On the Subject of gravity in general... split

[hoola]

on the subject of gravity in general, supposedly mass warps space and the action of gravitation stems from this behaviour. If so, then why does mass affect space? If space consists of a flux of virtual particles within it, is the distortion of the flux orbits the cause of "bent space", perhaps by perturbing the normal circular particle orbits into an ovoid? The strong example of this would be hawking radiation, from distortions of the orbits to the point of separation of the particles...If a particle orbit is lengthened by the change of orbit shape, perhaps the delay in the annialation of a particular particle once it appears in space is part of the underlying mechanism of gravitation. The extra time the particles exist would indicate a longer exposure of the particles natural charges to that particlar region of space, and that slightly longer exposure would manifest itself as an overall increase in energy available within that region...

Edited August 6, 2014 by hoola

[swansont]

We don't know why.

[Strange]

Perhaps because that is the definition of mass?

[hoola]

I mean to consider as possible candidate of one component of gravity, the warpage of the orbits of virtual particles as the components of space that do the actual "bending". Of course, that says nothing about why the mass bends the orbits in the first place, if indeed they do get bent....space gets bent with or without VPs, so one presumes some mechanism of space is altered which appears to measurement as "bending", and that bending results in gravitation. Since virtual particles are a fundamental component of reality, isn't it appropriate to consider the virtual particles as space itself?

[MigL]

Virtual particles are 'excitations' of a quantum field.

GR is a geometric theory of gravity which doesn't include gravitons.

Notice the difference ?

 

When we have a quantum field theory of gravity it will by necessity include virtual gravitons, but it may no longer be a geometric theory represented by the 'warping' of space-time.

[hoola]

Virtual particles exist below the plank length of time, and do not "show up" long enough for their full compliment of field properties to be expressed. If that is true, then perhaps the lengthening of their orbits by "bending space" will extend their duty cycle to above the plank time limit, therefore become existent long enough for a "hidden field" to express. That hidden field could be gravitation, or the graviton... The longer the 2 particles exist (above plank limit) before annialation, the stronger the field or more particles exchanged. This could be why microscopic particles seem to escape gravity, that they don't warp the local VP orbital relationships strongly enough to bring the particles' duty cycle above the plank limit, leaving space essentially flat and unresponsive...the event horizon of a black hole is again the ultimate expression of gravity with the attendant complete separation of particles with hawking radiation...the maximum distortion of the orbits...

Edited August 7, 2014 by hoola

[swansont]

Virtual particles exist below the plank length of time

 

No, that's not correct. Virtual particles existence is constrained by the parameters of the Heisenberg uncertainty principle, i.e. deltaE deltaT < hbar/2

[hoola]

whatever is restraining the VP existence time, the distortions of the VP orbit is the salient point. Thanks for pointing out my error...I thought I had read that the plank limit was the determinant factor...I can also imagine a possible reason the earlier universe had a period of contraction. Earlier increased overall matter density caused distortions to associated VP orbits, thus warping space and allowing an increased graviton exchange overall. Then when average density drifted lower, a critical percentage of VP orbit durations fell below the heisenberg limit, in a sense de-coupling space from low mass (microscopic) baryonic matter. This would ensure the contraction was halted as much of the universe became invisible to the graviton genesis mechanism that may be within space ...In my thinking the VPs are space, and their duration of existence determines the overall gravitational force expressed...from slight positive to highly negative..but I see a semantic issue with calling gravity a "negative" force. If gravity is really space warping, then space pushes down, so is in a sense positive also...as it results in an outward force, but applied in a (normally) downward fashion...so the VP force would be slight positive when at default state, then increasingly positive as orbit changes allow them to exist past the heisenberg limit. The greater the orbit durations, the smaller the particle masses can be coupled to space, hence greater graviton exchange. To somehow warp the orbits of VPs with some kind of engine would create a region of higher gravity force (a sort of gravitational monopole ?) and since it is a tensor force, no overall craft movement would be immediately practical. If the force could be delivered in a scalar form, then an exhaustless propulsion system might be possible...but even in tensor form, a craft with an artificially increased gravitational signature slingshot past a planet could turn it's gravity enhancer off at the closest approach to the planet, adding extra speed to the slingshot effect as it zooms away with normal gravity...

Edited August 8, 2014 by hoola

[Sensei]

The strong example of this would be hawking radiation, from distortions of the orbits to the point of separation of the particles..

 

Hawking radiation is hypothetical. You shouldn't talk about it as something verified and confirmed.

[phildukephd]

As far as I know "Gravitons" are theoretical constructs related to the supposed curvature of space and both Gravitons and curved space have not been proven experimentally.

 

If you assume that matter moves under the influence of gravity by the shortest possible route to conserve energy (why?) then the concept pf curved space can be a useful but untrue explanation. What is curved is space-time.

 

Gravity slows time down and the decrease in time is compensated for by the appearance of motion energy, that is acceleration. Then there is no need for gravitons, because there is no force of gravity, only conservation of time/energy.

