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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.
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
Nine thousand and one
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.
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.
This is what's commonly referred to as "overthinking it".
You're given an analogy so you don't have to understand the entire ruleset. If you then attempt to apply the ruleset that the analogy was trying to keep you away from, well...
What a depressingly stupid machine.
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 weaponise it
Fixed with the more likely path.
--- Users are like bacteria -> Each one causing a thousand tiny crises until the host finally gives up and dies.
"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.
And if you can amplify it, then maybe you could weaponise it
So the plan is to make soldiers heavier so they feel fat and too depressed to fight? Fiendish...
Blank until
It's legitimate, but it's also not peer-reviewed.
McFly you bozo. Those boards don't work on water unless you've got POWER! hehehehe
That's from people avoiding hurting their brains. It's also the cause of why people have this image of a black hole being this really deep funnel thingie rather than the actuality (which hurts the brain).
Think Flatland and curved space for a moment.
Mass bends space. The analogy is trying to get you to picture why going in what is to you a straight line is actually following that curve. An extreme example might be thinking about that flatlander finding themself in an extremely curved portion of space- deep within the above funnel for example- and what it would do to their "straight line path."
The hard part is moving that warping from two dimensions to three, and imagining it accurately. That's where the brain hurt comes in. That's why they resort to dragging out that rubber sheet and bowling ball example. There's no invisible gravity analogue making the ball "drop" into the well: it's the ball rolling along in what it thinks is a straight line, only the "floor" it's rolling on is warped, curving it's path.
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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