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Author Topic: At what speed does gravity propagate?  (Read 5821 times)

Offline cheryl j

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At what speed does gravity propagate?
« on: 10/11/2011 01:55:28 »
But if an object in space changes in some way that its gravity increased or decreased, how quickly would an object at a distance register this change?
« Last Edit: 13/11/2011 22:44:20 by chris »


 

Offline Supercryptid

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Re: At what speed does gravity propagate?
« Reply #1 on: 10/11/2011 03:32:27 »
According to currently accepted physics, the change would propagate at the speed of light.
 

Offline Phractality

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Re: At what speed does gravity propagate?
« Reply #2 on: 10/11/2011 04:20:22 »
But if an object in space changes in some way that its gravity increased or decreased, how quickly would an object at a distance register this change?
You are asking a hypothetical which is impossible. There is no known process by which a mass can appear or disappear. Masses can only move about a speeds less than the speed of light. So the obvious way to measure the speed of gravity is to look for a difference between where a mass is and the direction in which other masses are gravitationally attracted to it. That difference is referred to as aberation. This is easier said than done because you need a rather large mass to detect its gravity, and it needs to be moving at a significant fraction of the speed of light to have any measurable aberation.

It has been inferred from the Sun's gravitational effect on Earth, that we accelerate toward the present location of the Sun. If there is a speed of light delay upon the force of gravity, it seems reasonable that we would accelerate toward the direction where we SEE the Sun, in other words toward the stars that were directly behind the Sun 8 minutes ago. If that were the case, Earth (and all other planets) would be pulled into higher and higher orbits; there would be no such thing as a solar system. Based on that inference, it has been calculated that the effect of gravity, if not instantaneous, is at least 20 billion times faster than light.

However, the above deduction is not widely accepted in mainstream science. It is claimed that the equations of general relativity automatically nullify the speed of light delay on gravity, so that it has no observable effect.

Not the most prestigeous web site, but Metaresearch.org has extensive coverage of the speed of gravity debate between VanFlandern and Kopeikin.

I find some of VanFlandern's theories, like spontaneously exploding planets, to be just plain crazy. However, I do find his arguments on the speed of gravity to be persuasive.
 

Offline Nizzle

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Re: At what speed does gravity propagate?
« Reply #3 on: 10/11/2011 05:54:03 »
There is no known process by which a mass can appear or disappear.

Doesn't mass disappear in all exothermic reactions? (ie: converted to energy)
 

Offline swadewade8

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Re: At what speed does gravity propagate?
« Reply #4 on: 10/11/2011 06:05:55 »
From what I noticed about gravity is it is only relative to the atomic weight of the molecule/mass exerted upon another molecule/mass concerning size of an object it may be interacting with.  As far as the speed of light goes, I have not heard of anything traveling at that velocity aside from the initial 'big bang' or when a sub-atomic particle breaks free of having an atom split.Both are not due to gravity but to an extreme energy release due to an external force.  I might be wrong but, take into consideration when you drop a rubber ball on the ground. Does it travel at the speed of light? I won't answer that one for character purposes.  O.K. then,  I know there isn't a whole lot of information out there about sub-atomic particles only because of their short lived life spans and how elusive they are, but, did anyone know that they recently clocked a sub-atomic particle surpassing the speed of light?  I know Einstein stated nothing could travel faster than the speed of light.  To me if you can imagine it being possible it is.  I might be on a tangent right now concerning what is being discussed.  If this is possible, my suggestion to those in the astrophysicist field is to get on the math train in order to be able to explain how this is possible.  You just might find yourself in a book somewhere.  I am not a scientist as I have stated before, but I do know how to manage unknowns in general and see gaps that need closure as this will definitely need for all concerned.  Gravity also does seem to escape us all to a certain degree.  There are equations out there now on how to quantify on how it does interact with all surrounding.  This will sound wild (as it does to me) but how about we reverse the equations and come up with quantifiable math as a theory and develop models on how this could be achieved?  I have a feeling if one starts a new direction concerning gravity it may change into a certainty that can be modified and basically revolutionize our surroundings overall.   Just thought I would add some input today as I love science..  Thank you for listening!! :)  Have a great day all!
 

johan_M

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Re: At what speed does gravity propagate?
« Reply #5 on: 10/11/2011 07:25:20 »
Welcome to the forum.
 
