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Author Topic: What is the mechanism of gravity?  (Read 5837 times)

George Hilbert

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What is the mechanism of gravity?
« on: 02/02/2009 21:30:02 »
George Hilbert  asked the Naked Scientists:
   
Hello Dr Chris.

My question is this:

I have many times asked knowledgeable people about the mechanism of gravity.

Without fail, I always get a careful explanation of the effects of gravity.
By now, I know what gravity does and the observable effects. I would like to know how it does it. Is there some sort of particle exchange or other form of interaction between all bodies with mass that draws them together? If so, how? I suspect that this is one of those mysteries we have yet to solve, since it seems to escape the grasp of even the most educated in my experience.

Thank you and I love the podcast.

George Hilbert
Newport, Kentucky, USA

What do you think?


 

Offline Vern

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What is the mechanism of gravity?
« Reply #1 on: 02/02/2009 21:58:11 »
This is a very interesting question. I do have a speculative answer for it. However I can't discuss it here. You can find it in the New Theories Forum.

Modern physics has several versions of gravity. QM has the graviton which is a quantum of gravity and massive bodies exchange gravitons to produce gravity.

However I'm not a huge fan of QM so someone who is well versed in it will do a much better job than I. So I'll let them explain it.

String theory has a version of gravity, but it is so mathematically intense that I abandoned my attempts to comprehend it. Maybe a string theorist will pop in and explain the string-theory version.

Years ago there was a scheme called Push Gravity that had bodies being attracted to each other by some unidentified particles that pushed them into each other's shadow of the particles. It worked out mathematically but it was abandoned and you don't hear about it in the mainstream any more.
« Last Edit: 02/02/2009 22:42:23 by Vern »
 

Offline DoctorBeaver

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What is the mechanism of gravity?
« Reply #2 on: 02/02/2009 21:58:23 »
This is 1 of the great unknowns in physics. General Relativity postulates that gravity is a curvature of spacetime created by mass, but it does not explain how that curvature occurs.

As Vern said, quantum physics has the graviton - a particle that carries the force of gravity in the same way that a photon carries electromagnetism.
 

Offline LeeE

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What is the mechanism of gravity?
« Reply #3 on: 02/02/2009 23:00:44 »
This is 1 of the great unknowns in physics. General Relativity postulates that gravity is a curvature of spacetime created by mass, but it does not explain how that curvature occurs.

Aye, and there's the rub.

Quote
As Vern said, quantum physics has the graviton - a particle that carries the force of gravity in the same way that a photon carries electromagnetism.

Yup, but the problem with QM's graviton is that it really just shifts the problem  down a few levels and still eventually ends up with an abstract "and thus is gravity actioned".  Just as relativity doesn't give the mechanism whereby matter curves space-time, QM doesn't say exactly what a graviton does except in terms of other QM abstracts; exactly how does the graviton carry/mediate the force of gravity, and exactly what is the nature of this force of gravity that is being carried/mediated?  We're back to the original question again, without really getting anywhere.

Don't get me wrong; the graviton is a valid answer but perhaps, just like 42, we don't really understand the question even though it seems to be blindingly obvious.

I'm sure someone will figure it out one day though.
 

Offline Vern

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What is the mechanism of gravity?
« Reply #4 on: 03/02/2009 03:05:30 »
Quote from: LeeE
Yup, but the problem with QM's graviton is that it really just shifts the problem  down a few levels and still eventually ends up with an abstract "and thus is gravity actioned".  Just as relativity doesn't give the mechanism whereby matter curves space-time, QM doesn't say exactly what a graviton does except in terms of other QM abstracts; exactly how does the graviton carry/mediate the force of gravity, and exactly what is the nature of this force of gravity that is being carried/mediated?  We're back to the original question again, without really getting anywhere.

We have known since 1909 that relativity phenomena would develop naturally in flat space-time if the most elemental constituent of matter must always move at the invariant speed of light. I suspect that gravitation must be contained within that basic construct of matter also. The speculation linked in my first post in this thread expands upon that.

Quote from the link:
Quote from: H. Ziegler:
If one thinks about the basic particles of matter as invisible little spheres which possess an invariable speed of light, then all interactions of matter like states and electrodynamic phenomena can be described and thus we would have erected the bridge between the material and immaterial world that Mr. Planck wanted.
« Last Edit: 03/02/2009 03:16:30 by Vern »
 

Offline Vern

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What is the mechanism of gravity?
« Reply #5 on: 03/02/2009 21:55:06 »
I'm surprised that no one offered the string theory of gravity. Maybe it is too complicated. I found this description in another forum. I'm not really sure how these guys keep their wits about them.


Quote
More straight forwardly, there's T duality which requires circular dimensions. The state of a string is defined by its momentum (which comes in quantized chunks if you're on a periodic space) and its winding number, which is the number of times it wraps the circular dimension (obviously). This is a purely 'stringy' effect because you can't use points to wrap things. If you have a look on the Wiki page for T duality you'll see equations involving these momentum and winding numbers and the page explains how the non-zero winding numbers allow for the duality. Without this non-trivial  you wouldn't have winding numbers.

Also from Wiki
Quote
Strings and spacetime geometry

    The classical theory of spacetime geometry that we call gravity consists of the Einstein equation, which relates the curvature of spacetime to the distribution of matter and energy in spacetime. But how do the Einstein equations come out of string theory?
    If a closed string is traveling in a curved spacetime, then the coordinates of the string in spacetime feel this curvature as the string propagates. Once again, the answer lies on the string worldsheet. In order for their to be a consistent quantum theory in this case, the curved space in which the string travels must be a solution to the Einstein equations.
    Now this is really something! This was a very convincing result for string theorists. Not only does string theory predict the graviton from flat spacetime physics alone, but string theory also predicts the Einstein equation will be obeyed by a curved spacetime in which strings propagate.
« Last Edit: 03/02/2009 22:01:47 by Vern »
 

Offline yor_on

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What is the mechanism of gravity?
« Reply #6 on: 05/02/2009 00:26:55 »
If we go out from what we have.

And believe that Einsteins general and special relativity is a correct description.
Then spacetime is a bauble:)

Which we live in, just as those goldfishes in that bowl.
Now one could say.
But I think, I'm separate, I can do whatever I want.
Maybe, but not inside spacetime.

Spacetime is something contained in itself.
There is no straight lines in it geometrically seen.

There is a rule of least 'energy' spent though.
That rules us all, 'matter' as well as 'photons'.

Time is your definer of what was, is, and perhaps, will be.

There is another rule of what is meaningful for us.
Information.

It states that no information will travel faster than lightspeed in a vacuum.

All of those rules work inside 'spacetime'
Break them and you will be 'free'.

And gravity is a result of 'matters' symmetry with space.
And what we are?

The beholders.
« Last Edit: 05/02/2009 00:28:46 by yor_on »
 

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What is the mechanism of gravity?
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