 

It is experimentally proven that when atomic cocks are synchronized and one is flown around as high as possible, on return it is found to be running a (very) little faster than the one on the ground, showing that gravity does slow the flow of time.

 

It is proven experimentally that when subatomic particles are accelerated to near light speed they econtinue to xist up to 20 times longer than otherwise. This shows that acceleration and time flow rate are inversely related (but not inverse linearly). Then the reverse can be expected, that an decrease in time flow will produce acceleration.

 

As far as I know the mechanism by which matter affects time is unknown.

 

This explanation of how the acceleration force due to/called gravity comes about is Dr. Einstein's and it is good enough for me.

 

PD PhD

[swansont]

As far as I know "Gravitons" are theoretical constructs related to the supposed curvature of space and both Gravitons and curved space have not been proven experimentally

Since curved space is GR, I find it curious to see a claim that it's not been experimentally confirmed. GR is well-tested.

[ajb]

If you assume that matter moves under the influence of gravity by the shortest possible route to conserve energy (why?) then the concept pf curved space can be a useful but untrue explanation.

I am not exactly sure what you are saying here.

 

You can introduce an energy functional and minimise that to get the geodesic equations. You can also by thinking of the inverse of the metric as a Hamiltonian view geodesics as Hamiltonian flows.

[Nicholas Kang]

why does mass affect space?

 

I suppose this is the main question in this main topic.

 

Minor corrections, remember that it is mass-energy affects space-time. Try to rethink this question by using energy instead of mass and time instead of space or even mass-energy affects space-time. Maybe the answer lies between the fact that the mass may transform into energy by Einstein`s famous equation. These 2 formulae should have some similarities too.

 

E=mc²

 

E=hv/E=hf

 

 

Since virtual particles are a fundamental component of reality, isn't it appropriate to consider the virtual particles as space itself?

 

I think the answer is no because virtual particles are located in space-time and you seemed to mix both GR and QM together since you stated both VM and space in one sentence. I would advise you to refer several Theory of Everything to check your answers, maybe string theory is a famous candidate, though not many(or maybe no) experiments are done regarding this theory. Combining GR,SR and QM has been the ultimate quest to unite Modern Physics.

Edited September 16, 2014 by Nicholas Kang

[phildukephd]

Everything Nicholas Kang posts is quite good. IMO his Posts plus my one pretty much present what can be said on the subject in terms of our present understanding baswed on experimental verification. The rest is speculation.

Edited September 19, 2014 by phildukephd

[michel123456]

As far as I know "Gravitons" are theoretical constructs related to the supposed curvature of space and both Gravitons and curved space have not been proven experimentally.

 

If you assume that matter moves under the influence of gravity by the shortest possible route to conserve energy (why?) then the concept pf curved space can be a useful but untrue explanation. What is curved is space-time.

 

Gravity slows time down and the decrease in time is compensated for by the appearance of motion energy, that is acceleration. Then there is no need for gravitons, because there is no force of gravity, only conservation of time/energy.

 

It is experimentally proven that when atomic cocks are synchronized and one is flown around as high as possible, on return it is found to be running a (very) little faster than the one on the ground, showing that gravity does slow the flow of time.

 

It is proven experimentally that when subatomic particles are accelerated to near light speed they econtinue to xist up to 20 times longer than otherwise. This shows that acceleration and time flow rate are inversely related (but not inverse linearly). Then the reverse can be expected, that an decrease in time flow will produce acceleration.

 

As far as I know the mechanism by which matter affects time is unknown.

 

This explanation of how the acceleration force due to/called gravity comes about is Dr. Einstein's and it is good enough for me.

 

PD PhD

After this post it was answered that only Space expands.

So it is supposed that gravity curves Spacetime and also keeps space from expanding (because in gravitationally bound regions space does not expand) while doing nothing to Time. Looks like a contradiction to me.

Edited September 20, 2014 by michel123456

[Strange]

As far as I know "Gravitons" are theoretical constructs related to the supposed curvature of space and both Gravitons and curved space have not been proven experimentally.

 

As noted, curvature of space-time has been experimentally tested (but not "proven"; this is science: things are never proven).

 

Gravity slows time down and the decrease in time is compensated for by the appearance of motion energy, that is acceleration. Then there is no need for gravitons, because there is no force of gravity, only conservation of time/energy.

 

Gravitons are required if you want to describe gravity using quantum field theory (which may not be possible).

 

As far as I know the mechanism by which matter affects time is unknown.

 

It is well understood. See General Relativity for details.

 

After this post it was answered that only Space expands.

So it is supposed that gravity curves Spacetime and also keeps space from expanding (because in gravitationally bound regions space does not expand) while doing nothing to Time. Looks like a contradiction to me.

 

Gravity is the curvature of space-time (it doesn't "cause" the curvature of space-time).

 

The presence of local concentrations of mass causes the curvature of space-time (or, arguably, the presence of mass is the curvature of space-time) which we then perceive as gravity.

