Instantaneous communication over light-year+ distances.

[Kalessian]

This is kind of a tangent from the "artifical gravity" thread.

I was reading this part of Chuck's post:

Originally posted by: Woodchuck2000
Gravity is not energy. It is a warping of spacetime related to the mass of a body.

when I realized that not everyone is using the same definition for gravity.

Correct me if I'm wrong, please.

From what I've read, Chuck is right. Gravity is not really a direct expression of some wave or particle, like sound and light are. Instead, it's a physical attribute of space-time... a warping. I can't imagine 3 dimensions being warped, and I don't think anyone can, but it can be understood if you warp a 2-d piece of paper.

We know this for a few reasons. For example, according to relativity, nothing can exceed c. However, experiments have shown that the effect of gravity are instantaneous. If you could somehow introduce a large body of mass somewhere light years away, the second it was created we would all feel its gravitational effects (though they would be slight). Light, on the other hand, would not reach us from this body for years. Hence, gravity must be an attribute of space-time.

So far, we don't know how to communicate faster than that magic number, c. However, if gravity is instantaneous, wouldn't it be possible to send messages with gravity if we could somehow control it?

We would need that artificial gravity generator, of course. Then, we setup some sort of detector in space light years away, which would be very sensitive to gravity. We then pulse the generator, like morse code, and the detector picks up the specially timed pulses and reassembles the code.

How does that idea sound?


I also read something about crystalline resonance making it possible to communicate instantaneously, but I have no idea what that theory is about.

 

[Kalessian]

I'm sorry, I realize that you cannot create a device that's "sensitive to gravity".

Perhaps I meant a very sensitive accelerometer? I'm not sure what could do this.

Obviously, it's possible to detect the change in gravity, since our bodies could do that.

 

[TuxDave]

I honestly never read of an experiment where the effects of gravity is instantaneous. As far as I recall, if the sun vaporized into nothingness, we won't feel its effect for a couple of minutes.

 

[CrispyFried]

i dont recall any experiments about gravity be instantanous either..

 

[EightySix Four]

I can't think of any way to honestly see if it was... you would be limited by the speed of light to notice the changes. PLus how do you spontaneously create gravity to check?

 

[Xyo II]

Originally posted by: TuxDave
I honestly never read of an experiment where the effects of gravity is instantaneous. As far as I recall, if the sun vaporized into nothingness, we won't feel its effect for a couple of minutes.

thats because the light takes a couple of minutes to get here, he's talking about gravity

 

[Xyo II]

oh, and here's the article i was looking for that i didnt even mention:

 

[Kalessian]

Originally posted by: TuxDave
I honestly never read of an experiment where the effects of gravity is instantaneous. As far as I recall, if the sun vaporized into nothingness, we won't feel its effect for a couple of minutes.

Strange, I've always been taught otherwise. It appears that you are correct, however:

From http://www.ldolphin.org/vanFlandern/gravityspeed.html

1. Is gravity caused by a curvature of space and time?

A common way to explain why gravity can appear to act instantaneously, yet still propagate with a delay, is the rubber sheet analogy. (See cover illustration--top of page.) A large mass sitting on a rubber sheet would make a large indentation, and that indentation would induce smaller nearby masses to role toward the indentation. This is an analogy for curved spacetime, which is likewise supposed to be the cause of bodies accelerating toward large masses. The reasoning in the analogy further suggests that target bodies simply respond instantly to the local curvature of the underlying spacetime medium (like the rubber sheet). Therefore, any delay associated with altering that local curvature would not produce aberration, and the target body would appear to respond instantaneously to the source unless the source suddenly changed its motion.

The rubber sheet analogy is represented as a way of visualizing why bodies attract one another. However, in that regard, it is highly defective. A target body sitting on the side of an indentation would stay in place, with no tendency to roll downhill, unless there were already a force such as gravity underneath the rubber sheet pulling everything downhill. And this failure of the analogy helps us identify the precise problem with the curved space-time description of gravity - the lack of causality. Without consideration of why a target body is induced to accelerate through space, and how quickly it receives updates of information about how to accelerate through space, neither the space-time curvature explanation nor the rubber sheet analogy can help us understand why gravity appears to act so much faster than light.

Moreover, contrary to what the rubber sheet analogy implies, an orbiting body such as a spacecraft orbiting the Earth is not following the curvature of space near the Earth. As we remarked earlier, two spacecraft some distance apart in the same orbit could stretch a tether between them and pull it taut, thereby describing a straight line through space different from their orbital path. In more mathematical terms, the supposed curvature of space-time produced by a gravitational field is an effect proportional to the local gravitational potential , the variable part of which is in turn proportional to v2 / c2 ,where V is orbital speed. Yet, orbital curvature through space, like stellar aberration, is proportional to v/c, a much larger effect. For example, for the Earth orbiting the Sun, v/c is of order 10-4, and v2/c2 is of order l0-8. So we see that almost all of the acceleration of bodies through space is not a consequence of the curvature of space. In the GR explanation, the acceleration through space is due to the curvature of "space-time," a mathematical entity not to be confused with the combined separate concepts of space and time.