Quote
I might be wrong but, take into consideration when you drop a rubber ball on the ground. Does it travel at the speed of light?
  The force of gravity does move at the speed of light.It can be thought of as connecting at the speed of light.The gravitational force is known by physicists as a weak force. It is a type of accumulating force that, as you say, is built up by particles as they cluster together, such as the earth. So even though this force is quite weak, the accumulated force can be massive when it's taken over many particles. This is the force between the ball and the earth and connects at the speed of light and causes the ball to accelerate at 9.8m/s˛. All bodies accelerate at this speed to the Earth; because even though the force is greater for bigger masses, inertia also increases so this corrects the acceleration back to a constant value.
 
Quote
O.K. then,  I know there isn't a whole lot of information out there about sub-atomic particles only because of their short lived life spans and how elusive they are, but, did anyone know that they recently clocked a sub-atomic particle surpassing the speed of light?
  You are referring to the recent neutrino experiment. This has been due to a measurement error, apparently by GPS locations. I don't know of any particles that can exceed the speed of light, but if i'm wrong i'll be corrected soon enough by the experts.
 
Quote
I have a feeling if one starts a new direction concerning gravity it may change into a certainty that can be modified and basically revolutionize our surroundings overall.
Experimental results on gravity are always observed first and then equations are used to describe them. Unfortunately, it can't be the other way around as many inventors claim.
« Last Edit: 10/11/2011 09:32:15 by johan_M »
 

Offline imatfaal

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Re: At what speed does gravity propagate?
« Reply #6 on: 10/11/2011 10:15:33 »
There is no known process by which a mass can appear or disappear.
Doesn't mass disappear in all exothermic reactions? (ie: converted to energy)
  But energy and mass are equivalent and both give rise to space time curvature - so the energy would cause as much gravitational effect as the mass it replaced.
 

Offline imatfaal

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Re: At what speed does gravity propagate?
« Reply #7 on: 10/11/2011 10:22:42 »
...
Quote
O.K. then,  I know there isn't a whole lot of information out there about sub-atomic particles only because of their short lived life spans and how elusive they are, but, did anyone know that they recently clocked a sub-atomic particle surpassing the speed of light?
You are referring to the recent neutrino experiment. This has been due to a measurement error, apparently by GPS locations. I don't know of any particles that can exceed the speed of light, but if i'm wrong i'll be corrected soon enough by the experts.
...

The last time I looked there was no resolution to the OPERA/CERN anomalous speed of neutrino measurements.  I would be very surprised if it was due to GPS location mistakes - these readings and methodologies were published and have been massively scrutinised by metrology institutes all over the world.  Secondly MINOS and SuperK are in process of setting up experiments to check OPERA's results; and OPERA itself is running a variation of the initial experiment that will help eliminate the doubt - they would not be doing this if it was resolved.
 

Offline yor_on

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Re: At what speed does gravity propagate?
« Reply #8 on: 10/11/2011 11:49:42 »
Yep, it is a very strange outcome, and the experiment in itself discuss so small differences in time, relying on so much statistical evidence, that I doubt it will be solvable in the near future. There will always be room for doubt, and uncertainties. Now, if it had been about a constant instead, as 'c' is defined to be? But arguing that neutrinos can do FTL you will be in the situation where a neutrino of a tiny, but discernible mass, now 'moves' faster than light, that we still have to find a 'mass' for, that means that the only thing talking for a 'photon' having a mass is the theories, and experiments, telling us how incredibly small it would have to be to exist, much smaller than the neutrino.

So using this logic we now find that we define mass as something able to go FTL, with bosons being the exception. Very convincing.
 

