Thread: Gravity, light, and mass

i was watching this thing yesterday and it was saying how gravity moves at the speed of light. light has no mass, so gravity has no mass? so mass affects gravity? does mass affect light? can someone please tell me whats right or wrong with this and make sense of it all?

this is what i watched
http://www.youtube.com/watch?v=tpbGuuGosAY

Originally Posted by Darth Lord Sidious

i was watching this thing yesterday and it was saying how gravity moves at the speed of light. light has no mass, so gravity has no mass? so mass affects gravity? does mass affect light? can someone please tell me whats right or wrong with this and make sense of it all?

this is what i watched
http://www.youtube.com/watch?v=tpbGuuGosAY

One thing at a time. :wink:

1. Yes, the effects of gravity moves at the speed of light. Gravity, itself, does not seem to move but the hunt IS on for gravitational waves.

2. Correct - gravity has no mass.

3. No, mass does not affect gravity - gravity is a effect generated by mass.

4. No, gravity does not effect light directly. It can bend the path of light by bending the space-time surrounding a body with sufficent mass. Only the path the light must follow is affected, not the light itself.

Nice answer, Old Geezer. I've found this webpage about the measurement of the speed of gravity:

http://www.newscientist.com/article.ns?id=dn3232

And here's an alternate take on the speed of gravity:

http://metaresearch.org/cosmology/speed_of_gravity.asp

It's kind of a long read, but its interesting and it raises some questions from a point of view I think cannot be easily dismissed. It's legtimate physics also, as it's been linked from several establishment physics sites I've looked at.

Originally Posted by StarMountainKid

Nice answer, Old Geezer. I've found this webpage about the measurement of the speed of gravity:

http://www.newscientist.com/article.ns?id=dn3232

And here's an alternate take on the speed of gravity:

http://metaresearch.org/cosmology/speed_of_gravity.asp

It's kind of a long read, but its interesting and it raises some questions from a point of view I think cannot be easily dismissed. It's legtimate physics also, as it's been linked from several establishment physics sites I've looked at.

Thank you.

I'll comment just briefly on the information in that second link. The most obvious thing, of course, is that what's presented in the first link makes it quite clear that the second one is in error. :wink:

I saw several other distinct errors in that second write-up. One glaring mistake is that the author clearly doesn't understand the use of rubber-sheet geometry in describing curved space-time. He actually stated it in reverse - saying that the curved space is what causes gravity!! And after coming across that, I simply stopped reading.

Hi Old Geezer,
If you read the complet page I think the author brings up some interesting objections of the standard (GR) understanding of gravity. Ayway, in a sense I think both descriptions are correct. Mass is the cause of curved space, and curved space is the cause of gravity, or at least gravity's effect. And I would say gravity's effect is gravity.

One of the objections this author has about this is that if the speed of gravity is equal to the speed of light, then how do explain the seemingly instantaneous gravitational influences between objects? If two stars are revolving around each other, at each instant each star influences the other's orbit. If gravity travels at some finite speed, the speed of light, there would be a time lag in communicating this information. In other words, how quickly one star recieves updates of information of how to accelerate through space has an effect on its orbit. Orbits become unstable if forces propagate with finite speed.

If gravity propigates at finite speed, its effect from one star would reach the other star at a place behind the 2nd star's current position, as the 2nd star is always in motion and would continually be ahead in space of the gravitional information sent from the other star.

How do binary pulsars anticipate each other’s future position, velocity, and acceleration faster than the light time between them would allow?

Another point is, in the rubber sheet analoby of the curved space description, if we place a ball in a stationary position on the curved rubber sheet, what induces it to begin rolling down the curvature if gravity is curved spacetime and not a force? It would seem to me the ball would continue to just sit there without some force acting upon it to induce it to roll 'down' the curvature. Physicists explain it as "it just does", or it rolls down because this phenomenon is included in the GR theory.

So, there is the Standard Model which is generally accepted, but the SM is not 100% complete, and I think there can be legitimate objections to it, or parts of it.

