Does gravity have an effective range?

[pioneer]

The question I would like to pose and is, does a source of gravity have an effective or practical range within our current expanding universe? Here is my logic. If gravity implies GR, GR will cause a contraction in space-time that decays with distance from the object. The universe is also in motion, with many objects moving at relativistics speeds. This SR will also create pertubations in space-time. As such, when the effect of gravity gets really low, at long distances, background SR should create space-time noise that will make the affect of weak/distant gravity become indeterminant. In a static universe this would not be the case. But in a dynamic universe we have a velocity or SR based source of space-time ripples that shouldn't look to much different than weak GR space-time ripples.

 

An affective gravity range, before SR indeterminancy, would imply the matter within the expanding universe should clump via gravity locally in its affective range with little impact on global movement due to the noise. The accelerated expansion means the noise is getting louder focusing gravity's practical determinancy even closer condensing the galaxies more and more. This is not to say gravity doesn't go beyond, only that is becomes indeterminant or indecisive.

 

This resolves the paradox of how an accelerated expansion can lead to a universal contraction. The localization of effective gravity means local space-time reference is extending further and further into space due to distance contraction and time dilation in its reference. Eventually local reference will catch up to the perimeter and put on the brakes. Blackholes may be the goal of the accelerated expansion generating a local reference that can see beyond the perimeter of the expansion.

[Martin]

The question I would like to pose and is, does a source of gravity have an effective or practical range within our current expanding universe?...

 

I didn't follow anything you said after asking that question. However I understand the question. As far as is known, light, gravity waves, gravity influence all travel at the same speed.

 

At the present time, according to the prevailing world model, they all have an effective range of 16 billion LY.

 

That is, if we sent a flash of light at some distant galaxy, today. And the present distance of the galaxy, today, was more than 16 billion LY. then the light would never get there. because of the accelerating expansion. Not in the whole future history even if they waited forever.

 

Likewise if some advanced civilization made two black holes collide in order to send out an intense burst of gravitational influence, an abrupt ripple, then galaxies more than 16 billion LY away would never "see" that burst of gravitational waves. Not in the whole future, even waiting arbitrarily long time. Because of the expansion the information can never get there.

 

the 16 billion LY is called the "cosmological event horizon"

 

it is different from the "Hubble radius" which is only around 13.7 billion.

 

You might benefit from the Cosmology section of a college Intro to Astronomy textbook. need to learn about the standard mainstream model.

advise you to avoid popularizations like Hawking or Brian Greene. and avoid stuff from before 2002 or 2003

[Daecon]

The strength of gravity is inversely proportional to the distance from the source, so any effective range would be directly dependent on the mass of the source itself.

 

I think?

[Martin]

The strength of gravity is inversely proportional to the distance from the source, so any effective range would be directly dependent on the mass of the source itself.

 

I think?

 

that is certainly true. little masses don't have a sensible effect at long distances because of inverse square fall-off

 

In pioneer's case, he seems to be asking about a concept of range which is independent of the mass. That is what I tried to respond to. The range I discussed works no matter how big the mass is that you are playing around with---which may seem curious at first.

[pioneer]

Let me rephrase the question. If gravity is GR, which amounts to affects in space-time, then as we move away from a source, the space-time affect decreases with distance. SR or mass in motion also causes affects in space-time. Do these two space-time affects interact like waves such that long range space-time affects from gravity blend with SR space-time affects (waves) making the affect from the GR source indeterminant?

 

As an analogy picture a basketball in the middle of a lake bobbing up and down making waves. This is the gravity source with the waves in the water analogous to space-time affects that will diminish with distance. At a far enough distance the waves will get very subtle. If a bunch of water bugs were swimming near this distance zone, their little waves will create interference patterns with the almost decayed waves from the basketball. If we didn't know the position of the basketball and had to guess from all these waves the interference could make its position indeterminant. As we go closer to the basketball, its waves are stronger such that interference is less of a factor allowing the position of the basketball to become much more determinant. With respect to gravity, will SR space-time waves make distance sources of gravity lose track of objects due to SR space-time interference?

 

The answer to this question tells us whether gravity equals GR or whether gravity equals GR plus something more. In other words, if gravity equals GR then there should be GR/SR, interference that will limit the affective distance of GR sources to much shorter than 16 billion light years. If there is no impact inspite of SR space-time interference, than gravity would have to have something extra beyond GR space-time affects that can pass through space-time interference and remain determinant.

