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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."
Douglas Adams gave us that answer forever ago.
Either that's a scientist's prank or Douglas Adams really was right!
Attention wannabe comedians:
There is a 42 reference in this story. This your cue...this is your chance..the spotlight is on you to bring humor to the world and make countless references to Douglas Adams. Because he mentioned the number 42 in a book!
From the article:
"If there were an obvious interaction between a superconducting films and gravitational waves, wouldn't Gravity Probe B have picked them up somehow?.....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....."
I really do love those moments in science when something you have puzzled over for years may have an elegant answer after all.
Eagles may soar, but weasels don't get sucked into jet engines
Just like the concentric rotating benzels in Carl Sagans book Contact. Maybe he had a gravitational wave resonance thing happening there.
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I'm a leaf on the wind, watch how I soar...
-Lucy-
IANA Physicist but my understanding is that while gravitational waves can be reflected, it does not affect gravity at all. It is akin to having a grid reflect waves on the sea but still letting water flow through it (yes I know, these metaphors suck)
The Wise adapts himself to the world. The Fool adapts the world to himself. Therefore, all progress depends on the Fool.
Eugene Podkletnov has been claiming for some time to have produced gravity shielding using levitated superconducting disks. The scientific community has mostly rejected his work, although NASA was for a time attempting to reproduce it. There's an article on it from a few years back on wired:
This theory has implications that could revolutionize scientific thought across numerous fields. It may even provide some direction for the unified theory people to look in that isn't horribly complex and require inventing 1700 dimensions to make the math work.
Also if people don't understand how large 42 orders of magnitude really is 10 is one order of magnitude. 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000 is 42 orders of magnitude... Granted the numbers they are dealing with are very very small to start with and even 42 magnitudes larger is still pretty damn small this change in scale is mind boggling and shows much more we have to learn about the universe in general and the properties of superconductors in particular.
-Lify
I'll meet you at the intersection of "Should be" and "Reality"
Doesn't this discovery also lead to the possibility of building super-sensitive gravitational wave detectors that really work....... Remember this - If you can't measure a phenomena, you have little hope of truly understanding it.
Martin Tajmar also posits an a-posteriori explanation for the anomalous data from Gravity Probe B based upon Cooper-pair mass in Niobium superconductors in: arxiv.org/abs/0707.3806
Heim Theory predicted such effects in 1950s already. Droscher & Hauser have suggested mechanism based on Heim Theory which was a-priori prediction as commented in the cover story of New Scientist Jan 2006, 3 months before Tajmar's announcement on the ESA homepage.
Here is the latest paper from Droscher & Hauser which gives explanation for outcome of both Tajmar and GP-B experiments.
Personally I like this part:
Numerous experiments by Tajmar et al. were carried out since 2003, and first published in 2006 report on the generation of gravitomagnetic (spacetime twisting) and gravity-like fields (acceleration) in the laboratory. The gravitational effects measured were about 18-20 orders of magnitude larger than predicted by the Lense-Thirring effect of GR. In other words, the rotating niobium ring, having a mass of some 100 grams as utilized by Tajmar et al., produces a gravitational effect similar to the mass of a a white dwarf.
/Joss
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".
While that is definitely true, and an important caveat, the fact that there is a connection at all between electromagnetism and gravity was somewhat unexpected - physicists did expect to eventually unify the theories, but probably not in a way where one affects the other like this. Don't underestimate the importance of this discovery.
Plus, there may be corresponding interactions between, I don't know, petahertz-level magnetic or electric waves (not plain old photons, mind) that have larger, more useful effects on gravity. Maybe. At any rate, the possibility is open now; we're allowed to hope.
If you can reflect it, you can make a curved "mirror" to concentrate it to a single point in space.
If you can concentrate it, you can amplify it.
And if you can amplify it, then maybe you could directly measure its effects (something that has not been done yet)
And once you measure its effect directly, you can compare your results to the various theories (there are plenty)
If you compare results, you can refute some of the current theories, and maybe create others.
Then maybe you can use reflected and concentrated gravitational waves for long-distance communication? or for detecting matter in the farthest reaches of the galaxy...
We then have to ask what happens if you vibrate the semiconductor in a non-uniform but static gravitational field.
The ultimate success would be a gravity shield where we could setup standing waves that nulled out the gravitational field. Even if it turned out that the energy required to do this matched the gravitational potential energy of any object that had it's gravity nulled it would make a fantastic addition to a space elevator, the climbers would now only need to carry enough energy to overcome friction on their way up.
Tim.
God said, "div D = rho, div B = 0, curl E = -@B/@t, curl H = J + @D/@t," and there was light.
IANAP, I am a simple Java writing hack, and I may be too stupid to understand the explanation, but I find the analogy deeply unhelpful. On the other hand, the effect of gravity waves is easily understood; if I was receiving light from an obect travelling towards me and a gravity wave front passed along the line between us, either the light frequency would rise above nominal, fall below nominal and then return to nominal, or vice versa, as our relative velocity momentarily rose, fell and returned to nominal. There is no reflection involved, merely the normal behaviour of wavefronts, though I imagine the actual phenomenon would be more complicated because, of course, a pure single cycle of a sine wave never happens.