Originally Posted by StarMountainKid

Hi Old Geezer,
If you read the complet page I think the author brings up some interesting objections of the standard (GR) understanding of gravity. Ayway, in a sense I think both descriptions are correct. Mass is the cause of curved space, and curved space is the cause of gravity, or at least gravity's effect. And I would say gravity's effect is gravity.

One of the objections this author has about this is that if the speed of gravity is equal to the speed of light, then how do explain the seemingly instantaneous gravitational influences between objects? If two stars are revolving around each other, at each instant each star influences the other's orbit. If gravity travels at some finite speed, the speed of light, there would be a time lag in communicating this information. In other words, how quickly one star recieves updates of information of how to accelerate through space has an effect on its orbit. Orbits become unstable if forces propagate with finite speed.

If gravity propigates at finite speed, its effect from one star would reach the other star at a place behind the 2nd star's current position, as the 2nd star is always in motion and would continually be ahead in space of the gravitional information sent from the other star.

How do binary pulsars anticipate each other’s future position, velocity, and acceleration faster than the light time between them would allow?

Another point is, in the rubber sheet analoby of the curved space description, if we place a ball in a stationary position on the curved rubber sheet, what induces it to begin rolling down the curvature if gravity is curved spacetime and not a force? It would seem to me the ball would continue to just sit there without some force acting upon it to induce it to roll 'down' the curvature. Physicists explain it as "it just does", or it rolls down because this phenomenon is included in the GR theory.

So, there is the Standard Model which is generally accepted, but the SM is not 100% complete, and I think there can be legitimate objections to it, or parts of it.

Her is an alternative explaination that seems to upset a lot of old geezers,
Space is not curved, and light bends around a mass like the sun because both light and the sun emit gravitational waves and it is their inherent property of wave synchronization that not only bends the speeding light but also the force responsible for gravity, ie running the universe.

Originally Posted by StarMountainKid

Hi Old Geezer,
If you read the complet page I think the author brings up some interesting objections of the standard (GR) understanding of gravity. Ayway, in a sense I think both descriptions are correct. Mass is the cause of curved space, and curved space is the cause of gravity, or at least gravity's effect. And I would say gravity's effect is gravity.

One of the objections this author has about this is that if the speed of gravity is equal to the speed of light, then how do explain the seemingly instantaneous gravitational influences between objects? If two stars are revolving around each other, at each instant each star influences the other's orbit. If gravity travels at some finite speed, the speed of light, there would be a time lag in communicating this information. In other words, how quickly one star recieves updates of information of how to accelerate through space has an effect on its orbit. Orbits become unstable if forces propagate with finite speed.

If gravity propigates at finite speed, its effect from one star would reach the other star at a place behind the 2nd star's current position, as the 2nd star is always in motion and would continually be ahead in space of the gravitional information sent from the other star.

How do binary pulsars anticipate each other’s future position, velocity, and acceleration faster than the light time between them would allow?

Another point is, in the rubber sheet analoby of the curved space description, if we place a ball in a stationary position on the curved rubber sheet, what induces it to begin rolling down the curvature if gravity is curved spacetime and not a force? It would seem to me the ball would continue to just sit there without some force acting upon it to induce it to roll 'down' the curvature. Physicists explain it as "it just does", or it rolls down because this phenomenon is included in the GR theory.

So, there is the Standard Model which is generally accepted, but the SM is not 100% complete, and I think there can be legitimate objections to it, or parts of it.

Actually, I did read a few more parts of it. And I'm sorry, but I don't have the time right now to comment on everything you've just raised but I will touch upon this one thing: "Another point is, in the rubber sheet analoby of the curved space description, if we place a ball in a stationary position on the curved rubber sheet, what induces it to begin rolling down the curvature if gravity is curved spacetime and not a force? It would seem to me the ball would continue to just sit there without some force acting upon it to induce it to roll 'down' the curvature. Physicists explain it as "it just does", or it rolls down because this phenomenon is included in the GR theory.


