Gravity speed

[undidly]

What exactly is the problem with gravity ,and any changes in gravity,propagating at any speed,faster or slower than light.
It is not electromagnetic so is not limited by the electrical and magnetic properties of space.
Einstein says so is not an answer.
I ask in the unexplained because mainstream answers are just a repeat of the same old mistakes.
I know about observers who see violations of causality for FTL.Of course they do if they observe at light speed.If they observe at the speed of (or faster than) the effect they are studying then there is no anomaly.

[dryson]

The problem with the observer aspect of dealing with FTL travel is not as complicated as most would like it to be.

The simple answer to the observer aspect of FTL travel is that regardless of distance that you are from the ship traveling faster than the speed of light where the ship may seem to be going slower than the speed of light the constant of the ship traveling at the speed of light will remain the same.

The reason why a ship would seem to be traveling slower than it's actual speed of light is because of the distance between the observer and the ship. We know that light has a velocity and velocity means that the light photon will take a certain amount of time, or the measureable distance between point A or the starting point and B or the projected point of intersection or placement of the light photon on a device used to measure distance, to travel from point A to B.

This means that the closer you are to travel path of the light photon the faster that the photon will pass you, most likely you wouldn't even be able to see the light photon because of how fast the photon is traveling and how close you are to the event.

If your to pull yourself back to a distance where you were able to see the ship which is representing the light photon you would be able to see the ship accelerate to light speed and drop out of light speed. The reason being is that the ship is an object much larger then a light photon and would reflect any amount of light off of it's hull thus allowing the observer to witness the event of traveling faster than the speed of light, but regardless of how far you are away from the ship, even to the point of not being able to see the ship, the ship would have traveled at faster than the speed of light.

[origin]

This means that the closer you are to travel path of the light photon the faster that the photon will pass you, most likely you wouldn't even be able to see the light photon because of how fast the photon is traveling and how close you are to the event.

Wrong - the photon only travels at one speed, c. If the ship is traveling at 99% the speed of light the photons will pass you at c, no matter if the ship is traveling towards you or away from you. This is very basic stuff.

If your to pull yourself back to a distance where you were able to see the ship which is representing the light photon you would be able to see the ship accelerate to light speed and drop out of light speed. The reason being is that the ship is an object much larger then a light photon and would reflect any amount of light off of it's hull thus allowing the observer to witness the event of traveling faster than the speed of light, but regardless of how far you are away from the ship, even to the point of not being able to see the ship, the ship would have traveled at faster than the speed of light.

[yevaud]

As near as I know, there's no problem with gravity whatsoever. *Jumping up and down* Nope, still works fine.

[mabus]

What exactly is the problem with gravity ,and any changes in gravity,propagating at any speed,faster or slower than light.
It is not electromagnetic so is not limited by the electrical and magnetic properties of space.
Einstein says so is not an answer.
I ask in the unexplained because mainstream answers are just a repeat of the same old mistakes.
I know about observers who see violations of causality for FTL.Of course they do if they observe at light speed.If they observe at the speed of (or faster than) the effect they are studying then there is no anomaly.

This article may help http://en.wikipedia.org/wiki/Speed_of_gravity

I've isolated some key quotes which should help answer your question.

The speed of gravity, and of all disturbances, is more often called the speed of light c. Within the well accepted theory of special relativity, the parameter c is not about light, it is a unit conversion factor for changing the units of time to the units of space in a Lorentz transformation. It is then also the only speed which does not depend on the motion of the observer, and equals the speed of gravity and of light and of any other massless particle.

General relativity predicts that gravitational radiation should exist and propagate as a wave at the speed of light.

