What generates gravity?

[ChrisDK]

Hi everyone,

 

I am new here, but I have a question I have been thinking about a lot.

 

The force of gravity is one of the fundemental forces in nature. But my main question is, what actually generates the force itself? Now I know of course that gravity is proportional to the mass of an object, but that must mean that every atom on it's own, generates a very tiny amount of gravitational force - right?

So is it the nucleus, electrons, quarks, the charge of the atom or something entirely different that actually generates the force?

 

All the research I have been able to find about gravity, never really covers the subject of the force itself, but rather more it's effect on objects.

But why does mass attract other things in the first place?

 

Do any of you have any clue about this, or does anyone even know?

 

 

 

I hope the question makes sense

[D H]

The Newtonian view:

- Mass results in the gravitational force.

- The gravitational force makes masses move.

 

What makes this happen? Newtonian mechanics doesn't say. It just says what happens.

 

 

The relativistic view:

- Mass-energy tells spacetime how to curve.

- The curvature of spacetime tells mass-energy how to move.

 

What makes this happen? Relativistic mechanics doesn't say. It just says what happens.

 

 

That's all that physics has for now. Some physicists are working on moving beyond relativity. The two main fronts of attack are string theory and quantum gravity. Essentially, string theory attempts to extend quantum mechanics to cover gravitation while quantum gravity attempts to quantize gravitation. Neither approach is fully developed, and both still face significant challenges.

 

Suppose one or the other approach (or maybe some third alternative) did come to fruition. It's not as if this new theory will truly be the theory of everything, leaving nothing unspecified. This new theory will inevitably still have axiomatic statements, things plucked out of the clear blue sky because it works. Or, as your parents probably told you, "because we said so".

[Dekan]

The gravitational force seems hard to explain. Perhaps it isn't really a force at all.

Couldn't it be just a natural tendency for all matter to gather together - to be "at home", so to speak.

 

For example - suppose you see a stone lying peacefully at rest on the ground. The stone is at home, in natural contact with its fellow earth. Then suppose you disturb the stone's rest - by picking it up with your hand, gripping it, and lifting it up into the air. The stone is now placed in an unnatural position, poised in the air.

 

What happens if you release the grip of your hand - the stone, freed from your clutch, quickly moves, or falls, back down to the ground. And so resumes its natural place.

Does the stone's behaviour need to be explained in terms of outside forces acting on it.

 

Might it not be only a demonstration that all matter belongs together?

[juanrga]

Hi everyone,

 

I am new here, but I have a question I have been thinking about a lot.

 

The force of gravity is one of the fundemental forces in nature. But my main question is, what actually generates the force itself? Now I know of course that gravity is proportional to the mass of an object, but that must mean that every atom on it's own, generates a very tiny amount of gravitational force - right?

So is it the nucleus, electrons, quarks, the charge of the atom or something entirely different that actually generates the force?

 

All the research I have been able to find about gravity, never really covers the subject of the force itself, but rather more it's effect on objects.

But why does mass attract other things in the first place?

 

Do any of you have any clue about this, or does anyone even know?

 

I hope the question makes sense

 

The source of gravity is the stress-energy-momentum tensor [math]T^{\mu\nu}[/math] whose components are energy, momentum, and stress. In the non-relativistic approximation it reduces to mass. The tensor explains why massless particles as photons are affected (and generate) gravity.

 

Thus, in very broad terms, anything with energy generates gravity. The gravity generated by the Earth is the result of the gravity generated by each particle.

 

The concept of force is not fundamental, the relevant quantity is the gravitational potential. The force of gravity can be derived from it.

 

The reasons for which the force of gravity is attractive can be understood by studying the details of the gravitational interaction. It is found that this consists of spin-0 (repulsive) and spin-2 (attractive) terms, but their 'weights' are different (1/3 and 2/3 from memory) and do not cancel. Summing both contributions one finds a net attractive force.

[michel123456]

time

[StringJunky]

Gravity is not alone in defying an ontological description. If you read much by scientists you realise that descriptions of phenomena are written in terms of their parameters (measurements) and behaviour. The 'is' and 'why' of a thing aren't covered because it's considered outside the scope of physics and more the domain of philosophy/metaphysics.

