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### Author Topic: What effect does mass-energy density have on gravitational field strength?  (Read 19012 times)

#### yor_on

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #75 on: 14/10/2013 17:25:47 »
at webplodder: Your relative mass should increase I guess, as you accelerate your arm, as well as the balls mass should, but as soon as you both are uniformly moving, it must be gone:) Interesting idea, better check it with Pete though.
=

That's wrong, your relative mass will still be there, in a uniform motion as well as in a acceleration. What I was thinking of was inertia there, not relative mass. That is what will be gone in after you finished accelerating. That relative mass you have will be expressed as kinetic energy in a collision. And there your speed will matter, acceleration or no acceleration. The inertia is still existent in a uniform motion though, although unmeasurable for you. and the inertia accelerating, can in a uniformly constant acceleration (at one gravity), translate into the same gravity we meet on Earth. Maybe it's more correct to call it your arm feeling gravity :) accelerating? This is definitely Pete:s field of interest.

Hmm rereading it again: I must have meant that as soon as your arm stops moving it also has decelerated to the same speed it had before starting to throw a ball for example. And in so motto it is correct.
« Last Edit: 21/11/2013 17:32:04 by yor_on »

#### jeffreyH

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #76 on: 16/10/2013 21:42:48 »
Quote from: jeffreyH
The energy-momentum relation is not what I am investigating.
Sorry, but I don't see your point. I never mentioned that.

Quote from: jeffreyH
It is the simplified e=mc^2.
Huh? What does that mean? I.e. what is the simplified e=mc^2? Do you believe that there is there a non-simplified e=mc^2?

Quote from: jeffreyH
One thing to ponder. Is the Planck scale invariant with regard to the distortion of spacetime?
Yes. I believe so.

On the Planck scale issue, if the universe were measured out into Planck cubes and the cubes that were being traveled through by mass undergoing acceleration, would a length contraction be observed at that scale? On a macroscopic scale an observer external to the accelerating system would see length contraction. How can this be separated from the finer grained resolution?

What if contraction itself and the inherent momentum of the scaling factor produced the gravitational effect WITHOUT any elementary particle. Maybe we are looking for a graviton that doesn't exists. That might be the reason for all the failure. If momentum and mass-energy density are interlinked some strange effects may become apparent.
« Last Edit: 16/10/2013 21:47:20 by jeffreyH »

#### Pmb

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #77 on: 17/10/2013 15:26:43 »
Quote from: jeffreyH
On the Planck scale issue, ...
The Planck scale comes from quantum gravity. Since I don't know quantum gravity you're going to find me very silent on questions about the "Planck scale issue" including your questions here. Sorry. I just don't think it's wise to talk about physics I'm not familiar with. I wish more people felt that way.

#### jeffreyH

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #78 on: 20/10/2013 17:18:37 »
One thing that never gets mentioned with respect to gravitational issues is parallax. We take it for granted but there are issues to do with this effect on a local scale.

#### Pmb

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #79 on: 21/10/2013 07:42:52 »
Quote from: jeffreyH
One thing that never gets mentioned with respect to gravitational issues is parallax.
That's because there's no reason why it should. It has absolutely nothing to do with gravity. It only pertains to optical observation of celestial bodies. Why do you think it should have anything to do with gravity at all?

Quote from: jeffreyH
We take it for granted but there are issues to do with this effect on a local scale.
When making assertions like this its helpful to back it up with facts. E.g. what are these issues that you're referring to?

#### jeffreyH

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #80 on: 21/10/2013 21:33:49 »
Quote from: jeffreyH
One thing that never gets mentioned with respect to gravitational issues is parallax.
That's because there's no reason why it should. It has absolutely nothing to do with gravity. It only pertains to optical observation of celestial bodies. Why do you think it should have anything to do with gravity at all?

Quote from: jeffreyH
We take it for granted but there are issues to do with this effect on a local scale.
When making assertions like this its helpful to back it up with facts. E.g. what are these issues that you're referring to?

If you had a disc whose circumference was 300000000 meters you could never achieve one revolution per second as the angular momentum would reach light speed at the edges. Length contraction would be greater at the edges of the disc as it approached light speed which would mean that the spacetime distortion would produce strange parallax effects. Gravitation and momentum cannot be separated so these effects are important in understanding these forces.