The speed of gravity can be calculated from observations of the orbital decay rate of binary pulsars PSR 1913+16 and PSR B1534+12. The orbits of these pulsars around each other is decaying due to loss of energy in the form of gravitational radiation. The rate of this energy loss ("gravitational damping") can be measured, and since it depends on the speed of gravity, comparing the measured values to theory shows that the speed of gravity is equal to the speed of light to within 1%

In September 2002, Sergei Kopeikin and Edward Fomalont announced that they had made an indirect measurement of the speed of gravity, using their data from VLBI measurement of the retarded position of Jupiter on its orbit during Jupiter's transit across the line-of-sight of the bright radio source quasar QSO J0842+1835. Kopeikin and Fomalont concluded that the speed of gravity is between 0.8 and 1.2 times the speed of light, which would be fully consistent with the theoretical prediction of general relativity that the speed of gravity is exactly the same as the speed of light.

And finally another article on the subject which may help

http://math.ucr.edu/home/baez/physics/Relativity/GR/grav_speed.html

and http://www.mathpages.com/home/kmath451/kmath451.htm delves into the mathematics of it.


In simple terms, The theory of relativity tells us that Gravity propogates at C. We don't believe it does merely because "Einstein said so", but because the mathematics tells us so. Gravity moving at C is predicted by the mathematical model.
There have been some observational (and disputed) experiments which seem to confirm the prediction.

[ramparts]

On the one hand, it's true that it comes out of the math. This is, of course, a far more satisfactory answer than "Einstein said so" (which no physicist, by the way, will tell you ever, at least not any physicist worth a damn). However, this probably isn't so satisfactory if you don't understand the relevant math - which restricts to everyone but professional physicists and the more advanced students. Here's an answer that might be better: in special relativity, if a signal propagates faster than the speed of light, it's straightforward to show that in some reference frames, that signal actually travels back in time. This has huge problems for causality, the idea that if A causes B, then A had to happen before B. So if gravity travels faster than the speed of light, then it's possible to have object A influence B gravitationally (say, by changing its mass), and then have B react to that (by feeling the change in gravity) before A does anything! The mathematics of special relativity are much easier to understand than general relativity, if you have some basic algebra, maybe a bit of calculus, and some time to put into solving problems and thinking So looking at this question that way could be more helpful.

[undidly]

On the one hand, it's true that it comes out of the math. This is, of course, a far more satisfactory answer than "Einstein said so" (which no physicist, by the way, will tell you ever, at least not any physicist worth a damn). However, this probably isn't so satisfactory if you don't understand the relevant math - which restricts to everyone but professional physicists and the more advanced students. Here's an answer that might be better: in special relativity, if a signal propagates faster than the speed of light, it's straightforward to show that in some reference frames, that signal actually travels back in time. This has huge problems for causality, the idea that if A causes B, then A had to happen before B. So if gravity travels faster than the speed of light, then it's possible to have object A influence B gravitationally (say, by changing its mass), and then have B react to that (by feeling the change in gravity) before A does anything! The mathematics of special relativity are much easier to understand than general relativity, if you have some basic algebra, maybe a bit of calculus, and some time to put into solving problems and thinking So looking at this question that way could be more helpful.

"" Here's an answer that might be better: in special relativity, if a signal propagates faster than the speed of light, it's straightforward to show that in some reference frames, that signal actually travels back in time. This has huge problems for causality, the idea that if A causes B, then A had to happen before B. So if gravity travels faster than the speed of light, then it's possible to have object A influence B gravitationally (say, by changing its mass), and then have B react to that (by feeling the change in gravity) before A does anything.""

NOT before A does anything but before the observer can see A do anything.
IF the observer is observing a FTL event by light then the observer is incompetent.
Of course things appear out of order.
An observer using a method that is at least as fast as the FTL event will see that there is no error of causality.