While relativists have always been partial to the curved space-time explanation of gravity, it is not an essential feature of GR. Eddington (1920, p.109) was already aware of the mostly equivalent "refracting medium" explanation for GR features, which retains Euclidean space and time in the same mathematical formalism. In essence, the bending of light, gravitational redshift, Mercury perihelion advance, and radar time delay can all be consequences of electromagnetic wave motion through an underlying refracting medium that is made denser in proportion to the nearness of a source of gravity. (Van Flandern, 1993, pp. 62-67 and Van Flandern, 1994) And it is now known that even ordinary matter has certain electromagnetic-wave-like characteristics. The principal objection to this conceptually simpler refraction interpretation of GR is that a faster-than-light propagation speed for gravity itself is required. In the context of this paper, that cannot be considered as a fatal objection.

Lastly, we note experimental evidence from neutron interferometers that purports to demonstrate a failure of the geometric weak equivalence principle, that gravity is due to a curvature of space-time. (Greenberger & Overhauser, 1980) This experiment confirmed the strong equivalence principle (local equivalence of a uniform acceleration and a gravitational field), but its results are incompatible with the geometrical weak equivalence principle because interference effects in quantum mechanics depend on the mass. This is because the wave nature of the neutron depends on the momentum of the neutron, which is mass times velocity. So all phase-dependent phenomena depend on the mass through the wavelength, a feature intrinsic to quantum mechanics.

Since the experiment confirms the applicability of quantum mechanics even in the presence of gravity, including this non-geometrical mass dependence, the experiment seems to be a step in the undermining of the purely geometrical point of view, and "tends to bother theorists who prefer to think of gravity as being intrinsically related to geometry," according to the authors.

So I guess the whole curvature thing is wrong. Oh well, time for me to get some updated sources, I suppose.

 

[everman]

Quantum entanglement? I'm not aware of any distance limitation on it, theoretically you could transmit data faster than light speed though I think. It's been a while since I've read anything on it.

 

[illusion88]

How about through a wormhole? Perhaps it's even possible to create a wormhole with energy!

think on this.
Two singularities exist, one near you, and one near the person you are trying to communicate with. Perhaps with our infinatly advanced technology we are able to create these singularites at will.

Heres where it gets crazy. At some moment in time, these two singularities reach out through hyperspace, colide, and destroy eachother producing a wormhole, a tunnel through space. You can then send simple radiowaves through it to the otherside, communicating almost instantaneously. Of corse, we would have to find a way for the two singularities to meet in hyperspace (and we would have to find a way to hold it open )

 

[makken]

If i remember correctly, isn't electricity and magnetism also instantaneous? eg. if you have a sheet of metal and you suddenly introduce a gigantic magnet 2000 miles away, the metal will feel the pull from the magnet instantly

or if you have a negatively charged ball and you suddenly introduce a huge postilvely charged ball 2000 miles away... etc.

 

[Matthias99]

Originally posted by: makken
If i remember correctly, isn't electricity and magnetism also instantaneous? eg. if you have a sheet of metal and you suddenly introduce a gigantic magnet 2000 miles away, the metal will feel the pull from the magnet instantly

or if you have a negatively charged ball and you suddenly introduce a huge postilvely charged ball 2000 miles away... etc.

I'm pretty sure all EM phenomenon propogate at ~c. I didn't major in physics, but they did touch on some of this in the few EE classes I took.

Plus, if EM fields propogated instantly, you could use them to transmit information faster than light. This is the sort of thing that someone *might* have noticed by now.

Quantum entanglement? I'm not aware of any distance limitation on it, theoretically you could transmit data faster than light speed though I think. It's been a while since I've read anything on it.

You can't actually transmit information directly through quantum entanglement (at least IIRC). You *can* use it for quantum cryptography, to securely send a private key to someone -- but you need another communications channel to actually send the message through. Plus, you have to get the particles to the destination first, which currently cannot be done any faster than at the speed of light.

 

[Gravity]

I've never been known for my ability to communicate.

 

[TuxDave]

Originally posted by: Einstein Element

Originally posted by: TuxDave
I honestly never read of an experiment where the effects of gravity is instantaneous. As far as I recall, if the sun vaporized into nothingness, we won't feel its effect for a couple of minutes.

thats because the light takes a couple of minutes to get here, he's talking about gravity

I'm talking about gravity too.

 

[PowerEngineer]

Since electromagnetic radiation is light, its speed of propagtion is limited to the speed of light. The affect that the gigantic magnet has on a sheet of metal 2000 miles away seems instantaenous because it takes an exceedingly small fraction of a second to travel that distance.

Einstein's theory of general relativity predicts that gravity is also limited to the speed of light. This would mean that if the sun were to be somehow instantly wisked out of our universe, that it would be several minutes before both the light and gravity of the sun would simultaneously vanish from our earthly perspective.