[michel123456]

Gravity is not alone in defying an ontological description. If you read much by scientists you realise that descriptions of phenomena are written in terms of their parameters (measurements) and behaviour. The 'is' and 'why' of a thing aren't covered because it's considered outside the scope of physics and more the domain of philosophy/metaphysics.

 

Gravity is metaphysics???????

 

---------------

If you are incapable to answer a question, simply admit it.

Edited November 18, 2012 by michel123456

[timo]

If you are incapable of understanding a reply, it's not necessarily the fault of the one who wrote it.

[StringJunky]

Gravity is metaphysics???????

 

---------------

If you are incapable to answer a question, simply admit it.

 

No, trying to describe it ontologically is. The OP seems, from my interpretation, to be seeking an ontological answer:

 

"All the research I have been able to find about gravity, never really covers the subject of the force itself, but rather more it's effect on objects.

But why does mass attract other things in the first place?"

[zapatos]

Gravity is metaphysics???????

 

---------------

If you are incapable to answer a question, simply admit it.

I thought StringJunky's comment was very good and relevant to the conversation.

 

Perhaps Michel you should read his comment more carefully as he did not state that 'gravity is metaphysics', but that the "'is' and 'why'" of gravity is metaphysics.

 

And given that your contribution to the thread consisted entirely of the word "time", you may want to be careful about throwing stones. You know, glass houses and all that.

[michel123456]

No, trying to describe it ontologically is. The OP seems, from my interpretation, to be seeking an ontological answer:

 

"All the research I have been able to find about gravity, never really covers the subject of the force itself, but rather more it's effect on objects.

But why does mass attract other things in the first place?"

 

No.

DH answer was accurate and yours is BS.

[ACG52]

No.

DH answer was accurate and yours is BS.

 

 

This is just another way of saying 'I don't understand' without admitting you don't understand..

[michel123456]

I thought StringJunky's comment was very good and relevant to the conversation.

 

Perhaps Michel you should read his comment more carefully as he did not state that 'gravity is metaphysics', but that the "'is' and 'why'" of gravity is metaphysics.

 

And given that your contribution to the thread consisted entirely of the word "time", you may want to be careful about throwing stones. You know, glass houses and all that.

 

I disagree.

His answer was very bad.

Newton's answer was "hypotheses non fingo". And that is a correct answer.

------------

Gravity is not alone in defying an ontological description

Gravity is physics.

Time is physics.

No ontological question.

 

The OP question is: (bolded mine)

 

Hi everyone,

 

I am new here, but I have a question I have been thinking about a lot.

 

The force of gravity is one of the fundemental forces in nature. But my main question is, what actually generates the force itself? Now I know of course that gravity is proportional to the mass of an object, but that must mean that every atom on it's own, generates a very tiny amount of gravitational force - right?

So is it the nucleus, electrons, quarks, the charge of the atom or something entirely different that actually generates the force?

 

All the research I have been able to find about gravity, never really covers the subject of the force itself, but rather more it's effect on objects.

But why does mass attract other things in the first place?

 

Do any of you have any clue about this, or does anyone even know?

 

 

I hope the question makes sense

 

I gave a clue.

Edited November 18, 2012 by michel123456

[StringJunky]

No.

DH answer was accurate and yours is BS.

 

DH's answer was spot on and I got something from it hence I repped it. I was addressing something else which clearly is outside your scope of comprehension. What I wrote, that you call bullshit, is actually a distillation of what I have learnt from the physicists here concerning knowing the underlying nature of phenomena.

[zapatos]

I disagree.

His answer was very bad.

Newton's answer was "hypotheses non fingo". And that is a correct answer.

So...

 

Newton basically said 'I don't know why, and therefore choose not to give an answer'.

 

And StrinJunky basically said 'It's hard to say why, and physics does not answer that kind of question well'.

 

What exactly do you find so different about these answers?

[StringJunky]

So...

 

Newton basically said 'I don't know why, and therefore choose not to give an answer'.

 

And StrinJunky basically said 'It's hard to say why, and physics does not answer that kind of question well'.

 

What exactly do you find so different about these answers?

 

You understand me perfectly. Perhaps my words didn't translate well for Michel.

[michel123456]

DH's answer was spot on and I got something from it hence I repped it. I was addressing something else which clearly is outside your scope of comprehension. What I wrote, that you call bullshit, is actually a distillation of what I have learnt from the physicists here concerning knowing the underlying nature of phenomena.