[ramparts]

How do you observe using a method faster than light? All we have to observe is light. And by definition that can't travel faster than light

There's no such thing as simultaneity when we see the world using relativity. That's one of the most important (and utterly mind-boggling) discoveries that Einstein made in 1905. Let me make this a little bit clearer - and plain weirder: if you send me a signal faster than light, and I send you one back, you can very easily receive that signal before you send the first one. Faster than light information travel is a terrible thing

[tanstaafl76]

There's no such thing as simultaneity when we see the world using relativity. That's one of the most important (and utterly mind-boggling) discoveries that Einstein made in 1905. Let me make this a little bit clearer - and plain weirder: if you send me a signal faster than light, and I send you one back, you can very easily receive that signal before you send the first one. Faster than light information travel is a terrible thing

Sweet, now if I could only get that to work with NetFlix

[undidly]

How do you observe using a method faster than light? All we have to observe is light. And by definition that can't travel faster than light

There's no such thing as simultaneity when we see the world using relativity. That's one of the most important (and utterly mind-boggling) discoveries that Einstein made in 1905. Let me make this a little bit clearer - and plain weirder: if you send me a signal faster than light, and I send you one back, you can very easily receive that signal before you send the first one. Faster than light information travel is a terrible thing

""How do you observe using a method faster than light?""

Use the same method as the receiver of the FTL signal.
We do not yet know how to make the transmitter or the receiver.
Maxwell worked it out for radio and Hertz built it.

"" you can very easily receive that signal before you send the first one. Faster than light information travel is a terrible thing ""

Nonsense .
The FTL observer will "SEE" the transmission,then the reception,then the reply then the reception of the reply in
that order.
Observing by light will mix the order for some observers.They should know this and compensate.
When you observe (HEAR) thunder do you think that the lightning has traveled back in time because
it occurred a few seconds earlier.

[SpeedFreek]

Perhaps I should point out that violations of causality are not due to distant observers having to wait for the light to reach them, they are due to events happening in wrong order in their own frames of reference, which happens when information moves faster than c, due to that information having to move backwards in time, due to the relationship between time, space and c.

So, in your universe, how do time and space work with FTL?

Einstein showed us how c is the fastest that information (including gravity) can propagate. The precession of the perihelion of the orbit of Mercury shows us that Einstein's theory very accurately describes gravity that propagates at c, whereas Newtonian gravity, that is instantaneous, cannot account for Mercury's orbit.

How does FTL gravity account for the observations we already have that imply a speed of c for gravity?

What are you going to show us to make us believe you, rather than Einstein? What would Mercury have to say about it?

[ramparts]

What are you going to show us to make us believe you, rather than Einstein? What would Mercury have to say about it?

I should point out it's not a matter of believing either Einstein or some random guy on an internet forum. It's about the evidence. Thanks in large part to Einstein, we have pretty convincing math in favor of everything SpeedFreek and I have just been saying, and this math is backed up by some exquisite data. I have yet to see any such things from undidly.

[ramparts]

""How do you observe using a method faster than light?""

Use the same method as the receiver of the FTL signal.
We do not yet know how to make the transmitter or the receiver.
Maxwell worked it out for radio and Hertz built it.

Um... you don't seem to understand my question. My problem, sorry. You observe what you observe, regardless of how far it travels. When you observe sound waves, they're travelling at the speed of sound. You're not observing "at" the speed of sound. The sound waves come when they do. There isn't a "method" for observing faster than light. If something travels faster than light, and it's observable (as gravity certainly is), then you'll observe it, without need of some special method.

"" you can very easily receive that signal before you send the first one. Faster than light information travel is a terrible thing ""

Nonsense .
The FTL observer will "SEE" the transmission,then the reception,then the reply then the reception of the reply in
that order.
Observing by light will mix the order for some observers.They should know this and compensate.
When you observe (HEAR) thunder do you think that the lightning has traveled back in time because
it occurred a few seconds earlier.

The mathematics of what I've been saying are pretty standard. I recommend you go do some serious self-study before you run around saying special relativity is wrong.

