Speed of gravity

[damocles]

Could that coinside with an exponentially decreasing speed of light? Widly distorting everything from the age of the universe, speed of observed events, and redshift, to atomic clocks and radio-isotope dating?

 

http://www.setterfield.org/recent.h...iftandexpansion

 

No.

 

Setterfield overlooks one basic error in his hypothesis. If ZPE were increasing as he claims the universe would be getting locally hotter. It is not.

 

You have to look elsewhere for a viable hypothesis for the decreasing velocity of c.

 

Here is one possibility you might explore;

 

http://scholar.google.com/url?sa=U&q=http://www.iop.org/EJ/article/1126-6708/2000/11/017/jhep112000017.pdf

 

Understand however that it is a mathematical treatment, that the speed of light is variable only as a property of initial(and extremely short as in time delta and volume inflation constraints) spatial expansion and as the binding forces complete the differentiation, c velocity in a vacuum becomes an observer measured "constant" in reference to "local" space/time.

 

To my knowledge, there is no observational data to support this hypothetical mathematical treatment either, nor have any tested predictions possible from the hypothesis been put forth and tested.

[Qfwfq]

I once spent two hours argueing that sodium metal could be induced to explode on contact with water. The school science teacher in the group insisted it was impossible, and that it would only burn - and he had done the experiments to prove it!

How long ago are you talking about??? :eek2: It's an old trick that every chemist knows. I don't know why on Earth that school science teacher insisted it was impossible. :)

[nkt]

How long ago are you talking about??? :lol: It's an old trick that every chemist knows. I don't know why on Earth that school science teacher insisted it was impossible. :)

He was adamant that Sodium would only fizz, and that you had to use Potassium if you wanted fireworks. Of course, he was only using small bits in a water filled dish in a classroom, whilst I was throwing 1cm cubes on sticks into the river and shooting them with an airgun!

 

However, because he could safely say he had done it dozens of times, he knew it could never explode. Likewise, I had done it dozens of times, and knew it would. Then it comes down to who the crowd sides with, if evidence is unavailable.

 

I was only saying this to show my point, which is that there are different degrees of right for the same situation.

 

In my opinion, gravity is like charge, and cannot be created or destroyed, and so this causes issues when talking about the speed of gravity, since how fast does gravity move? It cannot move faster than light if it is coupled to a mass that cannot exceed the speed of light. However, I don't think it is like that, I think it is instantaneous. This doesn't break the rules, however, as the gravity is already there and acting, as the curve of space-time has already changed.

 

If you model the solar system, you have to (apparently) has gravity as an all pervasive instant force or it goes wrong. Likewise, our planet falls towards where the sun actually is, rather than where it looks like it is when the light gets to us (which is where it was 8 minutes before).

[Erasmus00]

If you model the solar system, you have to (apparently) has gravity as an all pervasive instant force or it goes wrong.

 

Not true. If you use general relativity (which predicts a speed c for gravity) to model the solar system, everything works just fine.

-Will

[Bobby]

In my opinion, gravity is like charge, and cannot be created or destroyed, and so this causes issues when talking about the speed of gravity, since how fast does gravity move? It cannot move faster than light if it is coupled to a mass that cannot exceed the speed of light. However, I don't think it is like that, I think it is instantaneous. This doesn't break the rules, however, as the gravity is already there and acting, as the curve of space-time has already changed.

 

 

Why couldn't gravity be the thing that spreads at C and light propagates through the gravitational field as with T1 = T2 ( 1 + gt/C^2).

 

 

If you model the solar system, you have to (apparently) has gravity as an all pervasive instant force or it goes wrong. Likewise, our planet falls towards where the sun actually is, rather than where it looks like it is when the light gets to us (which is where it was 8 minutes before).

 

Setterfield, or Sutterfield, or whatever his name is trying so sell books based on bad science. First, gravity does not propagate instantely, it travels as C. Secondly, one object does not orbit another object, rather they both orbita the center of gravity between the two objects. Thirdly, calculating the center of gravity is a little hard to explain. Basically it is where the sun and earth WERE, not where they are now. Since this point is somewhere near the sun, the earth is orbiting this point as it was abount eight minutes ago.

[Southtown]

Since this point is somewhere near the sun, the earth is orbiting this point as it was abount eight minutes ago.

That's pretty conclusive if you ask me. Got any links for that data?

[Qfwfq]

He was adamant that Sodium would only fizz, and that you had to use Potassium if you wanted fireworks. Of course, he was only using small bits in a water filled dish in a classroom, whilst I was throwing 1cm cubes on sticks into the river and shooting them with an airgun!

