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Factoid
2004-Mar-22, 11:33 PM
Can gravity be used as a communication tool?

Are there any scientific evidence out there that gravity could be potentially used as a communication tool of the future? If such a tool had existed it would unable communication faster the speed of light...in fact it would seem that it would be instant regardless of the distance). Any ideas? Thanks!

freddo
2004-Mar-22, 11:45 PM
Who says gravity propagates faster than light? :-?

Factoid
2004-Mar-22, 11:47 PM
Who says gravity propagates faster than light? :-?

I thought gravity is instant and always present. No?

TrAI
2004-Mar-23, 12:00 AM
Can gravity be used as a communication tool?

Are there any scientific evidence out there that gravity could be potentially used as a communication tool of the future? If such a tool had existed it would unable(supposed to be "enable"?) communication faster the speed of light...in fact it would seem that it would be instant regardless of the distance). Any ideas? Thanks!

Hmmm... Well, I guess if you managed to modulate your data onto a gravity wave you could transfer it that way, but i guess that would need a system that could, at least partly shield gravity or increase gravity to create the carrier and modulate the data onto it, or perhaps you could play with a couple of black holes, but i don't se how you could impress your data at any usable speed(if at all) at something of that mass... Anyway, the data would still not move faster then light, as far as I know, gravity field propagation is limited to c...

Manchurian Taikonaut
2004-Mar-23, 12:01 AM
I thought gravity is instant and always present. No?
no that Newton thinkings about gravity, Einstein theories says Gravity is the same speed as light, however Anti-gravity might be faster

Taibak
2004-Mar-23, 12:01 AM
Who says gravity propagates faster than light? :-?

I thought gravity is instant and always present. No?

Not necessarily. General relativity allows for the possibility of gravitational waves - and you'd need the waves if you wanted to carry information - but it predicts that those waves propagate slower than the speed of light.

AGN Fuel
2004-Mar-23, 12:19 AM
Can gravity be used as a communication tool?

Are there any scientific evidence out there that gravity could be potentially used as a communication tool of the future? If such a tool had existed it would unable(supposed to be "enable"?) communication faster the speed of light...in fact it would seem that it would be instant regardless of the distance). Any ideas? Thanks!

Hmmm... Well, I guess if you managed to modulate your data onto a gravity wave you could transfer it that way, but i guess that would need a system that could, at least partly shield gravity or increase gravity to create the carrier and modulate the data onto it, or perhaps you could play with a couple of black holes, but i don't se how you could impress your data at any usable speed(if at all) at something of that mass... Anyway, the data would still not move faster then light, as far as I know, gravity field propagation is limited to c...

I agree - I don't see how you could modulate the wave without expending a HUGE amount of energy that could be used to far more easily generate EM radiation. :-k (Mind you, if you could manage it, the energy expense would surely rid the airwaves of ShockJocks & Disco DJ's! May be worth it after all! :lol: )

The wave would not be instantaneous - it would require time to propagate from source to receiver.

Factoid
2004-Mar-23, 12:25 AM
It was actually a sort of precursor to another question.
Let assume we have the technology to go far, far away from
our solar system. Really, really far. What about communication?
How would we effectively communicate with Houston?

Taibak
2004-Mar-23, 12:40 AM
It was actually a sort of precursor to another question.
Let assume we have the technology to go far, far away from
our solar system. Really, really far. What about communication?
How would we effectively communicate with Houston?

I'm not sure you could communicate effectively. While the waves would propagate throughout the universe, at least in theory, you'd need a gargantuan receiver to communicate effectively and you'd need an outrageous amount of energy to produce even a weak signal. Like AGN Fuel said, good old EM radiation would probably be way more effective.

TrAI
2004-Mar-23, 01:16 AM
It was actually a sort of precursor to another question.
Let assume we have the technology to go far, far away from
our solar system. Really, really far. What about communication?
How would we effectively communicate with Houston?

I'm not sure you could communicate effectively. While the waves would propagate throughout the universe, at least in theory, you'd need a gargantuan receiver to communicate effectively and you'd need an outrageous amount of energy to produce even a weak signal. Like AGN Fuel said, good old EM radiation would probably be way more effective.

Yes, that is a good point, the gravity wave detector experiments uses large distances to detect them, as they are not detectable over small distances... It seems much easier to use all the energy to power a extremely high gain transmitter(burst type perhaps?) or a high power laser link, as the propagation speed wouldn't be any higher anyway...

Glom
2004-Mar-23, 11:44 AM
We might build a wormhole.

Maksutov
2004-Mar-23, 12:55 PM
Can gravity be used as a communication tool?