That's not at all as difficult to deal with as one might think. It's because gravity IS a force and it's that force which warps space-time AND produces the gradient that attempts to pull the ball "downward." So it's far from being a case of "it just does" - it fits perfectly with known and understood laws of physics. No magic there.

Originally Posted by "Dr. C. Michael Turner[/quote

Her is an alternative explaination that seems to upset a lot of old geezers,
Space is not curved, and light bends around a mass like the sun because both light and the sun emit gravitational waves and it is their inherent property of wave synchronization that not only bends the speeding light but also the force responsible for gravity, ie running the universe.

No alternative upsets me. But what I do find to be a bit disturbing is that someone would make such a claim with no supporting evidence whatsoever. That places it entirely within the realm of fantasy.

Dr. C MichaelTurner,
If gravity is a result of the propigation of gravitional waves which are known to travel at the speed of light, then how can orbiting objects instantly correct their paths in their orbits to comply with the gravitational source which they are orbiting, as they must do in order for their orbits not to decay?

Old Geezer,
If gravity is considered as a force, and this force travels at a finite speed, how does this explain the question I have posed in the above paragraph?

You say "gravity IS a force and it's that force which warps spacetime AND produces the gradient that attempts to pull the ball "downward" ". Let's say the ball I described is placed stationary on the gradient. What is the property of the gradient that attempts to pull the ball 'downward'? It can only roll 'down' the gradient if a force is acting on it.

If this force travels at some finite speed there would be some time interval before the force reaches the ball, unless the force is intrinsic with the gradient. Still, if the force and the gradient are considered as one phenomenon, every point in the gradient must be in communication with the source mass. If this communication travels at some finite speed, then again how do you explain the question in my first paragraph?

IMO; gravity, wave or not requires a source (matter) and remains part of that matter until the matter is gone. Energy from the time its emitted is its own entity, no longer having anything to do with the source. it will travel until absorbed by something if not then for infinity.

if this is correct and both travel at C then the effect of gravity on an object
would be curved appearing to take longer or less than C velocity. on the other hand waves of independent energy having been 8 minutes on there journey are absorbed by the speeding planet in orbit. that energy emitted at the time gravity attraction in its presumed curve which is effecting the planet will just keep going on its way.

this could make either observation correct if both are given supposed speeds in straight or curved, with out considering gravity has travel further.

as for shooting out into space if the sun and its gravity, were to instantly disappear, i don't know. gravity has an effect on all matter in the area. if the total of mass in the solar system, which the sun is now 99.85% of the total mass, was reduced by that %, then Jupiter would become a large % of that new total. it would probably take a little time, but the end results would be all our solar system remains heading in separate directions.

I don't quite agree with Star Mountain's objection that objects in orbit around each other would "miss" each other's gravitational signals if gravity propogated at a finite speed, but there should be some observational evidence to be found in their orbits.

If we have two objects, object A and object B, then object A should be pulled toward where object B was a moment ago instead of where object B is now. Also, object B would be pulled toward where object A was a moment ago.

What observations would this lead to?

It might not change anything at all about what we see. It might make the orbits slightly unstable. It might mean that the two objects orbit at a speed slightly faster or slower than what their masses and distances would normally indicate.

It would be funny if this observation killed dark matter......... wouldn't it?

Originally Posted by StarMountainKid

Dr. C MichaelTurner,
If gravity is a result of the propigation of gravitional waves which are known to travel at the speed of light, then how can orbiting objects instantly correct their paths in their orbits to comply with the gravitational source which they are orbiting, as they must do in order for their orbits not to decay?

Old Geezer,
If gravity is considered as a force, and this force travels at a finite speed, how does this explain the question I have posed in the above paragraph?

You say "gravity IS a force and it's that force which warps spacetime AND produces the gradient that attempts to pull the ball "downward" ". Let's say the ball I described is placed stationary on the gradient. What is the property of the gradient that attempts to pull the ball 'downward'? It can only roll 'down' the gradient if a force is acting on it.