 

[Cattlegod]

guys: gravity, light, EM waves ALL travel at the speed of light.

i believe gravitrons were proven in the 90's and someone won the nobel prize for it.

 

[EightySix Four]

QE is instant though?

 

[TheoPetro]

Originally posted by: Cattlegod
guys: gravity, light, EM waves ALL travel at the speed of light.

i believe gravitrons were proven in the 90's and someone won the nobel prize for it.

i could be wrong but i dont think they were proven at all. i had recently spoke to a physics prof about this and he was saying that there still looking for them. we think they have to be there because every other force is quantized so why not gravity. do ya have a link to who proved their existance maby?

 

[dainthomas]

Originally posted by: Matthias99

You can't actually transmit information directly through quantum entanglement (at least IIRC). You *can* use it for quantum cryptography, to securely send a private key to someone -- but you need another communications channel to actually send the message through. Plus, you have to get the particles to the destination first, which currently cannot be done any faster than at the speed of light.

Why not? Doesn't changing the state of one of the particles instantaneously affect the other? This could easily be used for communication.

That's what I tell myself when Obi Wan's talking to the Jedi Council on Coruscant from Kamino anyway.

 

[panipoori]

I dont think gravitrons have been found, although with CERN, physicists might be able to find em.

 

[Matthias99]

Originally posted by: dainthomas

Originally posted by: Matthias99

You can't actually transmit information directly through quantum entanglement (at least IIRC). You *can* use it for quantum cryptography, to securely send a private key to someone -- but you need another communications channel to actually send the message through. Plus, you have to get the particles to the destination first, which currently cannot be done any faster than at the speed of light.

Why not? Doesn't changing the state of one of the particles instantaneously affect the other? This could easily be used for communication.

From what I understand, not quite. While the particles are 'entangled', looking at the state of one immediately tells you what the state of the other one is, but you can't choose the state it is in. And once you have looked at them, they are no longer 'entangled'. So no, you can't transmit information like this.

Plus, you have to get the particles there in the first place.

 

[silverpig]

Originally posted by: Matthias99

Originally posted by: dainthomas

Originally posted by: Matthias99

You can't actually transmit information directly through quantum entanglement (at least IIRC). You *can* use it for quantum cryptography, to securely send a private key to someone -- but you need another communications channel to actually send the message through. Plus, you have to get the particles to the destination first, which currently cannot be done any faster than at the speed of light.

Why not? Doesn't changing the state of one of the particles instantaneously affect the other? This could easily be used for communication.

From what I understand, not quite. While the particles are 'entangled', looking at the state of one immediately tells you what the state of the other one is, but you can't choose the state it is in. And once you have looked at them, they are no longer 'entangled'. So no, you can't transmit information like this.

Plus, you have to get the particles there in the first place.

Pretty much.

Put a black marble and a white marble in a bag. What quantum mechanics basically says is that you really have 2 "grey" marbles in there at any time, each with equal probability of coming out black or white. You and a friend each grab a marble, don't look at it, and then walk away. You go home, and so does he. Still in your hand, the marble you carry is 1/2 black and 1/2 white with equal probability, as is his. The "instantaneous" bit about quantum entanglement works like such:

You open your hand to find a black marble. You instantly know that your friend has a white one. However, this doesn't send any information. It's not like you can tell your friend "I'll go home and if my wife has dinner ready, I'll get the white marble and make sure you have the black one to let you know." You can't signal him in any way using your marble.

 

[MobiusPizza]

Originally posted by: makken
If i remember correctly, isn't electricity and magnetism also instantaneous? eg. if you have a sheet of metal and you suddenly introduce a gigantic magnet 2000 miles away, the metal will feel the pull from the magnet instantly

or if you have a negatively charged ball and you suddenly introduce a huge postilvely charged ball 2000 miles away... etc.

Light is an electrromagnetic wave. Radio waves, microwave, X-rays, Gamma Rays, infra red are all examples of Electromagnetic waves

Electromagnetic waves propogates by a pair of oscillating magnetic field and electric field supporting each other. Since photon, which is a quata of electromagnetic wave, travels at speed of ligh; The converse must be true; that electic field and magnetic field travels at speed of light.

 

[Woodchuck2000]

It's actually been successfully shown that gravity propogates at the speed of light. If the sun were to suddenly disappear then we'd stop measuring its effect at the same time as the sunlight vanished.

Gravitrons are yet to be observed. This is probably because gravitational force is by far the weakest of the forces hence the quanta are very small.

Quantum entanglement doesn't propogate as such - you don't send out some kind of magical signal when you measure the spin of a particle. QE just is. Consider it a disproof of our convential concepts of locality within the universe rather then an FTL phenomena.

 

[BirdDad]

I think he is refering to that experiment where 2 entangled electrons are a galaxy apart.Change the spin of one and the other changes instantaniously.