 

In other words, if 16 billion light years is true, inspite of SR interference from fast large sources, then gravity is more than just GR. Or GR is only one affect stemming from gravity and not the only affect. The other affect ignors the SR space-time interference in space-time and can track all the way to 16 billion light years.

 

This brings up the next point, which makes use of the assumption that gravity equals GR without anything extra. As an analogy, if we take a stationary positive charge it will give off an electostatic force field. If we give it motion a secondary magnetic force field will appear. The two fields represent a unified force with two aspects. Is it possible that gravity acts the same way, with a stationary source giving off only GR. If we give it motion its analogous magnetic field (so to speak) is SR based space-time for a unified gravity field that is a space-time combo of GR and SR?

 

Extending the analogy, if two positive charges are in motion the relative motion will dictate whether their magnetic fields will add or subtract. In the case of unifed (GR/SR-space-time) gravity, i.e., moving GR source, the doppler shift appears to indicate that masses moving away from each other will see diminished or red shifted GR due to the affect of the SR (magnetic analogy) component of the dual space-time force. This should be the second part of the indeterminancy beyond SR noise.

 

So an accelerated expansion with GR-SR space-time should take less and less energy to accelerate the faster the expansion due to the red shift in the affect GR-SR space-time (gravity). Using conservation of energy, this implies more energy going into the affective range of gravity. This expands the local space-time reference allowing it to catch up to the expansion and put on the brakes, i.e., conservation of relativity.

[BenTheMan]

As an analogy picture a basketball in the middle of a lake bobbing up and down making waves. This is the gravity source with the waves in the water analogous to space-time affects that will diminish with distance. At a far enough distance the waves will get very subtle. If a bunch of water bugs were swimming near this distance zone, their little waves will create interference patterns with the almost decayed waves from the basketball. If we didn't know the position of the basketball and had to guess from all these waves the interference could make its position indeterminant. As we go closer to the basketball, its waves are stronger such that interference is less of a factor allowing the position of the basketball to become much more determinant. With respect to gravity, will SR space-time waves make distance sources of gravity lose track of objects due to SR space-time interference?

 

Inasmuch as I understand GR, I think you are mistaken. There are gravity wave solutions of Einstein's equations, independant of curvature solutions. What you are describing is gravity waves, which is something very different from, say, curvature caused by a very massive body.

 

We fully expect to see gravity waves coming from quasars and such, and we expect them to have all of the same properties of electromagnetic waves, in terms of interference patterns and such. The current round of experiments don't directly see gravity waves (google search LIGO), though the next generation space experiments (goggle ``LISA'') should have no problems. Note that we've also seen indirect evidence of gravity waves from looking at binary pulsars---work which received a Nobel Prize: http://nobelprize.org/nobel_prizes/physics/laureates/1993/illpres/discovery.html.

 

Further, the waves (again, inasmuch as I understand GR) don't cause attraction. The bug analogy you made is good for demonstrating this---the bugs are not drawn towards the basketball in the center of the pond, they only move up a little, then down a little. Gravity waves have pretty much the same effect:

 

 

Again, read the LISA or LIGO stuff on the web, and this picture may make more sense. Either way, there is no need to ``add'' anything to GR to get this behavior out.

[pioneer]

The point I was trying to make is both GR and SR cause changes in local space-time. GR does it stationary while SR with velocity but the affect on space-time should be very simipar. Both are present in the universe especially in the light of gravity and the rate of the expansion that is inferred from the red shift. GR and SR space-time affects should interfere and add/subtract affects. As such, if gravity is GR can the SR interference affect make gravity GR indeterminant with respect to locating distant objects?

 

Martin place the affective range of gravity at 16 billion light years. This should be too high if the SR interference affect is valid. If the 16 billion light years is indeed correct than GR alone is not sufficent to define gravity. It would have to have another component, which can act independantly of SR interference in space-time when gravity gets low in magnitude. One can not have it both ways since these are mutually exclusive.

 

The way the universe is laid out with respect to its basic unit of currency or galaxies, combined with the relatively narrow band width of galaxy size, and the bulk accelerated expansion relative to this galaxy size, strongly suggests that gravity does have a relatively low affective range somewhere in the order of magnitude of galaxy size. This limited affective range could be explain with the SR space-time noise created by the bulk universe accelerated expansion. This keeps GR consistent with gravity without needing any extra addendum. The extra addendum would only be needed if the 16 billion light years estimate of affective and determinant gravity was correct, which the observational layout and expansion of the universe does not appear to support. One has to add fudge factors to keep the range at 16 billions light years inspite of galaxies flying apart.