From scarped cliff or quarried stone she cries "A thousand types are gone, I care for nothing, no not one."
I understand the difference (the wave is simply a fluctuation of the medium), but are we really sure that gravity is only a curvature? the speed of gravity is not infinite, (IANAP, but from what I have read from various articles) it is the speed of light, so could it be that gravity is a sort of a particle, undetected so far, with properties similar to a photon? i.e. no rest mass, with only kinetic energy.
> This separation causes a polairisation in the material which then relaxes back at some
> point afterwards and emmits a gravity wave.
Seems as though that polarisation should be detectable in principle. It also seems as though one should be able to get a superconducting sheet to emit a pulse of gravitational radiation by applying an electrical pulse.
Warning: this article may contain humor, sarcasm, parody, and perhaps even irony. Read at your own risk.
There's a couple of proofs that P=NP, gravity waves, all these holy grails are in there. I wonder if they should rename this site: "Popular Mechanics Research"
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Yes, as with all classical field theories, when you quantize it you get a gauge boson. In this case it's called the graviton and current (incomplete) quantum gravity formulations have it pop out as spin-2 and massless. Remember kits fields are classical, gauge bosons are quantum mechanical.
McFly you bozo. Those boards don't work on water unless you've got POWER! hehehehe
So if the graviton is massless, how does it interact with matter?
Well, given a photon is massless, yet still interacts with matter, I'm really not sure where the problem is...
Disclaimer : IANAP, IAAMD. And we doctors aren't very renown for our skill in physics...
the analogy requires it to change path so as to lose potential energy and gain kinetic energy as a result of the perpendicular field. So the thought experiment seems to gravity as a deflected rubber sheet into which things fall because of another gravity in an external dimension. To make things worse, the rubber sheet is effectively 2D in a 3D universe.
Well, that's a way to interpret the rubber sheet metaphor and as you point out, it requires a sheet in a higher dimensional space and an additional perpendicular force. As it is enough to have a mental image of beads making turns on a sheet, it seem to be enough when taught in school.
From what I understand, the importance isn't the higher dimensional shape, it's the shapes of the cells on the grid that represent the rubber sheet on the illustration.
Physical bodies aren't bead rolling *on* the sheet. The sheet is the space-time itself. Physical bodies are travelling inside the sheet, crossing cells of the grid.
In the absence of that field the object would presumably travel through the space time deflection with unchanged velocity
And that's what happens. An object is simply going straight ahead, moving from one grid's cell to the next one.
But the 2D universe grid isn't regular as on a flat sheet. Big masses "wrap" the space around them and cells have strange deformed shapes.
It's just handy to paint those deformed cells as a bump.
And the object is simply following the same path as before, but as the cells it "crosses" are weirdly shaped, the point where the object leaves one cell isn't in line with the points where the object left the previous cells.
It follows a straight path, but as the terrain isn't even, the net result is a curve.
In our 3D universe, what form does the curvature take?
It's still a grid. It's now a 3D grid. Composed of small cubic cells. Except that, around big masses, the cells all of sudden aren't perfectly cubic anymore.
Thus if an object was following a subjectively straight path from on cell to the next, seen from the "outside" the path will be curved, because the cells have non-cubic shapes.
I've actually seen one exposition (for 100th anniversary of Einstein's annus mirrabilis) where it was indeed shown that way.
This model is nice because it helps understanding why massless thing such as light still recieve an effect (gravitational lensing) from big masses :
- on the high dimensional rubber sheet it won't work as they won be affected by the perpendicular "extra-gravity".
- but on the grid, they just run straight ahead in the cells and the cells happen to have been shaped into a curve. Thus "seen from far away", the resulting path is a curve. Massless light particle just happen not to make any curve around them on their own.
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Well, the strong force mediators -- the gluons -- are massless too, as are photons (electromagnetism). It turns out mass is not necessary to interact with matter. This is why physicists are so taken with "fields". You can define a number of fields in which a particle participates which are mutually exclusive, but all add up to define where a particle is and what it's doing.
This is why Higgs is so exciting. It's the Higgs field which is supposed to give baryons (normal matter) mass. The general idea is that the Higgs field takes up some of a particle's energy and causes it to give off gravity. The trade-off is that the particle cannot travel at the speed of light. Some people like to think of Higgs as a "dragging field", like a particle slogging its way through mud.
-l
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If gravitational waves can shake a superconducting sheet, will shaking a superconductive sheet create gravitational waves? Wouldn't that open things up to some amazing experiments?
Oh Gravity Probe B, why can't you be more like Gravity Probe A?
How, precisely, do petahertz EM waves differ from photons? Visible light is ~ 1PHz. All EM waves are photons; the only distinction is how obvious it is, which is an artifact of your observation technique and not the photon itself.