If this force travels at some finite speed there would be some time interval before the force reaches the ball, unless the force is intrinsic with the gradient. Still, if the force and the gradient are considered as one phenomenon, every point in the gradient must be in communication with the source mass. If this communication travels at some finite speed, then again how do you explain the question in my first paragraph?

This has been explained many times before but gravity is not thought to be instantaneous.

Originally Posted by StarMountainKid

Dr. C MichaelTurner,
If gravity is a result of the propigation of gravitional waves which are known to travel at the speed of light, then how can orbiting objects instantly correct their paths in their orbits to comply with the gravitational source which they are orbiting, as they must do in order for their orbits not to decay?

Old Geezer,
If gravity is considered as a force, and this force travels at a finite speed, how does this explain the question I have posed in the above paragraph?

You say "gravity IS a force and it's that force which warps spacetime AND produces the gradient that attempts to pull the ball "downward" ". Let's say the ball I described is placed stationary on the gradient. What is the property of the gradient that attempts to pull the ball 'downward'? It can only roll 'down' the gradient if a force is acting on it.

If this force travels at some finite speed there would be some time interval before the force reaches the ball, unless the force is intrinsic with the gradient. Still, if the force and the gradient are considered as one phenomenon, every point in the gradient must be in communication with the source mass. If this communication travels at some finite speed, then again how do you explain the question in my first paragraph?

As to the question in your first paragraph, you are only assuming it would cause a 'problem' when, it fact, it would not. Both bodies react to the average of the gravitational forces present at any given moment and that maintains harmony and balance in their relative motions.

It may not be common knowledge among the population but that's exactly how calculations are carried out in order to precisely plot the course of spacecraft probes. We already know in advance exactly where the target will be at what time in order to reach it with minimal course corrections (and those are needed primarily only because of minute imperfections in the guidance programs/hardware/timing.)

Now that we're on the subject of orbiting objects, here's and interesting page demonstrating different kinds of possible orbits. Half-way down the page under the heading 'Physics' and starting with "exploring orbits with Java", and continuing on through the blue high-lighted subjects.

http://burtleburtle.net/bob/index.html

Well if all goes well with LIGO and GEO 600 we will know the answer to this question shortly ; - )

Originally Posted by X=

Well if all goes well with LIGO and GEO 600 we will know the answer to this question shortly ; - )

Yes - and I'm really looking forward to it!!

Hopefully, they will be able to provide some definitive answers - either yea OR nay and provide real relief for the ideas.

Originally Posted by Old Geezer

Originally Posted by StarMountainKid

Hi Old Geezer,
If you read the complet page I think the author brings up some interesting objections of the standard (GR) understanding of gravity. Ayway, in a sense I think both descriptions are correct. Mass is the cause of curved space, and curved space is the cause of gravity, or at least gravity's effect. And I would say gravity's effect is gravity.

One of the objections this author has about this is that if the speed of gravity is equal to the speed of light, then how do explain the seemingly instantaneous gravitational influences between objects? If two stars are revolving around each other, at each instant each star influences the other's orbit. If gravity travels at some finite speed, the speed of light, there would be a time lag in communicating this information. In other words, how quickly one star recieves updates of information of how to accelerate through space has an effect on its orbit. Orbits become unstable if forces propagate with finite speed.

If gravity propigates at finite speed, its effect from one star would reach the other star at a place behind the 2nd star's current position, as the 2nd star is always in motion and would continually be ahead in space of the gravitional information sent from the other star.

How do binary pulsars anticipate each other’s future position, velocity, and acceleration faster than the light time between them would allow?

Another point is, in the rubber sheet analoby of the curved space description, if we place a ball in a stationary position on the curved rubber sheet, what induces it to begin rolling down the curvature if gravity is curved spacetime and not a force? It would seem to me the ball would continue to just sit there without some force acting upon it to induce it to roll 'down' the curvature. Physicists explain it as "it just does", or it rolls down because this phenomenon is included in the GR theory.