 

Let me add something extra at this point. If the universe is undergoing an accelerated expansion it will be bigger and expanding faster tomorrow. Also it was smaller and expansing slower yesterday. If we draw a line or curve through these three data points and extrapolate back in time 15 billion years, the early universe should have been very small with only a small expansion velocity but would also be accelerating expanding. The logical extrapolation of the curve back to near the beginning, through these three points implies a gentle beginning for the universe via a slow expansion that gradually speeds up, i.e, the universe did not begin with a bang but with a gentle push. One can use complex curves to get whatever one wants, but the simplest curve is often closer to truth.

 

What this implies, is the post beginning of the universe was almost pure GR with gravity having maximum range. As the expansion accelerates, SR noise begins to appear, a little at first and increases. This would cause the extreme determinant range of GR to get less and less. The result should be the uniform expansion becoming slightly discontinuous, due to the low SR noise helping to form the bulk superstructure. As the expansion continues to increase the SR noise, the superstructure GR begins to see the noise and breaks into smaller and smaller substructure until galaxies appears. One does not really need density pertubations, just SR noise due to an accelerated expansion to make galaxies via gravity indeterminancy, with the increasing SR noise increasingly limiting the affective range.

 

The next question is why the accelerated expansion of the universe and the increase in universal SR? To answer this we need to look at one basic observation stemming from particle accelerator data. It has to do with the observation that the substruture of say a proton does not last when it is outside the confines of the proton, compared to within a proton.

 

Without getting fancy but staying simple, the easiest explanation is that the substructure within the confines of a proton is time dilated. Once we break the time dilation the substructure loses its immortality. In other words, what we see in a particle accelerator is its true life expectancy. But when time dilated within the confines of a proton it appears to last for billions of years in our earth reference. This time dilation was given to it during the early part of creation. This substructure time dilation within a proton can't be due to GR since the mass is too small. As such, it needs to be an SR type affect due to a state that is close to C, i.e., almost energy. If we compare the 10-20 billion year life of a proton to the nano-sec life of the substructure once it leaves the proton V would have to be only a tiny blip below C to generate that much time dilation, i.e., almost energy. A simple lowering of the SR value within the subparticles should generates the massive collective SR output needed for expansion.

 

Because of SR noise lowers the affective range of gravity the SR output from the innards of protons, etc., can get less and less and still keep the acceleration going since gravity becomes less and less a factor. As such, as the universe evolves and bleeds the innards of SR there is less left over at the same time it takes less and less to keep the expansion going.

 

 

 

 

This post merged; strange synchronicity.

 

I have a tendency to extrapolate so forgive me for now. But the basic question still remains are the ripples in space-time due to GR and SR essentially the same, especially after they leave the moving source? If so do these add/substract or create interference that make the space-time affects from gravity GR see noise at long disances? It seems logical although it may be very hard to prove with experiment. But it does create reasonable doubt with respect to the practical range of gravity.

 

Looking at the universe, gravity is indeed showing practical affects within rhe scale of galaxies since these zones compress, rotate, etc.. But beyond that the universe is expanding with respect to the galaxies. One may say it is the shear distances that cause this problem. But if we extrapolate back in time when things were much closer, why didn't the universe expand only relative to the superstructure which was once closer?

 

I did speculate about the substructure of proton having its innards time dilated. Any other form of composite in chemisty does not lead to the chemical substructure vaporizing faster than the superstructure. We can plasma water into O and H and this substrcuture will last just as long. You do it to a proton and the time parameter of the innards is very different.

 

Rather than speculate dark matter and energy as something new, bleeding off innard SR can do what we need. SR output should be relativistic mass (virtual) or dark matter and the combo of time and distance relaticeitt forms virtual frequency/wavelength or dark energy. It is consistent but allows us to get to a possible source faster, which in turn, may allow us to similate dark matter and energy in the lab.

[Jacques]

Sorry I don't understand exactly how SR affect space-time. If we observe a moving clock, we will see that clock running slower. That is a SR effect. The mass of the moving clock will create a deformation of spacetime. This is a GR effect. I never read about SR deforming spacetime or I am missing something ???

Thanks in advence for your clarifications.