 

In a uniform distribution of mass, space will expand.

[MigL]

Expand OR contract. It is only the constant, non-changing ( size ) case which is unstable.

And which necessitated Einstein's fine-tuned 'biggest blunder' to maintain.

[michel123456]

 

As noted, curvature of space-time has been experimentally tested (but not "proven"; this is science: things are never proven).

 

 

Gravitons are required if you want to describe gravity using quantum field theory (which may not be possible).

 

 

It is well understood. See General Relativity for details.

 

 

Gravity is the curvature of space-time (it doesn't "cause" the curvature of space-time).

 

The presence of local concentrations of mass causes the curvature of space-time (or, arguably, the presence of mass is the curvature of space-time) which we then perceive as gravity.

 

In a uniform distribution of mass, space will expand.

Well, if gravity IS the curvature of Spacetime, why is it supposed that space (alone) does not expand in proximity of matter. I mean, why is it considered that gravity has no effect on time in the concept of space expansion. My question arises from the fact that we talk about space expansion, and not about Spacetime expansion. If you see the difference.

[MigL]

Gravity does affect time also.

It 'runs' slower in a gravitational well than far from it.

Just like space expands slower in a gravitational well than far from it.

 

So slow, in fact, that the gravitational attraction overcomes the expansion.

[swansont]

After this post it was answered that only Space expands.

So it is supposed that gravity curves Spacetime and also keeps space from expanding (because in gravitationally bound regions space does not expand) while doing nothing to Time. Looks like a contradiction to me.

 

I have to question the assertion that space is not expanding in gravitationally bound regions. Where did that come from? I think it's a different claim than saying that objects in these regions don't undergo expansion, owing to their attraction. "Space" and "objects" are not the same.

[Strange]

Well, if gravity IS the curvature of Spacetime, why is it supposed that space (alone) does not expand in proximity of matter.

 

I'm not sure what you mean by "why" but ...

 

The FLRW solution to the Einstein Field Equations (EFE) are based on a homogenous distribution of matter and show that, in such a case, space must either expand or contract. On a large scale, the universe is approximately homogeneous and so, not surprisingly, we observe expansion on that scale.

 

Solutions to the EFE for non-homogeneous distributions of matter do not describe space as expanding. And, again, that is what we observe.

 

I mean, why is it considered that gravity has no effect on time in the concept of space expansion.

 

It isn't. Gravity does have an effect in time.

 

My question arises from the fact that we talk about space expansion, and not about Spacetime expansion.

 

In GR, space-time is a static construct.

 

I'm not even sure what "expanding time" would mean. That time changes over time?

[elfmotat]

In GR, space-time is a static construct.

 

No it isn't. The metric is generally not static. The FLRW metric, for example, isn't time independent.

 

I'm not even sure what "expanding time" would mean. That time changes over time?

 

gtt could be time-dependent, sure. That's no more recursive than the fact that g_rr in, for example, the Schwarzschild metric is dependent on r. In other words, if the distance between two points in space can depend on where you are in space, then why couldn't the time between two events depend on where you are in time?

Edited September 23, 2014 by elfmotat

[michel123456]

 

I have to question the assertion that space is not expanding in gravitationally bound regions. Where did that come from? I think it's a different claim than saying that objects in these regions don't undergo expansion, owing to their attraction. "Space" and "objects" are not the same.

From wiki

 

"Metric expansion is a key feature of Big Bang cosmology, is modeled mathematically with the FLRW metric, and is a generic property of the universe we inhabit. However, the model is valid only on large scales (roughly the scale of galaxy clusters and above). At smaller scales matter has become bound together under the influence of gravitational attraction and such things do not expand at the metric expansion rate as the universe ages. As such, the only galaxies receding from one another as a result of metric expansion are those separated by cosmologically relevant scales larger than the length scales associated with the gravitational collapse that are possible in the age of the Universe given the matter density and average expansion rate."

[swansont]

From wiki

 

"Metric expansion is a key feature of Big Bang cosmology, is modeled mathematically with the FLRW metric, and is a generic property of the universe we inhabit. However, the model is valid only on large scales (roughly the scale of galaxy clusters and above). At smaller scales matter has become bound together under the influence of gravitational attraction and such things do not expand at the metric expansion rate as the universe ages. As such, the only galaxies receding from one another as a result of metric expansion are those separated by cosmologically relevant scales larger than the length scales associated with the gravitational collapse that are possible in the age of the Universe given the matter density and average expansion rate."

 

 

Yes, matter has become bound together and does not expand. Matter. Not space.

[michel123456]

 

 

Yes, matter has become bound together and does not expand. Matter. Not space.

In my understanding it is meant that for example the space between the Earth and the Sun does not expand, that the space between stars in the Milky Way does not expand, that the space between galaxies in a cluster does not expand, BUT that the space beween galaxy clusters does expand.

Edited September 27, 2014 by michel123456