Are there any scientific evidence out there that gravity could be potentially used as a communication tool of the future? If such a tool had existed it would unable(supposed to be "enable"?) communication faster the speed of light...in fact it would seem that it would be instant regardless of the distance). Any ideas? Thanks!

Hmmm... Well, I guess if you managed to modulate your data onto a gravity wave you could transfer it that way, but i guess that would need a system that could, at least partly shield gravity or increase gravity to create the carrier and modulate the data onto it, or perhaps you could play with a couple of black holes, but i don't se how you could impress your data at any usable speed(if at all) at something of that mass... Anyway, the data would still not move faster then light, as far as I know, gravity field propagation is limited to c...

I agree - I don't see how you could modulate the wave without expending a HUGE amount of energy that could be used to far more easily generate EM radiation. :-k (Mind you, if you could manage it, the energy expense would surely rid the airwaves of ShockJocks & Disco DJ's! May be worth it after all! :lol: )

The wave would not be instantaneous - it would require time to propagate from source to receiver.

I'm with you re the Disco DJ's. But the best use would be the "phasing out" of the FCC, allowing for a partial restoration of the First Amendment. Even if the gravity waves were 1/186,000 their normal speed, that would far out pace the brain waves of the FCC bureaucrats and wipe their stems clean (since there's no function in the present but non-functional higher regions, that's all we need to worry about). 8)

Anthrage
2004-Mar-23, 05:04 PM
I always thought that the best way to communicate over long (non-local) distances, would be to come up with some method of exploiting non-local communication. This may sound absurd, but given that quantum computers are not far off, after some time with that technology, we will no doubt learn things that make the concept somewhat less ludicrous.

The speed of light limitation is something that is always considered in the context of travel through space, but the issue of communication is one that is - outside of science fiction at least - seldom discussed. It's one of those things that, no matter how reasonably advanced a civilization is, will be a practical issue that will need to be dealt with. Even now, with our current Mars missions, the issue of communication lag is significant, and that will only increase once we send humans to the red planet.

You can bet that, unlikely ideas or no, a lot of thinking is going to be done about ways to get around this problem - well before faster than light space flight is seriously tackled. If a solution is ever found, my money is on the various quantum loopholes that exist. :)

eburacum45
2004-Mar-25, 09:28 AM
Gravity wave detectors are in development now; they are expected to be able to observe very distant and very ancient gravity events.
http://archive.ncsa.uiuc.edu/Cyberia/NumRel/LIGO.html

The problem with using gravity waves for communication is the difficulty in generating detectable waves; perhaps a pair of neutron stars could be electrically charged, then they could have vibrations induced by variations in the surrounding electical fields; these vibrations could carry data (I think) if done correctly.

Interestingly, some brane theories suggest that gravity waves could carry information into adjoining dimensional planes, whatever form these might take; to oversimplify appalingly, we could use gravity waves to communicate with other universes...

John Kierein
2004-Mar-25, 02:08 PM
In my gravity theory gravity travels at c. It is just the shadow cast by mass in the background radiation field. But Tom Van Flandern believes gravity travels instantaneously; and he produces arguments for this. If he were right you could move a mass and have the force from this motion detected at a distance instanteously and thus communicate instanteously. I disagree with Tom about this.

Conor_M
2004-Mar-25, 04:05 PM
Communicating over large distances is basically out of the question with modern technology - you will always be limited to the speed of light. Of course, we can still consider other alternatives.

Tachyons are a good option, and are always popular in science fiction. Just as we can't travel faster than the speed of light, tachyons can't travel slower than the speed of light. So, getting them to travel at high speeds is no problem. They do it automatically. The only real problem is that tachyons are purely theoretical, and there is absolutely no evidence of their existence.

The other option, has to do with "linked" particles. I've only heard of it once or twice, and so I really can't explain it much. Maybe someone here can say better than I. Some how, to particles can be created that are "linked" together, and anything that changes the state of one changes the state of the other (supposedly) instantly, and independently of distance. But, I don't know too much about, so that's about all I can say.

Grey
2004-Mar-25, 07:34 PM
The other option, has to do with "linked" particles. I've only heard of it once or twice, and so I really can't explain it much. Maybe someone here can say better than I. Some how, to particles can be created that are "linked" together, and anything that changes the state of one changes the state of the other (supposedly) instantly, and independently of distance. But, I don't know too much about, so that's about all I can say.
You can have two particles in an "entangled" state*, and you can show that they do indeed pass information to each other nonlocally (that is, instantaneously). Do a Google search on the EPR Paradox if you want to find out more. However, you can also show that the information is concealed in quantum randomness. The states of the two particles are correlated, and if you look at measurements of a large number of such systems, you can see that they must be communicating, but there doesn't seem to be any way to modulate this in a way that would allow you to communicate.