[losfomot]

Sorry I don't understand exactly how SR affect space-time. If we observe a moving clock, we will see that clock running slower. That is a SR effect. The mass of the moving clock will create a deformation of spacetime. This is a GR effect. I never read about SR deforming spacetime or I am missing something ???

Thanks in advence for your clarifications.

 

A person in a ship flying past the moon at 99% of c will experience the universe (space and time (or spacetime)) differently than a person on Earth watching him fly by the moon. But the person on Earth will not notice anything unusual about the gravity of the moon aside from factoring in the gravity that the mass of the spaceship contributes. Of course, the mass of the spaceship will be larger for the observer on Earth, which would mean that the ship would give off a stronger gravitational field then it would have at non-relativistic speeds... I suppose, in that sense, there is a mixing or overlapping of SR and GR effects.

 

I believe the OP is thinking along the lines that the universe is expanding, so a lot of it is moving at relativistic speed relative to us, the further an object is from us, the faster it is moving away, and the more massive it must be to us because of SR effects (Hence, more gravity). This probably WOULD be considered an addition of SR and GR effects if it were true. But SR effects do not apply to motion due to the expansion of the universe because this motion is not motion within spacetime, but rather motion due to the expanding of spacetime itself.

 

Of course, as I always like to state lately, I am far from an expert.

 

I believe the OP is thinking along the lines that the universe is expanding, so a lot of it is moving at relativistic speed relative to us, the further an object is from us, the faster it is moving away, and the more massive it must be to us because of SR effects (Hence, more gravity). This probably WOULD be considered an addition of SR and GR effects if it were true. But SR effects do not apply to motion due to the expansion of the universe because this motion is not motion within spacetime, but rather motion due to the expanding of spacetime itself.

 

Rereading the OP, maybe I'm wrong... I'm not entirely sure what he is trying to say.

[Jacques]

Of course, the mass of the spaceship will be larger for the observer on Earth, which would mean that the ship would give off a stronger gravitational field then it would have at non-relativistic speeds...

I see your point, but, I am not 100% sure, that topic was discussed in an other thread and the conclusion from expert was that this relativistic mass was not a gravity mass.

For sure the moving mass will deform spacetime but it is only GR effect I think...

[pioneer]

If we started with a stationary rocket, to make it reach relativistic speeds, we would need to input energy, such as fuel. The SR affects that result will be dependant on how much energy we add to the system. The reason this is so, is energy is needed to create relativistic mass, while relativistic mass is not dependant on relative reference but on energy input.

 

Let me give an analogy. It is called the 2-parameter SR workout. We go to a track and sit in a chair. We then focus on the fastest runner and using relative reference in space-time we pretend to be moving such that the runner appears stationary. Does this relative motion give us exercise? This is an illuison due to using only 2 out of 3 parameters of SR. If we use 3-parameter SR, which includes relativistic mass, then there is only one moving reference, which is the runner. We become stationary by this 3-parameter standard with relative reference more of a mind game.

 

 

That being said if we look at 3-parameter SR objects, the amount of SR is directly related to the amount of energy. Using 3-parameter SR and energy as the guide, it is not relative but absolute. This energy not only makes relativisitic mass but also an absolute amount of space-time affect. Again relative reference ignors energy dependance making the space-time affect relative. If we include energy the space-time affect isn't relative anymore but absolute with a very intimate connection to the amount of relativistic mass. In that respect it is like GR requiring mass to work with space-time alone not sufficient to create the entire affect.

 

So if we have large SR objects in space they define x-amount of energy. The amount of space-time affect is directly relative to this energy. The type of ripples in space-time, it can create, is also energy dependant. If we add energy than its absolute amount of SR will increase. This is the state of the moving objects in the expanding universe. We need to add energy to make them move at faster and faster speed. The ripples in space-time will change as time moves forward since they are accelerating.

 

If we look at GR the opposite is in affect. Gravity contains the most potential energy when the mass is all spread out. The mass lowers potential as the matter compresses and space-time contracts. This is the opposite of SR, which has more space-time affect at higher potential. So if the universe is accelerating expanding space-time via GR, this would be enothermic and would require a source of energy input. This is consistent with the accelerated movement of SR objects also being endothermic. Either way this will require a powerful source of energy to be possible.

