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."

Comments

Possible correlation?

[ma11achy]

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.

Re:Possible correlation?

[Kjella]

Yeah those moments are what you do it for... that and tenure :-)

Tenure is what you get when your experiments go as planned. The Nobel Prize is when they don't.

Re:Possible correlation?

[Paradise Pete]

I thought the Nobel Prize is for when you make up something and get everyone to believe it as fact.

That's an interesting idea you have. If you can convince enough people of it then you could win the Nobel Prize.

Re:Cue the Douglas Adams references!

[feitingen]

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!

I was thrilled, almost panicking when i read that, the amount of jokes i could make would be endless! Then i realized that none of them were actually good jokes.

Gravity wave detectors.

[Therefore I am]

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.

Reflected gravitational waves can be useful

[Anonymous Coward]

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...

Re:Reflected gravitational waves can be useful

[Arimus]

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.

"Indentation in rubber sheet"

[Kupfernigk]

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? Because it would only do so if there was an external gravitational field parallel to the deflection. In the absence of that field the object would presumably travel through the space time deflection with unchanged velocity, whereas 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. In our 3D universe, what form does the curvature take?

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.

Re:"Indentation in rubber sheet"

[vegiVamp]

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...

Re:"Indentation in rubber sheet"

[Anonymous Coward]

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.

Re:"Indentation in rubber sheet"

[William Baric]

No, this is not overthinking it, this is understanding the analogy for what it's worth. The problem is the analogy itself is using the "ruleset" it was trying to keep us away from. This analogy is the modern tortoise. It's not made to make us understand, it is made to make us stop asking questions.

And by the way, no one knows the entire "ruleset". No one really knows what is gravity. So being condescending is not a good idea.

Re:"Indentation in rubber sheet"

[vegiVamp]

You're quite right, on both counts, but if you don't use the kind of analogy that stops questions, you'll never get anything done when teaching people. Terry Pratchett calls this lies-to-children, because the principle is well-used throughout the educational system. You can't really explain to a six-year old that the Sun is a exothermic nuclear fission reaction that pretty much started itself due to the gravity of an increasingly large accumulation of helium, so you tell them it's a big ball of fire in the sky.

The point of this analogy, is to give you an extremely simplified idea of how gravity works by using what you already know, namely that stuff goes down by itself and that a marble on a sheet of rubber will make an indentation, so any other marble close enough to it, will roll down the indentation and get closer to the first one.

If you're at the point where you try to apply the ruleset to the analogy yourself, the analogy has basically become useless for you, and you need to move on to more authoritative sources on the subject for further understanding. And yes, eventually you'll hit the limit of current knowledge, or maybe become the next Einstein - we can only hope :-)

Re:We now know the question to the answer...

[Anonymous Coward]

Adolf Hitroll is trolling. That's not ironic. In any case, please don't reply to trolls.

Re:This is a-posteriori explanation of GP-B issue

[ObsessiveMathsFreak]

Heim Theory predicted such effects in 1950s already.

Yes it probably did. But then again, if you allow your theory to have six or eight or twelve extra dimension, and you allow elementary particles to be "multidimensional structures of space", then I imagine there would be very little effects which you could not in some way predict.

Re:We now know the question to the answer...

[evan_arrrr!]

Actually, we knew the question, too. What do you get if you multiply six by nine?

Re:So...

[Abcd1234]

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...

Re:So...

[Luyseyal]

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

Possible applications

[Stoutlimb]

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?

Re:So...

[evanbd]

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.