Offline Nizzle

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Re: At what speed does gravity propagate?
« Reply #9 on: 10/11/2011 11:59:46 »
There is no known process by which a mass can appear or disappear.
Doesn't mass disappear in all exothermic reactions? (ie: converted to energy)
  But energy and mass are equivalent and both give rise to space time curvature - so the energy would cause as much gravitational effect as the mass it replaced.

True, but mass stays put and energy dissipates. The sun's mass decreases every second, no?
 

Offline imatfaal

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Re: At what speed does gravity propagate?
« Reply #10 on: 10/11/2011 15:34:08 »
There is no known process by which a mass can appear or disappear.
Doesn't mass disappear in all exothermic reactions? (ie: converted to energy)
  But energy and mass are equivalent and both give rise to space time curvature - so the energy would cause as much gravitational effect as the mass it replaced.

True, but mass stays put and energy dissipates. The sun's mass decreases every second, no?

Yes and the mass/energy decreases by the amount of radiation that is given off.  The mass/energy lost through radiation - whilst seemingly vast in absolute terms is small in relative terms.  nb suns reactions are not exothermic chemical but are nuclear. 


But for the purposes of the op that is of course exactly the same time difference as the gravity change takes to reach us. so there is not instanteous loss of mass
 

johan_M

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Re: At what speed does gravity propagate?
« Reply #11 on: 11/11/2011 22:02:28 »
Hi Imatfaal,
What do MNOS SuperK and OPERA do as opposed to what CERN does?

I'm actually not sure what the main purpose of CERN is either ,except that it's to smash atomic particles at high speeds.
 There's a heck of a lot of Physicists working at CERN, so it must be a really big project (or projects) that they are working on.
 

Offline imatfaal

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Re: At what speed does gravity propagate?
« Reply #12 on: 13/11/2011 09:38:16 »
CERN is the European Centre for Nuclear Research and does a huge amount of experimental physics (they host the Large Hadron Collider - but also much more besides).  The second largest of CERNS experiments is the Super Proton Synchrotron - this provides a narrow and very high energy beam of protons.  These can be used to produce Muons - which in turn decay into, inter alia, mu-neutrinos.  CERN does a huge amount more that work with neutrinos - in fact the neutrino research is done 730km off site!

OPERA at Gran Sasso in Italy was set up to take advantage of CERN's ability to create beams of mu-neutrinos.  It is placed along the line of the neutrino beam described

MINOS (main injector neutrino oscillation switch) is a similar neutrino experimentation centre - which in turn uses neutrinos created at the accelerator at FermiLab in Chicago USA.  It has detectors up close in Chicago and in Southern Minnesota

SuperK is a non-directional neutrino detector that was setup to detect cosmic neutrinos but I believe also can see feeds from Japanese nuclear facilities.  It was at SuperK that experimental proof of neutrino mass and flavour oscillation was found

 
 

johan_M

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At what speed does gravity propagate?
« Reply #13 on: 15/11/2011 01:09:25 »
Quote
CERN is the European Centre for Nuclear Research and does a huge amount of experimental physics (they host the Large Hadron Collider - but also much more besides).  The second largest of CERNS experiments is the Super Proton Synchrotron - this provides a narrow and very high energy beam of protons.  These can be used to produce Muons - which in turn decay into, inter alia, mu-neutrinos.  CERN does a huge amount more that work with neutrinos - in fact the neutrino research is done 730km off site!

OPERA at Gran Sasso in Italy was set up to take advantage of CERN's ability to create beams of mu-neutrinos.  It is placed along the line of the neutrino beam described

MINOS (main injector neutrino oscillation switch) is a similar neutrino experimentation centre - which in turn uses neutrinos created at the accelerator at FermiLab in Chicago USA.  It has detectors up close in Chicago and in Southern Minnesota

SuperK is a non-directional neutrino detector that was setup to detect cosmic neutrinos but I believe also can see feeds from Japanese nuclear facilities.  It was at SuperK that experimental proof of neutrino mass and flavour oscillation was found
Thank you.
It seems as though most of these institutions are reseaching neutrinos?
  As we are discussing gravity, how does the Higgs Bosun particle fit in here? Why is this particle required? Is it not good enough to think of gravity as a field?
 

