Gravity travels through time?

[Enola Straight]

Gravity is a distortion in four dimensional spacetime...length, width, depth, AND TIME.

Does this imply that gravity from a massive body in the present is radiated into the past AND future?

[SirNitram]

Gravity is a distortion in four dimensional spacetime...length, width, depth, AND TIME.

Does this imply that gravity from a massive body in the present is radiated into the past AND future?

Of course.

We, for example, feel the Sun's gravitational field at a point 8 minutes 'downstream'.

(Why? Gravity travels at C.)

Now, what I think you mean, is does gravity influence time? Yes. The most shocking is with black holes, where one can outrun light by orbiting it near the event horizon.

[kojikun]

You try finding a logical explanation for all of this, however, and youll go nuts. figuring out what exactly is a FORCE is fecking impossible.

[Xenophobe3691]

Didn't Einstein say that Gravity was just the warping of Space-Time?

[SyntaxVorlon]

Since space time can be visualized as a grid, all a mass does is bend that grid into itself. It takes a significant amount of mass to do all that much to space time itself.
Gravity is the perception of that twist not the force twisting.

[kojikun]

Einstein and lots of others said that, but the logic doesn't follow. Geometry cannot accelerate anything in any direction without an already existing force. Things don't roll downhill if theres no gravity to pull them down, afterall.

Part of quantum mechanics is that forces are just virtual particles being emitted in every which direction by an object and they just have a higher probability of being on the far side of another object moving towards that object then they do the near side moving away. It works dandilly, but for the explanation of what determines the probability (math isnt a cause, remember) and what actually moves the VPs without them covering the space in between. Ofcourse, its very easy to explain away if we just say that everythings in a big computer.

[kojikun]

Gravity is the perception of that twist not the force twisting.

Can't be. Objects on the skein either follow the gridlines or follow the contours. If they follow the grid lines, then deformations in the skein are imperceptable because everything is skewed equally. If they follow contours something has to be moving in order to be affected, otherwise it just sits there. Countours can't accelerate objects.

[SyntaxVorlon]

Gravity is not the cause it is the effect. The matter is the cause, gravity is an effect of the existance of matter.
If you follow the gridlines, you are light. Light follows the gridlines, but the gridlines are BENT by the existence of matter.
Following the contours means you yourself cause them, as would a golfball on a taut rubber sheet with a bowling ball in the middle, just at a rate that is far greater, in a space far far far far far greater. This is just a misunderstanding from phenomenalogism.
However this:

If they follow contours something has to be moving in order to be affected, otherwise it just sits there. Countours can't accelerate objects.

Is completely wrong. Nothing in the universe ever sits perfectly still. Every piece of matter pulls and is pulled on everything within the reach of light.
Every photon travels along the threads of the skein, in a perfect straight line, it's just that the lines are curved.

Remember, light NEVER accelerates or deccelerates. If there were knots on each thread of the skein and light always passed them at the same rate then gravity would just be pulling the knots further apart or pushing them closer together. Even if pulled apart from eachother and appearing to span more distance, it is not the speed that is greater, it is the distance which has been made smaller due to gravity.

[kojikun]

If you follow the gridlines, you are light. Light follows the gridlines, but the gridlines are BENT by the existence of matter.

Its still irrelevant because if you follow the grid lines, theres no perceived difference. EVERYTHING is skewed equally.

[quote[Following the contours means you yourself cause them, as would a golfball on a taut rubber sheet with a bowling ball in the middle, just at a rate that is far greater, in a space far far far far far greater. This is just a misunderstanding from phenomenalogism.[/quote]

Not quite. Following contours is moving in the same direction relative to the surface youre moving over.

However this:

If they follow contours something has to be moving in order to be affected, otherwise it just sits there. Countours can't accelerate objects.

Is completely wrong. Nothing in the universe ever sits perfectly still. Every piece of matter pulls and is pulled on everything within the reach of light.

Circular reasoning. Curvature doesn't cause acceleration.

Every photon travels along the threads of the skein, in a perfect straight line, it's just that the lines are curved.

If the lines are curved, and the light follows the line, there is no perceived chage. If you curve a line, the destination is the same.

Remember, light NEVER accelerates or deccelerates. If there were knots on each thread of the skein and light always passed them at the same rate then gravity would just be pulling the knots further apart or pushing them closer together. Even if pulled apart from eachother and appearing to span more distance, it is not the speed that is greater, it is the distance which has been made smaller due to gravity.

