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Author Topic: Would a single mass have gravity?  (Read 5519 times)

Offline DoctorBeaver

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Would a single mass have gravity?
« on: 12/02/2008 15:16:40 »
If, in the entire universe, there was only 1 object - say, a planet - would it still have gravity outside of itself?

All the internal particles would feel each other's gravity, but would it still have an external gravitational field if there were no other object for it to act upon?

If gravity is a distortion of spacetime then, surely, that distortion would still be present regardless the absence of any other object. If, however, gravity is a force mediated by gravitons, would those gravitons still be radiating out from the mass or would there need to be another mass to entice them to come out to play?.

I've read quite a lot of literature that refers to gravitons, but what I don't understand (because I've never come across it) is how/why gravitons are supposed to be produced. Are they an intrinsic function of mass or only produced as the result of an interaction between masses? In the case of electrons, a photon is produced when 2 electrons interact; the electron does not send out photons willy-nilly. Are gravitons supposed to be the same?

And this leads to a supplementary question - what actually causes a particle to release a gauge boson? Does 1 particle "know" there's another particle nearby and send out a boson? If so, does that imply a deeper, more fundamental, force at work that triggers the release of the boson?


 

Offline lightarrow

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Would a single mass have gravity?
« Reply #1 on: 12/02/2008 19:08:45 »
If, in the entire universe, there was only 1 object - say, a planet - would it still have gravity outside of itself?

All the internal particles would feel each other's gravity, but would it still have an external gravitational field if there were no other object for it to act upon?

If gravity is a distortion of spacetime then, surely, that distortion would still be present regardless the absence of any other object. If, however, gravity is a force mediated by gravitons, would those gravitons still be radiating out from the mass or would there need to be another mass to entice them to come out to play?.

I've read quite a lot of literature that refers to gravitons, but what I don't understand (because I've never come across it) is how/why gravitons are supposed to be produced. Are they an intrinsic function of mass or only produced as the result of an interaction between masses? In the case of electrons, a photon is produced when 2 electrons interact; the electron does not send out photons willy-nilly. Are gravitons supposed to be the same?

And this leads to a supplementary question - what actually causes a particle to release a gauge boson? Does 1 particle "know" there's another particle nearby and send out a boson? If so, does that imply a deeper, more fundamental, force at work that triggers the release of the boson?

From gravitons ahead I've lost you...
 

Offline Soul Surfer

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Would a single mass have gravity?
« Reply #2 on: 12/02/2008 19:27:30 »
The normal visualisation is that of the electron (or another charged particle)an electron consists of a point mass and electric charge which consists of a fog consisting of undefined number of photon pairs continually apperaring out of the quantum mechanical vacuum and vanishing back into it within the uncertainty limits.  As two electrons approach each other some of the photons interact and behave like an exchange of energy which represents the force between the electrons as they interact. This could be one photon or a million  the end result will be precisely the same.  As a result of these photons an electron has a sort of jittery motion like Brownian motion and this can be measured.

Gravity and gravitons will be exactly the same sort of thing.  so particles don't need to "know" anything the fog of virtual gravitons and photons that are always there just interact to produce the force
 

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Would a single mass have gravity?
« Reply #3 on: 12/02/2008 19:35:47 »
I would have thought the issues regarding the exchange of gauge bosons are not really any different in principle from the dual slit experiment - in both cases, you have an apparent future event predetermined by events that in classical theory could not be known at the time the initial actions that lead to that event commence.
 

Offline DoctorBeaver

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Would a single mass have gravity?
« Reply #4 on: 12/02/2008 22:21:12 »
Ah, so it is all down to virtual particles. I was going to ask about those but dismissed them. I thought that as virtual particles appear & disappear everywhere then if they were responsible we would get EM & gravity everywhere too. That isn't the case, so I reasoned that virtual particles couldn't be the answer.

So how do they get around the "appearing everywhere but not causing EM or gravity everywhere" question? Is there some fundamental difference between virtual photons in the "fog" around electrons and those that appear elsewhere?

Also, is it the same for all gauge bosons? Or would W & Z bosons, having mass, behave differently?
 

Offline Soul Surfer

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Would a single mass have gravity?
« Reply #5 on: 13/02/2008 22:58:28 »
The virtual photons around the electron etc are excited by the presence of the electron and are in a way more real than the potential of virtual photons that exist in a vacuum with nothing in it
 

Offline DoctorBeaver

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« Reply #6 on: 14/02/2008 07:45:10 »
The virtual photons around the electron etc are excited by the presence of the electron and are in a way more real than the potential of virtual photons that exist in a vacuum with nothing in it

A bit like paparazzi around Kate Moss  :D

OK, that's making sense to me. But, surely, that would be a very short range force - like the weak or strong force. How would EM - or gravity - have an effect over much larger distances?
 

Offline Soul Surfer

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« Reply #7 on: 14/02/2008 09:57:10 »
remember photons have zero mass and in theory there is no lower limit to the energy a low frequency photon can possess  the "size" of a photon is elated to its wavelength and long wave radio in the UK uses 200Khz waves that are almost a mile long!  The frequency of photons involved in an interaction is also approximately related to the duration of that interaction and this may be seconds for longer range electromagnetic experiments in a lab.

That is the real problem with gravity because assuming that gravitons have the same relationship between frequency and energy as electromagnetic quanta  h.nu  most gravitational interactions take days or years to complete their cycles this means that the individual energy of the gravitons involved in most gravitational interactions that we are aware of is almost indescribably tiny and the wavelength extremely long.
 