#### Pmb

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #81 on: 22/10/2013 01:27:42 »
Quote from: jeffreyH
If you had a disc whose circumference was 300000000 meters you could never achieve one revolution per second as the angular momentum would reach light speed at the edges. Length contraction would be greater at the edges of the disc as it approached light speed which would mean that the spacetime distortion would produce strange parallax effects.
First let's be clear on something. The contraction of the circumference of a disk does not mean that there is any spacetime distortion whatsoever. The only way that spacetime can be distorted here is due to the energy of the rotating disk rotating such that parts of it have near superluminal speeds.

All you're really saying is that light is bent by gravity. Bringing in parallax only serves to confuse things. There's no need for it to be quite honest.

Let's be clear here. Parallax is defined as follows
http://en.wikipedia.org/wiki/Parallax
Quote
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines.
Bringing in parallax confuses things and as such I recommend not using it in this sense.

Quote from: jeffreyH
Gravitation and momentum cannot be separated so these effects are important in understanding these forces.
Why are you now bringing momentum into this? And why would you make such a statement as this? What does it have to do with the present subject? And momentum is not a force either.

Some of the stuff you say is really confusing Jeff.
« Last Edit: 22/10/2013 01:30:03 by Pete »

#### jeffreyH

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #82 on: 22/10/2013 10:01:35 »
Think of the parallax effects of frame dragging. This is a similar situation. This is the reason c^2 is related to mass-energy and not any other value. The effects at light speed and under gravitation have intimate links.

#### Pmb

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #83 on: 22/10/2013 10:23:23 »
Quote from: jeffreyH
Think of the parallax effects of frame dragging.
Since parallax has nothing to do with frame dragging I have no idea what you're talking about. Sorry.

Quote from: jeffreyH
This is a similar situation. This is the reason c^2 is related to mass-energy and not any other value.
The reason c2 relates mass to energy is due to its presence in the Lorentz trasformation. How you connect it otherwise is beyond. How did you come to such a conclusion?

Quote from: jeffreyH
The effects at light speed and under gravitation have intimate links.
"Under" gravitation? Is that an error? In any case you once more lost me.

#### jeffreyH

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #84 on: 27/10/2013 16:20:21 »
Quote from: jeffreyH
Think of the parallax effects of frame dragging.
Since parallax has nothing to do with frame dragging I have no idea what you're talking about. Sorry.

Quote from: jeffreyH
This is a similar situation. This is the reason c^2 is related to mass-energy and not any other value.
The reason c2 relates mass to energy is due to its presence in the Lorentz trasformation. How you connect it otherwise is beyond. How did you come to such a conclusion?

Quote from: jeffreyH
The effects at light speed and under gravitation have intimate links.
"Under" gravitation? Is that an error? In any case you once more lost me.

Under the influence of gravitation.

Think of mass for a moment. What property of mass produces gravitation? If we take a number of spheres 1 meter in diameter made of iron. If these spheres were contained within a mesh to produce a spherical shape we could produce something that looks like a planet. If the mass of the spheres plus the mesh was the same of the mass of the earth then what would the combined gravity be when placed in the same orbit as the earth? Each sphere has its own gravitation which drops in an inverse square relationship and individually are much weaker than that of the earth. A very pertinent point is whether the gravitation would accumulate under these conditions. Would we reproduce the field strength of the earth? Before I can elaborate on other ideas this point needs to a answered conclusively.

#### Pmb

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #85 on: 01/11/2013 15:05:39 »
Quote from: jeffreyH
Think of mass for a moment. What property of mass produces gravitation?
Mass doesn't have any properties. Mass is a property. Therefore your question is meaningless.

#### jeffreyH

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #86 on: 11/11/2013 23:06:57 »
Quote from: jeffreyH
Think of mass for a moment. What property of mass produces gravitation?
Mass doesn't have any properties. Mass is a property. Therefore your question is meaningless.

The properties of mass are surely gas, liquid, solid, plasma etc. Or if you prefer, states.

#### Pmb

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #87 on: 12/11/2013 00:01:50 »
Quote from: jeffreyH
The properties of mass are surely gas, liquid, solid, plasma etc. Or if you prefer, states.
Sorry but that's not going to work either my friend. :) Those are the properties of things that have mass, not the properties of mass.

