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Lab Tuned to Gravity's 'Ripples'
Krishna Dagli writes "One of the great scientific experiments of our age is now fully underway. Success would confirm fundamental physical theories and open a new window on the Universe, enabling scientists to probe the moment of creation itself. The experiment is trying to detect ripples created in the fabric of space-time that sweep out from merging black holes or exploding stars and detection would be a final test of Albert Einstein's General Theory of Relativity. "
Of course we should be investing in this technology. Even if it does cost us millions, nay even billions. Gravity is the single most important universal effect, and the sooner we know what it is, and how to manipulate it the better. A few billion upfront for that sort of tech is peanuts.
If the research doesn't pan out, then we will move on and create new hypothesis. You can only throw so much money at one thing at a time. If we fail, we redo.
just imagine the possibilities. Flying car anyone?
Baz
Plausible alternative hypotheses are nice to have, but shouldn't be a requirement for the simple reason that there might not be any plausible alternatives. Or at least none concievable with current knowledge, thus further necessitating the gathering of scientific proof as it can show whether you're missing some vital piece of knowledge.
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"It's important to have alternative hypotheses"
Is it? If I remember correctly the lack of an alternate hypothesis when Michelson and Morley failed to detect the aether caused Einstein to beging pondering special relativity.
This is the alternative model. The rest of us know that such waves actually propogate via infinitely long strands of pasta.
But seriously - if things all point to a likely model, and nothing (rationally) points to an alternative, why kill yourself (and your budget) documenting hollow alternatives just so that you're sticking to academic form?
Don't disappoint your bird dog. Go to the range.
Yes, let's be absolutely sure we're correct before testing a hypothesis. After all, what are hypotheses for?
Right now we are uncertain of the exact speed of gravity. Some measurements resulted in speed between 0.8 and 1.2 times the speed of light (according to this). If the speed of gravity is greater than the speed of light, does that violate the general relativity? There are many consequences.
It is important that we find what gravity is, because if it is a wave of particles, then maybe there is a possibility to find a way to shield gravity away. Shielding gravity would be a major step towards space exploration.
What are the alternative models if gravity waves simply don't exist?
There are already alternative theories, such as bosons named gravitons. That might just be a variation in interpretation of wave-particle duality, but since quantum gravity isn't the same thing as general relativity it passes muster. There are other gravitational alternatives proposed, usually flawed and/or not well accepted by the scientific community. And what impact this experiment wil have on the Higgs particle question, one way or another?
Your post seems to imply this is an all or nothing experiment. But GR wouldn't be challenged only by a null result. If the magnitude of any detected gravity waves is significantly different from expectations, the discrepancy will have to be explained. Often, these differences are more challenging to a theory. Unexpected behavior of a newly detected but predicted phenomena is also a major challenge to existing theories. I can't wait to see what kind of information can be obtained by some analog of Zeeman splitting in gravity wave spectroscopy, if such a thing exists. That will be far more revealing than any "Yup, that's a gravity wave" result.
In theory, there's no difference between theory and practice. In practice, there is.
I think gravity MUST be viewed as a longitudinal wave, not transverse. Here's a thought experiment.
Your thought experiment proves nothing. GR predicts that a "cup of neutrinos" will oscillate back and forth; it also unambiguously predicts that gravitational waves are transverse. Therefore, neutrinos oscillating back and forth is not proof that gravitational waves must be longitudinal; a counterexample exists.
More directly: your thought experiment has nothing to do with gravitational waves, it is only sensitive to static gravitational fields. Of course objects will accelerate in the direction of the gravitational field. This has nothing to do with whether the waves are parallel or perpendicular to their direction of propagation.
Note that if you did the same experiment with a test charge and a uniformly charged ball, you'd get simple harmonic motion, but electromagnetic waves are provably transverse: another flaw in your logic.
But we do invest in these areas. How do you think you get a gravitational wave detector in the first place? They don't build themselves you know. And aside from this, you need to have reasons to investigate (and therefore invest) in these technologies - this is an example of a large scale project which has the potential for practical and tangible gains in (as I posted before) laser technologies, control systems, material science and computational anaylsis. These are tangible scientific results in their own right with several industrial applications and assorted spin-off tech companies.
As to how many billions of dollars it takes - quite a lot. But the practical outcomes I've listed are what you get. Along with international co-operation - many countries working together for a common goal.
And another thing. It's gravitational wave detection. Not gravity wave detection, which is something completely different.
Large scale experiments are what research is all about. There comes a point in research where a table-top experiment just won't do.
If you can't think of something nice to say then don't say anything at all. No, REALLY.