 

However, because he could safely say he had done it dozens of times, he knew it could never explode. Likewise, I had done it dozens of times, and knew it would. Then it comes down to who the crowd sides with, if evidence is unavailable.

 

I was only saying this to show my point, which is that there are different degrees of right for the same situation.

I'd say he was simply wrong and it sounds surprising for a chemistry teacher. Mine were quite aware of it.

 

The airgun isn't really necessary. I've seen it done with water in a medium sized tin. The heat released by the reaction soon ignites the hydrogen. It's a somewhat hazardous thing to try. I don't recommend it.

[Southtown]

I don't think gravity is an entity, but more a characteristic of matter. Trying to understand gravity just leaves me wondering why bodies of matter share their mass with each other. If gravity is a particle than why doesn't matter change over time to reflect the "loss"?

[Bobby]

I don't think gravity is an entity, but more a characteristic of matter. Trying to understand gravity just leaves me wondering why bodies of matter share their mass with each other. If gravity is a particle than why doesn't matter change over time to reflect the "loss"?

 

No one probably knows what gravity "really" is. You can look at gravity as a force propagated by a gravitational field. You can also look at it as a force carrying particle. These particles aren't particles like a baseball, rather they are more like a small bundle of energy.

 

If two bodies of mass share their mass with each other, one body's loss would be the other's gain and vice versa.

[Southtown]

No one probably knows what gravity "really" is. You can look at gravity as a force propagated by a gravitational field. You can also look at it as a force carrying particle. These particles aren't particles like a baseball, rather they are more like a small bundle of energy.

What would be a gravitational field, though, beyond a textbook term? That wouldn't really answer anything by itself. I can see the energy particle, but then one would also wonder at the mechanism for that too, just like in the field scenario. Both are reasonable, but neither defined.

 

If two bodies of mass share their mass with each other, one body's loss would be the other's gain and vice versa.

I see, thanks. I was picturing a body being attracted by a binary pair's center of mass. But I just all-of-a-sudden realized that the center would actually be an addition of forces and not really a "joining" per se. HAHA (brain fart)

[Bobby]

What would be a gravitational field, though, beyond a textbook term? That wouldn't really answer anything by itself. I can see the energy particle, but then one would also wonder at the mechanism for that too, just like in the field scenario. Both are reasonable, but neither defined.

 

 

I see, thanks. I was picturing a body being attracted by a binary pair's center of mass. But I just all-of-a-sudden realized that the center would actually be an addition of forces and not really a "joining" per se. HAHA (brain fart)

 

 

Scientists have never liked whatthey call "Action at a distance". They much prefer an action as a direct result of physical processes. The three usual "actions at a distance" are electric charge, magnetism and gravity. To get around the "action at a distance" problem, scientists posit that the source of the action creates a space around them in such a way that another object within the field will be affected. Did anyone say "Wishy Washy?"

 

Magnetism is a manifestation of electric charge so magnetism is folded into electric charge.

An electric charge affects another electric charge. Whether there is an electric field in the absense of another electric charge is debatable. Likewise, gravity affects another mass. Looking at gravity as Newton saw it, a gravitational field probably wouldn't exist in the absense of another body of mass. Looking at gravity from Relativity's point of view, gravity determines the geometry (shape) of spacetime and would seem to exist in every point of view.

 

A gravitational field could be called a spacetime field with the following definition ==> A spacetime field is an infinite number of points infinitely close together with a means to measure position and time at each point."

[Southtown]

Scientists have never liked whatthey call "Action at a distance". They much prefer an action as a direct result of physical processes. The three usual "actions at a distance" are electric charge, magnetism and gravity. To get around the "action at a distance" problem, scientists posit that the source of the action creates a space around them in such a way that another object within the field will be affected. Did anyone say "Wishy Washy?"

Very interesting info, thanks. I found this at Wiki:

“

According to Albert Einstein's theory of special relativity, instantaneous action-at-a-distance was seen to violate the relativistic upper limit on speed of propagation of information. If one of the interacting objects were suddenly displaced from its position, the other object would feel its influence instantaneously, meaning information had been transmitted faster than the speed of light.”

—

http://en.wikipedia.org/wiki/Action_at_a_distance_%28physics%29

 

Looking at gravity as Newton saw it, a gravitational field probably wouldn't exist in the absense of another body of mass. Looking at gravity from Relativity's point of view, gravity determines the geometry (shape) of spacetime and would seem to exist in every point of view.