If gravity is distorting the skein, then the distortion isnt causing the perceived force and thus the distortion is superfluous. Geometry cannot explain forces because two objcets not moving relative to one another will not be affect by the geometry they cause because geometry is just the position of the skein, not motive forces.

[ClaysGhost]

Every photon travels along the threads of the skein, in a perfect straight line, it's just that the lines are curved.

If the lines are curved, and the light follows the line, there is no perceived chage. If you curve a line, the destination is the same.

There are changes. Time delay, redshift, distortion/shear and isotropic scaling/magnification. Enough mass and you will end up with multiple viable (and curved) paths from source to observer. You can go from one to three images of a single object with the appropriate mass distribution. All with the same destination, but each with observably different properties.

If gravity is distorting the skein, then the distortion isnt causing the perceived force and thus the distortion is superfluous. Geometry cannot explain forces because two objcets not moving relative to one another will not be affect by the geometry they cause because geometry is just the position of the skein, not motive forces.

I'm unclear as to what precisely you are referring to when you talk about the "skein". I'd like you to clarify. It seems like you're all taking the rubber sheet analogy very seriously.

[kojikun]

There are changes. Time delay, redshift, distortion/shear and isotropic scaling/magnification. Enough mass and you will end up with multiple viable (and curved) paths from source to observer. You can go from one to three images of a single object with the appropriate mass distribution. All with the same destination, but each with observably different properties.

All of which is irrelevant because I was talking about following grid lines.

I'm unclear as to what precisely you are referring to when you talk about the "skein". I'd like you to clarify. It seems like you're all taking the rubber sheet analogy very seriously.

It's a neat word refering to the fabric of space.

[CJvR]

I might have gotten this wrong but wasn't there recently an experiment conducted that indicated that gravity propagate as the speed of light?

[kojikun]

I might have gotten this wrong but wasn't there recently an experiment conducted that indicated that gravity propagate as the speed of light?

Yep. We detected the gravity of jupiter precisely in line with where the light from jupiter was coming from, and thus determined that gravity was moving at the same speed as light. That means that objects moving through space leave a gravitational wake, a big cone of spreading gravity behind them. The REAL question however is when the gravity source disappears fast enough does the gravity oscillate back and forth between positive and negative values? IE, if an object is moving really fast, or jupiter disappears suddenly, is the gravity wake going to fluctuate or just vanish?

[SyntaxVorlon]

IIRC Gravity has only direction and magnitude, not polarity. I would assume that gravitic waves act in a way that follows normal waves, in that they can have peaks and troughs, though because of monopolar gravity the maginitude would be the absolute value at the peak and trough. We know points exist where gravity is cancelled out. LaGrange points. So if one mapped the LaGrange points and accounted for the wave properties, we could find peak spots of gravity throughout the solar system.

If the object is moving at relativistic speeds then it would produce gravitonic flux for nearby celestial bodies. For a split second a solar system would be accelerated toward the objects vector, though because of the doppler effect it would probably become extremely weak immediately afterwards.

[ClaysGhost]

All of which is irrelevant because I was talking about following grid lines.

I thought objects follow geodesics in spacetime. What are you referring to as gridlines? Lines of what? Constant what?

It's a neat word refering to the fabric of space.

I was hoping you were going to define it, rather than resort to that damn fabric.

[ClaysGhost]

IIRC Gravity has only direction and magnitude, not polarity. I would assume that gravitic waves act in a way that follows normal waves, in that they can have peaks and troughs, though because of monopolar gravity the maginitude would be the absolute value at the peak and trough. We know points exist where gravity is cancelled out. LaGrange points. So if one mapped the LaGrange points and accounted for the wave properties, we could find peak spots of gravity throughout the solar system.

LaGrange points are not a consequence of gravitational waves.
Gravitational waves can be polarised.

[kojikun]

Syntax: We don't know whether gravity has polarity or not tho. It might for all we know, but we won't know because we will never find any natural source of negative gravity because it would have seperated out in the early universe long ago. Then again, that mysterious fource keeping the universe expanding (even accelerating!) might be negative gravity objects pushing on positive gravity objects causing circumferential force which would cause radial 4D force. Also, gravity could be wavelike without there being peaks, because if gravity is caused by mass, the mass is keeping it permanently in one direction, likely holding a guitar string down. Release it, however, and it bounces back and forth because its releasing stored energy.

