Gravitational Fields vs Space Curves

BdS

BdS

Registered Senior Member
I’m trying to figure out if gravitational fields and gravity interactions can produces the same results as space curves to cause gravitational attraction.

I keep getting stuck at the gravity field potential at radius x from the source is somehow related to the curve distance x and curve angle or something.


Any chance fields can produce the same results as curves?
 
Without going into the maths of the subject you touched, I do have an unconvential explantion where curvature is gravity. It's been written down in an article called 'Metric Science'.
For a direction of an answer to your question I would have a good look at the chapter 'Gravitation in relation to curvature', it might somehow give you an answer. Though very unconventional physics.
More on http://www.sciforums.com/threads/theory-of-everything.162280/
 
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BdS said:
I’m trying to figure out if gravitational fields and gravity interactions can produces the same results as space curves to cause gravitational attraction.
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They can produce pretty much the same results in most low mass conditions, but the Newtonian "force" gravity breaks down fairly quickly as mass rises, after which it start producing false results.

I assume you have studied the Eddington Experiment? It pretty much clinched Einstein's curved spacetime theory.
 
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BdS said:
I’m trying to figure out if gravitational fields and gravity interactions can produces the same results as space curves to cause gravitational attraction.
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You'll have to define "gravitational fields", "gravity interactions" and "space curves" for me, since I'm not quite sure what you're asking.

The Newtonian picture of gravity uses gravitational fields to describe gravitational attraction, and it works fine in a lot of circumstances. The general relativistic picture of gravity uses curved spacetime to describe gravitational attraction, and it works even better.

I keep getting stuck at the gravity field potential at radius x from the source is somehow related to the curve distance x and curve angle or something.
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Maybe it would help if you posted the relevant mathematics. Show us where, exactly, you're getting stuck.

Any chance fields can produce the same results as curves?
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Newtonian gravity and relativity produce similar results in a lot of cases. Is that what you're asking? What kind of results are you looking for? What are you trying to describe or calculate?
 
One other thing is speed. Although not attraction, Gravitational waves in GR travel at the speed of light. With Newton, the influence of the change of positon of mass would be instantaneous over the field.
According to Newton's theory of gravity, when a mass changes position, the entire gravitational field throughout the universe changes instantaneously, and the resultant gravitational forces are instantly changed accordingly.

But Einstein's Theory of General Relativity - the most commonly accepted description of gravity - asserts that no information can travel faster than the speed of light, including information on the positions of mass in the universe, which is communicated through the gravitational field.,
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https://www.ligo.org/science/GW-GW.php
 
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James R said:
You'll have to define "gravitational fields"
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Umm, didn't they detect gravitation waves a few years ago?
Is the gravitational wave, a wave in the gravitational field?
In relativity is there spacetime curves and gravitational fields/waves? And is that why its different to Newtons field only theory?
Like a magnetic field, but its a gravity field.

DaveC426913 said:
but the Newtonian "force" gravity breaks down fairly quickly as mass rises
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James R said:
The Newtonian picture of gravity uses gravitational fields to describe gravitational attraction, and it works fine in a lot of circumstances.
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Can Newtons field theory be modified to produce the same results as relativity? Why when mass is added does Newtons field theory produce incorrect results? It must be missing something? DM, DE, curves or ?

James R said:
Newtonian gravity and relativity produce similar results in a lot of cases. Is that what you're asking?
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Yes sort of, I was confused because sometimes I read people talking about curves and sometime fields so I was trying to compare them. I didn't think Newton fields and Einstein curves and both are valid under certain conditions, Dave's post linked the correlation for me.
 
BdS:

Roughly speaking, Newtonian gravity is a sort of approximation to general relativity, which works well enough as long as the gravity is not too strong. It is not really possible to modify Newtonian gravity to make it more like GR, because the two descriptions of what gravity is are fundamentally different. Newtonian gravity describes gravity as a force that acts on mass. GR describes gravity as an effect of curved spacetime, that curvature being due to mass (and some other things).

Gravitational waves are really a prediction of GR, not so much Newtonian gravitation.
 
Came across this brilliant youtube on quantum fields while searching. Worth watching.
 
BdS said:
I’m trying to figure out if gravitational fields and gravity interactions can produces the same results as space curves to cause gravitational attraction.

I keep getting stuck at the gravity field potential at radius x from the source is somehow related to the curve distance x and curve angle or something.

Any chance fields can produce the same results as curves?
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1. The speed of the gravitational field is limited, equal to the speed of light c, so there will be a chasing effect between the gravitational field and the object. This effect is similar to the Doppler effect of waves.