What's an "FTL observer"? I'm not talking about any observers travelling faster than light. I'm talking about a signal travelling faster than light relative to two observers (one which sends the signal, and one which bounces it back). There's no "observing by light" in this case. The only observations made are those of your superluminal signal - in this case, say, gravity. No light necessary.

[undidly]

""How do you observe using a method faster than light?""

Use the same method as the receiver of the FTL signal.
We do not yet know how to make the transmitter or the receiver.
Maxwell worked it out for radio and Hertz built it.

Um... you don't seem to understand my question. My problem, sorry. You observe what you observe, regardless of how far it travels. When you observe sound waves, they're travelling at the speed of sound. You're not observing "at" the speed of sound. The sound waves come when they do. There isn't a "method" for observing faster than light. If something travels faster than light, and it's observable (as gravity certainly is), then you'll observe it, without need of some special method.

"" you can very easily receive that signal before you send the first one. Faster than light information travel is a terrible thing ""

Nonsense .
The FTL observer will "SEE" the transmission,then the reception,then the reply then the reception of the reply in
that order.
Observing by light will mix the order for some observers.They should know this and compensate.
When you observe (HEAR) thunder do you think that the lightning has traveled back in time because
it occurred a few seconds earlier.

The mathematics of what I've been saying are pretty standard. I recommend you go do some serious self-study before you run around saying special relativity is wrong.

What's an "FTL observer"? I'm not talking about any observers travelling faster than light. I'm talking about a signal travelling faster than light relative to two observers (one which sends the signal, and one which bounces it back). There's no "observing by light" in this case. The only observations made are those of your superluminal signal - in this case, say, gravity. No light necessary.

I wrote SEE in capitals because I did not mean literally to do with light

""There's no "observing by light" in this case. The only observations made are those of your superluminal signal - in this case, say, gravity. No light necessary.""

This is what I have been saying from the start.
OBSERVE (not light ) the superluminal signal and there is no causality problem.Things are in the correct order.

[ramparts]

Hi undidly,

I'm still pretty confused by what you're saying. There absolutely is a causality problem, no matter what you're observing. If I send you a superluminal signal and you send it back to me, then (under certain conditions) I'll receive the signal you send back before I send the original signal. This is, of course, a pretty big problem for causality. This is encoded in cold, hard math and can't really be argued with, and especially not by appealing to classical phenomena like thunder and lightning. If you're familiar with algebra and calculus, I'd be more than happy to point you to references. If not, I'm afraid there's not much I can do that will satisfy your intuitions - special relativity isn't intuitive. But that doesn't mean it isn't right

[undidly]

Hi undidly,

I'm still pretty confused by what you're saying. There absolutely is a causality problem, no matter what you're observing. If I send you a superluminal signal and you send it back to me, then (under certain conditions) I'll receive the signal you send back before I send the original signal. This is, of course, a pretty big problem for causality. This is encoded in cold, hard math and can't really be argued with, and especially not by appealing to classical phenomena like thunder and lightning. If you're familiar with algebra and calculus, I'd be more than happy to point you to references. If not, I'm afraid there's not much I can do that will satisfy your intuitions - special relativity isn't intuitive. But that doesn't mean it isn't right

""I'll receive the signal you send back before I send the original signal. This is, of course, a pretty big problem for causality. ""
I'm sure we agree that ""before I send the original signal"" is impossible.
You seem to be saying "the math is OK so FTL is impossible.
I am saying the math may be wrong and FTL may be possible without the causality problem.
I have asked a few times but no one explains if the results are valid if obtained by dividing by the square root of a negative number as required by the Lorenz formula if applied to FTL.
Maybe the formula is not valid for FTL.
Time goes slower and slower up to C and then ?.

[ramparts]

""I'll receive the signal you send back before I send the original signal. This is, of course, a pretty big problem for causality. ""
I'm sure we agree that ""before I send the original signal"" is impossible.
You seem to be saying "the math is OK so FTL is impossible.
I am saying the math may be wrong and FTL may be possible without the causality problem.