As an analogy, suppose that you and I each have a magic coin, and if we toss the coins at the same time, they'll always land the same way, no matter how far away we are from each other. But flipping one of the coins over manually doesn't affect the other one at all. It's only if you toss them randomly that they match. So if we compare tables of results, we can see that the coins are "talking to each other" faster than light, but they won't let us use the same mechanism to do so. That's more or less the way these correlated states work.

* Technically, any two particles that have ever interacted can be considered entangled, so this argument pretty much applies to all the particles in the universe. The issue has been described in terms of certain stronger levels of entanglement for which this behavior is easy to calculate, and which has been experimentally verified. So it's kind of like all the particles in the universe are whispering behind our backs, but they won't let us in on the conversation. Seems like a grand joke of the universe to me. :D

informant
2004-Mar-25, 08:25 PM
I think they're talking about us... ;)

tlbs101
2004-Mar-25, 10:22 PM
I had this idea:

Create a stream of quantum-linked photon pairs and split the pairs into 2 different spacial directions (this can be done in the laboratory with current technology). Send both streams into a long, ultra-low-loss fiber optic loop (again, possible with today's technology). Load up each fiber loop with as many (quantum-paired) photons as they can carry (I am talking kiloJoules of energy, here).

Now you can take one of these loops with you some far distance away. To send a message, simply modulate the polarization of the photons in the loop (many commercial products available for this). To receive the message (instantaneously) at the "base" loop, simply observe the bulk changes in polarization (again, possible with current commercial technology).

The only problem with this is there are no lossless fiber optics, polarization modulators, or fiber "Y" connectors, so you might lose your ability to send ANY message at all because you have lost all of your paired photons before you get "far away". That's why I advocated saturating the fiber with paired photons. One thing that would help would be to use photons with energies that the particular fiber would be most transmissive to.

Anthrage
2004-Mar-25, 10:45 PM
This is exactly the type of thing I was talking about. Crazy as it sounds, I think we are going to have some rather incredible breakthroughs in this area in the next 10 to 15 years - especially if we have additional practical motivations for exploring the technology. Which, I hope, we will. :)

JohnOwens
2004-Mar-25, 11:11 PM
That's pretty much exactly what I was considering for eventual instantaneous communications in the future for some SF stuff I might eventually write (referring to what tlbs101 wrote). If I do, though, it would probably be developed after most of the action, sometime around 700-800 years in the future. I've got some interesting possibilities lined up for confusion caused by lightspeed delay. Things can be so much more interesting when you make things difficult for your characters/societies! :wink:

frogesque
2004-Mar-25, 11:38 PM
I suppose in theory any pendulum could be modulated by transducer to vary its lenght as it swings back and forth to create gravity waves with a signal superimposed on the regular vibration because there will be a corresponding (minute) alteration in the Earth's own gravity field as the mass oscillates back and forth.

I can just see the headlines: Andromeda rocks to Earth Gravity FM ! :D

Wiley
2004-Mar-26, 01:14 AM
Even if we could modulate gravity waves, we would be emitting the waves in every direction. This is incredibly inefficient. The simple reflector antenna does an excellent job of sending radio waves in one direction. To send information via gravity waves efficiently, we would also need a method to guide the waves, something analogous to the reflector antenna. So here's the question fellow BABB members: how can we build "gravity wave" guides?

JMV
2004-Mar-26, 02:04 AM
I had this idea:

Create a stream of quantum-linked photon pairs and split the pairs into 2 different spacial directions (this can be done in the laboratory with current technology). Send both streams into a long, ultra-low-loss fiber optic loop (again, possible with today's technology). Load up each fiber loop with as many (quantum-paired) photons as they can carry (I am talking kiloJoules of energy, here).

Now you can take one of these loops with you some far distance away. To send a message, simply modulate the polarization of the photons in the loop (many commercial products available for this). To receive the message (instantaneously) at the "base" loop, simply observe the bulk changes in polarization (again, possible with current commercial technology).

The only problem with this is there are no lossless fiber optics, polarization modulators, or fiber "Y" connectors, so you might lose your ability to send ANY message at all because you have lost all of your paired photons before you get "far away". That's why I advocated saturating the fiber with paired photons. One thing that would help would be to use photons with energies that the particular fiber would be most transmissive to.

That won't work.

It is easy to be misled into thinking that one could use entanglement to send signals faster than the speed of light, in violation of Einstein's special theory of relativity, but the probabilistic nature of quantum mechanics stymies such efforts.

Naturally, many people have wondered if this effect could be used to transmit information faster than the speed of light.
Unfortunately, the quantum rules make this impossible. Each local meassurement on a photon, considered in isolation, produces a completely random result and so can carry no information from the distant location. It tells you nothing more than what the distant meassurement result probabilites would be, depending on what was meassured there.