2. The time and space described by GR is actually the Doppler effect of the gravitational field
F = (G*M*m/R^2) * (c-v/c)

3. The contribution of the Doppler effect of the gravitational field to Mercury's precession is exactly 43.05" per century.
 
BdS said:
Is the gravitational wave, a wave in the gravitational field?
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Gravity is spacetime geometry.
A gravitational wave is a ripple in spacetime itself...the same as other spacetime geometry caused by massive objects like lensing observations and frame dragging.
 
paddoboy said:
Gravity is spacetime geometry.
A gravitational wave is a ripple in spacetime itself...the same as other spacetime geometry caused by massive objects like lensing observations and frame dragging.
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What you describe is GR's gravitational field model, or space-time model. This is just a physical model.

I am describing the Newtonian model of gravitation, but only amended the Newtonian equation of gravitation.

There must be a Doppler effect between objects with relative speed. Its essence is the chase effect. Both waves and objects have this effect.
 
There must be a chase effect between anything with a finite speed, and we can also call it a relative speed effect.

Mercury's precession 43" allowed GR to establish its position in the scientific community. Using the Doppler effect of the gravitational field, the contribution of Mercury's precession can also be accurately calculated as 43.05". Can this re-establish Newton's status?

Newton's gravitational equation is a gravitational calculation equation when the speed of the gravitational field relative to the object is c. When the speed is not c, continue to use Newton's gravitational equation, there will be a calculation deviation, we must consider the chasing effect between objects.

As a simple example, when the spacecraft moves away from the earth at a speed of c, can the earth's gravitational field still affect the spacecraft?
This question can be answered by elementary school students. They will tell you that the earth's gravitational field cannot catch up with the spaceship.
 
BdS said:
Came across this brilliant youtube on quantum fields while searching. Worth watching.
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Can anyone give me an opinion as to whether the science in this video is completely conventional?

I am especially interested in his description of the magnetic field as being substantative.

Is this just an appeal to a layman's sense of intuition or is that an acceptable way to frame the scientific understanding of the phenomenon.

I have brought this up elsewhere and some people have insisted that the field is simply an array of measurements ,(of ,say a test particle) across a region ...

Others though have insisted that fields as as "real" as you like.

Are both descriptions valid ,complimentary even?

Or is one more correct than the other?

Btw is David Tong respected in his profession? Would he be counted as a foremost popularizer of his subject ,(he is definitely entertaining)?
 
geordief said:
Can anyone give me an opinion as to whether the science in this video is completely conventional?

I am especially interested in his description of the magnetic field as being substantative.

Is this just an appeal to a layman's sense of intuition or is that an acceptable way to frame the scientific understanding of the phenomenon.

I have brought this up elsewhere and some people have insisted that the field is simply an array of measurements ,(of ,say a test particle) across a region ...

Others though have insisted that fields as as "real" as you like.

Are both descriptions valid ,complimentary even?

Or is one more correct than the other?

Btw is David Tong respected in his profession? Would he be counted as a foremost popularizer of his subject ,(he is definitely entertaining)?
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As he is professor of physics at one of the best universities for physics in the UK, and as he is lecturing at the Royal Institution, I would say yes he is respected. Unfortunately the video is an hour long so it's hard to comment on.

But fields are how matter is modelled these days, in QFT, so they are "substantive" in that sense. Also, what happens when you stub your toe on a table leg is a result of mainly electrostatic repulsions between charged wave-particle entities, so electrostatic fields are substantive in that sense too. :biggrin:

P.S. since magnetic fields arise from the effect of relativity on electrostatic fields, then they would be as well.
 
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exchemist said:
P.S. since magnetic fields arise from the effect of relativity on electrostatic fields, then they would be as well.
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Does that imply that if, as a false hypothesis the universe conformed to a Galliliean relativity or even to some privileged frame of reference that magnetism would not be the phenomenon that we know?

Is it a prerequisite for em radiation to have an invariant speed no matter what one's frame of reference for there to be magnetism at all or would it just behave differently?
 
DaveC426913 said:
It's an hour long. :rolleye:
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I think I have already seen that video before (and forgotten the bones of it)

Perhaps I assumed that it was fairly widely known about .....

QFT is just something I know about only vaguely or "diffusely" and ,from that video it seems that the maths involved are extremely complicated ,sometimes very very successful and sometimes mediocrely so.
 
geordief said:
Does that imply that if, as a false hypothesis the universe conformed to a Galliliean relativity or even to some privileged frame of reference that magnetism would not be the phenomenon that we know?

Is it a prerequisite for em radiation to have an invariant speed no matter what one's frame of reference for there to be magnetism at all or would it just behave differently?
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If there were no Lorentz contraction then there would be no magnetism, according to my superficial chemist's understanding. But then we wouldn't have EM radiation either, of course! :biggrin:
 
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