#### jeffreyH

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #88 on: 13/11/2013 18:58:43 »
Quote from: jeffreyH
The properties of mass are surely gas, liquid, solid, plasma etc. Or if you prefer, states.
Sorry but that's not going to work either my friend. :) Those are the properties of things that have mass, not the properties of mass.

Yes mass is a property of matter but properties can themselves have properties. Colour, for instance, has the properties of luminescence and brightness. I specifically did not relate the properties to matter as I believe it is the mass that is the defining factor with relation to gravitation. An atom will have less gravitation than a molecule, which in turn has less gravitation than a solid made up from molecules.
« Last Edit: 13/11/2013 19:00:21 by jeffreyH »

#### Pmb

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #89 on: 14/11/2013 01:13:31 »
Jeff - This is getting way off subject and I'm not interested in this side track. What exactly is it you wish to discuss or ask me about? Thanks! - Pete

#### jeffreyH

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #90 on: 14/11/2013 18:35:50 »
Jeff - This is getting way off subject and I'm not interested in this side track. What exactly is it you wish to discuss or ask me about? Thanks! - Pete

Well I suppose what I want to discuss is this.

The Jeans criteria for gas collapse under gravitation. What does this process tell us about gravity?

#### Pmb

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #91 on: 15/11/2013 00:20:07 »
Jeff - This is getting way off subject and I'm not interested in this side track. What exactly is it you wish to discuss or ask me about? Thanks! - Pete

Well I suppose what I want to discuss is this.

The Jeans criteria for gas collapse under gravitation. What does this process tell us about gravity?
I don't know. That's astrophysics and in astrophysics I'm a layman, just like you. :)

#### JP

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #92 on: 15/11/2013 02:23:48 »
The Jeans criterion seems to be fairly straightforward from that link.  Basically,  a bunch of particles of gas in space will tend to attract each other and coalesce to form a star.  However, in actuality, gas particles move about due to the temperature of a gas and this motion can keep them from clumping together (if they get too close, they'll bump into each other and fly apart again).  Basically, if there's enough mass in a cloud of gas compared to the temperature of that gas, it will coalesce into a star.  If the temperature is too high compared to the mass, it will stay a cloud of gas and not form into a star.

#### jeffreyH

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #93 on: 17/11/2013 23:03:02 »
The Jeans criterion seems to be fairly straightforward from that link.  Basically,  a bunch of particles of gas in space will tend to attract each other and coalesce to form a star.  However, in actuality, gas particles move about due to the temperature of a gas and this motion can keep them from clumping together (if they get too close, they'll bump into each other and fly apart again).  Basically, if there's enough mass in a cloud of gas compared to the temperature of that gas, it will coalesce into a star.  If the temperature is too high compared to the mass, it will stay a cloud of gas and not form into a star.

Interesting. So then a fall in kinetic energy should initiate gravitational collapse for a mass of sufficient density. This appears to show that gravitation tends to aid in the solidification of matter somehow. Does this also suggest that spin 2 particles operate to initially reduce kinetic energy for matter moving away from the source of gravitation? What better way to add matter to a mass than hurling it inwards.
« Last Edit: 17/11/2013 23:22:06 by jeffreyH »

#### jeffreyH

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #94 on: 18/11/2013 18:44:15 »
This train of thought got me thinking about singularities with regard to the mass-energy density topic. If increase in gravitation reduces kinetic energy and the reduction in kinetic energy leads to time dilation (rate of atomic change slows down) then the singularity is an inevitable consequence of gravity and the ideal equalibrium for such a force. A question of interest would be this. What would an observer outside the earth determine would be the speed of an object falling to earth under gravitation? How many metres per second of acceleration would they record as compared to an earth bound observer?

P.S. Does this imply zero kinetic energy at the singularity? Could frame dragging occur because it is moving around a time-free zone and is forced to do so because of the consequences of the lack of kinetic energy at the singularity?
« Last Edit: 18/11/2013 18:52:34 by jeffreyH »

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##### Re: What effect does mass-energy density have on gravitational field strength?
« Reply #94 on: 18/11/2013 18:44:15 »