Andreas
2004-Mar-26, 02:18 AM
Now you can take one of these loops with you some far distance away. To send a message, simply modulate the polarization of the photons in the loop (many commercial products available for this). To receive the message (instantaneously) at the "base" loop, simply observe the bulk changes in polarization (again, possible with current commercial technology).
Wouldn't a big loop be rather inconvenient since you could send only one bit before it becomes useless? That is, unless you could sort out photons and manipulate/measure them in previously agreed on order. Many small loops would be more useful, but certainly not very handy.

dcihsm
2004-Apr-12, 06:09 PM
Take a look at...
http://www.gctspace.com/research/communications.html

Demigrog
2004-Apr-12, 06:59 PM
I had this idea:

Create a stream of quantum-linked photon pairs and split the pairs into 2 different spacial directions (this can be done in the laboratory with current technology). Send both streams into a long, ultra-low-loss fiber optic loop (again, possible with today's technology). Load up each fiber loop with as many (quantum-paired) photons as they can carry (I am talking kiloJoules of energy, here).

Now you can take one of these loops with you some far distance away. To send a message, simply modulate the polarization of the photons in the loop (many commercial products available for this). To receive the message (instantaneously) at the "base" loop, simply observe the bulk changes in polarization (again, possible with current commercial technology).

The only problem with this is there are no lossless fiber optics, polarization modulators, or fiber "Y" connectors, so you might lose your ability to send ANY message at all because you have lost all of your paired photons before you get "far away". That's why I advocated saturating the fiber with paired photons. One thing that would help would be to use photons with energies that the particular fiber would be most transmissive to.

That won't work.

It is easy to be misled into thinking that one could use entanglement to send signals faster than the speed of light, in violation of Einstein's special theory of relativity, but the probabilistic nature of quantum mechanics stymies such efforts.

Naturally, many people have wondered if this effect could be used to transmit information faster than the speed of light.
Unfortunately, the quantum rules make this impossible. Each local meassurement on a photon, considered in isolation, produces a completely random result and so can carry no information from the distant location. It tells you nothing more than what the distant meassurement result probabilites would be, depending on what was meassured there.

More specifically, the polarity of the photon is undefined until it is measured. When it is measured, instantaneously the entangled second photon assumes the opposite polarization angle of the first photon. Unfortunately, as the polarization angle is random, it doesn’t help any because the “receiver” with the second photon has no way to tell whether it is “creating” the angle or if the sender did it. If you send the measured angle via a slower-than-light method you can prove that information did indeed transfer faster than light, but you cannot tell what it was until your slower-than-light data catches up.

This technique so far has yielded ways to tell if fiber optics have been wiretapped, but no FTL communications.

Apparently, one little side effect of the technique, if it did work, would be the ability to send messages back in time. Accelerating one of tlbs101’s loops to a significant fraction of c would put it in a different time frame from its paired loop.

tlbs101
2004-Apr-12, 08:14 PM
I am talking about a loop that is perhaps a kilometer in length (circumference), and to modulate the polarity with the message, forcing the entire loop to become polarized to the modulated signal (as the photons pass through the modulator). The maximum frequency of modulation would be limited by the light-speed of the photons in the refractive media, around the loop.

Because the photons had been paired with their counterparts in the "base" loop, they would also be forced to exhibit a change in polarization. I am not talking about a single photon, here, but billions and billions of them. At the base loop, detectors would indeed "change" the quantum state of the polarization of the photons forced by their distant pairs to a known state, but statistically there should be a majority that follow the forced polarization, thus conveying the message.

The SA articles do not take this into consideration.

Demigrog
2004-Apr-12, 08:52 PM
I am talking about a loop that is perhaps a kilometer in length (circumference), and to modulate the polarity with the message, forcing the entire loop to become polarized to the modulated signal (as the photons pass through the modulator). The maximum frequency of modulation would be limited by the light-speed of the photons in the refractive media, around the loop.

Because the photons had been paired with their counterparts in the "base" loop, they would also be forced to exhibit a change in polarization. I am not talking about a single photon, here, but billions and billions of them. At the base loop, detectors would indeed "change" the quantum state of the polarization of the photons forced by their distant pairs to a known state, but statistically there should be a majority that follow the forced polarization, thus conveying the message.

The SA articles do not take this into consideration.

How would you modulate the polarization? Simply measuring the polarity just gives you a random angle, so modulation would be indistinguishable from noise to the receiver. You also cannot force a specific polarization angle without breaking the entanglement (as far as I know, otherwise we’d have had entanglement based communications decades ago).