So gravitation is either characteristic of matter or space. LOL What I don't understand (thanks to the dreaded van Flandern) is how curved space would initiate motion. I can see how it would distort motion, like slowing an upward bound object and accelerating a falling object. But objects at rest tend to stay that way, right? And an upward toss should come to rest, but not be reversed into a fall, if gravity is simply curved space. The rebuttal I read to this, if I remember right, vaguely stated that energy was not needed to initiate a falling object and that van Flandern was misunderstanding of relativity. What do you think?

[Erasmus00]

I can see how it would distort motion, like slowing an upward bound object and accelerating a falling object. But objects at rest tend to stay that way, right? And an upward toss should come to rest, but not be reversed into a fall, if gravity is simply curved space. The rebuttal I read to this, if I remember right, vaguely stated that energy was not needed to initiate a falling object and that van Flandern was misunderstanding of relativity. What do you think?

 

Its not just warped 2 dimensional space, its warped 4-D space. In 4D everything moves in lines, (a stationary particle travels forward in time.) Now, if the time dimension is warped as well, then this causes motion because the line doesn't stay pointed in the time direction, if this is making any sense.

-Will

[Southtown]

Its not just warped 2 dimensional space, its warped 4-D space. In 4D everything moves in lines, (a stationary particle travels forward in time.) Now, if the time dimension is warped as well, then this causes motion because the line doesn't stay pointed in the time direction, if this is making any sense.

-Will

Yeah I think I get ya. Warped space doesn't cause motion, but warped space + time does. Thanks, Will, that makes sense. Although, I'm not totally clear on the concept of warped time, nor of time as a spacial dimension.

[Bobby]

If one of the interacting objects were suddenly displaced from its position, the other object would feel its influence instantaneously, meaning information had been transmitted faster than the speed of light.”

 

 

This sounds reasonable but it doesn't work this way. Suppose the sun suddenly ceased to exist. This would not be felt by the Earth for about 8 minutes.

 

 

 

 

I can see how it would distort motion, like slowing an upward bound object and accelerating a falling object. But objects at rest tend to stay that way, right?

 

Your understanding is correct. Curved spacetime doesn't initiate motion. An object must already be moving to be affected by a curved spacetime.

 

 

 

And an upward toss should come to rest, but not be reversed into a fall, if gravity is simply curved space.

 

 

IMO curved spacetime is a mathematical gimmick to make gravitational fields easier to use. If you mapped a gravitational field using clocks and rulers, there would be a difference in measurements at different places. The measurements are real. To call the measurements a warped spacetime gives the measurements a physicalness they don't deserve.

 

 

 

The rebuttal I read to this, if I remember right, vaguely stated that energy was not needed to initiate a falling object and that van Flandern was misunderstanding of relativity. What do you think?

 

I think van Flandern is a disgrace. Misstateing something in ignorance can be forgiven. Deliberately misstateing something cannot.

 

The apparent creation of energy in a gravitational field is just that, it is apparent, not real.

Consider someone in a spaceship without windows performing experiments. There would be no changes in energy. It is only when you view one frame of reference from a different one that energy becomes apparent.

[Southtown]

This sounds reasonable but it doesn't work this way. Suppose the sun suddenly ceased to exist. This would not be felt by the Earth for about 8 minutes.

So actions-at-a-distance were only assumed and do not occur?

 

Your understanding is correct. Curved spacetime doesn't initiate motion. An object must already be moving to be affected by a curved spacetime.

Then how would spacetime thinking explain people standing still on the surface of the earth feeling a constant downward pull? Rotation of the earth?

 

IMO curved spacetime is a mathematical gimmick to make gravitational fields easier to use. If you mapped a gravitational field using clocks and rulers, there would be a difference in measurements at different places. The measurements are real. To call the measurements a warped spacetime gives the measurements a physicalness they don't deserve.

Now you're talking my language. :) But then would you say a gravitational field is a property of matter/energy and not space/time?

[Bobby]

So actions-at-a-distance were only assumed and do not occur?

 

 

Then how would spacetime thinking explain people standing still on the surface of the earth feeling a constant downward pull? Rotation of the earth?

 

 

Now you're talking my language. :) But then would you say a gravitational field is a property of matter/energy and not space/time?

 

 

Action at a distance was never assumed, rather it was a problem to be explained by the introduction of fields.

 

 

I don't much care for the idea of a spacetime, but to answer your question, the force represented by a spacetime map would start at the edge of the Earth's gravitational field and extend downward to the center of the Earth.

 

 

I think all scientists would agree that gravity is associated with mass/energy. Spacetime is used as a tool to give shape to a gravitational field. The problem I have with spacetime is it has evolved as if it is something physical that can be measured. Spacetime cannot BE measure, spacetime IS the measurement.