Theory of Gravity

[fredreload]

So gravity is described by General relativity as the bending in spacetime. The moon circles around the earth also because of gravitational force based on Newton's Theory of Gravitation. But is the moon's gravity caused by earth's bending of spacetime? Gravity feels more like radio waves to me then the bending of spacetime

[StringJunky]

So gravity is described by General relativity as the bending in spacetime. The moon circles around the earth also because of gravitational force based on Newton's Theory of Gravitation. But is the moon's gravity caused by earth's bending of spacetime? Gravity feels more like radio waves to me then the bending of spacetime

They are two separate theories. Both the Moon and Earth attract each other.

 

 

 

Gravity feels more like radio waves to me then the bending of spacetime

Relativity and Newton's are the only theories that are empirically supported. Scientists are working on a theory of quantised gravity (gravitons) where virtual particles are exchanged but it has not yet come to fruition.

[ajb]

But is the moon's gravity caused by earth's bending of spacetime?

As the Moon itself have mass (energy) it does act as a source of gravity, it curves space-time itself. However, in basic treatment we assume that the Moon is a 'test particle' moving in the space-time curved by the Earth. By test particle we mean that it is acted upon by gravity but does not act as a source of gravity.

 

In full, one has to model the two bodies together, but as general relativity is highly non-linear this is not an simple task.

 

 

 

Gravity feels more like radio waves to me then the bending of spacetime

In what sense? There are lots of formal similarities between general relativity and electromagnetic theory, so what you say maybe okay. But as it stands I do not know what you are actually saying.

[fredreload]

Well, that means the sun would have to bend spacetime as far as Neptune for all nine planets to orbit around it. I find that hard to believe. Higher mass planet is able to catch on sun's gravity, sort of like how God particle give other particle mass

[ajb]

Well, that means the sun would have to bend spacetime as far as Neptune for all nine planets to orbit around it.

Gravity is a long range force so the influence of the Sun goes on forever... but of course it is swamped by other sources after some point.

 

One defintion of the Solar System is in terms of the objects for which the Sun is the main gravitational influence: that is estimated to be something like about two light years! (Though by Solar System we usually mean up to the Oort cloud ~ 50,000 AU )

 

 

I find that hard to believe.

Okay, but we have the mathematics and observations that tell us gravity is a long range force.

 

 

Higher mass planet is able to catch on sun's gravity, sort of like how God particle give other particle mass

I do not quite understand this statement. And by 'God particle' you mean the Higgs field?

 

I do not see a direct link between the Higgs mechanism and planets being influenced by the Sun.

[swansont]

Well, that means the sun would have to bend spacetime as far as Neptune for all nine planets to orbit around it. I find that hard to believe. Higher mass planet is able to catch on sun's gravity, sort of like how God particle give other particle mass

You can accept one description of an influence that has unlimited range, but not another? That's irrational.

[fredreload]

Gravity is a long range force so the influence of the Sun goes on forever... but of course it is swamped by other sources after some point.

 

One defintion of the Solar System is in terms of the objects for which the Sun is the main gravitational influence: that is estimated to be something like about two light years! (Though by Solar System we usually mean up to the Oort cloud ~ 50,000 AU )

 

 

 

Okay, but we have the mathematics and observations that tell us gravity is a long range force.

 

 

 

I do not quite understand this statement. And by 'God particle' you mean the Higgs field?

 

I do not see a direct link between the Higgs mechanism and planets being influenced by the Sun.

 

Yes the influence of the gravity from the sun goes a long way on object of different mass. If you do the Newton's gravitation's calculation it should work out here. My focus is that I don't think the spacetime in Neptune is bent by the sun. So when the mass increases it seems the planet picks up the gravitational force from the other mass based on the equation. But how does the planet picks up the gravitational force? Like a magnetic field exerting current on a wire, speculation

Edited May 21, 2016 by fredreload

[swansont]

What you think is less important than what you can demonstrate. The fact is that GR extends just as far as Newtionian gravity.

[elfmotat]

 

Yes the influence of the gravity from the sun goes a long way on object of different mass. If you do the Newton's gravitation's calculation it should work out here. My focus is that I don't think the spacetime in Neptune is bent by the sun.

 

Newtonian gravity is an approximation of General Relativity when gravity is weak and objects are moving slowly compared to light. So, obviously, they need to agree on the range of gravity. If Newtonian gravity's range is infinite, GR's range must also be infinite. Whether or not you think it's true is irrelevant to whether or not it's actually true.

 

 

Like a magnetic field exerting current on a wire, speculation

 

What speculation? Electromagnetism is described by 1) field equations which describe how the EM-field behaves, and 2) an equation of motion which describes how objects behave when they interact with the field. Similarly, GR is described by field equations and an equation of motion. There is no speculation -- observation fits these models.

[fredreload]

 

Newtonian gravity is an approximation of General Relativity when gravity is weak and objects are moving slowly compared to light. So, obviously, they need to agree on the range of gravity. If Newtonian gravity's range is infinite, GR's range must also be infinite. Whether or not you think it's true is irrelevant to whether or not it's actually true.

 

 

 

What speculation? Electromagnetism is described by 1) field equations which describe how the EM-field behaves, and 2) an equation of motion which describes how objects behave when they interact with the field. Similarly, GR is described by field equations and an equation of motion. There is no speculation -- observation fits these models.

Well, r^2 can really reduce the force acting by m1 and m2 according to the Newtonian description. I agree that you cannot plug in an infinite value for either of the masses. Right well the mass creates a field which produce gravity acting on the other masses, speculation

[elfmotat]

Well, r^2 can really reduce the force acting by m1 and m2 according to the Newtonian description.

 

What do you mean? Are you under the impression that spacetime curvature is not dependent on your distance from a gravitational source? Because it is.

 

I agree that you cannot plug in an infinite value for either of the masses.

 

While this is true, I'm not sure how it's relevant. I never said anything of the sort.

 

Right well the mass creates a field which produce gravity acting on the other masses, speculation

 

No, not speculation, fact. This is what we observe.

[ajb]

Yes the influence of the gravity from the sun goes a long way on object of different mass.

 

If you do the Newton's gravitation's calculation it should work out here.

Formally the influence of gravity is infinite in range.

 

 

My focus is that I don't think the spacetime in Neptune is bent by the sun.

In Neptune or around Neptune?

 

So when the mass increases it seems the planet picks up the gravitational force from the other mass based on the equation. But how does the planet picks up the gravitational force? Like a magnetic field exerting current on a wire, speculation

You now need to show us the mathematics to make such a link between the theory of gravity and electromagnetism.

 

 

Right well the mass creates a field which produce gravity acting on the other masses, speculation

How is this speculation?

 

We know using general relativity how energy-momentum (loosley mass) acts as a source of the gravitational field. This are Einstein's field equations!

[fredreload]

Right, I just found it, thanks for pointing me in the right direction