So, there is the Standard Model which is generally accepted, but the SM is not 100% complete, and I think there can be legitimate objections to it, or parts of it.

Actually, I did read a few more parts of it. And I'm sorry, but I don't have the time right now to comment on everything you've just raised but I will touch upon this one thing: "Another point is, in the rubber sheet analoby of the curved space description, if we place a ball in a stationary position on the curved rubber sheet, what induces it to begin rolling down the curvature if gravity is curved spacetime and not a force? It would seem to me the ball would continue to just sit there without some force acting upon it to induce it to roll 'down' the curvature. Physicists explain it as "it just does", or it rolls down because this phenomenon is included in the GR theory.


That's not at all as difficult to deal with as one might think. It's because gravity IS a force and it's that force which warps space-time AND produces the gradient that attempts to pull the ball "downward." So it's far from being a case of "it just does" - it fits perfectly with known and understood laws of physics. No magic there.

Have you ever seen a film of a bridge vibrating due to the resonating of the structure of the bridge with the wind and the bridge colaspes. Where is the curved space in that. It is an example like a singer breaking a glass. It is a function of Harmonic resonation ( Gravity wave synchronization) I know you don't like it or will admit it but your challange has just been answered in a non curved space answer.

Dr. C Michael Turner,
Ok, I'm beginning to understand your concept of gravitational wave synchronization.

Originally Posted by Dr. C. Michael Turner

Have you ever seen a film of a bridge vibrating due to the resonating of the structure of the bridge with the wind and the bridge colaspes. Where is the curved space in that. It is an example like a singer breaking a glass. It is a function of Harmonic resonation ( Gravity wave synchronization) I know you don't like it or will admit it but your challange has just been answered in a non curved space answer.

Now that's just plain silly! Neither of those shows any such thing as you are claiming. (And yes, I've seen the film of the Tacoma Narrows bridge many times.)

It certainly does have to do with harmonic resonation (no capital "H" required, by the way) but your claim about gravity waves in those cases are rather ludicrous. They are the result of physical (mechanical) vibrations and nothing more.

An afterthought: I can't even believe you would try to use those examples. Sorry, but you've answered nothing and only dug yourself into an even deeper hole than before.

Originally Posted by "Dr. C. Michael Turner

Have you ever seen a film of a bridge vibrating due to the resonating of the structure of the bridge with the wind and the bridge colaspes. Where is the curved space in that. It is an example like a singer breaking a glass. It is a function of Harmonic resonation ( Gravity wave synchronization) I know you don't like it or will admit it but your challange has just been answered in a non curved space answer.

So what are you trying to say with this illustration? Are you saying that a gravity wave caused the the bridge failure?

The problem with the bridge analogy is that we're assuming there is a medium for the wave to vibrate in already (the bridge, in this case). How would a gravity wave travel through empty space?

Originally Posted by X=

Originally Posted by "Dr. C. Michael Turner

Have you ever seen a film of a bridge vibrating due to the resonating of the structure of the bridge with the wind and the bridge colaspes. Where is the curved space in that. It is an example like a singer breaking a glass. It is a function of Harmonic resonation ( Gravity wave synchronization) I know you don't like it or will admit it but your challange has just been answered in a non curved space answer.

So what are you trying to say with this illustration? Are you saying that a gravity wave caused the the bridge failure?

You can't be this slow, please look at the principles.

Originally Posted by kojax

The problem with the bridge analogy is that we're assuming there is a medium for the wave to vibrate in already (the bridge, in this case). How would a gravity wave travel through empty space?

You seem to have an open mind, at least not judgemental and that I thank you.
Anyhow I define nothing as non-existence so empty does not mean anything to me. I believe space is something let me be traditional and call it an ether. But I believe it is generated from with in all matter as a point of origin, matter to energy transfer into wave form, the gravitational wave. The basic unit if space unfolded, generated soon after the big bang and continues to be generated by all matter. The area of continously generated gravitational wave is space and the unfolding of the gravitational wave is the essence of time. The Universe is finite and unwinding to an end to the story. My opinion alone.