 

One simple explanation for the energy to create this affect, is an output that results as GR increases, due to loss of gravity potential in the mass. If you think about it, such an ouptut will induce a uniform expansion of the universe, relative to the galaxies, since these are the basic units of gravity currency in the universe. It would only work if gravity has an affective range somewhere at the level of galaxies. The affective range of GR only works within this galaxy range, but the energy output keeps going outward to an energy to fuel the acceleration. The acceleration induces an evolving space-time ripple interference.

 

Gravity is an odd duck compared to the other three forces in the sense that the other three forces give off some type of measureable energy when they lower potential. For example, EM force will create motion and give off energy when the potential lowers. Gravity potential will create motion, like EM force, but does it give off some form of energy? It is not obvious such that maybe this energy is different, i.e., dark energy. Virtual energy would be the easiest way to transfer potential between GR and SR since relativity create virtual mass/energy affects.

[BenTheMan]

Gravity is an odd duck compared to the other three forces in the sense that the other three forces give off some type of measureable energy when they lower potential.

 

So you can't measure kinetic energy? Doesn't your car have a spedometer?

[losfomot]

So if we have large SR objects in space they define x-amount of energy. The amount of space-time affect is directly relative to this energy. The type of ripples in space-time, it can create, is also energy dependant. If we add energy than its absolute amount of SR will increase. This is the state of the moving objects in the expanding universe. We need to add energy to make them move at faster and faster speed. The ripples in space-time will change as time moves forward since they are accelerating.

 

The velocities of these objects are not relativistic. That is to say that SR does not apply to these velocities. If an object was to give off ripples in spacetime due to SR, it would NOT be an object whose velocity is due to the expansion of space.

[pioneer]

If we look at the gravity equations, the math accommodates gravity acting all the way to infinity. But for all practical purposes it should get so small at a certain distance to be considered negligible. If two mass were stationary even this negligible could act causing the bodies to attract.

 

But if you look at our universe, things are not stationary. In fact, the red shift appears to indicate an expansion with things moving at relativistic velocities. Since GR is modelled as compression in space-time and SR can also cause changes in space-time, does the SR create space-time noise that makes the affective range of weak gravity become ambiguous at long distance?

 

This is a very loose analogy and should not be taken literally. We have a basketball in the middle of a large lake, which is bobbing making waves. As the distance increases, the circumference of the wave front increases, such that the amplitude energy gets distributed lowering the height. Eventually, the waves will be so small that they get hard to see.

 

If there are some small waterbugs swimming near our equipment, which is already having a hard time to triangulate the basketball's position because of the subtety of the wave, the little bugs will add noise. The noise is small but the waves from the basketball are also very small. We may be able to filter out the noise but the extra effort makes it harder.

 

If you look at the expansion of the universe, especially an accelerated expansion the SR noise is getting louder causing gravity to look closer. I often wondered why the universe is expanding relative to galaxies, which seem to have sort of a bandwidth of size. It does not expand in a random way that included a bandwidth of size that is much larger to reflect the random affect of effective gravity able to reach all the way to infinity. This suggested the affective gravity, due to SR noise, makes it look close. It may still be able to see all the way, but the noise creates indeterminancy.

 

This theory can explain the paradox of how an acceleration expansion will lead to an eventual compression of the universe. With the SR of the acceleration expansion increasing the SR noise, gravity and GR is induced to look closer or its determinant range sort of gets pulled in. The expansion, itself moves the mass apart compounding this problem. The closer determinancy of gravity in the light of segregated matter, will allow local GR to increase at a much faster rate. It is not being pulled apart by other galaxies thereby avoiding some type of counter affect.

 

The increase in local GR also means the space-time reference is compressing. Eventually, that reference will catch up to the expansion. In other words, if we could travel at C, extreme distances would appear to be pulled into our reference point due to distance contraction. When the local zones finally can generate extreme GR reference, the local reference will begin to appear like it emcompasses the edge of the expansion. At that time the brakes are applied. The compressed GR reference essentially allows gravity to see much better through the SR noise, allowing it determinant range to extend further and further to the edge.

 

The theory also creates simple reasoning for why galaxies from a contiuum of matter, assumes BB for the sake of argument. Forget about the very beginning but lets start with an expanding continuum The SR will also create noise. The affective range of gravity is all the way to the perimeter, but the SR noise causes tweaks in the otherwise uniform gravity profile. The result are slight gravity ambiguities that increase with time until the determinant vision clears.

 

I think it would be useful for someone to come up with an experiment to prove or disprove the affect of SR noise on the determinancy of gravity.