Clay: Geodesics would be, I am guessing, contour, which is fine, noones saying they done. But that aint the thing thats making us move towards the dents. And I can't define the skein because its just a reference term. My best guess, however, is that its some 4th dimensional object onto which we're stuck. That, or the skein is just a mathematical thing in a giant computer program of which were a part. I like the last one there

[Andrew J.]

Einstein and lots of others said that, but the logic doesn't follow. Geometry cannot accelerate anything in any direction without an already existing force. Things don't roll downhill if theres no gravity to pull them down, afterall.

I think you're taking the "object making a dent in a rubbe4r sheet" a little too literally, kojikun.

[kojikun]

No no, go read about Riemann and the like. Or better yet, buy Michio Kaku's Hyperspace -- it has a whole bunch of chapters on how they tried to use geometry to explain forces because geometry doesnt rely on invisible magic forces.

[ClaysGhost]

Syntax: We don't know whether gravity has polarity or not tho.

Gravitational waves can have polarisation...are you two talking about something else?

It might for all we know, but we won't know because we will never find any natural source of negative gravity because it would have seperated out in the early universe long ago.
Then again, that mysterious fource keeping the universe expanding (even accelerating!) might be negative gravity objects pushing on positive gravity objects causing circumferential force which would cause radial 4D force.

If negative energy had condensed into discrete objects like this you'd expect to see disruptions in galaxies, if you saw galaxies at all. You wouldn't expect (or I wouldn't expect) the acceleration to only appear at great distances, because the condensation into discrete/clumpy masses should exaggerate the effect locally.

Also, gravity could be wavelike without there being peaks,because if gravity is caused by mass, the mass is keeping it permanently in one direction, likely holding a guitar string down. Release it, however, and it bounces back and forth because its releasing stored energy.

Yes. LaGrange points are just the result of superposition of static gravitational fields (well, relatively static fields). Different from a travelling gravitational wave generated by an accelerating mass.

Geodesics would be, I am guessing, contour, which is fine, noones saying they done.

Geodesics are free-fall trajectories in spacetime. If I have your model correctly, then contours in the rubber sheet would be some of the possible geodesics.

But that aint the thing thats making us move towards the dents.

I think you should consider the equivalence principle. Gravitational fields can produce the same effects as non-inertial fields (accelerations of the coordinate system). Non-inertial forces like the centrifugal "force", the coriolis "force" etc are an artefact of the reference frame that you're using. Remember the famous "trolley standing in an unaccelerated train". When the train accelerates, and passengers on the train see the trolley accelerate in the opposite direction, they can't point to any body-body force acting on the trolley. And as far as someone on the track is concerned, the trolley isn't accelerating at all (these are obviously perfect, frictionless castor-wheels, the kind that exist only in physics exams..).

So, forces that appear and disappear depending on what reference frame you're in. Are they caused by virtual particles too? If it's not clear already, I'm wary of this whole "gravity from quantum mechanics" thing. At least GR is testable now, and has passed tests applied to it.

And I can't define the skein because its just a reference term. My best guess, however, is that its some 4th dimensional object onto which we're stuck. That, or the skein is just a mathematical thing in a giant computer program of which were a part. I like the last one there

Someone once asked me what I meant by the "fabric of spacetime" and I realised that I was assuming its definition. I think of the "fabric" as a collection of free-fall trajectories in space. Distortions in the "fabric" are actually alterations in these free-fall trajectories (geodesics). No "forces" act directly - instead, gravitational fields alter the set of reference frames in which a body experiences no non-inertial forces, and hence the free-fall path of that body.

I'm not a fan of the computer program thing. You can end up transferring what you don't know in physics to a computer science problem, or more likely to the Wachowski brothers.

[Enola Straight]

Okay, the light we see from the sun was emitted 8 1/2 minutes ago; if gravity travels at c then it also was emitted 8 1/2 min ago, too; radiation from the past to the future.

If Gravity is 4D, can it radiate from the Future to the Past?

[SirNitram]

Okay, the light we see from the sun was emitted 8 1/2 minutes ago; if gravity travels at c then it also was emitted 8 1/2 min ago, too; radiation from the past to the future.

If Gravity is 4D, can it radiate from the Future to the Past?

There's some babbling on this in Manifold: Space, on the subject of... Oh damn, I've forgotten... Square Roots have both a positive and negative answer? Or was it some other peice of math? You can see how on the ball I am today...

In short, it's possible things can radiate backwards as well as forwards, but we've not seen it.. yet.