Julian The Apostate
Vyemm Raider
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Yeah its pretty cool. If the sun instantaniously disappeared we would still orbit it like it was still there for approx 7 minutes.
Science!! Fucking magnets, how do they work?
- Thread starter Flunklesnarkin_sl
- Start date
There are some new experiments out there including a new ESA satellite mission that are looking for gravitational waves.
String theorists will go ape shit if any of them find evidence of their existence.
String theorists will go ape shit if any of them find evidence of their existence.
i'm trying to be simple here. I thought that if i also mentioned the Speed of Gravity(Light), the metric expansion of the universe, and all the other factors present when you deal with such enourmous distances, it would have been harder to understand the basic concept i was trying to explain
are you saying they are trying to confirm or not if Gravity is a wave ? and this goes against current String Theory predictions?
As I understand it, if you find waves you also find particles. Most if not everything that behaves like a wave also behaves like a particle simultaneously. Find gravitational waves, find evidence of gravitons. The graviton helps go a long way toward proving string theory in some form or fashion. One of the problems with string theory is with current energy levels it looks like every other proven theory out there, you need much higher levels of energy to see the particles/objects that would help prove that string theory is the more fundamental theory which can be simplified down to all those other existing theories. Gravitational waves/particles are one such object.
Cad
scientia potentia est
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How is it shown that the effects of gravity move at the speed of light? Since gravitation is tied to mass, and mass can't exceed the speed of light (so changes in mass/movements of mass can't exceed the speed of light) how do we prove that the effects of gravity also move at the speed of light?
Lithose
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By predicting how light will bend.
The experiment was conducted by carefully charting how radio waves from the quasar, J08421835, were distorted in the night sky as Jupiter passed through the field of view. In 1999, Kopeikin laid out what Einstein?s theory should predict about the pattern of distortion ? then found that September?s ?once-in-a-decade? alignment should allow for a test of the theory.
He turned to Fomalont, who enlisted the aid of the National Science Foundation?s Very Long Baseline Array, a continent-wide network of radio telescopes. A 330-foot (100-meter) radio telescope in Effelsberg, Germany, was added to the network to increase the accuracy of September?s observations.
?We had to make a measurement with about three times more accuracy than anyone had ever done, but we knew in principle that it could be done,? Fomalont said. Sunspot activity during the observations gave the researchers some cause for concern, but in the end, the data achieved a precision equal to the width of a human hair seen from 250 miles (400 kilometers) away, the researchers said.
If the speed of gravitational propagation were infinite, the apparent position of the quasar should have moved in a perfect circle due to the bending of the radio waves, Kopeikin said. Instead, it inscribed an offset ellipse, shaped roughly as would be expected if the speed of gravity and the speed of light were equal.
There are arguments, but I believe another experiment was done using red shift from some other object which concluded this experiment as valid. This is above what I know/understand, but I read about it a little while ago because the effects of gravities speed are a big part of validating or not validating theories that use extra dimensions (Which was part of Green's book on string theory.)
A simple explanation is instantaneous gravity is equivalent to instantaneous information transfer, which violates the speed of light limitations.
A more theoretical explanation is that all forces need a mediator. Electromagnetisms mediator is the photon, which we know moves at the speed of light. We also know it is massless and thus can attain the highest speed allowable for anything in the universe. Gravity's mediator is the theoretical graviton, which current mathematical theories state must be a spin2 massless particle. Being a massless particle itself would allow it to propagate at the speed of light. In practice it would propagate slower due to the non-zero energy density of space.
A more theoretical explanation is that all forces need a mediator. Electromagnetisms mediator is the photon, which we know moves at the speed of light. We also know it is massless and thus can attain the highest speed allowable for anything in the universe. Gravity's mediator is the theoretical graviton, which current mathematical theories state must be a spin2 massless particle. Being a massless particle itself would allow it to propagate at the speed of light. In practice it would propagate slower due to the non-zero energy density of space.
Cad
scientia potentia est
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If I'm understanding that experiment correctly, they're saying they measured the effect of jupiter's gravity on the quasar's emissions which were lensing around jupiter to reach Earth, correct?
I freely admit to being a non-scientist, but whats the delay (or lack of delay) associated with gravity in this situation thats measurable as less than infinite/speed of light??
iannis
Musty Nester
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Well, they're measuring the bend of the light coming from a known point. That bend is caused by the gravity of jupiter. If gravity were an instantenous force it would have been acting on the light being emitted since the emission and result in a different shape than if gravity were a bounded force acting on the light being emitted once it "got in range".
So in effect, with enough observational resolution, the two different effects would result in two different shapes -- but only one can be true. And that's what the experiment tested for, what shape it made.
At least that's what I took from it. I'm guessing that if you did the same experiment with a different source (like the light bouncing off of one of jupiters moons or something, fuck if I know. An orbiting laser on the far side of jupiter?) that the observed shape would be circular rather than elliptical since the lensing effect IS ongoing from the point of emission.
So in effect, with enough observational resolution, the two different effects would result in two different shapes -- but only one can be true. And that's what the experiment tested for, what shape it made.
At least that's what I took from it. I'm guessing that if you did the same experiment with a different source (like the light bouncing off of one of jupiters moons or something, fuck if I know. An orbiting laser on the far side of jupiter?) that the observed shape would be circular rather than elliptical since the lensing effect IS ongoing from the point of emission.
Lithose
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Iannis has my guess. Essentially that with a big enough data set you should be able to determine what a pattern looks like with instant gravity and what it looks like with light speed--they found a pattern that seemed to obey light speed gravity. But I also don't understand the complexities of it, but whenever I read a physics book written for laymen they mention red shift experiments as being proof of gravity obeying the speed limit--and I trust what they say because the guys who write them seem to know their stuff.
That's a horrible fucking article. They didn't create a universe. They didn't create a multiverse. They created a metamaterial, physical analog in which light behaves weirdly.
gogusrl
Molten Core Raider
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