gravitational Wave.


NotBrad

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I think the popular press has a tendency to describe every attention-getting scientific experimental result as a “breakthrough”, while the scientists involved and scientifically literate spectators understand that experimental results fall into 2 main categories: “successes” that agree with theoretical predictions, and “failures” that don’t. Failures are usually more exciting an important than successes. Arguably the most famous example is the 1887 Michelson–Morley experiment, which invalidated contemporary Newtonian physics theories of light, creating a theoretical void that was filled in 1905 by Special Relativity.

 

The 11 Feb 2016 LIGO results are a “success”. They validate predictions of the theory of general relativity made in 1916 by Einstein and Rosen. Over the next few decades, Einstein, Rosen, Eddington and others wavered on the theory, vacillating between predicting gravitational waves propagate only a short distance in space, that they were just “ripples in space” that didn’t do carry physical energy, eventually, now with Feynman joining in in the 1950s (see the “sticky bead argument”), reaching the current consensus that they travel unlimited distances and do carry energy – that is, that they are radiation. This was convincingly verified in 1974 by Russell Hulse and Joseph Taylor by careful observation of the change in orbital period of a binary pulsar (for which they got the 1993 Nobel prize), but even though most were confident of what the results would be, many physicists (especially folks like Kip Thorne) were obsessed with directly measuring gravitational radiation by the tiny effect it has on space. This obsession if what drove the creating of the multi-billion dollar LIGO and Virgo interferometers.

 

The usefulness of gravity wave detectors doesn’t end with testing General Relativity, though. More important than what first generation detectors like LIGO can do, I think, is what making and operating them teaches about how to make later generation, especially space-based, ones, because these could be sensitive enough not just to detect the most violent gravitational radiation producing events, but give detailed gravitational maps of the universe. Such “gravitational astronomy” has the potential to be much more powerful than EM radiation astronomy, because “dark” parts of the universe that aren’t visible from EM radiation yet have gravitational effects could be directly detected, and the great outstanding theoretical problems they involve illuminated.

 

It’s an exciting time to be an astronomer!

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CraigD, your post is a bit schizofrenic, you say that successes are more boring than failures and then you go on to say how cool it is to be able to see the dark era (actually you say parts, which I know includes also stuff in our own galaxy behind dust not only the early universe) :-)

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CraigD, your post is a bit schizofrenic, you say that successes are more boring than failures and then you go on to say how cool it is to be able to see the dark era (actually you say parts, which I know includes also stuff in our own galaxy behind dust not only the early universe) :-)

He talks to myself sometimes too, sometimes I laugh at his jokes, but most the time I just cry in the corner and try not to listen.

 

Hard to ignore a voice that follows you everywhere...

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