Order of Kilopi
If the universe was infinite in size wouldnt there be infinite gravity?
Gravity propogates at speeds in excess of the speed of light. ( how fast does gravity propogate)?
If gravity can propogate faster than the expansion of the universe.
Using the ant and the rope thing ...
and assuming that the universe is infinitely large
and assuming that a gravitational field extends forever
the gravitational pull at any point in space would be infinite???
Is that right?
Established Member
Only if it contained infinite mass.Originally Posted by tommac
Gravity propagates at the speed of light and we think the amount of mass in the universe is finite, therefore the rest of your post doesn't really apply.Gravity propogates at speeds in excess of the speed of light. ( how fast does gravity propogate)?
Order of Kilopi
Can you please show source of this? I have been reading differently.
Order of Kilopi
If there was infinite gravity wouldn't we be back at the singularity?
Order of Kilopi
Ummmm ... wouldnt an orbit be unstable if gravity propogated at the speed of light?
I am pretty sure that gravity propogates at speeds much faster than the speed of light if not instantaneously.
Order of Kilopi
Hah ...
This is more of a thought experiment that real life question.
But I think at the end it would prove that either gravity is not instantaneous or that the universe is not infinite.
Order of Kilopi
How can a black hole have gravity then?
Order of Kilopi
Where did you read about this? i raised this as my first question on this forum and most answers indicated that it propagates at the speed of light along with the other known forces. I am still unclear so would like to find out either way.
Established Member
If the universe is truly infinite in spatial extent there should be infinite mass as long as the mass density is non-zero, right?
Order of Kilopi
only if the all infinite spatial extent was filled with mass?
Established Member
Does Gravity Travel at the Speed of Light?
First speed of gravity measurement revealed
Order of Kilopi
I guess in a way it does prove that the mass density is not infinite if it was then surely space would contract to zero?
Order of Kilopi
Where did you read about this? i raised this as my first question on this forum and most answers indicated that it propagates at the speed of light along with the other known forces. I am still unclear so would like to find out either way.
Heh ... nothing would work then ... Who told you that it was at the speed of light ... that is rediculous. That would mean a black hole could not have gravity. That would mean that nothing could be in orbit ... Think about the effects on the earth if there was a delay of gravity from the sun.
Order of Kilopi
OK ... in GR. ... yes speed of light ... but relative to us it is instantaneous.
That is what it is saying right?
Established Member
No, we think gravity travels at the speed of light relative to us, just like light does. Did you read the second link?
Order of Kilopi
I have! and i have just read the 2 links provided by Speedfreek there is strong mathematical evidence to support either way, all depending on our definition of how we describe gravity, Newtonian or by GR. I wonder whether the underlining constant of C is actually the constant of space-time expansion and that the forces we known are instantaneous but are perceive to propagate at that speed because of this?
Order of Kilopi
Does GR ignore aberation?
Established Member
Do me a favor and google "precession of mercury" . We will continue once you have consulted this test of GR.
Order of Kilopi
I think even in GR it propogates faster than the speed of light if you take abberration into account.
I have! and i have just read the 2 links provided by Speedfreek there is strong mathematical evidence to support either way, all depending on our definition of how we describe gravity, Newtonian or by GR. I wonder whether the underlining constant of C is actually the constant of space-time expansion and that the forces we known are instantaneous but are perceive to propagate at that speed because of this?
Order of Kilopi
Yes this proves to support very strongly that GR describes the true effect of gravity.
Established Member
And the underlying difference between Newton and GR is that Newton had gravity propagating instantly, whereas in GR it propagates at the speed of light.
Order of Kilopi
Order of Kilopi
Explain this argument to me, please.
Order of Kilopi
http://www.sciencedirect.com/science...606db9eff773eaExplain this argument to me, please.
I am not sure if I have it right so I could tell you what I think but it is probably best if you read it yourself.
Established Member
So is speedfreek implying that there is an infinitely large universe that is only partially filled with mass? If this were the case, what stops all that mass from gravitationally attracting itself? There would be an "edge" to matter and object on the edge would feel a net gravitational attraction toward the center of the mass distribution.
Order of Kilopi
I read the link and i,m not sure it is saying that in GR gravity propagates faster than C
"aberration in general relativity is almost exactly canceled by velocity-dependent interactions, permitting cg=c. This cancellation is dictated by conservation laws and the quadrupole nature of gravitational radiation"
Established Member
If I spill a gallon of beer on the floor and wait 10 minutes. Now I come back and walk a small distance away from where I dropped the beer. My feet are wet. Did the spill travel at the speed of beer or was it instantaneous since my socks are wet as soon as they touch the ground.
It's important to understand that once gravity has propagated to a certain place, the effect on a moving mass is instantaneous. The speed of gravity is still the speed of light.
Did you research the precession of mercury, bro?
Order of Kilopi
There could be a net gravitational effect towards the center of the mass distribution of the finite mass spread. But maybe expansion of space could counter act this for now. Prior to the discovery of accelerating spatial "expansion" was this not the theory of the big crunch?
Order of Kilopi
Well put! this was the way i was thinking but could not put it into clear understanding to post.
Established Member
The original question was
Define infinite gravity. In my definition, you need infinite mass-density to produce infinite gravity. What is your definition of infinite gravity? Am I barking up the wrong tree here?If the universe was infinite in size wouldnt there be infinite gravity?
Second point, who said the universe is infinite? I am certainly not implying that the universe is infinite, that's for sure. I tend to go with "finite but unbounded".
Last edited by speedfreek; 2008-Apr-29 at 10:00 PM. Reason: clarification
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