 

I am tired of that kind of answer.

There is no harm to admit that "I don't know why does mass attract other things in the first place".

Clever people don't dismiss the question, clever people investigate.

 

So...

 

Newton basically said 'I don't know why, and therefore choose not to give an answer'.

 

And StrinJunky basically said 'It's hard to say why, and physics does not answer that kind of question well'.

 

What exactly do you find so different about these answers?

 

That is not what Newton answered.

 

-----------

And, ending the disgression, Chris is still waiting for clues.

 

IIRC the current model says that gravitation originates from mass. (that is not metaphysics, isn't it?) Mass curves the "fabric of space" and "tells how mass must move" along geodesics.

Edited November 18, 2012 by michel123456

[StringJunky]

I am tired of that kind of answer.

There is no harm to admit that "I don't know why does mass attract other things in the first place".

Clever people don't dismiss the question, clever people investigate.

 

 

 

That is not what Newton answered.

 

I don't know why does mass attract other things in the first place. Happy?

 

That's not what I was addressing, DH covered that in his excellent and clear reply.

[swansont]

No.

DH answer was accurate and yours is BS.

And "time" isn't BS?

 

Anyway, Stringjunky's answer was fine, as far as it was applicable.

[michel123456]

And "time" isn't BS?

 

Anyway, Stringjunky's answer was fine, as far as it was applicable.

 

You have to make the following syllogism:

 

Gravitation comes from mass.

 

Mass is a form of energy.

 

Mass-energy follows a conservation law.

 

Conservation law means "does not change as the system evolves"..."over time"

 

So the clue is:

time.

 

If one can prove that mass is the source of time, then gravitation and time can be linked directly.

[zapatos]

That is not what Newton answered.

According to this Newton said "I have not as yet been able to discover the reason for these properties of gravity from phenomena, and I do not feign hypotheses".

 

Forgive me for paraphrasing.

 

And, ending the disgression, Chris is still waiting for clues.

You are being obtuse. Chris was looking for understanding, not an actual 'clue'.

 

You have to make the following syllogism:

 

Gravitation comes from mass.

 

Mass is a form of energy.

 

Mass-energy follows a conservation law.

 

Conservation law means "does not change as the system evolves"..."over time"

 

So the clue is:

time.

 

If one can prove that mass is the source of time, then gravitation and time can be linked directly.

Are you trying to confuse Chris more?

 

Whose question are you providing a clue to? Chris did not ask how to link gravitation and time.

[swansont]

You have to make the following syllogism:

 

Gravitation comes from mass.

 

Mass is a form of energy.

 

Mass-energy follows a conservation law.

 

Conservation law means "does not change as the system evolves"..."over time"

 

So the clue is:

time.

 

If one can prove that mass is the source of time, then gravitation and time can be linked directly.

Until such time that you can prove this, it is conjecture and further, it does not follow from your logic.

[michel123456]

Until such time that you can prove this, it is conjecture and further, it does not follow from your logic.

 

A conjecture is an upgrade of BS.

 

Anyway no one reached the banana yet.

Edited November 19, 2012 by michel123456

[juanrga]

Gravity is not alone in defying an ontological description. If you read much by scientists you realise that descriptions of phenomena are written in terms of their parameters (measurements) and behaviour. The 'is' and 'why' of a thing aren't covered because it's considered outside the scope of physics and more the domain of philosophy/metaphysics.

 

As Steven Weinberg writes in the preface of the volume I of his textbook on quantum fields:

 

our purpose in theoretical physics not just to describe the world as we find it, but to explain --- in terms of a few fundamental principles --- why the world is the way it is.

 

Bold face from mine.

Edited November 19, 2012 by juanrga

[StringJunky]

our purpose in theoretical physics not just to describe the world as we find it, but to explain --- in terms of a few fundamental principles --- why the world is the way it is.

(My bold)

 

Note: He is not addressing a fundamental article or phenomena like gravity....he is using the word world at the macro level and in the collective sense. Gravity is a part of the world and we use gravity to explain why things at the macro level do what they do. This discussion is not about the world...it is talking about a much more fundamental component of it and at that level things start to become more axiomatic ie resist deeper analysis.

Edited November 19, 2012 by StringJunky