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Reflected Gravitational Waves
WSOGMM sends in an arXiv blog post about reflecting gravity waves. The speculation is that reflected gravity could go some ways toward explaining the odd readings being returned by Gravity Probe B. "In the couple of weeks since he introduced the idea that superconducting sheets can reflect gravity waves, Raymond Chiao from the University of California, Merced, has been busy with a couple of buddies working out how big this effect is... Chiao and co. ask how big the effect of a gravitational wave on a thin superconducting sheet is compared to the effect on an ordinary conducting sheet. The answer? 42 orders of magnitude bigger."
Nine thousand and one
I'm a leaf on the wind, watch how I soar...
-Lucy-
IAAP (ok i used to be), and I commend this distinction - its important to realise that gravitational waves are not the same thing as gravity.
Gravity is (from one point of view) just the curvature of spacetime. Its the large sagging indentation in the rubber sheet of spacetime that a massive body creates. Gravitational waves are fluctuations in this curvature, not gravity itself.
The distinction is somewhat akin to acceleration and velocity - consider a car (hurrah!) travelling with a very high velocity, which accelerates very slightly for a short period. If you could reflect the velocity, it would turn around instantly. Reflecting the acceleration however, causes no immediately obvious change. The car's still travelling bloody fast, in the same direction.
The gravitational waves caused by the earth's motion & rotation are so minute that gravity probe b's measurements, taken over a whole year, still took many months of processing before they could even be detected. Gravity waves are far too weak to have any practical purposes, and certainly not in "anti gravity".
You know what's too bad? The anomalous effects in GPB have been explained, peer reviewed, etc, in the final report http://einstein.stanford.edu/content/final_report/GPB_Final_NASA_Report-020509-web.pdf
And, AFAIK, it was "expected" from build imperfections in the spheres, and has nothing to do with gravity waves. Maybe there's something hidden there, but it's probably a very small signal not the huge (compared to the target) wobbling due to the process described there.
how long until
Here is correct link to ariv paper of Dr Martin Tajmar:
http://arxiv.org/abs/0707.3806
/Joss
"Indentation in rubber sheet" I never got that, nor did my physics teacher (who started out as a real physicist.) If we imagine gravity as a deflection in a rubber sheet, why does the object "fall" into it?
The answer is, it doesn't fall onto it. It's called an analogy.
You are thinking of this rubber sheet as existing in our 3 dimensions, when it would better work as a dimension of its own.
If analogies don't work for you, then the technical answer is the objects mass causes the indentation or the 'falling into it' as you say. This mass causes a warp in spacetime, and the warping itself is what we SEE as gravity, not what gravity is however, since that is a force of nature that results from mass (or so it seems) which we can't directly observe yet, we can only observe its effect on things with mass.
Now, WHY mass causes gravity (or the indentation on the sheet, or for the body to 'fall' into said sheet), to give us an effect we can see, we don't know yet. Hopefully this discovery can help us get closer to that understanding.
But the biggest mistake is to think of the object 'falling into' a sheet, since that description itself uses gravity as both the description of the event, and the event itself. They are not at all the same, so there is no magic 2nd gravity field. That 2nd field you are thinking of results 100% from the poor analogy and of course doesn't exist, it just helps some people wrap their mind around the effect in a visual way.
Basically, the falling on a sheet visual seems more helpful to right-brained people, while the maths itself is more helpful to the left brained people.
Neither representation (visual or the maths in the theory) is complete or correct at this point, so both are bound to cause confusion if you are looking for the end-answer.