I mean, the math could be wrong in the same way that Barack Obama could be a figment of my imagination rather than the actual President. But I'm pretty sure the enormous celebration on campus last Election Night was real, and I'm also pretty sure the math behind special relativity is rock solid. It's very basic math and has survived over a century of scrutiny without a scratch. If you want to suggest that the math is wrong, I'd ask if you have a reason why, but I know what the answer's going to be

I have asked a few times but no one explains if the results are valid if obtained by dividing by the square root of a negative number as required by the Lorenz formula if applied to FTL.
Maybe the formula is not valid for FTL.
Time goes slower and slower up to C and then ?.

The Lorentz factor does become imaginary for a speed faster than light, because, as you say, you're taking the square root of a negative number. This is one sign that when you go faster than light, bad things happen But that formula has to do with the velocity between two reference frames, not necessarily the signal propagating between them (note, for example, that the Lorentz factor goes to infinity for a signal at the speed of light, but obviously we can discuss light sent between two frames). You can derive what I've been talking about by considering two frames moving at some speed v<c relative to each other, and tracking (through the Lorentz transformations) three events (the sending, relay, and final reception of the signal) in both frames.

[harper05]

Hi undidly,

The math concepts explained are definitely not wrong.. However there are probably other ways to transfer information "FTL". Some of the ways we have pondered deal with "entanglement" google that. Also teleportation of qubits. Or photon teleportation. These do not violate causality for very specific reasons.

And does anyone know what was to come of Dr. Wangs little cesium chamber experiment? From what I can remember he shot a photon into a chamber of super cooled cesium gas. Before the photon had finished entering the chamber it was projected out the other side and detected some 60 ft away. This did not seem to violate causality, but I havent seen any peer review criticism since it happened.. At least I cant find it, only the original articles from early 2000, 2001. Thanks

[ramparts]

Not sure what experiment you're referring to, but you make a good point - it's information which can't travel faster than light. There are loopholes when there is no transfer of information. This is why, for example, there's no problem with the universe expanding faster than the speed of light, as has come up in other threads around here recently.

[harper05]

Superluminal Phenomena,

My understanding here is, physical phenomena, where the speed of
information, and energy transfer, is higher than light speed, exist. Furthermore have been observed in lab. experiments.

(P. Eckle, A. N. Pfeiffer, C. Cirelli, A. Staudte, R. Dörner, H. G. Muller, M. Büttiker, U. Keller,
Attosecond Ionization and Tunneling Delay Time Measurements in Helium, Science,
Vol. 322. no. 5907, pp. 1525 – 1529 (2008))

Experiment from which they conclude that an electron can tunnel
through the potential barrier of an He atom in practically no time was carried
out in 2008. One conclusion here is (though not mine, and prob. disproved by the gravitational interactions of GRB's discovered recently) that electron can be understood as an
energy transfer via "quanta of space" and so its speed is infinite.

Some have also used "quanta of space" as a medium to describe the speed of gravity as instantaneous. (Wich also may be disproved by the gravitational interactions of GRB's discovered recently.) in ref. to the speed of gravity, not quanta of space.

Here is another, a different, photon teleportation exp.
http://news.bbc.co.uk/2/hi/3576594.stm

this is a usefull explanatory piece,
http://cerncourier.com/cws/article/cern/28175

this exp. is very cool!
http://www.sciencedaily.com/releases/20 ... 141137.htm

My Conclusion is,
Quantum information transfer, and quantum energy transfer, via particles
have a light speed. finite speed. "c"
Quantum information transfer and quantum energy transfer, (tunneling, entanglement, teleportation)
via "x" are immediate. Or have infinite speed.
where x = unknown

note: When physicists say "teleportation", they are describing the transfer of key properties (like spin) from one particle to another, without a physical link. My understanding is the transfer of key properties is indeed information, as it could be used to transfer say dialogue or data, actual information.