BlackHole

No. Gravity waves travel at c. Van Flandern is misrepresenting or misinterpreting the physics.

 

There are other speed of gravity threads.

 

Speed of gravity faster than light?

How fast is gravity?

 

Kopeikin's experiment isn't the only one. There are binary pulsar orbital decay observations' date=' too.[/quote']

 

I also think gravity must propagate at c in vacuum, otherwise mass-energy conservation would be violated (locally).

'']Relativity predicts that gravity moves at c. There have been some experiments done on this, and they agree that gravity seems to move at c.

In 2003 they announced that the speed of gravity is c but i think there was experimental bias. The issue is not completely solved yet.

The speed of gravity is also a problem. According to special relativity no useful information can be transmited faster than light but it appears gravity can.

This does not make sense to me. QM is not some 'real thing' waiting to be discovered, digested and understood. QM is our interpretation[/u'] of observations. You have perpetrated a tautology. Shame on you.

True, all physical theories are our interpretation of nature.

QM is a description of one particle states. To allow particle pair production you need QFT

The problem is with Schroedinger's equation. It is not relativistic, reducing to Newtonian mechanics rather than relativistic mechanics in the correspondence limit.

Many theories fail to explain why matter has mass. They simply don't address it - it doesn't make them wrong.

 

 

The vacuum has no matter' date=' so I don't see the connection to gravity nor to magnetism.

 

The experiments showing modification of the vacuum depends on having conductors to affect the EM fields. Again, what's the connection?[/quote']

 

There is no connection between gravity and magnetism but there might be a deeper analogy between the electroweak interaction and gravitation. In order to do that one has to localize the energy of the gravitational field which has been proven to be a very difficult task.

 

Regards

I'm not sure whether our present understanding of electromagnetism is correct. I'll have to work on Maxwell equations.

According to the BBT, 70% of the universal energy density is in the form of dark energy but no one knows what it is.

No. Evidence supports GR' date=' so gravity behaves as if it is a geometric phenomenon, to the best of my understanding.

 

Gravity does not change its behavior under conditions where magnetism does, e.g. I can shield a region from magnetic field to a very large degree, but the gravity is unchanged in that region - I can't shield gravity.[/quote']

 

But space curvature cannot explain why matter has mass. Matter falls due to it's mass.

 

The source of gravity is the quantum vacuum itself. The vacuum can be visualized as consisting of a sea of virtual electron-positron pairs that can only be released or separated when sufficient energy is made available. This area will benefit from a better understanding than currently available.

I think the most common evidence for such statements is that the poster hasn´t understood both of them so they obviously have something in common.

 

Now seriously: The striking resemblance of electrostatics and gravity (=electrostatics with only positive charges) in the classical theory is rather obvious. So if it´s easy to expand electromagnetism to a covariant form (=in a form that´s suitable for special relativity) one might think that one can apply a similar procedure of generalization to gravity.

 

Now if the resemblance is so strong' date=' shouldn´t this procedure be quite straightforward? Why has noone tried this so far? Will I win a Nobel Prize if I do that?

Well, of course some people allready tried the most obvious approach. But doing so you´ll very quickly find out that there´s one very important difference between electromagnetism and gravity, namely the charge. The electromagnetic charge is conserved under any processes which is a very nice property. The corresponding charge in gravity would be the "relativistic mass" since in contrast to the "rest mass" it´s also a conserved quantity. This charge density, however, has different properties of transformation under coordinate transformations. It transforms like a 00-component of a tensor of 2nd order as opposed to the charge density in electromagnetism which transforms as a 0-component of a vector. That´s the reason why you can´t build a vectorial theory of gravity like the vectorial one of electromagnetism.[/quote']

 

The big difference between gravitation and magnetism is that we don't know of any particle for gravitation, therefore we cannot overemphasize the field theoretic approach like Maxwell did on EM.

Unless you're going to provide evidence, this thread will be closed. Assumptions because you think [/i']something is or is not are not up for discussion.

Depends what you mean by "evidence". In cosmology all observations make use of prior assumptions. I might be able to give mathematical evidence that gravity is not space curvature.

The speculation "something with the quantum vacuum" by itself is basically devoid of any scientific value.

Dr. Swansont, do you agree with me that gravity is not a geometric phenomenon?