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Would a single mass have gravity?
« Reply #8 on: 14/02/2008 10:55:39 »
The virtual photons around the electron etc are excited by the presence of the electron and are in a way more real than the potential of virtual photons that exist in a vacuum with nothing in it

What do you mean by "the presence" of an electron?  Do you mean they come into contact with an electron, or can remote sense the proximity of an electron - and if the latter, then are we not back to a cyclic logic - there must then be some field around an electron other than a electric field (since the the photon is the vector for an electric field) which links that photon to a nearby electron.
 

Offline DoctorBeaver

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« Reply #9 on: 14/02/2008 12:41:20 »
The virtual photons around the electron etc are excited by the presence of the electron and are in a way more real than the potential of virtual photons that exist in a vacuum with nothing in it

What do you mean by "the presence" of an electron?  Do you mean they come into contact with an electron, or can remote sense the proximity of an electron - and if the latter, then are we not back to a cyclic logic - there must then be some field around an electron other than a electric field (since the the photon is the vector for an electric field) which links that photon to a nearby electron.

George - that's what I meant by "a deeper, more fundamental force".
 

Offline syhprum

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« Reply #10 on: 14/02/2008 20:38:07 »
We have even longer photons now weve dropped down to 198Khz
 

Offline Soul Surfer

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Would a single mass have gravity?
« Reply #11 on: 15/02/2008 15:20:07 »
Another someone  The virtual photons are actually emitted by the electron as it interacts with the quantum mechanical vacuum.

The model of an electron moving along is that it emits a virtual photon and heads off in a slightly different direction for a while before absorbing it again and returns to its original path. The energy change and times are within the envelope of the uncertainy principle this means that the electron follows a jiggly path generally headed in the direction it is moving as defined by its momentum.  There may be an undefined number of virtual photons around at any time
 

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Would a single mass have gravity?
« Reply #12 on: 15/02/2008 15:54:59 »
So the photons are essentially captive in the vicinity of the electron (if one assumes the vicinity can extend out to an infinite distance before being reabsorbed by the same electron again, but still captive within that)?
 

Offline DoctorBeaver

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« Reply #13 on: 15/02/2008 18:04:13 »
So the photons are essentially captive in the vicinity of the electron (if one assumes the vicinity can extend out to an infinite distance before being reabsorbed by the same electron again, but still captive within that)?

But, surely, wouldn't they come under the influence of other electrons that they were closer to? Then again, there's this thing about photons being everywhere at once because they are travelling at light speed.

This is going to make my brain hurt  [xx(]
 

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« Reply #14 on: 15/02/2008 23:53:40 »
So the photons are essentially captive in the vicinity of the electron (if one assumes the vicinity can extend out to an infinite distance before being reabsorbed by the same electron again, but still captive within that)?

But, surely, wouldn't they come under the influence of other electrons that they were closer to? Then again, there's this thing about photons being everywhere at once because they are travelling at light speed.

This is going to make my brain hurt  [xx(]

But how would it know it was closer to another electron - unless it is subject to a force from the other electron?

I could understand it maybe easier if it did not so much interact with the alien electron, but with photons sent out from the alien electron.
 

Offline DoctorBeaver

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« Reply #15 on: 16/02/2008 08:04:11 »
So the photons are essentially captive in the vicinity of the electron (if one assumes the vicinity can extend out to an infinite distance before being reabsorbed by the same electron again, but still captive within that)?

But, surely, wouldn't they come under the influence of other electrons that they were closer to? Then again, there's this thing about photons being everywhere at once because they are travelling at light speed.

This is going to make my brain hurt  [xx(]

But how would it know it was closer to another electron - unless it is subject to a force from the other electron?

I could understand it maybe easier if it did not so much interact with the alien electron, but with photons sent out from the alien electron.

How would it "know" the other photons were from an alien electron? They don't wear different coloured hats.
 

Offline Soul Surfer

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« Reply #16 on: 16/02/2008 10:18:44 »
Of course the virtual photons would react ot the presence of another electron (and its virtual photons) that is precisely what the electromagnetic force and the exchange of photons is all about!
 

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« Reply #17 on: 16/02/2008 10:22:11 »
How would it "know" the other photons were from an alien electron? They don't wear different coloured hats.

I think the bigger problem is that as bosons, photons do not interact - they just pass through each other - so that idea goes out of the window.

Then there is the other problem - photons have no polarity (although they have polarisation) - so what is the difference, in photonic terms, between a positive and negative electric charge?
 

Offline Soul Surfer

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« Reply #18 on: 16/02/2008 10:55:14 »
It is of course the electrons that respond to the presence of the virtual photons and not the photons themselves, which ignore each other.  The point is it is not a specific photon sent from one electron to another that creates the interaction but a whole load of virtual photons which addd up to the final interaction.  It's just a lot simpler to think of the interaction as being due to one specific photon and the result is just the same.
« Last Edit: 16/02/2008 10:57:32 by Soul Surfer »
 

Offline DoctorBeaver

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« Reply #19 on: 16/02/2008 20:29:11 »
It is of course the electrons that respond to the presence of the virtual photons and not the photons themselves, which ignore each other.  The point is it is not a specific photon sent from one electron to another that creates the interaction but a whole load of virtual photons which addd up to the final interaction.  It's just a lot simpler to think of the interaction as being due to one specific photon and the result is just the same.

Ah, that makes sense. Thank you, Ian.
 

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Would a single mass have gravity?
« Reply #19 on: 16/02/2008 20:29:11 »

 

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