Offline Phractality

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At what speed does gravity propagate?
« Reply #14 on: 15/11/2011 05:05:19 »
  As we are discussing gravity, how does the Higgs Bosun particle fit in here? Why is this particle required? Is it not good enough to think of gravity as a field?
A field is a mathematical description of an effect. If you want to understand the effect, you must look for its cause.
 

johan_M

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At what speed does gravity propagate?
« Reply #15 on: 15/11/2011 20:10:04 »
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As we are discussing gravity, how does the Higgs Bosun particle fit in here? Why is this particle required? Is it not good enough to think of gravity as a field?
A field is a mathematical description of an effect. If you want to understand the effect, you must look for its cause
I don't think that's the reason. This would then lead to "what causes the higgs bosun".It must be because there are some theoretical equations that show effects that cannot be explained by gravity fields.
 

Offline Geezer

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At what speed does gravity propagate?
« Reply #16 on: 16/11/2011 06:22:25 »
I think the correct answer is "nobody knows".

If gravity is communicated by the hypothetical massless graviton, you'd kinda think it would propagate at the same speed as light.

Personally, I happen to think the graviton will remain hypothetical because gravitational attraction is due to "holes" in spacetime in the vicinity of matter. However, as I haven't one shred of evidence to support my idea, I better shut up.
 

Offline imatfaal

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At what speed does gravity propagate?
« Reply #17 on: 16/11/2011 09:34:40 »
If the graviton exists then it is almost certainly massless - and if it is massless it will go at the speed of light.  Gravitational waves - the propagation of the field of which the graviton is the proposed (gauge?) boson;  GR predicts that grav waves travel at c - there are experiments in progress to check this - if the waves travel at c then I guess the boson must as well
 

johan_M

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At what speed does gravity propagate?
« Reply #18 on: 17/11/2011 04:28:19 »
Imatfaal; what is the definition of a bosun?
 

Offline imatfaal

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At what speed does gravity propagate?
« Reply #19 on: 17/11/2011 10:15:48 »
a bosun - a contraction of boatswain, is a petty officer on a naval vessel.

a boson - named after Satyendra Nath Bose, is a form of subatomic particle.  Boson's have integer spin and do not comply with the Pauli exclusion principle - they are separated from Fermions which have fractional spin.  Some bosons - including the gauge bosons are fundamental/elementary within the best model at the moment - the Standard Model; these are the photon, the gluon, the W± and Z bosons, and potentially the graviton and the Higgs. These elementary bosons are the "force-carrying" particles of the forces of nature, the photon mediates the Electromagnetic force, the gluon the strong nuclear, the  W± and Z the weak nuclear, the graviton gravity and the Higgs, well that's difficult.  Anything else with integer spin which obeys certain rules (called Bose-Einstein statistics) is a composite boson - a helium atom, all mesons etc
 

Offline yor_on

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At what speed does gravity propagate?
« Reply #20 on: 18/11/2011 16:25:54 »
I think of it as a four dimensional net Cheryl. Four dimensional as times arrow constantly 'moves & change it' as it is coupled to mass and its 'relative motion'. And just as with a spider net can 'vibrate' at sound speed, as the fly comes into it, so can this gravitational 'net' vibrate at 'c' depending on the 'mass' changing 'position'. You could see it as all mass send out messages telling all other mass where they are, creating the conceptual 'threads of gravity'. Assume that something moves away from you then the 'thread' will become stressed, that stress will propagate from the initial point of 'relative motion' towards the 'receiving/responding point' at 'c'.

So gravity is everywhere in my definitions, even where people like to assume it to be a 'flat space'. There are no stretches of 'flat space' as I see it, even though it makes a lot of sense to define it such conceptually.
« Last Edit: 18/11/2011 16:30:08 by yor_on »
 

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At what speed does gravity propagate?
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