That makes absolutley no link to magnetics, other than magnetics is also a force. This has been discussed already

I might be totally wrong here but i think curvature is not the source of gravitation. It's something with the quantum vacuum.

What's the evidence that supports this?

I know it's a half-baked assumption but i think gravity is a force.

I haven't had the chance to read the whole article' date=' but I read enough to know that the author intends to be taken seriously.

 

In the part I read through carefully, he is discussing braking radiation, and comparing light emitted by electrons, when they are accelerated, and comparing inertial accelerations, to gravitational accelerations.

 

I've been aware of a problem there for a very very long time. I'm not sure if he is mathematically saying something I already know, but the very fact that he is thinking about the issue, shows that he understands the location of a problem with the EEP.

 

There is something to his article.

 

Regards[/quote']

 

I was thinking about this. General relativity might be wrong in rejecting gravity as a force. I think it is a force. Gravity and magnetism could be related phenomena. All we need is a vacuum theory.

 

Regards

But it has been demonstrated that gravity deflects light.

I'm not sure that the equivalence principle holds true in all reference frames. From the equivalence principle we get the stress-energy tensor which states that energy gravitates.

Since the earth's center is also the center of mass, gravitation in the center should be zero (the forces cancell out).

However i believe gravity has something to do with the vacuum. If light (or any electromagnetic radiation) is not effected by gravitation then all we need is a vacuum theory.

This is all hypothetical and probably never happens this way.

 

I'm trying to picture a particle that occupies the very centre of gravity for a planet for instance. Is that little particle generating the gravitational pull that is holding the planet together? Why isn't that particle pulled away from the centre by the surrounding mass? Could gravity be pulling in all directions within an object with mass? Seems as if mass doesn't do the attracting but its something else. Can someone clear this up for me? I know you guys/gals have come through before.

In QFT there was an experiment which demonstrated that two parallel laser beams do not interact which made me think that light doesn't really gravitate. On the other hand, two anti-parallel laser beams do interact (for some reason).

Maybe the answer lies in a vacuum theory, but others prefer dark energy, strings and so on.

Do you mean a fourth spatial dimension or a temporal dimension? I imagine space-time as an abstract 4-dimensional sphere but motion takes place only through the three spatial dimensions.

Kind regards

Time dilation is the result of mass-energy conservation. When mass is accelerated toward light speed, physical processes slow down due to mass-energy conservation. Therefore clocks run slower.

The EEP assumes the complete physical equivalence of a gravitational field and a corresponding acceleration of the reference system. I know this principle is supported by many experiments.

But recently i read an unknown article which seems to contradict the equivalence principle. I don't know how seriously to take it. You can read the entire book here.

SR has formulas in v.

 

Differentiate them to give you formulas in a.

 

Then investigate the meaning of the symbolic statements' date=' and decide whether or not the meaning is inconsistent with something you already know. This is a rather complex task by the way.

 

Regards[/quote']

 

I was wrong. Special relativity can handle accelerating reference frames. In special relativity velocities are relative but acceleration is treated as absolute. In general relativity all motion is relative.

[indent']I understand, but what if any measurements taken in a turning frame are indistinguishable from uniform motion? may we apply SRT there?[/indent]

I'm no expert but i think relativity applies only to inertial reference frames. In the case of an accelerating reference frame, special relativity does not apply.

I'd hardly place stars in the same catagories as planets.

 

Nice try coving your mistake' date=' though.[/quote']

 

And you are right. The OP was talking about planets, not about stars.

 

While there are no nuclear reactions taking place in the earth's core, it's a very hot place indeed. That's why the inner core is composed of solid iron.

Any evidence that fusion is actually taking place in planet cores?

Of course nuclear fusion reactions takes place. In the sun's core, four protons or hydrogen nuclei fuse together to form one alpha particle or helium nucleus. The alpha particle is about 7% less massive than the four protons.

The rotating ring is an accelerated frame of reference, while the constancy of the speed of light © applies only in inertial frames of reference (uniform motion).

Planetry cores are definitely not hallow (a vacuum). Actually it's a very dense place. It's where nuclear fusion takes place. Nuclear fusion is a process in which two nuclei join, forming a larger nucleus and releasing or absorbing energy.